F&S International Edition 2019

D 11665 F

All New Business Structure Fusion of Experience

International Edition

2019

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Air filters for g general ventilation · Developing p g a tester for automated in-line filter testing g · Bagasse g extracts fractionation byy combination of membrane and chromatographic g p technologies g · A setup p for measuring g passenger p g car brake dust particles p emissions · Numerical and experimental p investigations g on loading-dependent g p p particle deposition p in electret filter media · Washing gp performance p prediction off horizontal vacuum belt filters for different wash modes · Deodorizing g filters containing g visible light g p photocatalysts y for air purifiers · Automatic water disposal p for heavyy dutyy and industrial applications pp - removal of hydrocarbons y to ensure environmental p protection · A new set-up p for characterisation off p particle collection efficiencyy on elastic single g fibres · Experimental p characterization of p particle structure re-arrangement g and detachment from a steel fiber exposed p to hot air flow · Generation and characterisation off reactive/inert particle p aerosols · Back cleanable air filter elements for critical dust systems y - US HEPA, IFA H and EN1822 HEP PA · A comparative p investigation g of soluble filter cakes upon p contact with liquid q droplets p · VisionAir Clean for clean room air change g rate optimization p · Experimental p studyy on the p preparation p of ceramic fiber filter elementt for hot g gas filtration · Hydrodynamic y y Influences in Dissolved Air Flotation · Reducing gp pressure drop p of coalescence filtration media byy p patterned modification of wettabilityy · Methods to increase the filtration p performance of metal woven wire cloths · Performance of two online p particulate matter measurement principles p p in a fertilizer industrial prilling p g tower · Filtering g of high g solids concentration media using g complex p p powerful to the flow · Some aspects p of application pp nanostructured filter media in air and water filtration · The effect of membrane structure p prepared p from carboxymethyl y y cellulose and cellulose nanofibrils for filtration and biochromatograph g p ic separation p · Feedbacks on p performance tests with Filtralite® media compared p to conventional media filters at p pilot scale · A p probabilistic-statistical model of change g in p particle size distribution in fine filters · Investigating g g the cleaning g efficiencyy of filters clogged gg with metallic nanoparticles p · Co Combined p porous mesh metals for filters and capillary p y fencing g devices · Geometrical model of the p porous structure of the permeable p material and the new experimental p method off determinig d g its structural characteristics · Interaction between p polysaccharide y and p protein on membrane foulingcaused g byy microbial metabolite · Effect of ethanol concentration on n filter cake characteristics in microfiltration of ye y ast suspension p · Powder sampling p g with a p pressure p portt on the high g p pressure natural g gas filter for differential p pressure g gauge g · Cha aracterization of an electrostaticallyy charged g water spray p y for reducing g fine dust emissions · Experiments p on the rearrangement g behaviour of dust in wall flow filters · Two yyears of filter testing g experiences p according g to new ISO 16890 · HEPA/ULPA filter leak testing g for production p control using g solid PSL (Polystyrene-Latex) ( y y ) aerosol · Experimental p methods in i dust emission p prediction · Bionics in application pp : Superhydrophobic p y p functional textiles for the removal of oil contamination from water · Simulation and experiments p on the ca ake formation in dust filtration with fabric filters · Influence of the deliquescence q and efflorescence off hygroscopic yg p salt particles p on the performance p of surface filters · A susta sustainable, modular and lean solution for p pocket filter assemblyy · Flow through g randomly-oriented y fibrous filters · Numerical and experimental p investigation g of filter cake formation during g solid-liquid q separation p byy resolved CFD-DEM coupling p g · A new methodology gy for continuous scanning g of p particle aerodynamic y diameter and application pp to filtration p performance assessment of a room air p purifier · Advances in p plasma deposition p of functional nanocoatings g for filtration applications pp · Efficiencyy of collection of p particulate matter and maximum p pressure drop p of p precoating g · Cost and energy gy saving g through g automatic backwash filter in PE production p · Cabin air quality q y and energy gy savings g in electric vehicles byy using g a smart filtration system y · Characterization of p performance relevant media p properties p in oil mist filtration · Dynamic y simulation of mechanical dewatering g of compressible p cake in decanter centrifuges g · Sustainable p production in the metal industryy - 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The firstt melamine meltblown nonwoven · Determining g the filtration p properties p of different p protein crystals y in the centrifugal g field using low volume samples p · Optimization p of g gas input p t in aqueous q two-phase p flotation ((ATPF)) for enzyme y p purification · New Development p in Bag g Filtration · Benefits of single g p photometer technology gy in an automated filter tester · The influence of slip p flow on Filtration simulations on the nano scale · High g speed p laser drilling g of p precise micro and nano holes in metallic surface filters · Bio-inspired p separation p - Formulation of an innovation model and ideation tool to boost innovation in the sector of separation p technology gy · Filtration p performance of PAN fiber p produced byy centrifugal g spinning p g using g DMSO and DMF as solvent · Performance of Nanofiber Filters and HEPA in the collection of nanoparticle p for air filtration · A methodology gy for estimating g water droplet p sizes and predicting p g filter performance p in diesel fuel and lube oil applications pp · Filter cloths: Bluetes anti-abrasion resin · Network model of p porous media - Review of old ideas with new methods · Fractionating g of finest p particles using g the crossflow filtration · Bekaert Bekipor p ® Metal Fiber Media Filtration Solutions for Hydraulics y · High-pressure g p operation p of spiral p wound membrane elements: The relevant aspect p of p permeate channel fluid dynamics y · Best Practice for Liquidq Liquid q separation p with cartridge g coalescers · Effect of aeration on hollow fiber microfiltration characteristics of activated sludge g · Filtration modeling g and simulation with GeoDict, from filter media to filter element · Identification of fiber characteristics of a filter media based on artificial intelligence g ((AI)) with GeoDict · Comparison p of different discharg ging g methods and test aerosols for measuring g the efficiencyy of electret filters · Assessment of commercial cartridge g filters for usage g in low-cost household water treatmentt systems y · FILOS - Module I: The novel software for the reliable analysis y of filtration test data and suspension p characterization including g washing g and deliquoring q g of filter cakes · FILOS - Module II: The novel software for the reliable selection, performance p prediction p and optimization p of filters for the cake forming g filtration of suspensions p · CENTRISTAR - A novel software for filter centrifuges g · Benefits of filter presses with artificial intelligence p g ((AI)) support pp in the chemical and mining g industries · Heat exchange g simulation for single g HF membrane module using g CFD modeling g · The effectt of p particle sedimentation on the p performance of p pressure filters · Collection efficiencyy of a bag g after 3 yyears of use in a bag g filter · The Krauss-Maffei Peeler centrifuge g with pneumatic cake discharge p g · Development p and p performance test of MIL-88 based filter structure using g electrophoretic p deposition p · Experimental p studyy of the separation p degradation g of dyes y using g composite p p photocatalytic y membrane treatment · Novel sintered metal filter elements: Performance evaluation in biomass gasification g conditions · A flexible approach pp for meso-scale filtration modelling g based on Open-Source p CFD · Influence of fiber size distribution on the p permeabilityy of fibrous filters · Production and characterization of filter media obtained byy electrospinning p g for applications pp in air filtration · Assessment of filter media p properties p for automatic selff-cleaning g filters · Development p of microfiltration membranes of biodegradable g biomass p plastics with the aid of surfactants and their application pp to depth p filtration · Associating g filters by series for optimizing p g the retention capacity p y off nanoparticles p · Sludge g solids concentration: Which are the limits? · Simultaneous dust and noxious gas g separation p in an entrained-flow adsorber on surface filters · Filter testing g regarding g g separation p efficiencyy in terms of airborne fungal g spores p · Droplet p size measurement of cutting g fluid aerosols · Aspec p ts of air filter testing: g dust loading g · Proof-of-concept pt of a newlyy developed p device for the coupled p g generation and separation p of crystalline y p particles · Energy gy reducing gp polymeric y filtration mesh · Influence of oil droplet p size distribution on the fouling g mechanisms of UF/MF membranes during g filtration of oil nano-emulsions · Whyy dewaterabiltyy of sewage g sludge g occurs upstreamp a model to q quantifyy the effects · Low p pressure drop p media for A+ filters · Investigation g of filter cake characteristics regarding g gp particle shape p and wettabilityy · Process simulation and characterization of nonwoven inhomogeneities g and their negative g effect on filtration due to local flow rate heterogeneities g · 0.45 micron g grade microfiltration composites p for solid liquid q separation p · Measurement of the p porosityy of spherical p p particle deposit p formed byy filtration: Discussion on the Peclet number; effect · Combinatorial optimization p of double-layered y filtration media for higher g p performance · Multipore p ™: The state-of-the-art wire mesh · Air separation p from a hydraulic y tank using g special p meshes · Understanding g the role off cake structure in the filtration of needle-like crystals y in the p pharmaceutical industryy · Behavior of metallic filters used to p protect HEPA filters in case of vapor p release · Evaluation of process p strategies g to homogenize g the lautering g filter cake structure and enhance wort production p · Investigation g of the Filtration Kinetics of Depth p Filter considering g Tomographic g p Data · Exentis Group p AG: Industrialized Additive Manufacturing g · New approaches pp for p phosphate p recoveryy applying pp y g iron hydroxide y containing g material in adapted p sorption p processe · Testing p g the efficiencyy of p process filtration of viruses in g gases with p protein nanoparticle p surrogates g ·Ap probability and statistical model of p particle separation p in hydrocyclones y y · New synthetic y nano-aerosol for accelerated realistic ageing g g of air filters · Optimizing p g spunbond p nonwovens for filter media production p using g a novel approach pp of machine learning g and fiber/fluid simulations · Separation p and dewatering g of biological g microparticles p from low concentrated suspensions p byy using g the energy gy efficient thin film filtration · Microsand cross flow filtration in cooling g towers water circuit - a sustainable approach pp for hvac systems y · Size characterization of p plastic microparticles p · Modelling g off the mechanical aging g g behaviour of PLA-based nonwovens and monofilaments under filter application-relevant pp conditions · Clarification of low concentrated microalgae g suspensions p byy decanter centrifuge g · Environmental issues of waste tire recycle y system y · Filtered dryy stack tailings: g The 'state of p play' y for high g capacity p y tailings g filter p plants · The effect off normal load on the shear yyield stress of suspensions p · New p physical y p principle p of dilution system y for crankcase ventilation filter testing g · Filter media testing g in accordance with ISO 16890 · A multi-scale studyy of the p permeabilityy of compressed p nonwoven filter media · Measuring g the maximum p pore size of a filter, choosing g the most statisticallyy robustt parameter · Flow resistance evaluation through p g nonwoven filter media · Experimental p assessment of deposition p of synthetic y fibrous dust within the ductwork of residential ventilation ® systems y · Measuring g PM2.5 for cleanable filter media in ISO 11057 or ASTM D6830 tests using g an optical p aerosol spectrometer p Promo LED · Pore Size of the Spunlaced p Nonwovens and Optimization p of the Parameters for Air Filtration Application pp · Characterisation of micron p pore size filter media comparison p of methods ·Predicting g collision efficiencies of colloidal nanoparticles p in single g spherical p and fibrous collectors: A numerical study · Tackling urgent water related p problems in the mining g industryy using g membrane processes · Filters with low tortuosity produced in a roll to roll process…

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Highlights 2018

Dear Readers,

In Germany and the neighbouring countries, the F&S magazine has been quite an institution for the past 32 years – after all, it is the only German-speaking trade journal exclusively dedicated to filtration and separation technology but also to the treatment of disperse substance systems.

Our readers and advertisers especially value F&S because of the high quality of the published articles and essays that were often trendsetting and also describe today’s valid standards.

For the nineteenth time, we have now had a small part of our broad editorial spectrum translated into English. These are contributions that were published in the year 2018.

By doing so, we want to provide the contents of our magazine to process engineers in non-German-speaking countries as well.

Again, this is only a small selection of our articles. With a complete translation of all the articles that were published in the year 2018, you would now hold a thick book of nearly 450 pages in your hands.

We hope you enjoy reading our International Edition and would be pleased to receive your feedback.

If you would like to find out more about the German F&S, please do not hesitate to contact us at the address given below (also see imprint: page 66).

With best regards

Eckhard von der Lühe Publisher

VDL-Verlag GmbH Heinrich-Heine-Straße 5 D - 63322 Rödermark Phone: + 49 (0) 60 74 / 92 08 80 Fax:

+ 49 (0) 60 74 / 9 33 34

E-mail: evdl@vdl-verlag.de Internet: www.fs-journal.de

F & S International Edition

No. 19/2019

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Contents powered by water

We t ake care of clar ity!

NEW Robust, easy to clean PolyCera® membranes extend the range of ultrafiltration and nanofiltration performance beyond conventional ceramic and polymeric membranes New polymer material, supplying ceramic – like robustness with the flexibility of a polymeric membrane Feedspacer up to 120 mil (3 mm) Spiral wound element design, f its into standard RO pressure vessels Fully back washable up to 1.7 bar High suspended solids tolerance Oleophobic – less fouling Chlorine stability up to 100.000 ppmh BTEX stability Wide operating pH range (1-13,5) xchangeWide resins · Filter material · Filterrange cartridges Filter 0 operating temperature up to· 90 C ho n Co Cont ntro roll ller erss · Pr Pres essu sure re ves esse sels ls · Mem embr bran anee ch chem emic ical alss · Io Ion n tral control valves · UV - Disinfection · Electrodeionization al · Filter cartridges · Filter housings · Pressure tanks · Cent · Mem embr bran anee ch chem emic ical alss · Io Ion n ex exch chan ange ge res esin inss · Fi Filt lter er mat ater eria ia fection · Electrodeionization Controllers · Pressure vessels tio ion n · Pr Pres es · · - Dis isin infe fect ct ange resins · Filter material · Filter cartridges · Filter housin ollers · Pressure vessels · Membrane chemicals · Ion exchang rol valves · UV - Disinfection · Electrodeionization Controlle cartridges · Filter housings · Pressure tanks · Central contro e chemicals · Ion exchange resins · Filter material · Filter ca ctr trod odei eion on · · mbr bran anee ch ure tanks · Central control valves · UV - Disinfection · Electr ilter material · Filter cartridges · Filter housings · Pressure t re vessels · Membrane chemicals · Ion exchange resins · Filt trol valves · UV - Disinfection · Electrodeionization Control cartridges · Filter housings · Pressure tanks · Central contro ne chemicals · Ion exchange resins · Filter material · Filter c ectrodeionization Controllers · Pressure vessels · Membrane

▼ Highlights 2018

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Process technology and conditions used for water and wastewater treatment Report from the 12th Water Technology Conference held in Aachen H. Lyko

6

Improving the resource efficiency of irrigation using reverse osmosis for the desalination of brackish well water and salty sewage effluents Th. Peters

12

A wide range of submerged membrane modules for use in MBRs and other applications H. Lyko 20 Sewage sludge disintegration through the use of a centrifuge A report from Hiller GmbH

24

Industrial water: The importance of efficient water usage and the digitisation of water management in the process industry H. Lyko

25

Cloud computing for simulation and web applications in line with Industry 4.0 S. Poss, K. Schmidt, S. Ripperger, S. van den Berg

29

Future of process and plant technology

33

Combined separation processes for downstream processing in biotechnology J. Barth

35

Method for the design and optimisation of dynamic surface filters with respect to the specific filtrate flow rate and energy demand J. Barth, S. Ripperger

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▼ Improving the resource efficiency of irrigation using reverse osmosis for the desalination of brackish well water and salty sewage effluents

Phone +49 (0) 2166 62199-0 Fax +49 (0) 2166 62199-26 E-Mail: sales@inaqua.de

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F & S International Edition

No. 19/2019

Contents Highlights 2018

Manufacturing, characterising and using innovative textile filter media A report from the 14th textile filter symposium H. Lyko

45

The testing of air filters for use in general ventilation technology and as automotive cabin air filters A comparison of the developments in the field of particle filtration over the last 25 years F. Schmidt

52

Sensor technology used in air and gas filtration – main topic at the 9th IUTA filtration day H. Lyko

57

Fine dust monitoring developments Report from the “PM2.5 monitoring – What’s Next?” network meeting H. Lyko

60

Dedusting technology for organic dusts with reliable containment Th. Schwalbe

64

▼ Industrial water: The importance of efficient water usage and the digitisation of water technology used by the processing industry

Filter Solutions for Home & Profession.

▼ Combined separation processes for downstream processing in biotechnology

F & S International Edition

No. 19/2019

Hengst Filtration for industry and environmental provides a host of different industries with filtration solutions that are tailored to their specific needs.

They provide cleanliness and hygiene for private homes and ensure filtration and protection for plants and the investment goods used by trade and industry for professional applications. Individual filtration solutions for every customer requirement - feel free to contact us!

5

Highlights 2018

Process technology and conditions used for water and wastewater treatment Report on the 12th Water Technology Conference held in Aachen H. Lyko * The 12th conference, which was jointly hosted by the Aachen Institute for Chemical Process Engineering (CVT, part of the Aachener Verfahrenstechnik AVT), and the Institute for Environmental Engineering (ISA) at RWTH Aachen University, also celebrated its 20th anniversary. A lack of exciting and current topics for this biennial conference with its accompanying industrial exhibition was nowhere in sight. Working experience gained from existing plants for the treatment of municipal and industrial wastewater as well as the treatment of drinking water and the latest research results and new developments in material and process development were all discussed [1].

Key topics included water reuse, energy consumption during wastewater treatment, trace substance elimination, the cleaning of special industrial wastewater, nutrient recovery as well as measurement and process control technologies.

While trace substance elimination was a focal topic at the 11th conference, the recovery of nutrients is another redhot topic that has become the focus of considerable research. The recovery of nutrients and material recovery from wastewater is dealt with in a separate specialist article in the F&S Global Guide of the Filtration and Separation Industry /2/. Inter alia, this contribution also summarizes presentations given at the Aachen conference.

Trace substance strategies in Germany and Switzerland Whether and to what extent trace substance elimination processes will shortly have to be used in German clarification plants and which precautionary measures will have to be taken in order to prevent these substances from getting into municipal wastewater was discussed as part of the stakeholders‘ dialogue about the federal government‘s trace substance strategy. This dialogue was launched in November 2016 with a kickoff event and the Federal Environment Ministry and the Federal Environment Agency were also in attendance.

Dr Jörg Wagner, from the Federal Environment Ministry, opened the lecture programme with an overview of the activities and results of this dialogue to date, which were published in a „Policy Paper“ [3] at the end of June 2017 and according to previous estimates, funding of around 10 billion € will be needed for implementing a 4th cleaning stage in larger municipal clarification plants.

The preparation and enacting of a legal regulation covering the elimination of trace substances is deemed to be difficult with regard to the different conditions and financial options for the federal states, political attitudes towards the topic and the prevailing competition with other important tasks for which public funds are needed. Recommendations that will meet with the broadest possible approval later on will be prepared through the involvement of all * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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stakeholders. Participants in the dialogue are representatives from the manufacturing industry, the water industry as well as representatives from physician, pharmacist and hospital associations, consumer protection advisors and the environmental associations as well as the German cities association and the cities and municipalities federation. It was decided at an early stage to use the term „trace substances“ and not „micro-pollutants“ as the first

term does not contain any assessment of the harmfulness of the substances.

The individual topics for which action recommendations have been published are shown in Fig. 1. The recommendations covering the downstream measures (4.1 - 4.4) also include measures for removing them from wastewater, which were the main focus of this event. A technicallyoriented framework will be created to limit the „continuous but rather boundless and

Fig. 1: Overview of the topics of the treatment recommendations previously developed in the stakeholder dialogue about the federal government‘s trace substances strategy [3]. Concerning the topics marked *, minority votes are available from one or two (Section 5, costs) of the organisations represented. They are listed separately in the policy paper.

F & S International Edition

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Highlights 2018

therefore arbitrary discussions between experts and people who might be affected“ (see Wagner‘s short version in the conference proceedings) [1]. A major hurdle that must be overcome is the development of a financing model for the measures that will have to be implemented. A decision must be made here between the ‚polluter pays‘ principle and the ‚solidarity principle‘ (cost allocations). It must also be decided whether the pricing of products containing the relevant trace substances is intended to have a controlling effect or not. In February 2018, the second phase of the stakeholders’ dialogue officially started with a kick-off event in Berlin. The goal of the second phase was to concretise the recommendations for action that were given in the above mentioned policy paper [3].

It should be noted at this point that, regardless of the status of the stakeholder dialogue and the absence of a nationwide regulation at the time of the conference, 19 large-scale plants for eliminating trace substances were already in operation in Germany and 11 of these are in BadenWürttemberg and the other 8 are in North Rhine-Westphalia. They are the two federal states in which competence centres are specifically committed to this problem.

These German plants are also shown in the overview map which can be called up from the VSA platform under: „Micro-pollutants process engineering“ (VSA = Swiss Water Pollution Control Association, see www.micropoll.ch). In the event‘s concluding session, Aline Meier, a member of this platform, summarised the status of the activities previously implemented in Switzerland and drew up an interim balance. A new water protection regulation came into force on January 1,

2016. This states that clarification plants must implement measures to eliminate trace substances if one of the following criteria applies to them: -> 80,000 PE, -> 24,000 PE in the catchment areas of lakes, -> 8,000 PE and a >10% discharge with regard to organic trace substances in untreated wastewater -> 8,000 PE if purification is needed due to special hydrogeological conditions (for highly heterogeneous karst and fissure aquifers).

The aim of the retrofitting measures is to achieve an 80% purification performance for 12 typical and pre-defined trace substances.

The financing of the measures, for which the estimated total value is approximately 1.2 billion CHF, will be assumed by all of the Swiss clarification plants, including those that do not have to provide trace substance elimination processes and approximately 75% will be raised via a fund. Three additional large-scale cleaning stages were already in operation at the start of year 2018, seven were under construction and 17 others were in the planning stage (see www.micropoll.ch).

The main task of the VSA platform is to function as a „knowledge centre“ that collects, summarises and distributes all of the acquired information. The Swiss strategy could also be seen as a form of „learning by doing“: The previously known processes for eliminating trace substances were implemented and the water was examined to see whether the expected positive effects had occurred in the water. If not,

then the range of measures would have to be extended.

Process engineering developments for eliminating trace substances Adsorption and oxidation processes are represented in roughly equal proportions in the Swiss plants and hybrid processes have also been implemented in some of the plants. Adsorption processes are used in the majority of the large-scale plants in Germany. The current state of the experience gained in Switzerland has now been published [4]. Activated carbon adsorption and ozone oxidation are listed as the standard processes used there and no technically or economically competitive alternatives are currently to be seen. Whereas all of the installed ozone oxidation processes roughly follow the same processing pattern, there are generally two possibilities for the use of granulated or powdered activated carbon (GAC or PAC) for activated carbon adsorption, each having several options for its technical implementation.

The projects presented in Aachen covering adsorption with powdered activated carbon dealt with the various methods used for removing the substances from the water as well as with the development of new types of activated carbon to be used for this purpose.

Should a clarification plant be fitted with a downstream PAC dosing system and a deep bed filtration system (so-called Ulm process), then activated carbon slippage is to be expected without any flocculation, especially with particle fractions <10μm. Therese Krahnstöver, from the University of Applied Sciences in North-

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Highlights 2018

Fig. 2: Principle of aerosol-mediated separation of tensides and the decrease of the tenside concentration in the liquid with processing time (Image: Institute for Communication and Management of Chemical Processes in Industry, Bergische Universität Wuppertal) Polymer solution + PSS Bore solution + PEI/PDADMAC Spinneret

Fig. 3: Principle diagram of the manufacturing process for hollow fibre membranes with internal coating by polyelectrolytes in a single step (reprint with permission of ACS App. Mater Interface 2016. 8. 19145-19157. Copyright 2016 American Chemical Society)

West Switzerland, reported on the study of the coagulation mechanism during flocculation with iron salts and with the help of online particle counting and particle size measurement inside the agitator tank [5].

A temporal decrease in the proportion of <10 μm particles, which depends on the flocculation conditions, was recorded. The dwell time in the reactor and the prevailing shear load also had an effect in addition to the flocculating agent‘s concentration.

Stoichiometric iron dosing was considered to be optimum process here. The energy input as well as the shear loading of the resulting flakes should not be too high, in which case PAC can no longer be practically detected in the filter outlet.

Membranes present an alternative to deep bed filtration as they can also retain the ultrafine activated carbon fraction as an absolute barrier to the particles. PAC dosing options upstream of a tertiary membrane stage after the conventional clarification plant exist for combining PAC adsorption with membrane filtration as well as for dosing PAC directly into an MBR reactor and the tertiary membrane 8

stage can also be designed as a submerged or pressure-driven system. Sven Baumgarten, from GE Water & Process Technologies, reported on a research project in which these processing versions were studied at the Neuss-East clarification plant with regard to their large-scale feasibility and achievable elimination of micro-pollutants that is dependent on the PAC dosage. In this study, which was carried out with project management by SWECO GmbH, the general suitability of both the PAC MBR process and the PAC dosage prior to downstream ultrafiltration was determined, whereby both of the membrane processes tested on a semi-technical scale exhibited better elimination performances than when the PAC dosage was implemented ahead of the existing deep bed filter. The PAC MBR version also tended to show better results than the PAC UF version, both with regard to the degradation of COD as well as the trace substances. It was assumed here that the activated carbon was partially masked by colloidal substances from the wastewater matrix. Baumgarten also considered

downstream UF membranes to be more susceptible to fouling because they were only confronted with substances that were difficult to filter and all of the other water ingredients were sedimented beforehand during the final purification process. A hybrid process with direct PAC metering without using a contact reactor was currently being optimised upstream of an ultrafiltration plant in the pilot process installed at the Dinslaken clarification plant. Grit Hoffmann, from DuisburgEssen university, reported on previous laboratory studies and the activities involving the pilot plant. A more detailed description of this project can be found in [6].

In a project run by ISA from RWTH together with the University of Hohenheim, the focus is not so much about the process engineering used in the activated carbon application but more about the alternative production of the same directly in the clarification plant. Julian Firk, et al., used the fine screening material or as raw material the production of coal, which they extracted from the sand trap at a clarification plant. This solid consists mainly of fragmented toilet paper and is therefore very rich in cellulose. This solid was converted into carbon by a HydroThermal Carbonisation (HTC) process. HTC converts the biomass into a carbon-rich solid in water under high pressure (10 - 40 bar) and at a temperature inbetween 180° and 270°C. This was sieved out from the reaction mixture, ground down and thermo-chemically activated at 450° or 550°C through the addition of KOH. The HTC process is also generally suitable for use with sewage sludge. It has a lower carbon content at higher concentrations of heavy metals than the fine screening material, which is why it is less suitable for use as a starting material for activated carbon. The HTC activated carbons, which were previously produced from the fine screenings, have not yet shown the performanceof eliminating methylene blue model substance that is achieved by commercial activated carbon for wastewater purification.

The use of ozone oxidation requires post-treatment in order to remove any residual ozone and any transformation products arise out from the trace substances during the ozone treatment. Heidemarie Schaar, et al., from the TU in Vienna, compared three after-treatment processes with regard to their potential for the continuous removal of trace substances.

The ozonisation reactor‘s outlet was fed into two pressureless decaying tanks, an anthracite deep bed filter and a pressure filter containing activated carbon granulates. Only the last version showed a clearly measurable and continuous removal of trace substances, but this was substance-dependent.

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Highlights 2018

Reuse of purified wastewater Continuous treatment measures used for recovery are gaining in importance in regions with increasing water scarcity. Northern Brazil is a region that is particularly affected by water scarcity.

Processes that can be applied to purify previously unused quantities of wastewater for reuse or for artificial of groundwater recharge are being developed and tested as part of BRAMAR, a German / Brazilian research project (www.bramar. net). The water qualities to be achieved are divided into four levels according to their intended use: Water for washing and cleaning purposes, for irrigation, water for cooling and evaporation as well as water for groundwater recharge. Reports about two subprojects from this project, in which several Brazilian universities and state institutions, institutes from RWTH Aachen University (coordinating), the TU in Braunschweig and the University of Göttingen are involved, were presented in Aachen. Vera Kohlgruber, from ISA at RWTH Aachen university, studied the ultrafiltration of the discharge from the stabilising ponds. These ponds are widely used for municipal wastewater treatment in the northeast of Brazil, but their discharges do not meet the quality requirements for reuse for hygienic reasons and because their solid contents are too high.

A two-line UF plant with a common pre-filtration and parallel strands, each consisting of acid / alkali dosing and and flocculant dosing followed by UF units, was installed in João Pessoa. The UF units contained PES capillary modules made by inge GmbH. Extensive preliminary tests have already been carried out in Germany using statistical test planning methods, in which wastewater from the Soers clarification plant near Aachen was used. The effects of the flux, pH, flocculant type and dosing parameters on the transmembrane pressure difference was determined in these tests and in a further series of full factorial tests run at the plant in Brazil.

The most influential parameter proved to be the flux, followed by a combination of flocculant and pH value factors.

The setting for a flux that allows stable operation with maximum permeate yield is very important for final optimisation.

Further tests to optimise pH and flocculation were awaited. EnviroChemie, together with Aachener Verfahrenstechnik, also installed a membrane bioreactor pilot plant in a fruit juice plant in João Pessoa as part of BRAMAR. The composition of the wastewater and the pH value were subject to greater fluctuations than in municipal clarification plants as they depend on the season and the fruit that was treated.

Christoph Bohner, from EnviroChemie, was able to show that the MBR plant had good adaptability to these conditions F & S International Edition

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and that more than 97% of the COD was degraded during normal operation. The plant will be extended by one reverse osmosis, one activated carbon and one ozonisation plant for the production of the various water qualities for reuse that were previously mentioned above. It should be possible to make a statement about the costs incurred for the provision of recycled water when the tests end.

If, in addition to water scarcity, there is also no economically ecologically or acceptable possibility of discharging the wastewater, then water treatment is an option until a dry residual material (ZLD means Zero Liquid Discharge) is obtained.

Concentrating the residue beyond the concentration level realisable when using normal reverse osmosis and the subsequent evaporation or drying of the solids are both energy-intensive and cost-intensive steps. Robin Wünsch, from the University of Applied Sciences in NorthWest Switzerland, looked at using forward osmosis for the treatment of the concentrate from a reverse osmosis plant in which the secondary effluent from an industrial wastewater treatment plant (chemical industry) was pre-concentrated. The aim of his work was to find a suitable, i.e. inexpensive, non-toxic and easily regenerable extraction solution, the contents of which would permeate poorly through the FO membrane and go into the solution to be concentrated and become lost.

From the salt solutions chosen by him, the sodium chloride and sodium sulphate solutions proved to be less suitable than a magnesium chloride solution. This was traced back to the lower permeability of the membranes with bivalent magnesium.

By using this solution it was possible to concentrate a factor 2 wastewater concentrate emerged from reverse osmosis up to factor 6. Softening was recommended as the pre-treatment for the treated wastewater, which still had high TOC and high calcium and carbonate concentrations.

Treating industrial wastewater Very specific solutions are often used for removing certain ingredients, but they depend on the industrial sector and the wastewater composition. Torsten Hackner, from Huber SE, reported on the treatment of textile wastewater with high PolyVinyl Alcohol (PVA) and COD contents using a membrane bioreactor with a VRM membrane system and upstream dissolved air flotation. The flotation membrane / bioreactor combination has already proven itself on a large scale in another textile company. Flotation used in the pilot plant had already removed 40% of the DOC, nearly 28% of the COD and a good 24% of the PVA, which relieved the subsequent membrane bioreactor. The total elimina-

tion target of 90% COD and DOC could not be fully achieved, whereas the 93% PVA reduction was above the 90% target value. It was pointed out here that a ready-made pilot plant with a fixed reactor volume relative to the membrane surface cannot represent the optimum solution because it was not designed specifically for this wastewater. The membrane filtration process could be operated stably with a flow rate of 10 l/(m2h) but it should be lowered slightly in a large-scale plant in order to increase process reliability.

An aerosol-based process for the elimination of perfluorinated and polyfluorinated tensides from the rinsing and processing waters used in electroplating was developed at the University of Wuppertal, (see [7] as well). These substances, which are very undesirable in wastewater because they are biopersistent and toxic, are used as wetting agents in galvanic processes such as the chrome plating of components.

They prevent the formation of dangerous aerosols that contain chromium. Ion exchangers are currently used to remove these substances from wastewater. This process is not very effective due to the salts contained in the water. The ion exchanger process becomes even more uneconomical if the less environmentally damaging wetting agent 6:2 FluoroTelomer Sulphonic acid (6:2 FTS) is used as the ion exchanger cannot be regenerated by using aqueous solutions. Dr. Marc Constapel explained the aerosol-based process, which appears to be relatively uncomplicated (see Fig. 2).

The trait of the tenside to accumulate on the phase boundaries is utilised and this phase boundary is made available in the form of gas bubbles blown into the bottom of the vessel. The tenside loaded bubbles rise to the surface of the water, where they burst and release aerosol droplets that contain high concentrations of tenside.

After separating the doplets from the air the tensides are returned to the process.

Model solutions used in laboratory tests showed that the effectiveness of the process increased when dissolved salts were present. High elimination rates of 99.8% or even higher were realised using both model solutions and wastewater samples from an electroplating plant.

Measuring technology used in water treatment In a session that covered measurement and process control technologies, many questions were answered in connection with the general operation of clarification plants, the operation of membrane plants as well as the elimination of trace substances and the microbial contamination of water flows. Simple and robust methods for continuous monitoring that can, if possible, be used online are needed.

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Highlights 2018

UV absorption and fluorescence spectroscopy applications for monitoring the elimination performance of adsorption and ozone oxidation systems used for removing trace substances were studied at the TU in Vienna, but fluorescence spectroscopy has the disadvantage that it is not available as an online measuring method.

These studies were part of the KomOzAk Austrian research project in which the measurement procedures described were applied to a large-scale pilot plant fitted with a GAC pressure filter and ozonisation [8]. UV absorption was measured both online and in the laboratory, but fluorescence spectroscopy was only carried out in the laboratory and the liquid chromatography and mass spectrometry (LS / MS) analysis became the reference method. The measurement methods being studied provided results that correlated well with the concentrations determined via LS / MS. Determination of the microbiological contamination is another important measurement task used for quality control. Flow cytometry has been in use at the IWW Centre for Water in Mülheim for some time now as an alternative to time-consuming sampling and cultivation laboratory processes, which only produced delayed results. Gabriela Schaude and Andreas Nocker described the basis and history of this method, which was originally developed for medical applications.

In flow cytometry the bacteria are made visible against the background of other particles present in the water through the use of fluorescent dyes and they are then sent through a narrow capillary where they can be recorded separately and counted by a laser beam. One can obtain the concentration of all cells or living cells (with an intact cell membrane) by using one or two dyes. Cells with a high DNA content can also be distinguished from those with a lower DNA content in intact cells. The important features of this method, which is expected to be available online in the near future, are the reduction in the time needed (cell counting is possible within 15 minutes) and the fact that all of the cells are recorded. This will result in a re-evaluation of the microbial contamination of the waters as the common cultivation methods are not applicable to all of the bacteria found in the water. It is assumed that the total cell numbers have been significantly underestimated by the cultivation methods that were used in the past.

Membranes with customised properties One of the most important markets for membranes is water treatment and new developments clearly have a high market potential here. The development of layer-by-layer nanofiltration membranes, which Prof. Matthias Wessling first report10

ed on in his welcoming address, promises two improvement options compared to commercial Thin-Film Composite membranes (TFC membranes). Firstly, alternately coating a porous polymer or ceramic membrane with positively and negatively charged polyelectrolytes allows membranes with both precisely defined separation properties and defined permeability to be produced. Secondly, this type of coating tolerates membrane backwashing, which cannot be applied to conventional TFC hollow fibres. The properties of the coated material depend on the type of polyelectrolyte and the number of layers, the coating solution‘s composition, the receiving substrate‘s properties and the coating‘s parameters. Daniel Menne [9] has created a huge number of membranes on polymeric and ceramic substrates and he has studied their relationships. Even though the separation properties of these types of membranes used in the nanofiltration of ultra-filtrates from a nearby clarification plant were not as good as those of a commercial nanofiltration membrane, the remarkable advantages of LbL membranes have already been defined. It is also possible to produce membranes with high salt retention and high permeability even for larger organic molecules (> 6000).

Furthermore, the aforementioned high stability realised during backwashing was present and, last but not least, the ceramic substrates used in the LbL membranes can be recycled, i.e. the polyelectrolyte film can be removed and reapplied several times without changing the separation properties.

Kisten Remmen, from the University of Applied Sciences in North-West Switzerland, studied the suitability of LbL modified hollow-fibre membranes for recovering phosphoric acid from the solution obtained from the wet chemical degradation of sewage sludge ash. Phosphoric acid should pass through the membrane when this solution is undergoing nanofiltration and any metals that are also present in the solution will remain in the retentate.

Commercial PES hollow-fibre membranes were coated with positively charged polyelectrolyte PDADAMC (PolyDiAllylDimethylAmMmonium Chloride) and negatively charged PSS (PolyStyrene Sulphonate) in 4 to 9 bi-layers on commercial ultrafiltration membranes made from Sulphonated PolyEtherSulphone (SPES) and PolyEtherSulphone (PES) for this work. The filtration experiments were carried out using sample solutions that contained phosphoric acid and an aluminium salt. It was possible to find a number of layers (6 bi-layers) in which the permeability was high for phosphoric acid and low for aluminium, which resulted in a greater phosphoric acid yield than that obtained when using a commercial, acid-stable nanofiltration membrane. The

LbL membranes also exhibited permeability that was 60 times higher.

The LbL technology described above is based on a ready-made substrate, which is subsequently functionalised by the overflowing of a polyelectrolyte solution.

Hannah Roth reported on the alternative production of this type of coated membrane in a single step, namely during the spinning process in which the hollow-fibre is produced. The classic wet spinning process is superimposed through phase inversion with a cross-linking reaction on the lumen side of the resulting hollow-fibre (Fig. 3). A more detailed description of the process is given in [10]. This manufacturing method produces hollow-fibres that have nanofiltration characteristics with regard to their separating properties and pure water permeability. No reduction in salt retention was seen even after many backwashing cycles.

Reference literature: [1] J. Pinnekamp, M. Wessling (Hrsg.): Wassertechnologie in der Wasseraufbereitung und Abwasserbehandlung, 12. Aachener Tagung Wassertechnologie, Aachen 2017, ISBN 978-395886-186-2 [2] H. Evers, I. Gehrke, H. Lyko: Recovery of nutrients and valuable materials from wastewater and liquid residues, F&S Global Guide of the Filtration and Separation Industry 2018-2020, 2018, pp. 232 − 240 [3] BMUB/UBA (Hrsg.) Policy-Paper: Empfehlungen des Stakeholder-Dialogs „Spurenstoffstrategie des Bundes“ an die Politik zur Reduktion von Spurenstoffeinträgen ind die Gewässer, Eds. T. Hillenbrand, F. Tettenborn, M. Bloser; Bonn: Bundensministerium für Umwelt, Naturschutz, Bau und Reaktorsicherheit / Dessau: Umweltbundesamt, s. www.bmub.bund.de/N54257/ [4] P. Wunderlin, A. Meier, J. Grelot: Elimination von Mikroverunreinigungen auf ARA – Aktueller Stand der Verfahren und künftige Entwicklungen, Aqua & Gas Nr. 11 (2017), pp. 60 – 70, availabe under www. micropoll.ch [5] T. Krahnstöver, T. Wintgens: Optimizing the flocculation of powdered activated carbon in wastewater treatment by dosing iron salt in singleand two-stage processes, Journal of Water Process Engineering Vol. 20 (2017), pp. 130 – 137 [6] G. Hoffmann, S. Panglisch: Generating synergy effects in hybrid processes by the example of interconnecting membrane filtration and powdered activated carbon dosage; F&S Global Guide of the Filtration and Separation Industry 2018-2020, 2018, pp. 204 − 210 [7] I. Ebersbach, S.M. Ludwig, M. Constapel, H.-W. Kling: An alternative treatment method for fluorosurfactantcontaining wastewater by aerosol-mediated separation, Water research 101(2016), pp. 333-340 [8] N. Kreuzinger, J. Haslinger, L. Kornfeind, H. Schaar, E. Saracevic, F. Hell, C. Walder, M. Müller, A. Wagner, A. Wieland: KOMOZAK-Endbericht: Weitergehende Reinigung kommunaler Abwässer mit Ozon sowie Aktivkohle für die Entfernung organischer Spurenstoffe; Österreichisches Bundesministerium für Land- und Forstwirtschaft, Umwelt- und Wasserwirtschaft (Hrsg.) 2015, availabe under https://www.bmlfuw.gv.at/service/publikationen/ wasser/KomOzAk---Langfassung.html [9] D. Menne: Layer-by-Layer-Design of Nanofiltration Membranes, Dissertation RWTH Aachen 2017 [10] C. V. Gherasim, T. Lülf, H. Roth. M. Wessling: DualCharged Hollow Fiber Membranes for Low-Pressure Nanofiltraiton Based on Polyelectrolyte Complexes: One-Step Fabrication with Tailored Functionalities, ACS applied materials & interfaces 8 (29) 2016, pp.

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Highlights 2018

Improving the resource efficiency of irrigation using reverse osmosis for the desalination of brackish well water and salty sewage effluents Th. Peters* Resource efficiency has become an important objective also in worldwide environmental politics as it can be deduced from documents published by the Commission of the European Community (CEC) or in the frame of the German Resource Efficiency Programme (ProgRess) as well as the United Nations Environmental Programme (UNEP).

Using the relevant standards can make a contribution to the conservation of natural resources. These include, amongst others, a reasonable use of water as well as the reduction of environmental pollution in order to preserve the living conditions of present and future generations.

As drought conditions and water pollution crises multiply, water is no longer viewed as a free commodity in processing environments. According to the United Nations, one-fifth of the world’s population lives in water-scarce areas; another 25 percent are already facing water shortages; and the food sector uses 70 percent of the world’s freshwater supplies.

The food and beverage (F&B) industry’s reliance on the water as a direct ingredient and an input to agricultural production makes it particularly vulnerable to the problem of dwindling water supplies. This in mind it is understandable that the United Nations World Water Development Report 2017 entitled “Wastewater: The Untapped Resource” addresses the opportunities arising from improved wastewater management and seeks to inform about the importance of managing wastewater as an undervalued and sustainable source of water, energy, nutrients and other recoverable by-products, rather than something to be disposed of or a nuisance to be ignored.

In a world where demands for freshwater are continuously growing, and where limited water resources are increasingly stressed by over-abstraction, pollution and climate change, great opportunities arise from improved wastewater management that include the production of water for irrigation from sewage effluents. But as in some areas this kind of wastewater has an increased salinity one step in the treatment process needs to be desalination, usually by the membrane process reverse osmosis. The same applies if salty well water needs to be used as source water for irrigation. Thereby a reliable control of the treatment efficiency is of eminent importance.

Details addressing the use of reverse osmosis considering decentralized solutions for desalination of salty sewage effluents in Spain and of brackish well water in Peru that contribute to improve the resource efficiency of irrigation will be presented.

1. Resource efficiency Resource efficiency, the ratio between a certain benefit or result and the resource use required for it, has become an important objective in national and international environmental politics. The EU Commission has taken up this topic first in 2005 and then in 2011 with a flagship initiative under the Europe 2020 strategy.

The German government has adopted the German Resource Efficiency Programme (ProgRess) in 2012. On the UN level, the International Resource Panel of the United Nations Environmental Programme (UNEP) has worked in detail on topics like the use of metals, water, land etc. [1].

* Dr.-Ing. Thomas Peters Dr.-Ing. Peters Consulting for Membrane Technology Rheinfährstr. 201 41468 Neuss, Germany Tel.: +49 (0) 2131 228963 Fax: +49 (0) 2131 228965 dr.peters.consulting@t-online.de

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According to the European Commission resource efficiency means using the Earth’s limited resources in a sustainable manner while minimising impacts on the environment. It allows us to create more with less and to deliver greater value with less input [2].

In terms of classical environmental management, resource efficiency can be increased in individual processes and material flows in an enterprise, but much greater potential lies in taking a comprehensive strategic view of products over their entire life cycle. The more consequent the approach to resource efficiency and conservation, the more successful will be the effect of the measures. This goes for individual companies but in many cases also for whole economies. Eventually, resource efficiency is supposed to stimulate future-proof innovations and attractive business models [1].

Using the relevant standards with the aim to take this issue to the level where practical action is taken can make a contribution to the conservation of natural resources [1], including, but not limited to

- the use of raw materials, - the use of land, - the reduction of environmental pollution, - the use of water and thus to preserve the living conditions of present and future generations.

2. The importance of water As drought conditions and water pollution crises multiply, water is no longer viewed as a free commodity in processing environments. According to the United Nations, one-fifth of the world’s population lives in water-scarce areas; another 25 percent are already facing water shortages; and the food sector uses 70 percent of the world’s freshwater supplies. The food and beverage (F&B) industry’s reliance on the water as a direct ingredient and an input to agricultural production makes it particularly vulnerable to the problem of dwindling water supplies.

This in mind it is understandable that the United Nations World Water Development Report 2017 entitled “Wastewater: The Untapped Resource” addresses the opporF & S International Edition

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Highlights 2018

tunities arising from improved wastewater management and seeks to inform about the importance of managing wastewater as an undervalued and sustainable source of water, energy, nutrients and other recoverable by-products, rather than something to be disposed of or a nuisance to be ignored [3, 4].

The report’s title – Wastewater: The Untapped Resource – reflects the critical role that wastewater is poised to play in the context of a circular economy, whereby economic development is balanced with the protection of natural resources and environmental sustainability, and where a cleaner and more sustainable economy has a positive effect on the water quality. Improved wastewater management is not only critical to achieving the Sustainable Development Goal on clean water and sanitation (SDG 6), but also to other goals of the 2030 Agenda for Sustainable Development [3].

In a world where demands for freshwater are continuously growing, and where limited water resources are increasingly stressed by over-abstraction, pollution and climate change [5], neglecting the opportunities arising from improved wastewater management is nothing less than unthinkable.

Facing the worldwide water stress, possible solutions should be considered in the sequence a. reasonable use of potable water, means avoiding wasting water as it happens today in many areas, b. reuse / recycle water after treatment / purification of wastewater, c. production of potable water by desalination of seawater or brackish water, or e.g. treatment of contaminated surface water.

For the majority of these cases the most successful, resilient and resource efficient solutions can be based on membrane technology, if the related plants are designed manufactured and operated adequately [5, 6].

This approach can be deduced partially from the graph “Electricity consumption in the water sector increases by 80 % over the next 25 years” as per Figure 1 [7] showing a significantly increasing share of desalination, as here membrane technology is the most frequently used solution.

But other than this prediction it is believed, that in the future water reuse will play a more significant role than it can be deduced from this graph. Thereby the interactions between increasing water demand, progressive application of resource efficient water treatment technologies and increasing acceptance of purified wastewater are expected as driving forces [5, 6].

In this context it should be recalled, that water can be distinguished by its function into e. g. drinking water, irrigation water, cooling water, backwater or process water.

Thereby the aspects that are of special importance with water as a resource are its geographical location and its regeneration rate. This is because its availability depends on the respective climate zone and the local ground and surface water supply [1].

But water is also interesting as an environmental medium, because its sink function ensures important ecosystem services such as clean drinking water [1].

This aspect is addressed amongst others in the Sustainable Development Goal 6 (SDG6) specified as “Ensure availability and sustainable management of water and sanitation for all”. Basis for this comprehensive request is the perception, that

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Fig. 1: Electricity consumption in the water sector, source: Uhlenbrook, [7]

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Fig. 2: Storage reservoir for treated wastewater for 75,000 m³ at Son Servera

access to safe water and sanitation and sound management of freshwater ecosystems are essential to human health and to environmental sustainability and economic prosperity [8].

One issue in this regard with increasing importance is the sector “irrigation water”.

From this very broad spectrum for the use of water with diverse locally varying multiple interactions two applications that can contribute to reduce the water stress are

A

B

Fig. 4: General situation at Son Servera

Fig. 5: Impression of the golf course Son Servera

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Fig. 3: Sign with description of the Son Servera irrigation project designed for 6,000 m³/d

described by way of example. These solutions are based on the use of the membrane process reverse osmosis (RO): i) desalination of salty sewage effluents in Spain and ii) desalination of brackish well water in Peru Thereby both technological approaches can contribute to improve the resource efficiency of irrigation.

C

3. Desalination of salty sewage effluents According to information provided on Mallorca in the frame of a general water related assessment, for the irrigation of golf courses on this island must be used by law biologically treated municipal waste water being prohibited the utilization of potable water [9, 10]. On Mallorca, the largest of the Balearic Islands belonging to Spain, actually exist 23 golf courses with a significant water demand.

As one possible contribution to meet this requirement at different locations on Mallorca dams for storing the effluents of biological waste water treatment plants connected with related water distribution networks have been built. One example is the community Son Servera at the east coast, where a dam with a capacity of 75,000 m3 (Figure 2) was installed and commissioned in 2010, supported by the Spanish Government and local authorities and co-financed by the European Union as per teh sign in Figure 3.

The sewage treatment plant of Son Servera treats the waste water of a very touristic area that because of different reasons is characterised in the summertime by an increased salinity with an electric

Fig. 6: View with storage reservoir of Son Servera and the golf course Sa Pula

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Highlights 2018

Fig. 7: Set-up of the demonstration plant in the pumping station

Fig. 8: Transport of the demonstration plant and auxiliary equipment.

conductivity of about 3,800 μS/cm. Due to the related high concentration of chloride (Cl) of about 900 mg/L this water cannot be used for irrigation in general, being the limit for the irrigation water specified as 500 mg Cl/L [10].

As per unofficial information the higher salt concentration in this special touristic influenced area on Mallorca results from different sources [10]. Included are the use of saline waters for sanitary flushing purposes in the hotel sector and e. g. the wastewater from the regeneration of the large number of softeners that are in operation because of the usually high hardness of the well water in this area.

Figure 4 shows the typical situation for this area: a touristic nucleus at the coast of the Mediterranean Sea with nice sandy beaches that attract an increasing number of tourists (A), the nearby wastewater treatment plant (B) and the storage reservoir for the biologically treated wastewater (C) with the pumping station feeding the irrigation network (on the left side of the storage reservoir ).

The network for irrigation water is connected to this pumping station and another feeding system operated by gravity. These supply irrigation water from the storage reservoir to agricultural areas in use and private gardens within a distance of few km as well as to the golf course of Son Servera (Figure 5) and the golf course Sa Pula (Figure 6).

As solution for reducing the salinity the treatment of a partial stream with the desalination process reverse osmosis using open channel membrane elements and a downstream blending of the permeate with untreated water has been suggested. Thereby the suggested open channel design of the membrane elements allows for a longer-term robust operation of the plant without the need for a sophisticated pre-treatment, as it is necessary for conventional spiral wound membrane elements. This very successful special design allows also for a highly efficient cyclic cleaning of the membranes.

In a first approach with a mixture of 50% permeate and 50% raw water the target to obtain irrigation water with an acceptable salt concentration could be reached. Thereby, in order to separate and thus eliminate the bacteriological contamination of this sewage effluent, the partial stream that is not treated with the desalination process, in a large-scale plant needs to be treated with microfiltration or, better, ultrafiltration.

Based on this suggestion a test has been organized with a demonstration plant equipped with a reverse osmosis module using an open channel membrane element with 7 m2 membrane area made available from ROCHEM Technical Services (R.T.S.) [11]. Figure 7 shows the set-up for the test installed in the pumping station mentioned above, Figure 8 the method used for transporting the demonstration plant and necessary auxiliary equipment from

Germany and via ferry Barcelona – Palma de Mallorca to the site.

The trial was a success. Data will be reported after final evaluation in collaboration with the related authorities. The possible solutions and the future procedure on site are under discussion, whereby for the full-scale plant the use of nanofiltration is assessed as alternative.

Modern nanofiltration (NF) membranes show similar salt rejection rates for the main components dissolved in the water as reverse osmosis (RO), but can be operated with a lower energy demand. Thereby it is agreed that crucial for this application in contaminated wastewater is the use of membrane elements with open channel design.

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4. Desalination of brackish well water in Peru

Fig. 9: Coastal areas of Peru, source: [12]

Fig. 10: Process diagram for reverse osmosis for desalination of brackish water, source: [12]

Note: Source for the information disclosed in this paragraph is the reference [12].

The coastal regions in the north and in the south of Peru (Figure 9) offer very good conditions for the development of agriculture. But the limiting factor is water shortage.

These regions are dominated by a deficit of natural water resources. Water is not available in the mandatory quality, the necessary regularity and the quantity that is required for the development of areas for irrigation, that otherwise could be a motor for the growth of the economy of the country.

The water shortage provokes additionally serious problems related with the supply of potable water to the inhabitants of the region, as frequently the water related conditions requested even in the legislation of the country cannot be fulfilled However, in the whole region abundant subterranean water resources are available that are not usable because of a higher salinity.

In order to reduce the water related problems in the coastal region of Peru by producing water for human consumption and for irrigation purposes a solution has been developed that is based on the use of reverse osmosis. The process includes pretreatment with sand filter and cartridge filter, addition of chemicals for preventing scaling, two reverse osmosis stages for optimising the permeate recovery rate and the possibility to blend feedwater with final permeate for adapting the quality of the product to the local requirements (Figure 10).

As basis for the design of these plants a range for the salinity of the brackish water between 3,000 and 5,000 mg/L has been selected. For the product an electric conductivity of < 1,000 μS/cm at 25 °C or < 500 mg total dissolved solids are requested.

The plants are delivered as modular units according to the “plug & play” concept for capacities of 300, 500, 800, 1,000, 1,500 and 2,000 m3/day. Figure 11 shows such a reverse osmosis unit for 2,000 m3/d.

The energy supply via grid or diesel generator can be adapted to the local conditions, solutions using solar energy and wind power are under discussion.

Financing models considering OPEX and CAPEX for different scenarios are available from the manufacturer. Updated example will be presented at the FILTECH Congress.

Figure 11: RO plant with a permeate capacity of 2,000 m3/day, source: [12]

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5. Remarks addressing the improvement of resource efďŹ ciency During the long-time assessment of different projects related with the use of pressure driven membrane processes in combination with municipal wastewater treatment plants for using the efďŹ&#x201A;uent as source for irrigation water, different possibilities for improving the resource efďŹ ciency of this global strategic approach have been identiďŹ ed. The contemplated processes are tools related to the most important steps on the way to the sustainable reuse of biologically treated wastewater that is asked for more and more. This includes the production of irrigation water up to the â&#x20AC;&#x153;direct potable reuseâ&#x20AC;? (DPR) assessed with increasing efforts [13].

It has to be emphasized that the better and more efďŹ cient the biological treatment, the more successful will be the effect and the operational results of the membrane based processes.

The mentioned possibilities include the optimisation of the operation of biological wastewater treatment plants and possible signiďŹ cant cost reductions for related areas in the range of 30 to 50 %. On the basis of a continuous independent international product evaluation methodology (CIIPEM) for these issues to be actually

Hairs

Fig. 12: Sieving residue including hairs, source: nrw Anlagentechnik, [14]

â&#x20AC;&#x153;best of the bestâ&#x20AC;? the following solutions are considered: 5.1 Pre-treatment: Necessary is a very efďŹ cient pre-treatment of the wastewater fed to the sewage treatment plant by separating â&#x20AC;&#x201C; beside FOG and sand â&#x20AC;&#x201C; also all solids as far as possible using proven optimised screens in order to allow bacteria to reduce or eliminate the organic matter dissolved in the wastewater, without the need to waste the

activity of these usually efďŹ cient natural tools for eliminating the solids present in the wastewater.

One example is the Contec screen using perforated screen plates [14]. This is operated also very successfully in sewage treatment plants equipped with membrane bioreactor MBR technology avoiding the usual problems with accumulation of sludge and hairs in the modules. An example for the efďŹ cient separation of particulate matter is shown in Figure 12.

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5.2 Mixing and aeration: These most important process steps in biological wastewater treatment are realised best by using an optimised mixing and aeration system as per Figure 13 [15].

Of importance for many situations seems to be that the implementation of these devices does not necessarily require

to build a new plant as these can be inserted usually in existing basins.

5.3 Aeration process control and monitoring: Significant cost reductions can be obtained by evaluating the measurement of the oxygen content of the gas leaving

the aeration basin surface in comparison with the oxygen content of the gas entering the tank.

This allows for determining the oxygen transfer efficiency of the aeration system and thus to operate the aeration itself on an optimal level and at highest performance.

Such a device is the ALPHAMETER [15] as per Figure 14.

5.4 Sludge dewatering: Improving the sludge dewatering results by about 25 % has different advantages, including significant cost reductions. A system designed for this purpose is shown in Figure 15 [16].

5.5 Modules for Membrane BioReactor (MBR): Amongst the new developments the AQQA ultrafiltration module (Figure 16, source [17]) is considered a significant improvement based on a new filter plate and a new concept for the fixation of the membranes.

Fig. 13: Comparison of the oxygen distribution with a conventional mixing system to the mixing and aeration system HYPERCLASSIC, source: INVENT, [15] left: Oxygen distribution with insufficient mixing – poor purification performance right: Oxygen distribution with good mixing & homogenization – excellent purification performance

5.6 Control of the treatment efficiency: A reliable monitoring of the treatment efficiency and the possibility for remote control and monitoring as well as data acquisition are – in addition to the item IT security – of eminent importance for wastewater treatment plants as well. New developments allow for e. g.

5.6.1 microbiological real-time monitoring (15 minutes) with ColiMinder based on detecting bacteria by their metabolism [18] 5.6.2 real-time measurement of the spectral adsorption coefficient for identifying organic components dissolved in the water [19] 6. Conclusions

Fig. 14: ALPHAMETER, source: INVENT, [15].

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There are different possibilities for improving the resource efficiency of irrigation, especially if the urgently necessary reuse of treated municipal wastewater is envisaged.

But even if it has to be considered strongly that “each case is different” there are a few aspects that are universally valid. These include the evaluation if the different treatment steps in such a sewage treatment plant could be optimised using state of the art technology. Furthermore, it should be assessed meticulously if modern technologies, including optimized membrane processes, should be installed for resolving the new kind of environmental problems related to the different frame conditions resulting from the contemporary urban development.

Thereby a reliable control of the treatment efficiency is of eminent importance.

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Fig. 15: Schematic diagram of FlocFormer process, source: aquen, [16]

Fig. 16: AQQA ultrafiltration module, source: Weise [17] 7. References [1] Resource efficiency - Methodological principles and strategies. Verein Deutscher Ingenieure, VDI-Richtlinie 4800 Part 1, 2016 [2] http://ec.europa.eu/environment/resource_efficiency/, visited on 11.07.2016 [3] http://www.unesco.org/new/en/natural-sciences/ environment/water/wwap/wwdr/2017, visited on 16.09.2017 [4] WWAP (United Nations World Water Assessment Programme) 2017. The United Nations World Water Development Report 2017: Wastewater - The Untapped Resource. Paris, UNESCO [5] Peters, Th.: THE POSSIBLE ROLE OF MEMBRANE TECHNOLOGY IN A THIRSTY WORLD. Proceedings, 12th World Filtration Congress, 11-15 April 2016, Taipei, Taiwan [6] Peters, Th.: DECENTRALISED PRODUCTION OF POTABLE WATER BASED ON MEMBRANE TECHNOLOGY. Proceedings, FILTECH 2016, 11- 13 October 2016, Cologne, Germany [7] Uhlenbrook, St.: SDG 6 Synthesis Report 2018. http://Synthesis-Report_ppt_stockholm2017_28August2017.pdf

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[8] http://sustainabledevelopment.un.org/sdg6, visited on 03.01.2018 [9] Peters, Th.: Optimización del funcionamiento de una E.D.A.R. y de la calidad de agua de regadío.

Presentation, 29.09.2016, Palma de Mallorca, Spain [10] Comunidad de Regantes de la EDAR de Son Servera, TRAGSA, Palma de Mallorca and Nadal, P., Predio Son Jordi, Palma de Mallorca, September 2017 [11] courtesy of ROCHEM Technical Services, Hamburg, Germany [12] Garcia, A.: SOLUCIONES TECNOLÓGICAS PARA EL TRATAMIENTO DE AGUA. Company presentation, NORTH LINE, Madrid, Spain [13] Pankratz, T.: UNIVERSITY SEEKS DPR DEMO PLANT. WDR, 11.09.2017 [14] courtesy of nrw-Anlagentechnik, Hückelhoven, Germany [15] courtesy of INVENT, Erlangen, Germany [16] courtesy of aquen, Clausthal-Zellerfeld, Germany [17] courtesy of Weise Water GmbH, Henningsdorf, Germany [18] Vienna Water Monitoring Solutions (VWMs), Zwerndorf, Austria [19] Endress + Hauser Messtechnik, Reinach, Switzerland

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A wide range of submerged membrane modules for use in MBRs and other applications H. Lyko * MBR (Membrane BioReactor) technology produces benefits from combining biological wastewater purification with virtually complete separation of suspended solids. It can be used in all plant sizes, ranging from a small clarification plant for single-family houses to wastewater purification for cities with over a million inhabitants. The prospect of designing wastewater purification plants to be more compact and complete than is possible with a conventionall activated sludge process has boosted the spread of MBR technology. In addition to municipal wastewater purification, it is used for industrial wastewater treatment and for decentralised wastewater treatment, i.e. on ships, in military camps or hotel complexes. The high effluent quality from an MBR creates the basis for the reuse of purified wastewater in many cases. Numerous plants and components for MBR processes, including many modules designed for submerged use, were presented at last year’s IFAT in Munich. The wide range of such modules inspired the following article about module technology. Various manufacturers have not limited the MBR operating mode whereby the module is submerged in the liquid that has to be filtered and the permeate is extracted just to biomass separation. Other applications include the treatment of drinking water, process water and swimming pool water. Products that were not exhibited in Munich have also been considered here in order to take into consideration the wide range of modules that are available. However, I do not claim that my article is a complete market overview.

Module types and membrane materials As can be seen from Table 1, the submerged modules can essentially be subdivided into two groups: hollow-fibre modules and flat-sheet modules. Flat-sheet modules include those with rigid plates (e.g. Toray, Kubota, Rising Sun) and those with self-supporting, flexible membrane pockets / laminates (e.g. from MicrodynNadir, Huber, WTA Technologies). The latter have the advantage of being backflushable when compared to classic plate modules. Backflushing is also possible with a number of flat membrane modules, where the both sides of the membrane are welded onto rigid, polymer plates with integrated channels (e.g. Alfa Laval, Newterra). With hollow-fibre modules, the two fibre arrangement versions exist in open rectangular fields (Suez (Zeeweed), Mitsubishi) with fibres fixed at both ends and the partial or complete enclosure of fibre bundles potted on one side (Koch Puron, Membion). These designs reflect different hydraulic concepts, some of which are described in more detail below.

To my knowledge, the tubular module from Memos Membrane Systems occupies a special position as it is the only tubular module capable for submerged operation.

Tubular modules are more frequently used in MBR with separate pressure-driven membrane systems due to their high solids tolerance. The filtration direction of this * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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submerged tubular module is the same as that of the hollow-fibre modules, i.e. from the outside to the inside. The Huber VRM module is the only rotating membrane system that is used in vacuum operation for activated sludge separation, even though various membrane systems with rotating membranes are still available on the market for use in pressure-driven biomass separation processes.

Polymers predominate amongst membrane materials. According to a blog by British MBR expert Prof. Simon Judd [1], ceramic membranes account for around 10% of all products used in all of the MBR plants and this includes pressure-driven downstream membrane plants. PVDF (polyvinylidene flouride) is by far the most commonly used polymer, followed

by PES (polyethersulfone), PE or PP (polyethylene or polypropylene) and the less commonly used PTFE (polytetrafluoroethylene). The huge popularity of PVDF in membranes used for water filtration initially appears astonishing, as this hydrophobic material tends to foul from the hydrophobic organic ingredients found in raw water. However, PVDF is prized for its high mechanical strength and resistance to the cleaning chemicals that have to be used in MBR technology. An example of a submerged module with PTFE hollow-fibres is the Poreflon module made by the US manufacturer, Sumito Electric.

These membranes, which are also used in pressure-driven modules, are both highly mechanically and chemically resistant (the temperature resistance of up to 200°C only plays a minor role in wastewater

purification) and they are also characterised by their tolerance to very high solid concentrations of up to 15,000 mg/l and to increased oil content in wastewater.

Fig. 1: Revised flat-sheet module from AlfaLaval

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The pore sizes / separation efficiencies of the membranes that are used are in the micro- and ultra-filtration ranges. Other reasons might sway the separation limit choice apart from the fact that the retention capacity of the membrane must definitely meet the stipulated filtrate quality requirements. The expected higher filtrate flow at the same transmembrane pressure difference speaks in favour of using a microfiltration membrane, which means that lower energy consumption can also be expected during the filtration process. However, a large part of the energy consumption and other MBR membrane filtration operating costs are generated from crossflow aeration and cleaning measures for controlling and removing fouling layers. The fouling tendency depends not only on the water constituents but also on the membrane’s pore size and the roughness of the membrane’s surface, which also depends on the type of polymer being used. This is described by Mioshi et al. in [2]. They also found that the fouling tendency of a hydrophobic PVDF membrane decreases with increasing pore size, whereas a cellulose acetate membrane shows a tendency that is the precise opposite. In addition to the surface properties of the membrane, the particle / molecule size of the fouling agent relative to the pore size also plays a role here, i.e. the question being whether it will penetrate into a pore and irreversibly block it or not (see [3] as well).

Tab. 1: Offer of MBR modules for submerged operation; manufacturers named in alphabetical order, specified pore sizes/cut-offs are nominal values

New flat membrane technology developments Alfa Laval presented a total of three innovations for its MBR module at IFAT (see Fig. 1). The revised permeate collecting system, which was promoted under the name ‘LowResist’, reduces the transmembrane pressure difference needed for filtration to such an extent that gravity-driven filtration can be run in a water depth of 1 m above the module without the need for a vacuum pump. A reduced tendency to pore fouling is also expected due to the lower transmembrane pressure difference.

The S-shaped design of the aerator unit (S aerator) makes it self-cleaning: as soon as the aerator nozzles become clogged, the air pressure inside the tube increases and this causes the nozzles to be blown free and it also rinses out any water that has penetrated into the tube. Quick-swap technology facilitates the assembling and dismantling of MBR systems as the membrane packs and frames can be moved in and out separately and reassembled. Less free working height is needed for loading and unloading the filtration tanks when used in buildings or underground installations.

The module’s handling was the focus of the technical change that Microdyn-Nadir

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made to its BioCel-L module. This is now available without side panels, which makes it easier to clean and maintain together with 360° access.

Supratec Membrane GmbH have been producing flat PVDF membranes according to their own specifications since 2017 and they presented their MBR-600 module with a 600 m2 membrane surface in Munich (see Fig. 2). The membranes, which have a pore width of around 0.03 μm, and the spacers are laminated on both sides to a polyester nonwoven used as the support medium. This design makes the membranes backflushable. The module is provided with an aerator manufactured by a sister company. According to the information available on the stand, the company will soon be able to produce up to 5 million m2/a of membranes in Europe.

Until the IFAT 2018, large-scale reference plants are known in China.

Weise Water presented its Aqqa flat membrane module, which is fitted with a PES membrane that has a pore size of <0.04 μm (see Fig. 3). It has an extremely high pure water permeability of 1,400 l/(m2 h bar) and it tolerates a maximum backflush pressure of 350 mbar, which is very high for this type of module.

The maximum operating temperature of 50°C is also 10 K higher than that of other modules fitted with polymer membranes.

The membrane plates can be exchanged separately. Another special feature, which is not possible with many polymer modules, is that the membranes may become dry and the modules are also delivered in this condition. Modules fitted with polymer membranes that are made by other

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Highlights 2018

Fig. 2: Supratec MBR-600 flat membrane module (Image: Supratec Membrane GmbH)

manufacturers are packed and delivered in a preservative solution and they must also be stored in this solution if they are going to be taken out of operation for longer periods of time.

WTA Technologies manufactures flat membrane modules with membrane pockets as laminates on a nonwoven fabric that is used as a carrier and drainage medium.

Membrane blocks and modules are available in various standard sizes as well as special designs that use different membrane materials, but the choice depends on the customer’s specifications. A special feature of the membrane packs is the patented corner casing (see Fig. 5), which is simultaneously used for anchoring the membrane pockets and for permeate drainage. Applications can be found not only in MBR processes, but also for treating swimming pool water and in the purification of difficult wastewaters, e.g. process wastewater containing oil.

Special features of hollow-fibre modules Hollow-fibre modules have long been known for their very high membrane surface density and for the fact that they are always backflushable. The filtration direction in submerged hollow-fibre mod22

Fig. 3: Aqqa module with a 160 m2 filter surface (Image: Weise Water GmbH)

ules is from the outside to the inside.

The Zeeweed system counts as one of the best-known hollow-fibre membrane modules and it is now manufactured and sold under the Suez umbrella. The Leap MBR configuration was developed a few years ago for use in wastewater purification. It optimises the membrane surface density and the size of the filtration tank, the type of aeration and the air volume in such a way that air and energy consumption is reduced when compared to the previous system. Furthermore the filtration efficiency is increased. This module technology is used both as a replacement for existing Zeeweed systems and as a new installation, for example, in one of the world’s largest MBR plants, the Henriksdal municipal clarification plant in Stockholm [4]. The same module design with a higher packing density (Zeeweed 1000) and membranes with a slightly reduced pore diameter can be provided for applications with lower solids content in raw water, e.g. for drinking water treatment or the pre-filtration of seawater or brackish water before desalination through reverse osmosis. Mitsubishi is also able to provide submerged modules for wastewater and drinking water applications thanks to their Sterapore hollow-fibre membranes made from PVDF and PE with separation

efficiencies for micro- and ultra-filtration.

The Puron module from Koch Membrane Systems was developed to overcome a major disadvantage of classic hollow-fibre modules, i.e. the tendency to clogging, which can only be overcome by careful presifting of the wastewater. The fibre-reinforced hollow-fibres are only potted at the lower end and closed individually at the upper end so that the flow generated by the air bubbles flows up and is carried along the membranes, together with the sludge components and any hairs or fibres, can all escape freely upwards. The efficiency of this system has recently been improved by varying the aeration. In the new Pulsion MBR version, very large air bubbles move like a piston through the channel formed by the cylindrical shelfand they carry along all of the solids that can no longer permanently attach themselves to the membrane. Consequently, air consumption and the energy needed for aeration are both reduced. The liquid’s recirculation velocity through the membrane bundle is also increased, which results in increased filtration efficiency and a smaller membrane surface requirement for handling the same capacity.

After the American company Koch Membranes completely discontinued its module production in Germany, the coF & S International Edition

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Highlights 2018

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Fig. 4: Detailed view of filter plates used in an Aqqa module (Image: Weise Water GmbH)

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Fig. 5: UF-SB (UltraFiltration Single Block) membrane block used as the basic module for a submerged Type H2L module (Image: WTA Technologies)

inventor and founder of the original Puron GmbH, Dr Klaus Vossenkaul, founded Membion GmbH with the aim of developing a new, more efficient MBR module that would be compatible with the modules made by their main competitors. A prototype of this module was created as part of a DBU project [5], and it was also verified within this project that the newly developed module could reduce energy consumption by 30 to 50% compared to the reference plant, the Nordkanal clarification plant that uses Zeeweed modules (reference consumption from 2015). An essential component of this module with cylindrically enclosed hollow-fibres is a specially developed base element that, in addition to feeding and distributing the activated sludge, should also ensure that the air is fed in and distributed. A permeate outlet is also integrated into this base element. A module frame concept, in which several modules are combined into a stack, as well as the arrangement of several stacks into a large module with a membrane surface of 1,500 m2 were also developed. A demonstration plant was planned be used in the second part of the project for long-term testing at the Simmerath clarification plant, which belongs to the Eifel-Ruhr water association. Whether this project has actually started and if any results have been obtained from it has not yet been disclosed.

Reference literature: [1] Judd, S.: The material question – choosing MBR membrane materials. 13 December 2017 The MBR Site by Judd and Judd Ltd., www.thembrsite.com [2] Mioshi, T.; Yuasa, K.; Ishigami, T.; Rajabzadeh, S.; Kamino, E.; Ohmukai, Y.; Saeki, D.; Ni, J.; Matsuyama, H.: Effect of membrane polymeric materials on relationship between durface pore size and membrane fouling in membrane bioreactors. Applied Surface Science 2015, 33, S. 351 − 357 [3] Terna Iorhemen, O.; Hamza, R.A.; Tay, J.H.: Membrane Bioreactor (MBR) Technology for Wastewater Treatment and Reclamation: Membrane Fouling. Membranes 2016, 6(2),33. DOI:10.3390/membranes6020033 [4] Grundestam, J: Stockholm’s Future Wastwater treatment – Building the worlds’s largest MBR; F&S Global Guide of the Filtration and Separation Industry 2016-2018 [5] Vossenkaul, K.; Volmering, D.: Effiziente Energieausnutzung in Membranbioreaktoren durch Einsatz eines innovativen Membranfilters – Teilprojekt 01: Herstellung und Test eines Funktionsmusters. Abschlussbericht über das von der Deutschen Bundesstiftung Umwelt (DBU) geförderte Vorhaben AZ-32805-01. September 2015 F & S International Edition

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Sewage sludge disintegration through the use of a centrifuge A report from Hiller GmbH * The result of the ever-increasing sludge disposal costs is constant pressure to optimise sludge treatment in sewage treatment plants. The process engineering approach together with the economic advantages of advanced sludge treatment through the use of a disintegration process is not new. Various physical or chemical solution approaches all point in the direction of these objectives: - reduced viscosity and better pumping properties - increased degradation of the organic content (i.e. extended retention time within the digestion tank) - increasing the gas yield - improving the drainage process Being a manufacturer of high-performance centrifuges, Hiller GmbH has gained specific experience from working in this application sector.

The following processes are combined through the fitting of a lysing device in a thickening centrifuge: WAS thickening WAS disintegration WAS liquefaction (reduces the viscosity of the thickened WAS) Hiller is currently the only decanter manufacturer that can provide its own references and the corresponding design and process engineering experience. A research project based on this topic is currently underway and the project is under external scientific supervision at a municipal wastewater treatment plant in southern Germany in order to be able to make more detailed statistics available.

Hiller will be exhibiting a decanter with a lysing device at this year’s IFAT in Munich and they will present their findings to visitors to their exhibition stand (Hall A1, Stand 150).

The processing approach It is normal for the excess sludge to be mechanically thickened before it is mixed with the primary sludge in order to obtain an ideal raw/mixed sludge consistency before digestion. Thickening the excess sludge reduces the amount of sludge that has to be added inside the digestion tank. This will result in energy savings, better use of the digestion tank and longer retention times within the digester. This will result in a subsequent reduction in the quantities of digested sludge and the digested sludge’s dewatering properties are also improved.

Centrifuges made by Hiller can be operated with an additional built-in lysing device (Fig. 1). This lysing device is installed in the sludge discharge opening area and the existing kinetic bowl energy is used to disintegrate the sludge (Fig. 2). This means that the additional power consumption of 0.02 to 0.05 kW/kgDR (relative to the dry residue (DR)) can also be kept correspondingly low.

The disintegration effects that occur within the thickened WAS (Waste Activated Sludge) are mainly caused by the impacting and shearing forces generated by the knife blades that rotate at high circumferential velocity inside the labyrinth and the lysing chamber.

The WAS disintegration occurs in the full flow of the thick sludge entering the lysing device. This means that only the thickened WAS that was thickened in the thickening centrifuge is lysed and that no lysate enters the separated centrate water.

Mechanical construction: The lysing device consists of a labyrinth inside a lysis chamber with window openings. The fork blades that are mounted on the centrifuge’s bowl rotate inside the lysing chamber and they are protected against wear by tungsten carbide plating. The thickened WAS is ejected at high speed through the discharge openings in the thickening centrifuge and it then flows through the lysing chamber in axial direction.

Simple on-site disassembling of the lysing device as well as unrestricted conventional operation of the thickening decanter are also possible. No other plant technology is needed after the lysing device. * Hiller GmbH Schwalbenholzstr. 2 84137 Vilsbiburg, Germany www.hillerzentri.de

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Fig. 1: Hiller DP45N decanter without (above) and with (below) a lysate dish

Fig. 2: Hiller DP45N decanter with a lysate dish

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Industrial water: The importance of efficient water usage and the digitisation of water management in the process industry H. Lyko * In 2018, industrial water treatment specialists presented their components, plants and services at two of the most important processing technology trade fairs, IFAT in Munich and ACHEMA in Frankfurt, with only a four week break inbetween the two events. The most important topics outlined in the preliminary and trend reports provided by the trade fair organisers and the exhibitors are the demand for maximum efficiency with regard to treating this indispensable and valuable resource and progressive digitisation. “Water 4.0”, as digitisation is often referred to, should also be primarily seen as a tool for increasing the efficiency of the water treatment and water supply processes.

Water treatment in the chemical industry The chemical industry has a huge demand for water and it often produces chemicals in countries with a known scarcity of water. According to the German Chemical Industry Association, chemical companies are now using a single litre of water nearly six times. The chemical industry is also able to contribute highly specialised products to help produce clean water.

Membrane polymers and ready-to-use membrane products as well as highly specialised ion exchangers enable the chemical industry to supply the materials needed to remove particles and dissolved organic substances and salts. This includes the chemical group called Lanxess, which delivers ion exchangers that are specifically designed for certain water contaminants and reverse osmosis modules, which are all developed and produced in-house.

They often use these components in * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

hybrid processes. Both technologies are used for producing process and cooling water as well as for industrial wastewater treatment. A successful example of the combined use of ion exchangers and

membrane technology is the treatment of around 24,000 m3/d of wastewater from cotton processing in the region around Tirupur, which is the centre of the cotton processing industry in India.

Fig. 1: Coconut shells being used as a raw material for the production of activated carbon, also

by Donau Carbon (Image: Messe München).

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Highlights 2018

Adsorption is another process used to selectively eliminate specific pollutants from wastewater. Lanxess supplies iron oxides for this process. Users in many places also rely on activated carbon, which is produced from different raw materials and is also used in different forms (powdered or granulated carbon). Donau Carbon presented an extensive range of activated carbons at both events and they included those produced in the Philippines from coconut shells. Users can lease or purchase activated carbon filters in various sizes and make use of the full service that includes both the replacement and regeneration / disposal of loaded activated carbon.

Biological wastewater treatment The chemical and pharmaceutical industries pre-treat their wastewater and even operate their own clarification plants, as municipal clarification plants would be overburdened by the often complex pollutant mixtures found in industrial wastewater.

Biological decomposition of organic water constituents, which is the standard of urban water treatment, is also included in many industrial wastewater treatment plants in which a high organic load has to be degraded. Essential success factors for a high biological degradation rate are an efficient oxygen input into the aerobic stage as well as good mixing. Linde now includes a mobile oxygenation system in its product range that is especially aimed at small- and medium-sized companies. However, mixing organs used in anaerobic systems must not cause any turbulence on the water surface as turbulences facilitate the introduction of oxygen. Invent is a company that also provides stirring and gas supply systems that meet these requirements for use in clarification plants and they are also robust enough for use with the frequently aggressive and salt-containing wastewater discharged by the chemical industry.

Oxidation of persistent wastewater constituenwts Oxidation processes based on ozone, hydrogen peroxide or UV light are available for use with substances that are not biodegradable. Several IFAT exhibitors presented oxidative pollutant decomposition systems: EnviroChemie, who are based in Roßdorf, have developed a plant based on hydrogen peroxide and UV light that removes pharmaceutical residues from wastewater discharged by the pharmaceutical industry. Linde, one of the IFAT exhibitors, also showed an oxidative treatment system that uses ozone.

Tertiary wastewater treatment and MBR technology Reusing water from clarification plant effluents reduces the need for fresh water in industrial plants as well as the costs involved in discharging the wastewater. This approach is essential for maintaining production in production facilities located in regions with water scarcity. The first step towards reusing the wastewater from clarification plants with chemical / physical and biological wastewater treatment processes is solid / liquid separation downstream from the final clarification tank. Tertiary filtration retains the residual suspended matter, such as activated sludge, micro-plastics, precipitation flakes from the phosphorus reduction process as well as activated carbon powder. Invent Umwelt- und Verfahrenstechnik AG has developed the iFILT diamond filter for this application (see Fig. 2) and it can also be used in many industrial clarification plants such as those installed in the paper and textile industries, those installed for water treatment in fish farming or those used in the beverage industry for treating rinsing water. Veolia is able to look back on many years of experience gained with the Hydrotech disc filter and this system was exhibited once again at this year’s IFAT. It is used in combination with an MBBR system (Moving Bed Biofilm Reactor) or an Actiflo system (this combines various physical clarification techniques such as flocculation and sedimentation) in the industrial water treatment sector.

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Fig. 2: Inside the iFILT diamond filter, a view of the mechanically coupled filter wheels, which are fitted with high-quality stainless steel filter meshes (Image: Invent Umwelt- und Verfahrenstechnik AG).

MBR technology, as opposed to tertiary filtration, is often the technology of choice when reusing purified wastewater is aimed at.

It does not need final sedimentation, which saves the space needed for this system. Whereas the previously mentioned filtration processes work with separation efficiencies in the one- or two-digit micrometre range, submerged ultrafiltration modules work in the 100 - 150 kDa range. All of the major component suppliers and equipment manufacturers who participated in the development of this technology were represented at IFAT. They continue developing the technology and they are also able to build on their experiences gained from a wide range of industrial and municipal applications. Alfa Laval presented a new version of its submerged membrane system at IFAT. This differs from its predecessor due to a modified permeate outlet with a lower pressure drop, the self-cleaning S Aerator aeration system and the QuickSwap system, which enables specific membrane packs to be easily replaced in existing plants.

In the case of challenging wastewater treatment tasks, such as landfill leachate treatment, modules used in pressure-driven processes can also be used as part of an MBR process as alternatives to submerged membrane modules. CUT Membrane Technologie, which is based in Erkrath, reported on a measurement campaign to test the suitability of tube modules with 50 kDa ultrafiltration membranes for further reducing the organic load (measured as COD) after the biological stage. Membranes with an MWCO that were previously used in this process produced a filtrate with a COD of 800 mg/l. This value can be reduced to 600 mg/l by using 50 KDa modules. In general, it is possible to use finer degrees of separation with pressure-driven membranes, because one can work with a higher transmembrane pressure difference than with submerged systems. For example, this plays an important role in reducing wastewater charges for indirect discharge and protecting downstream treatment systems such as activated carbon filtration or reverse osmosis. The study is still ongoing.

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Highlights 2018

Water technology R&D A broad forum was given to the topic of water in all its facets every day at the exhibition and it is not just in the exhibition halls but also in the supporting programmes at both exhibitions. The BMBF’s WavE support measure (future-orientated technologies and concepts for increasing the availability of water through the reuse and desalination of water) with its 13 individual projects and its cross-sectional topics was also a focal point at both events.

At IFAT, projects related to membrane technology were presented at the German Society for Membrane Technology’s “The world of membrane technology in Germany – innovations for sustainable development” event.

Digitising water and wastewater treatment processes The term “Water 4.0” has already come into common usage in addition to “Industry 4.0”. At IFAT 2016 the German Water Partnership announced the establishment of its own working group on this topic and published a brochure under the same name (F&S 4/2016 reported on this).

For the chemical industry and other sectors characterised by high water consumption, the digitisation of water and wastewater treatment cannot be separated from actual production nor can it be separated from municipal wastewater management that has also been digitised. A digitised water treatment plant must also be able to communicate with water-consuming or wastewater generating plants as well as the provider of fresh water and the recipient of wastewater at the boundaries of a process or production facility.

Digitisation includes all of the water technology hierarchical levels ranging from the sensor in the field to the control and operating levels, management and controlling levels through to modelling and simulation within the network or in the cloud using autonomous, so-called Cyber Physical Systems (CPS). This is understood to mean the vertical integration of industrial water management. The objective is to develop water and wastewater treatment plants into adaptive plants that interact with their environment and react independently and flexibly to changes without losing any efficiency.

Digitisation opens up a range of optimisation and cost reduction potentials just at the plant level: Predictive maintenance, which can be made possible by the continuous transmission of status data from specific plant components or even entire plants, will prevent unplanned shutdowns and increases operational safety.

Evaluating, simulating and optimising all of the individual components will enable their potentials to be optimally exploited and bottlenecks can also be eliminated through simulation-supported improvements.

3D visualisation of plants and production cycles helps to eliminate weak points, to reduce workloads and routine work travel routes and it also makes the material flow more efficient.

Simulation-supported planning of new plants and the integration of new components into an existing plant offers considerable savings potential, especially with regard to time. Commissioning times will also be significantly reduced by training the operator’s staff in the use of virtual systems.

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Highlights 2018

Fig. 3: Water technology digitalisation using dashboards, energy management software, visualisation software and direct on-site plant operation, a cloud solution and all this with modern encryption techniques for data security (Image: Flowchief GmbH).

The horizontal integration of water management provides an option for the progressive networking of all of the production stages and the water-technology plants (water treatment, wastewater treatment, cooling water circuits) throughout the entire plant cycle. The recording, transferring and analysing of all of the important data also plays a role here, such as being able to better predict the production-dependent water demand and the resulting wastewater load.

Flowchief, one of the IFAT exhibitors who also provides several water management software solutions (as can be seen in Fig. 3), presented examples of the practi-

cal implementation of digital technologies in water-technology plants. They include dashboards (computer-assisted display panel development) that enable operators to always keep an eye on their company’s most important data. The e-Gem energy management software takes over the entire recording of energy consumption in clarification plants or waterworks and it generates consumption reports and visualises them in the form of Sankey diagrams.

The FlowChief cloud-based portal enables manufacturers, integrators or large associations to centrally manage distributed plants and processes. In order to guarantee the required data security for these solu-

Fig. 4: Smart and efficient municipal and industrial water treatment using Veolia’s Aquavista platform

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tions, data transmission is implemented through consistent and certificate-based end-to-end encryption, both for the remote technology between the PLC and the control centre as well as for user access to the system. An optional 2-factor authentication process can be activated for each user to ensure secure log-ins. Thanks to native web technology, remote access software such as TeamViewer, which produces a security gap that is difficult to manage, can be dispensed with.

Veolia presented its Aquavista digital services platform a few months ago and it is a cloud-based solution designed to make it easier for municipalities and industrial companies to manage their water efficiently. Fig. 4 shows you the functions that this platform provides and you can see that humans still have a part to play here. All of the water treatment technologies that Veolia presented at IFAT are currently being optimised for use with this digital service.

As can be seen from the Achema trend report on the digitisation of industrial water technology, one of the future challenges will be to link municipal requirements and wastewater or water flows not only structurally, but also in terms of information technology, to create a water recycling economy and then to link industrial and municipal water management with each other as well. In a position paper that Dechema presented at Achema, the potentials and challenges of industrial water management digitisation were examined in detail. This position paper has been available at: www.dechema.studien since June 12, 2018.

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Highlights 2018

Cloud computing for simulation and web applications in line with Industry 4.0 S. Poss, K. Schmidt, S. Ripperger *, S. van den Berg ** 1. Introduction Cloud computing involves the use of IT services (e.g. software, storage, computing capacity) via a data network (internet, intranets). If a network that is being used is only accessible to a specific organisational unit, i.e. an intranet, then this is the organisation’s internal cloud. In this case one can also call it “private cloud computing”.

According to “Cloud monitor 2018”, which was published by KPMG and Bitkom Research and summarises the results of a survey of 557 companies with 20 employees or more, it found that 51 per cent of the companies used private cloud computing in 2017 /1, 2/. It was only 38 per cent during the previous year. With a private cloud, the infrastructures that are needed, such as server computers or data storage, can be located within the company or in an external data centre. The survey found that companies are increasingly outsourcing the operation of private * Stefan Poss, B. Eng. Dr.-Ing. Dipl. Math. Kilian Schmidt Prof. Dr.-Ing. Siegfried Ripperger IT for Engineering (it4e) GmbH Morlauterer Str. 21, 67657 Kaiserslautern www.it4e-gmbh.de ** S. van den Berg T-Systems International GmbH, Bonn

Private Cloud Computing • Internal Private Cloud Internal IT structure according to the cloud concept. Infrastructure and data remain within the company.

• Managed Private Cloud An outsourced provider operates a cloud for the company.

Infrastructure remains within the company.

• Hosted Private Cloud An outsourced provider operates a cloud for the company.

Infrastructure is run in the service provider’s data centre.

• Community Cloud Private cloud that is used by a limited circle within a company, e.g. a specific sector or department.

Fig. 1: Private Cloud: own solution with or without a service provider (according to "Cloud Monitor 2017" /1, 2/.)

clouds to external IT service providers. At the time of the survey, only 13 per cent of the companies still operated private clouds completely by themselves. Four years ago, the proportion was twice as high at 26 per cent.

The Internet of Things (IoT) and Industry 4.0 also offer the potential for factories to link mobile machines and devices to a cloud via the public internet /3/. Public cloud computing enables

companies, organisations or even private individuals to use IT services in conjunction with a cloud via the public internet.

The cloud can be set up internally or externally relating to an organisation and then be offered for use (see Fig. 1 as well).

These IT services can be adapted to meet the demand and invoiced in conjunction with the cloud. Therefore, public cloud computing provides the basis for a new business model. It is important that the

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Highlights 2018

Cloud

People Purchasing

Machine Process

Costs / € / year

Fig. 2: Networked system characteristic of industry 4.0

Overall costs / € / year Energy costs / € / year Filtration time until change / days

Filter elements / € / year

Fig. 3: Cost types as a function of the operating time of filter elements used in ventilation systems.

customer clearly benefits from using the cloud. For example, a software provider can offer the use of software via a cloud as well as the computing capacity that it involves, so that a customer can rely on the hardware provided via the cloud and does not need his own hardware for this.

The software service can also be invoiced according to demand so that the customer does not need to obtain his own expensive licenses and the service does not have to be used in keeping with its cost. Public cloud computing also offers many options with regard to the remote monitoring of plants and machines. For example, it enables data analyses to be run using specially developed software tools. A large amount of plant and machine data can be evaluated on a when-needed basis and the on-site data storage costs can also be reduced.

Evaluations can also be carried out in the cloud in conjunction with other recorded data, e.g. from other plants or machines, or from business processes. The evaluation results can then be transferred to PCs or mobile devices via the web browser, so

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that the visualised data can be accessed from any location. Such solutions enable several plants or machines to be monitored remotely. Operational planning, service or spare parts procurement data can also be taken into consideration. This will create an “intelligent” system that will enable what initially appears to be a vast amount of data to be viewed and analysed within a specific context. The data connection is an important component for companies to be able to work flexibly and efficiently when working with public cloud computing.

Professional internet connections and cloud access are provided by network operators such as Deutsche Telekom. Examples of these services are: “EthernetConnect” (2.5 Mbit/s up to a maximum of 10 Gbit/s) or “DeutschlandLAN Connect IP” (50 Mbit/s up to 1,000 Mbit/s).

Public cloud computing is developing slowly despite the advantages and options listed above. Nevertheless there has still been an increase over the years.

According to the previously mentioned “Cloud Monitor 2018” survey, 31 per cent

of the companies surveyed used public cloud computing in 2017. This was only 29 per cent in 2016. More and more companies are taking the opportunity to improve data security through the use of public cloud solutions.

Many potential users worry about data security, especially with regard to a cloud application. Deutsche Telekom holds an European seal of approval, which guarantees that the data will be stored in the EU and that the strict European data protection and data privacy laws will always be adhered to. The Euro-Cloud seal of approval was introduced before 2011 and it is awarded in Germany after an audit by the Cloud Services Industry Association in Germany (see www.eurocloud.de) and it also mentions the location of the data centre.

2. Software and Infrastructure as a Service (S and IaaS) The design and calculation of processing plants and devices is no longer conceivable without the use of computer technology. It is used to run extensive calculations, store and organise data records as well as simulating and visualising complex processes within the devices and plants. Plant and/or material behaviour can be studied through the use of simulation, before the actual plant is implemented.

This is an advantage that is being used more and more, especially with complex and difficult to evaluate processes. It enables development times to be shortened and it also reduces development costs, as the expenditure needed for the trials will be significantly reduced.

Different simulation methods together with the corresponding software can be provided. They include large programs that can numerically solve a large number of physical / mathematical model equations.

Through the use of flow diagram programs complex processes can be handled including the links between the basic processes as well as the input and output variables (e.g. material flows, energy flows, information). The physical effects and processes within the processing stages can also be taken into consideration through the use of model equations.

Plant and devices geometries can be designed using CAD programs (CAD = Computer Aided Design) and displayed using the embedded 3D visualisation functions. Associated strength calculations can also be run using the Finite Element method (FE method). This enables stresses and deformations of complex components to be calculated under load.

Computational Fluid Dynamics (CFD) are used to simulate flow processes. The suitable programs provide options for sim-

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Highlights 2018

ulating and visualising flow fields and the connected processes, such as heat transfers within devices and machines. When CFD simulation is used in conjunction with other simulation programs, users are also able to analyse and predict the mechanical behaviour of components as well as the fatigue and vibration properties.

The Discrete Element method (DE method) can be used to simulate the behaviour of both stationary and moving bulk solids from the sum of many individual contacts between the particles. Various microscopic particle / particle or particle / wall interactions can also be taken into consideration depending on the contact law.

Simulations provide an insight into the force distribution inside a bulk material (e.g. within a filter cake) as well as the force of particles on components. Flow forces acting on the particles can be taken into consideration in the DEM calculations by interlinking into a CFD program.

It is advisable to make a comparison of the results from the simulation calculation with measured values after taking the comparable boundary conditions into consideration.

All these simulations need to be able to access the relevant software and the high computing power that you will need to use.

The use of software is usually associated with the purchasing of a license, for which a 5-digit sum of Euros is often charged.

However, paying this amount is only worthwhile if you simultaneously invest in expensive hardware. But other solutions are also possible in conjunction with cloud computing. it4e GmbH provides other simulation tools and services within the Open Telekom Cloud in addition to the ability to use their DNSlab simulation program /4 - 6/. DNSlab is used to generate the fine structures (e.g. of filter media) and for the numerical flow simulations. It is also used in conjunction with micro-Computer Tomography (μ-CT) for taking really complex structures into consideration. The pressure drop and particle separation processes can then be calculated with great accuracy in conjunction with the flow simulation. Cloud computing enables cost-effective, short-term program usage. The high computing power provided within the cloud is used simultaneously.

operation. So-called fouling indicators that indicate the pressure difference across the on-site filter, are customary.

One of the systems developed by it4e GmbH for monitoring depth filters used for gas and liquid filtration not only monitors the filter’s status, but also determines, with a certain probability, the economically optimum time for changing it based on empirical data and the actual parameters measured at the filter.

This is based on software that records and evaluates the local on-site parameters in conjunction with sensor data. It enables the operator to plan the filter change at an early stage. The sensors also record the pressure change depending on the operating time or the filtered volume, etc. Temperature or concentration fluctuations as well as operational interruptions can also be taken into consideration during the evaluation. The determining of the optimum change time will be based on the empirical data, as the cost of the new filters and any further expenditure involved in changing the filter as well as the energy costs due to the pressure drops.

Fig. 3 shows examples of determined cost types as a function of the operating time of the filter elements used in ventilation systems. The optimum changing time is determined by the minimum overall costs, which is, in the case shown in the example, after an operating period of approx. 175 days. In this case the filters will be changed when the pressure difference reaches approx. 120 Pa instead of a normal pressure difference of more than 500 Pa. Today, many filters are only changed when a specified maximum pressure difference is reached. It has been proven that in many of these cases changing the filter at this time does not correspond to the optimum economic option.

Overall costs are mostly too high due to the excessive energy costs.

CO2 emissions will also be reduced if the energy costs are reduced.

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Another characteristic of industry 4.0 is the networking of stationary or mobile machines and plants, which enables integrated data recording, analysing and graphic processing and displaying to be run in real time (Fig. 2). Machine or plant components can be given their own IP addresses and networked into the internet.

They will then become a smart product in the Internet of Things or in cyber-physical systems with integrated, internet-based services.

Different processes and relationships will then become transparent and they can also be monitored and controlled from any location and at any time. This will enable supply-chain optimisation through projecting the requirement situation as well as globally coordinated product production and distribution.

Networking is based on communications and information technology. It has enabled the creation of an Internet of Things (IoT), services and data that can then be used to control highly complex processes. Cloud computing is able to collect and evaluate data from widely distributed plants. It is a core technology on the way to “Industry 4.0” when used in conjunction with measurement and sensor technology. it4e GmbH has been working on the monitoring of separation processe, particularly with depth filters, in recent years. Such filters are installed in numerous stationary and mobile plants and are needed to ensure smooth operation. Despite a considerable increase in their service lives, they still need to be replaced, even during normal operation. Necessary replacements during operation can cause a production stoppage and major production downtime.

This is why the status of the filters is often monitored during

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Open Telekom Cloud LTE Server

Mobile sensor Encrypted internet connection

WLAN

Client

Stationary sensor

Fig: 4: Application scenarios for “Open Telekom Cloud“

The system is also capable of taking into consideration deviations from normal filter operation, e.g. due to intermittent fouling or particle separation. This is possible because the calculation will be run at specific time intervals based on the actual pressure values that were determined. The ability to effectively adapt to the conditions present in each case is a characteristic that distinguishes the system. The system is designed to be open, so that any other data that are important with regard to filter reliability or plant operation, etc., can be taken into consideration during filter monitoring and the calculation will then be based on it.

Preventive (predictive) maintenance will be enabled by comparing data measured during product usage to data determined during product development.

Data signals from stationary or mobile plants can be recorded and evaluated wirelessly in a cloud through the use of a process computer. Thus, temperature, flow and pressure can be monitored for filters on engines, transmissions or hydraulic systems for critical conditions, e.g. at low temperatures. Critical states can be detected by using suitable algorithms and automatic intervention can be made if necessary, so that the intended states are always maintained. Data from other sources, e.g. service team planning data, can also be taken into consideration in conjunction with a cloud. This will enable flexible preventive maintenance to be implemented.

4. Using a public cloud for preventive maintenance it4e GmbH provides the simulation software and the evaluation of sensor data on a virtual server in a public cloud, so that no dedicated IT resources have to be provided or purchased on the customer’s or user’s side. As with other cloud appli-

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cations, a PC’s standard desktop is used to display, manage or transfer information (e.g. from a USB stick).

More specifically, the public cloud used by it4e is the Open Telekom Cloud, which is an OpenStack based IaaS provided by Deutsche Telekom. The graphical user interface used in the Open Telekom Cloud allows the user to select and configure individual components. You can choose from computing, storage, networking and management services. Other platform services such as various databases or virtual IT workstations as well as software services for big-data analyses are also available.

The process runs as follows: – set up the server that you need in the Open Telekom Cloud – install the software on the server – set up the access authorisations.

The hardware and software can be used as usual afterwards.

Data protection and data security aspects play a very important role in the Open Telekom Cloud in addition to its flexible scalability. Data is processed and backed up in highly secure twin-core data centres owned and operated by Deutsche Telekom in Germany. Data processing is subject to the strict provisions of the Federal Data Protection Act. Certification in compliance with Trusted Cloud Data Protection Profile (TCDP) 1.0 also attests that the Open Telekom Cloud – currently one of the few clouds available on the market – provides companies with the technical conditions needed to meet the future requirements of the European General Data Protection Regulation.

All of the services are subject to their own strict specifications and are regularly audited and certified by independent institutions in order to ensure that they meet the latest security and data protection requirements.

Extract from the certifications and quality assurance procedures used by Open Telekom Cloud: – TÜV Trusted Cloud Service - IT security, operation and data protection – CSA STAR Level 2 - international data security certificate – TCDP 1.0 – ISO 9001 - Quality management – ISO 20000 - Service management system – ISO 22301 - Business continuity management system – ISO 27001 - Information security management system – ISO 27017 - Cloud data security – ISO 27018 - Data protection in the cloud – Zero Outage - Certified service process – DQS ISO27001 - Certified privacy & security assessment process 5. Summary Today, the majority of data is recorded, processed and stored digitally. The use of a cloud is very common in many companies.

A. Fürst recalled the development of the electricity supply in Germany at the end of the 1870s and beginning of the 1880s in connection with this development /7/.

Most factories were producing electricity in their own small power plants back then.

A power supply from the grid was either non-existent, too expensive and/or unstable. Only with increasing electrification did the companies shut down their own power plants and connected themselves up to the grid. This freed up resources and the companies were able to focus more on their core business. Similar considerations are the reason why today’s IT infrastructures are being moved from their own data centres into a cloud.

Reference literature: /1/ Bitcom Presseinformation vom 12.06.2018 „Zwei von drei Unternehmen nutzen Cloud Computing”; www.bitcom.org /2/ P. Heitkamp, M. Vogel, A. Pohls: Cloud Monitor 2018: Eine Studie von KPMG im Zusammenarbeit mit Bitkom Research (2018) /3/ S. Ripperger, Industrie 4.0 und mögliche Auswirkungen auf die Produktions- und Prozesstechnik. Filtrieren und Separieren 30 (2016), Nr. 1, S. 6-12 /4/ S. Ripperger, K. Schmidt, Entwicklung von Geweben als Filtermedien unter Berücksichtigung der numerischen Strömungssimulation. Filtrieren und Separieren 29 (2015), Nr. 6, S. 378-381 /5/ A. Hellmann, M. Pitz, K. Schmidt, F. Haller, S. Ripperger, Characterization of an OpenPored Nickel Foam with Respect to Aerosol Filtration, Efficiency by Means of Measurement and Simulation Aerosol Science and Technology, Volume 49, Issue 1, Pages: 16-23, 2015, DOI: 10.1080/02786826.2014.990555 /6/ A. Hellmann, S. Rief, K. Schmidt, R. T. Kocaman, D. Aibibu, C. Cherif, S. Ripperger, S. Antonyuk Simulation der Partikelabscheidung und des Druckverlustes von Schutz- und Filtertextilien bei einer Gasdruchströmung. Filtrieren und Separieren 31 (2017), Nr. 4, S. 268-274 /7/ A. Fürst, Abschied vom eigenen Rechenzentrum?

BWK – Das Energie-Fachmagazin 69 (2017), Nr. 9

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Future of process and plant technology* Individualisation does not only apply to cars, clothes or your breakfast cereals.

The chemical and pharmaceutical industry is also facing an increasing demand for customised products. The resulting short development and product life cycles are a challenge to conventional plant concepts.

Modular plants are globally on the rise in order to meet the changing customer expectations. They allow for flexibility in terms of production capacity (e.g. by “numbering up” or parallelisation), product variety (by changing reaction modules or downstream processing steps), raw materials and location (e.g. mobile modules). Broadly available standardised modules increase competitiveness, especially if they are used by many companies and are thus produced in large numbers at low cost.

Modularisation from the planning phase on The benefits from modularisation can be reaped right from the planning phase.

Reusing engineering information and closed data handling throughout the project phases can lead to an accelerated engineering phase and shorter time to market. To achieve this goal the utilisation of a standardised modular planning workflow is essential prior to physical modularisation.

In order to achieve versatile continuous production units and to enable decentralised production, a physical modularisation of process plants can be applied. Then modules are defined in such a way that functions defined in PED definition are maintained. This physical modularisation can take place on the apparatus, plant or logistics level on site as well as in the production network. If a physical modularisation is desirable, the compatible modules are constructed as adaptable units and are assembled to form multi-purpose plants. During the production phase, the exchangeability of single modules simplifies maintenance and service and reduces changeover times. Operational data obtained during production can be directly used by the plant engineer to define maintenance strategies and to optimise already planned modules for prospective projects. * The article is based on an “ACHEMA Trend Report” from DECHEMA Ausstellungs-GmbH Theodor-Heuss-Allee 25 60486 Frankfurt am Main Tel: +49 (0) 69 7564 -100

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Following the production phase, the plant will be dismantled while information and physical components can be reused. This ensures continuous improvement and the reapplication of operational experience.

Physical modularisation: module follows function To implement a systematic modularisation approach from the process development to the dismantling of the plant, a process is first virtually divided into equipment groups that belong to the same part of the process. This reduces the complexity of a process and creates reusable building blocks. All planning documents required for the construction of such modules are merged in functional process units that are called Process Equipment Design modules (PED) which are saved in databases. A PED incorporates at least one main equipment item, providing the desired unit operation together with all needed peripheral components. Within each PED the main equipment items can be exchanged to adapt to different operating conditions. Each PED is stored as a database element containing all information and documents.

PEDs should be accompanied by simulation models, which allow for the configuration of modules, starting from a description of the PED functionality. The PEDs are then categorised in functional units, the process and service units.

Process units are in direct contact with reactants, process or waste streams (e.g. storage and dosage, reaction, downstream, formulation, and packaging). Service units have supporting functions for one or more process units such as utility and energy supply, and do not have direct contact with the process streams. This distinction and the related database should allow for different reuse scenarios to speed up the time to market.

Single PEDs can be combined to form a Process Plant Design (PPD). The PPD conforms to the scope of performance of a modular plant and comprises all documents that are needed for a successful construction and operation. It defines the positions and connections between PEDs and virtually represents the desired process.

Modular equipement is at the core To enable an efficient, yet versatile production environment, the availability of reliable process equipment for industrial small scale processing is a fundamental prerequisite. This includes validated model descriptions for process-intensified equipment as well as robust devices providing industrial grade reliability. A single piece of equipment can be defined as modular if it provides one of the following features: - Inherently modular design, providing serial or parallel numbering-up of basic elements (e.g. channel reactor prepared for numbering-up of channel number and length) or another key feature dedicated to reusing the equipment.

- Inherently modular design, providing configurable elements to adapt to various operating conditions (e.g. modular process control systems providing variable integration of modules into the master system).

- Series of equipment providing the same functionality at different operational scales (e.g. a pump series providing different volumetric flow ranges utilising the same operational principle).

Physical modularisation is suitable for multiproduct / multi-purpose plants, in which frequent reconfigurations of the process structure are common between product campaigns. Additionally, an integration of small scale continuously operated equipment into pilot or multi-purpose batch plants can be realised to enable highly efficient hybrid production concepts. In this case, the plant consists of individual Process Equipment Assemblies (PEAs). A PEA represents the physical implementation of a PED, following additional geometrical and technical design guidelines, to ensure compatibility of independently planned modules. During the production phase, the exchangeability of single modules simplifies maintenance and service and reduces changeover times.

A plant in a container The combination of various PEAs to form production plant is described by the Process Equipment Frame (PEF). The

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Highlights 2018

PEF contains the geometric conditions and safety-related specifications of the installation environment and covers the supply of all PEAs. Containing the overall process control system of arranged PEAs, the PEF is considered as an independent production unit. For standalone or decentralised production scenarios, the integration of PEAs into a PEF can be performed in modified freight containers, which can provide a fully integrated infrastructure to form a mobile and reconfigurable production environment, requiring only basic utility supply on site.

To take full advantage of intensified continuous processes, key steps must be taken towards long-term stable, tightly controlled and fully automated production. In this context, process analytical technologies (PAT) play a crucial role.

Based on their information the critical process parameters (CPP) can be monitored, controlled, and optimised in order to achieve the desired product quality or to detect changes in critical quality attributes (CQA).

To enable an efficient implementation of PAT tools, the required measuring methods (including appropriate measuring/sampling points) should be defined at an early planning stage. Ideally, the same analysis methods are applied throughout process development and scale-up from lab to pilot or production scale. This makes an accelerated implementation of PAT tools possible.

Prerequisites for modular plants are a deeper understanding of micro reaction technology, process intensification, and continuous production – all areas that have seen tremendous research efforts and – not least – public funding over recent years. Research projects such as F3 Factory or the ENPRO initiative have proven that the modularisation approach is feasible and can be implemented. The vision of the F3 Factory project was a radical modular approach for a rapid process development and the implementation of novel flexible and sustainable processes with an improved CapEx and OpEx. In the successful case studies, the potential of intensification and modularisation for the chemical industry was demonstrated.

During the project first design guidelines and standards were applied that enhanced the flexibility of a production plant by exchangeable PEAs. The vision comes to life Besides publicly funded projects, chemical companies as well as suppliers have already started to implement modularisation in their different fields of

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application. Lacking a common understanding of the degree of modularisation and standardisation, various ways have been used to implement modularisation in these companies.

- BASF uses customised containers for small-scale production with the advantage of customised construction workshops and subsequent transportation to the production site of interest.

- Evonik uses containers as a special kind of standardised mobile infrastructure platform (Eco Trainer) for fast process development and subsequent small-scale production. This concept has successfully been demonstrated for electronic chemicals in the past. In addition, Evonik is establishing a modular frame concept similar to the F3 Factory concept for process development in a pilot plant environment.

- Merck is operating in an environment in which time to market is the most sensitive fact for introducing new products into the market. The small-scale continuous production plants follow the Multi Process Plant concept, which ensures a high flexibility in combination with process intensification.

- Clariant differentiates between modular plant concepts that address specific needs like market entry (fast and reliable) and types of technology transfer (sampling, piloting, and training). At present, Clariant is working on pilot projects with focus on formulations and chemical reactions.

- Invite offers engineering services for modular plants following the F3 Factory concept. This includes basic and detailed engineering as well as testing at a technical center especially equipped for modular process containers.

In addition to the implementation of these concepts in the chemical companies, there are more and more suppliers applying these concepts in their business.

ZETON offers the construction of modular lab-, mini- and pilot plants for different chemical sectors. Integrated Lab Solutions (ILS) builds compact lab- and mini-plants especially for high throughput experimentation with ME. Hte provides technologies and services for enhanced R&D productivity with focus on high throughput technology platform and modular systems for catalyst testing. Lonza and Ehrfeld offer modular microreactor systems for continuous production. Furthermore, HiTec Zang developed a lab automation system that allows for a quick realisation of batch sequence protocols. However, these mod-

ular concepts are still based on individual standardisation concepts and lack a common standardisation approach.

Making the jigsaw fit: standardisation Nonetheless, building modular plants is a completely new approach. In order to reach the goal of a completely modularly designed and built plant, a lot of effort especially regarding the standardisation of equipment and automation technology is still necessary.

A key prerequisite for the modular approach will be the development of standard solutions for problems occurring repeatedly and the definition of guidelines for designing new PEDs. Examples for standard applications are storage, dosing or mixing. These typically do not represent competitive knowledge and can be developed in a joint effort by multiple companies and manufactured by suppliers.

This could substantially reduce plant manufacturing costs. On the other hand, PEDs will have to be designed individually or existing PEDs need to be modified, either because no suitable PED is available, or because certain boundary conditions make individual design inevitable.

Interfaces are required to interconnect PEAS among one another and to local infrastructure. These interfaces have to match the requirements of a large variety of potential processes. This can only be achieved with flexible interfaces suitable for adaption to local boundary conditions.

Even though interfaces have to be standardised for connections frequently applied, a certain degree of freedom is still needed to adapt the interface to local requirements. This will allow for a quick PEA installation and plant reconfiguration in multi-purpose plants. In cases of frequent exchange, rigid interfaces are required that allow for quick PEA connection and disconnection. However, this may cause substantial additional costs. It will thus be important to find a reasonable compromise between standardisation and flexibility.

This report is an excerpt from a White Paper “Modular Plants” prepared by the temporary ProcessNet working group „Modular Systems“ in a close cooperation between industry and research institutions.

It provides the current state of the joint efforts to improve the modularisation of plant technology in the chemical industry.

The whole report is available at http:// dechema.de/dechema_media/modularplants.pdf

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Highlights 2018

Combined separation processes for downstream processing in biotechnology J. Barth * The manufacturing process of biotechnological products such as monoclonal antibodies (mAb), blood plasma proteins, and vaccines comprises the downstream processing steps for the purification of the fermentation broth to obtain a sterile product solution. The purification process involves removing the insoluble and soluble impurities.

In order to remove the different impurities different separation processes have to be combined. These include clarifying via filtration or sedimentation processes and both chromatography and sterile filtration processes.

By improving the separation processes used in the initial clarification stage the load of the more complex downstream separation processes can be reduced. A robust purification process and savings in plant and operating costs can be achieved by using an optimal combination of separation processes.

Introduction Host cell fermentation is followed by product purification in biotechnological production processes. With intracellular products initial cell disruption is necessary. Afterwards, both soluble and insoluble impurities exist in the fermentation broth in addition to the dissolved product, e.g. cellular debris (with intracellular products) or complete host cells (with extracellular products), HCP (Host Cell Proteins), and endotoxins. Separating and purifying the products from the fermentation broth is realised over several processing stages in the downstream processing chain.

The productivity of the host cells has increased as a result of improved fermentation processes and cell strains. This is why the fermentation broths now contain higher concentrations of dissolved products as well as soluble and insoluble impurities.

These higher concentrations make high demands on the separation processes used.

Different separation processes can be used in the specific processing stages necessary to separate and purify the products. The various separation processes, that are used, all have different retention characteristics with regard to the impurities that have to be separated. Besides this, they also have different sensitivities with regard to other impurities. Therefore, the optimal combination and adjustment of the specific processing stages must be determined in order to achieve a high product purity as well as a high robustness and long service life of the entire purifying process.

Purpose of the purifying process and the separation methods used The purpose of the purifying process is to remove insoluble impurities, such as biomass, aggregates and fine particles, soluble impurities, such as HCP, DNA, and endotoxins, as well as microbiological contaminants, such as bacteria and viruses, in order to obtain a pure and sterile product. Sedimentation and/or filtration processes are used to remove the insoluble impurities.

Chromatography processes have to be used to remove the soluble impurities. Sterile filtration is always the final stage used to separate the microbiological contaminants (bioburden).

The entire purifying process should be as robust and versatile as possible. Robustness designates the insensitivity to fluctuations in the concentration and the composition of the feed suspension. The more robust the purifying process is, the more versatile it will be.

Versatility designates that the processes can be used for different products. A versatile purifying process can be adopted without the need for modification when the product is changed and it does not have to be replanned or redeveloped.

Removal of insoluble impurities Insoluble impurities such as biomass (host cells and cell debris), aggregates, and fine particles have a broad particle size distribution in the range of dPt = 0.02–100 μm (cf. Chmiel [1]). Therefore, multi-stage separation processes are usually necessary to remove them

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* Dipl.-Ing. Jakob Barth Kaiserslautern E-Mail: Jakob.Barth@mv.uni-kl.de

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Highlights 2018

separators. An exception to this are the tubular centrifuges made from polymer materials which CEPA presented at the Achema 2018.

An alternative to centrifugation is acoustophoretic sedimentation using the cadence acoustic separator made by Pall [2]. The suspension flows through separating chambers in which an acoustic field with a standing sound wave is generated. Fine particles aggregate in the standing sound wave’s nodes until the aggregates sediment due to their size. The process works continuously. The separating chambers are available as sterile disposables complete with connectors.

Fig. 1: Layout of the Stax CF Cake Filtration capsules made by Pall.

Copyright Pall Corporation.

in order to clarify the fermentation broth. In principle, it is possible to use filtration and sedimentation processes. The concentration of cells and fine particles in the suspension (cell density and turbidity) as well as the applicability of filtering aids, such as diatomaceous earth, must be considered as the criteria for selecting suitable separation processes.

Depth filtration processes The use of depth filtration processes is possible with cell densities of cn,Sus < 35·106 1/mL and turbidities of ΦSus < 3,000 NTU (cf. Pall [2]). Multiple filter stages or asymmetrical filter media with pore size gradients are necessary due to the broad particle size distribution.

The advantage of using depth filtration processes is the availability of filter cartridges and capsules of different sizes for use with different volumetric flow rates from laboratory to production scale. Filter capsules are available as sterile disposables complete with connectors. Using disposables allows the omission of filter cleaning, sterilisation, and validation steps.

Surface filtration processes with filtering aids With suspensions that have cell densities of cn,Sus > 35·106 1/ mL and/or turbidities of ΦSus > 3,000 NTU the required filter area for depth filtration processes becomes impracticably large and the filter’s service life becomes impracticably short. Using surface filtration processes with filtering aids (e.g. diatomaceous earth) is a possible alternative in this case (cf. Pall [2]).

The filtering aid forms a loose and permeable filter cake in which the insoluble impurities are retained. Without filtering aids the biomass would form a very dense filter cake, and the resistance of this type of filter cake is impracticably high. Filters of various sizes and sterile disposable filters complete with connectors (e.g.

Stax CF Cake Filtration capsules made by Pall as shown in fig. 1) are also available for use in surface filtration processes.

Sedimentation processes If the use of filtering aids is not possible due to processing reasons or disposal problems, then suspensions with cell densities of cn,Sus > 35·106 1/mL and/or turbidities of ΦSus > 3,000 NTU can only be treated by sedimentation processes for pre-clarification and subsequent depth filtration processes (cf. Pall [2]). Sedimentation processes have a greater specific energy demand than pure filtration processes.

The apparatuses that are traditionally used for sedimentation processes are batch or continuously operating centrifuges and separators. Disposables are normally only available for laboratory-scale centrifuges due to stability reasons. Cleaning, sterilisation, and validation steps are normally required with centrifuges and

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Removal of soluble impurities Soluble impurities, such as HCP, DNA, and endotoxins, are present in the fermentation broth in a dissolved, complex mixture.

Their separation usually occurs over two processing stages (cf. 3M [3]): The required product is isolated from the clarified fermentation broth during the capture stage. The impurities that remain dissolved at low concentration are removed from the product solution in the subsequent polishing stage. Chromatography processes are used in both stages. The two stages make different demands on the respective chromatography processes due to the different concentration of the solutions.

Column chromatography The traditional chromatography processes are column chromatography processes. The chromatography columns contain a fixed bed of porous particles. The functionalised surfaces are inside the pores of the particles.

The advantage of column chromatography processes is the large functionalised surface inside the particles. This gives chromatography columns a large capacity for retaining soluble impurities. The disadvantage of column chromatography is that the mass transport to the functionalised surfaces inside the pores of the particles is mainly diffusive. Therefore, chromatography columns require very long residence times and correspondingly large fixed bed volumes.

The investment costs for chromatography columns are high due to the large amounts of functionalised particles as the column material. Therefore, they are normally used in several chromatography processes and for different products. A chromatography column needs cleaning, sterilisation, and validation steps between the different chromatography processes and when changing products.

The cleaning and sterilisation steps, using aggressive media, each result in partial denaturing of the functionalised surfaces. The service life of the chromatography columns is therefore limited by the number of cleaning and sterilisation cycles that are performed (cf. 3M [3]).

Membrane chromatography Membrane adsorbers have been developed for some chromatography processes (cf. Sartorius [4]). The functionalised surfaces are inside the pores of membranes.

The advantage of membrane chromatography is the flow of the process solution though the pores with the functionalised surfaces. Therefore, the mass transport to the functionalised surfaces is essentially comvective, and the residence times and the volumes of the membrane adsorbers, that are required, are considerably less than those for column chromatography processes. The disadvantage of membrane chromatography is the reduced capacity for retaining the soluble impurities.

The investment costs for membrane adsorbers are lower due to the smaller amounts of functionalised material. They are also available as sterile disposables complete with connectors (e.g.

Sartobind capsules made by Sartorius as shown in fig. 2). Using disposables allows the omission of membrane adsorber cleaning, sterilisation, and validation steps.

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Highlights 2018

Because of their lower capacity, membrane adsorbers can be used primarily in the polishing stage, where impurities dissolved at low concentration are removed.

Column chromatography processes are used mainly in the capture stage.

Removal of microbiological contaminants (sterile filtration) Microbiological contaminants are removed by sterile filtration in the final processing stage in order to obtain a sterile product. Membrane filters with pore sizes in the range of dPr = 0.1–0.2 μm are used for sterile filtration (cf. Pall [2], 3M [3]).

Membrane filters are available as filter cartridges and capsules in different sizes for different volumetric flow rates from laboratory to production scale. The filter capsules are available as sterile disposables complete with connectors.

Filtration processes with improved retention If more impurities can be removed by the filtration process in the initial stage, the load of the subsequent purifying stages can be reduced. Improved retention of various contaminants can be realised through various filter modifications (cf. 3M [3]).

The retention of ultra-fine particles can be improved by using a correspondingly fine filtration stage. Thereby, the chromatographic material in the subsequent chromatography stage is less rapidly loaded and inhibited by the ultra-fine particles.

Thus, the cleaning interval of the chromatography column can be extended. As the chromatographic material is partially denatured during each cleaning, the service life of the chromatography column can be extended too.

The retention of microbiological contaminants can also be improved by using a correspondingly fine filtration stage. This reduces the filter area required in the final sterile filtration stage and also results in lower plant and operating costs.

The retention of soluble impurities can be improved by functionalising the filter medium. This effects better separation properties of the chromatography column in the capture stage. Thus, both the residence time and the corresponding fixed bed volume can be reduced. Under certain circumstances it might even be possible to replace a chromatography column with a membrane adsorber. The improved retention of soluble impurities in the preceding purification stages often makes it possible to replace a chromatography column with a membrane adsorber in the polishing stage. This also results in lower plant and operating costs.

Application example A filter with improved retention properties for insoluble and soluble impurities has been introduced by 3M (cf.

3M [3]) with the Emphaze AEX hybrid purifier. It has a multi-layered nonwoven filter medium with a pronounced pore size gradient shown in fig. 3, which not only retains the biomass but also significantly reduces the ultra-fine particles. An asymmetric membrane with a minimum pore size of dPr = 0.2 μm also ensures the reduction of the microbiological contaminants. Furthermore, the nonwoven medium is functionalised with a cationic Q-functional hydrogel that significantly reduces the soluble impurities.

Fig. 2: Different sizes of Sartobind capsules made by Sartorius. Image courtesy and property of Sartorius AG, Göttingen (Germany).

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In the clarification stage of the purification of monoclonal antibodies (mAb) a particle retention up to a particle size of dPt < 30 nm and a uniform filtrate turbidity of ΦF < 5 NTU are realised (cf. 3M [3]).

HCP reduction in the range of 20–40 % and DNA reduction by more than 4 log levels is achieved. The bioburden can be reduced by more than 6 log levels. With this improved retention for insoluble and soluble impurities in the first purifying stage, a 10-fold reduction in HCP and a more than 1,000-fold reduction in DNA in the product stream can be realised in the chromatography stage. The chromatography column’s capacity loss is reduced and its service life extended. The throughput is increased during the sterile filtration stage, thus a reduction of the filter area is also possible.

Simultaneous removal of various contaminants in a single processing stage simplifies the production process. Plant and operating cost are lower due to the reduction of the load of the more complex chromatography and sterile filtration stages.

References [1] Chmiel, H., ed.: Bioprozesstechnik. 2nd ed.

Heidelberg: Spektrum Akademischer Verlag, 2008.

ISBN 978-3-8274-1607-0 [2] Pall Corporation: Harvesting Technology Guide for mAb Processes [online]. Company publication, 2018 [accessed on 16.10.2018]. Available under: https://www.pall.com/content/dam/pall/biopharm/ lit-library/gated/misc/18.07009_USD3216_Cell_ Harvest_BRO.pdf [3] 3M: 3M Emphaze AEX Hybrid Purifier Serie.

Company publication, 2017.

[4] Sartorius: Fast and Efficient Contaminant Removal with Sartobind [online]. Company publication, 2018 [accessed on 30.11.2018]. Available under: https://www.sartorius.com/us-en/applications/ biopharmaceutical-manufacturing/mabs/mabsdownstream/mabs-polishing

Fig. 3: Multi-layered nonwoven filter medium with a pronounced pore size gradient of the Emphaze AEX hybrid purifier made by 3M. Image courtesy and property of 3M Deutschland GmbH. 37

Highlights 2018

Method for the design and optimisation of dynamic surface filters with respect to the specific filtrate flow rate and energy demand J. Barth, S. Ripperger * For the dynamic surface filtration, a number of different filters, both with and without moving parts, is used.

They employ different concepts to create the relative movement between the filter medium and the suspension that is filtered. The flow field inside the filters is often complex. Thus, the resulting filtrate flow rate at a given energy demand is usually determined experimentally. A newly developed method facilitates the calculation of both the specific filtrate flow rate and the specific energy demand for different filters. In the following paper, both the calculation and the design with respect to the specific filtrate flow rate and the calculation and optimisation with respect to the specific energy demand will be presented.

1. Introduction One part of the research efforts in process engineering is directed towards the development of mathematical models for the description of the analysed processes. For complex processes a piecewise description and/or separate models may be necessary. They result in a set of coupled equations that have to be solved numerically in many cases to simulate the process. The benefit of the models is twofold: First, they enable a better understanding of the process described. This understanding may extend to spatial and temporal scales that are not accessible experimentally.

With suitable methods, a visualisation of the process is possible. Second, a physically sound and suitably parameterised model can predict the effect of a change of certain process parameters, e.g. the flow properties of a fluid or geometrical changes to the filter. This enables the study of different filter or plant configuration variants with fewer actual physical prototypes and experiments. Thus, the time and cost requirements for development and optimisation are reduced.

In this paper, a new method for the design of both filter apparatuses without and filter machines with moving parts for dynamic surface filtration and their optimisation with respect to the specific filtrate flow rate and the specific energy demand will be presented. The method for modelling and estimating both the specific filtrate flow rate and the specific energy demand is described first. Then its application is demonstrated by transfering the results for the specific filtrate flow * Dipl.-Ing. Jakob Barth Prof. Dr.-Ing. Siegfried Ripperger Kaiserslautern E-Mail: Jakob.Barth@mv.uni-kl.de

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rate from a channel module to a rotating disc filter. The dependence of the specific energy demand on selected process parameters is given for both the channel module and the rotating disc filter. Thus, the ideal filter and plant configuration and process parameters with respect to the specific energy demand can be determined.

2. Model and method for estimating the specific filtrate flow rate and the specific energy demand in dynamic surface filtration The most common type of dynamic surface filtration is cross flow filtration: The suspension to be filtered flows across the filter medium in capillary, tubular, or channel modules. Other concepts and filters to create the relative movement between the suspension and the filter medium include e.g. rotating disc (radial shear gap) filters in which the suspension passes slowly through the filtration chamber with the rotating filter discs with the filter medium attached to the rotating discs.

In dynamic surface filtration the formation of a filter cake is impeded by suitable cross-flow conditions. In contrast to static surface filtration, a steady-state filtrate flow rate is reached at steady-state process parameters, especially filtration pressure and cross-flow conditions. This steadystate operation can be maintained for an extended period. The models described below always refer to the steady-state conditions.

2.1 Model for the specific filtrate flow rate The common models for the design of dynamic surface filters give the volumetric filtrate flow rate per area (specific filtrate flow rate) for a certain suspension

and a certain filter at any given filtration pressure and/or cross-flow conditions.

Usually, these models, are based on experimental results for the specific filtrate flow rate. With these models a transfer of the results to other filters usually is not possible. Therefore, a new method has been developed to do this. It is based on an empirical model for the dependence of the specific filtrate flow rate on the filtration pressure and the wall shear stress.

The specific filtrate flow rate vF is determined by the following process and material parameters: filtration pressure ΔpF, wall shear stress τW, solids volume concentration of the suspension cV,Sus, temperature of the suspension θSus, dynamic viscosity of the liquid phase of the suspension (filtrate) ηF, flow resistance of the filter medium RFM, and properties of the solid phase of the suspension. For the dependence of the specific filtrate flow rate on all the process and material parameters, empirical or physical models have been identified. In this paper,, only the dependence on the filtration pressure and the wall shear stress for a certain suspension at constant solids concentration and temperature will be considered.

At low filtration pressure, less than the limiting filtration pressure ΔpF < ΔpF,lim, practically no deposition of particles on the filter medium occurs, so no particle layer is formed. Thus, the specific filtrate flow rate is determined by the material and model parameter effective flow resistance of the filter medium RFM (membrane controlled regime) and increases linearly with the filtration pressure: (1) At high filtration pressure, greater than the limiting filtration pressure ΔpF > ΔpF,lim deposition of particles on the filter F & S International Edition

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medium occurs, so a particle layer is formed. Thus, the specific filtrate flow rate is limited to the limiting specific filtrate flow rate vF,lim by the flow resistance of the particle layer (layer controlled regime) and is independent of the filtration pressure: (2) Combining eq. (1) and (2), the dependence of the specific filtrate flow rate on the filtration pressure can be expressed more concisely:

DIE DRAHTWEBER

(3) The limiting specific filtrate flow rate is determined by the flow of the suspension across the filter medium. The process parameter characterising the cross-flow conditions irrespective of the filter type is the wall shear stress τW. The dependence of the limiting specific filtrate flow rate on the wall shear stress can be modelled using a power law: (4) with: kτ shear stress parameter nτ shear stress exponent reference filtrate flow rate vF,0 τ0 reference shear stress The shear stress parameter and the shear stress exponent are empirical model parameters. The reference filtrate flow rate and the reference shear stress can be chosen arbitratily, while the values of the model parameters change accordingly.

The dependence of the specific filtrate flow rate on both the filtration pressure and the wall shear stress is modelled according to eq. (3) and (4):

(5) The local filtration pressure and wall shear stress can be calculated using any suitable method: Model equations, if they exist for the flow in a filter, enable easier estimation of the model parameters by fitting the model to the experimental results and usually require less computational cost. If no model equations exist Computational Fluid Dynamics (CFD) simulations can be used to calculate the flow in any filter. In this case, the estimation of the model parameters is more laborious and the computational costs are usually higher.

2.2 Local and average specific filtrate flow rate Across the filter area of a certain filter, the local filtration conditions (local values of the filtration pressure or wall shear stress) may vary: The local filtration pressure decreases linearly along the module in capillary, tubular or channel modules due to the frictional pressure drop on the concentrate (suspension) side. In rotating disc filters it decreases with the radius of the filter disc due to the hydrostatic pressure on the filtrate side as the filtrate on the inside rotates with the filter disc.

The local wall shear stress is almost constant in capillary, tubular or channel modules as long as the filtrate flow rate is substantially smaller than the suspension flow rate. In rotating disc filters, on the other hand, it increases with the radius of the filter disc due to the increasing circumferential velocity of the filter disc, and hence the increasing relative movement between the filter disc and the suspension.

From the different local filtration conditions different local values of the specific filtrate flow rate may result. Different cases will be discussed for the different filters in sec. 3.

Eq. (5) models the dependence of the local specific filtrate flow rate vF on both the filtration pressure and the wall shear stress F & S International Edition

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Highlights 2018

· Fig. 1: Plant configuration with a channel module, feed flow rate Vin , · · loop flow rate VSus , and filtrate flow rate VF.

across the filter area AF. However, the quantity that is measured experimentally and that is relevant for the application of the process is the average specific fil– trate flow rate vF, as has been shown by Altmann [1]: (6) Solving the integral analytically to obtain a closed-form expression for the average specific filtrate flow rate is possible only for a few special cases. In most cases, solving the integral and calculating the average specific filtrate flow rate can only be done numerically.

2.3 Estimation of the specific energy demand The different filters for dynamic surface filtration can be operated in different plant configurations. The specific energy demand eF is caused primarily by the energy demand for maintaining the average filtration pressure Δ–pF in capillary, tubular, or channel modules (pressure in the filtration chamber pF in rotating disc filters) and for maintaining the flow of the · suspension VSus across the filter medium in capillary, tubular, or channel modules (rotational speed of the filter disc nF in

rotating disc filters). Given a suitable plant design, the energy demand for the flow of the suspension and the filtrate · VF in the rest of the plant is negligible in comparison.

Thus, for the channel module operating in a suitable plant design (see fig. 1) the specific energy demand is:

solids volume concentration cV,Sus = 0.52 % b.v. at a temperature of θSus = 20 °C is used as a model system. It has a density of ρSus = 1019 kg/m3 and a dynamic viscosity of ηSus = 1.23·10-3 Pa s. A flat sheet membrane Accurel PP 2E HF (R/P) from the Membrana GmbH with a nominal pore size of dPr = 0.2 μm is used as a typical microfiltration filter medium.

(7) For the rotating disc filter (see fig. 2) with the torque of the rotating filter disc MF the specific energy demand is:

3.1 Experimental estimation of the model parameters in the channel module The filtration characteristics of the suspension are investigated in a custom-made channel module. It has a flow cross section of AK = 40 x 3 mm2 = 120 mm2 (which results in a hydraulic diameter of dK,h = 5.58 mm) and a length of LK = 360 mm. The active filter area is AF = 30 x 360 mm2 = 0.108 m2. The filtration pressure decreases linearly from the pressure at the channel inlet pSus (x = 0) along the channel (x-coordinate) due to the frictional pressure drop on the concentrate (suspension) side. The wall shear stress is constant for the entire filter area.

Both quantities can be calculated easily employing the equations for turbulent flow in a channel (Blasius equation):

(8) When the method for the estimation of the specific filtrate flow rate described above is applied, all the quantities for the estimation of the specific energy demand are calculated.

3. Application example As an example for the application of the model and method, the dynamic surface filtration of an aqueous mineral suspension is presented. A suspension of aluminium oxide (Al2O3) CT 3000 LS SG from the Almatis GmbH in pre-filtered water with a

Fig. 3: Experimental and calculated results for the dependence of the average specific filtrate flow rate v–F on the average filtration pressure – ΔpF at different values of the wall shear stress τW (equivalent to the mean loop flow rate vK ) with the aluminium oxide (Al2O3 ) suspension in the channel module.

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· Fig. 2: Plant configuration with a rotating disc filter, feed flow rate Vin , · · loop flow rate VSus , filtrate flow rate VF and rotational speed of the filter disc nF .

Fig. 4: Local filtration pressure ΔpF determined via Computational Fluid Dynamics (CFD) simulation for the filtration area of the rotating disc filter at an average wall shear stress of –τW = 124 Pa (equivalent to a rotational speed of the filter disc of nF = 2000 1/min) and a pressure in the filtration chamber of pF = 1.2 bar.

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Fig. 5: Local wall shear stress τW determined via Computational Fluid Dynamics (CFD) simulation for the filtration area of the rotating disc filter at an average wall shear stress of –τW = 124 Pa (equivalent to a rotational speed of the filter disc of nF = 2000 1/min).

(9) (10) ReK channel Reynolds number vK mean flow velocity The experiments are performed at values in the range of Δ–pF = 0.2–1.2 bar for the average filtration pressure and τW = 50–150 Pa for the wall shear stress (equivalent to vK = 4–7 m/s for the mean flow velocity). The experimental results for the average specific filtrate flow rate are given in fig. 3 together with the average values calculated according to the model in eq. (5) and (6). The values for the model parameters are obtained by fitting the model to the experimental results: RFM = 5.31·1010 1/m kτ = 4.25·10-5 for vF,0 = 1 m3/m2 s nτ = 0.63 for τ0 = 1 Pa It can be seen that at low values of the average filtration pres– sure ΔpF < 0.3 bar the values of the average specific filtrate flow rate are the same for all values of the wall shear stress. The average filtrate flow rate increases linearly with the average filtration pressure. In this range of the average filtration pressure, the local filtration conditions for the entire filter area are in the membrane controlled regime, as the values of the local filtration pressure are less than the limiting filtration pressure ΔpF ≤ ΔpF,lim. At higher values of the average filtration pressure, the values of the average with:

specific filtrate flow rate increase asymptotically to their respective limiting specific filtrate flow rates. In this range of the average filtration pressure, the local filtration conditions start to shift from the membrane controlled to the layer controlled regime, as the values of the local filtration pressure reach the respective limiting filtration pressures. At high values of the average filtration pressure – ΔpF > 0.8 bar, the values of the average specific filtrate flow rate have reached the respective limiting specific filtrate flow rates for all values of the wall shear stress. In this range of the average filtration pressure, the local filtration conditions for the entire filter area are in the layer controlled regime, as the values of the local filtration pressure are greater than the limiting filtration pressure ΔpF > ΔpF,lim.

Furthermore, it can be seen, that the transition between filtration conditions completely in the membrane controlled regime and completely in the layer controlled regime occurs over a wider range of the average filtration pressure at increasing values of the wall shear stress (equivalent to increasing mean flow velocity).

In this range of the average filtration pressure, the local filtration conditions start to shift from the membrane controlled to the layer controlled regime (see above). The limiting filtration pressure is between the values of the local filtration pressure at the channel inlet and the channel outlet ΔpF,in < ΔpF,lim < ΔpF,out. The frictional pressure drop along the channel ΔpK = ΔpF,in – ΔpF,out increases with the wall shear stress (equivalent to the mean flow velocity) according to the equations for flow in a channel. Thus, the transition occurs over a wider range of the average filtration pressure.

3.2 Transfer of the results to the rotating disc filter With the values for the model parameters, that have been obtained in the channel module, the average specific filtrate flow rate in a rotating disc filter can be calculated. The rotating disc filter used is a laboratory filter CRD-01-152 SS from the Novoflow GmbH. It has a single custom-made filter disc for the use of the flat sheet membrane. The active filter area has a diameter in the range of dF = 40–127 mm. Due to the different construction of the filtrate side, the effective flow resistance of the filter medium is greater than that in the channel module: RFM = 1.46·1011 1/m. The shear gap between the filter disc and the wall of the filtration chamber · is sF = 47.6 mm. The flow rate of the suspension is VSus = 1 L/min.

For the calculation of the specific filtrate flow rate in the rotating disc filter, the local filtration pressure ΔpF and wall shear stress τW have to be calculated first. While the pressure in the filtration chamber pF is constant, the filtration pressure decreases with the radius of the filter disc due to the hydrostatic pressure on the filtrate side. It can be calculated easily employing the equations from basic fluid mechanics: (11)

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Fig. 6: Local specific filtrate flow rate vF of the aluminium oxide (Al2O3 ) suspension calculated according to the model in eq. (5), based on the results of the Computational Fluid Dynamics (CFD) simulation, for the filtration area of the rotating disc filter at an average wall shear stress of –τW = 124 Pa (equivalent to a rotational speed of the filter disc of nF = 2000 1/min) and a pressure in the filtration chamber of pF = 1.2 bar.

Fig. 7: Experimental and calculated results for the dependence of the average specific filtrate flow rate v–F on the pressure in the filtration chamber pF at different values of the average wall shear stress –τW (equivalent to the rotational speed of the filter disc nF ) with the aluminium oxide (Al2O3 ) suspension in the rotating disc filter.

The wall shear stress, on the other hand, increases with the radius of the filter disc due to the increasing circumferential velocity.

Schiele [2] has given equations to model the local wall shear stress with the local disc Reynolds number ReF:

increasing circumferential velocity (see above). On the other hand, the local specific filtrate flow rate exhibits a distinct maximum at approximately half the radius of the filter disc: At small values of the radius of the filter disc, the local filtration pressure is high, while the local wall shear stress is low. Thus, the local filtration conditions are in the layer controlled regime, and the local specific filtrate flow rate is low due to the low limiting specific filtrate flow rate. At great values of the radius of the filter disc, the local filtration pressure is low, while the local wall shear stress is high.

Thus, the local filtration conditions are in the membrane controlled regime, and the local specific filtrate flow rate is low due to the low filtration pressure.

The experiments are performed at values in the range of pF = τW 0.4 –2.2 bar for the pressure in the filtration chamber and – = 3 –124 Pa for the average wall shear stress (equivalent to nF = 200 –2000 1/min for the rotational speed of the filter disc). The experimental results for the average specific filtrate flow rate are given in fig. 7 together with the average values calculated according to the model in eq. (5) and (6).

It can be seen that, in contrast to the results in the channel module, at low values of the pressure in the filtration chamber pF < 0.8 bar the values of the average filtrate flow rate are no longer the same for all values of the average wall shear stress (equivalent

(12) (13) (14) Additionally, Computational Fluid Dynamics (CFD) simulations of the flow in the rotating disc filter at a pressure in the filtration chamber of pF = 1.2 bar and an average wall shear stress of – τW = 124 Pa (equivalent to a rotational speed of the filter disc of nF = 2000 1/min) have been performed. The models for the local filtration pressure and wall shear stress according to eq. (11), (12), and (13) agree with the simulation results given in fig. 4 and 5, respectively. With these, the local specific filtrate flow rate is calculated according to the model in eq. (5) and given in fig. 6.

It can be seen, that the local filtration pressure decreases with the radius of the filter disc due to the hydrostatic pressure on the filtrate side, while the local wall shear stress increases due to the

Fig. 8: Calculated results for the dependence of the specific energy – demand eF on the average filtration pressure ΔpF at different values of the wall shear stress τW (equivalent to the mean loop flow rate vK ) with the aluminium oxide (Al2O3 ) suspension in the channel module.

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Fig. 9: Calculated results for the dependence of the specific energy demand eF on the pressure in the filtration chamber pF at different values of the average wall shear stress –τW (equivalent to the rotational speed of the filter disc nF) with the aluminium oxide (Al2O3 ) suspension in the rotating disc filter.

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to the rotational speed of the filter disc).

Even if the local filtration conditions for the entire filter area are in the membrane controlled regime, as the values of the local filtration pressure are less than the limiting filtration pressure ΔpF ≤ ΔpF,lim, the values of the local filtration pressure are not the same at different values of the rotational speed of the filter disc. At higher values of the rotational speed of the filter disc, the local filtration pressure according to eq. (11) is lower for the entire filter area. At higher values of the pressure in the filtration chamber, the values of the average specific filtrate flow rate increase asymptotically to their respective limiting specific filtrate flow rates, as in the channel module. In this range of the pressure in the filtration chamber, the local filtration conditions start to shift from the membrane controlled to the layer controlled regime. At high values of the pressure in the filtration chamber pF > 1.2 bar, the values of the average specific filtrate flow rate have reached the respective limiting specific filtrate flow rates for all values of the average wall shear stress (equivalent to the rotational speed of the filter disc), as in the channel module. In this range of the pressure in the filtration chamber, the local filtration conditions for the entire filter area are in the layer controlled regime, as the values of the local filtration pressure are greater than the limiting filtration pressure ΔpF > ΔpF,lim.

Furthermore, it can be seen, that the transition between filtration conditions completely in the membrane controlled regime and completely in the layer controlled regime occurs over a wider range of the pressure in the filtration chamber, at increasing values of the wall shear stress (equivalent to the rotational speed of the filter disc). In this range of the pressure in the filtration chamber, the local filtration conditions start to shift from the membrane controlled to the layer controlled regime (see above). The limiting filtration pressure is between the values of the local filtration pressure at the outer and the inner radius of the filter disc ΔpF (rout) < ΔpF,lim < ΔpF (rin). The difference between the local filtration pressure at the outer and the inner radius of the filter disc due to the hydrostatic pressure on the filtrate side increases with the average wall shear stress (equivalent to the rotational speed of the filter disc), according to eq. (11). Thus, the transition occurs over a wider range of the pressure in the filtration chamber.

3.3 Comparison of the specific energy demand for different filters and plant designs When the new method for the estimation of the specific filtrate flow rate is applied, all the quantities are calculated that are required for the estimation of the F & S International Edition

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specific energy demand according to eq.

(7) or (8), respectively. Thus, the comparison of the specific energy demand for different process parameters, filters, and plant designs is possible. In fig. 8 and 9 the dependence of the specific energy demand on the average filtration pressure (for the channel module) or the pressure in the filtration chamber (for the rotating disc filter) is shown for four different values of the average wall shear stress, respectively. Fig. 8 shows the dependence for the channel module according to eq.

(7). Fig. 9 shows the dependence for the rotating disc filter according to eq. (8). All results shown are calculated according to the model equations with the values for the model parameters from sec. 3.1.

It can be seen, that the different filters and plant designs exhibit qualitatively different dependences of the specific energy demand on the average filtration pressure or the pressure in the filtration chamber: In the case of the channel module, it can be seen, that at low values of the average – filtration pressure ΔpF < 0.3 bar the specific energy demand is independent of the average filtration pressure, but increases with the wall shear stress (equivalent to · the loop flow rate VSus). In this range of the average filtration pressure, the local filtration conditions for the entire filter area are in the membrane controlled regime. Thus, the filtrate flow rate increases linearly with the average filtration pressure, and an increase of the energy input due to the filtration pressure results in a corresponding increase of the filtrate flow rate. According to eq. (7), the specific energy demand is therefore independent of the average filtration pressure. At the same time, however, the filtrate flow rate is independent of the wall shear stress. Thus, an increase of the energy input due to the loop flow rate results in no increase of the filtrate flow rate. According to eq. (7), the specific energy demand therefore increases with the wall shear stress.

At higher values of the average filtration pressure, the specific energy demand progressively increases with the average filtration pressure, until the maximum slope is reached. At high values of the – average filtration pressure ΔpF > 0.8 bar, the curves of the specific energy demand for all values of the wall shear stress (equivalent to the loop flow rate) approximately coincide. In this range of the average filtration pressure, the local filtration conditions for the entire filter area are in the layer controlled regime. Thus, the filtrate flow rate is independent of the average filtration pressure, and an increase of the energy input due to the filtration pressure results in no increase of the filtrate flow rate. According to eq. (7), the specific energy demand therefore increases with 43

Highlights 2018

Tab. 1: Different dynamic surface filters, plant configurations, and values of the process parameters to achieve an average specific filtrate flow rate of v–P = 2100 L/m2 h: average filtration pressure – ΔpF and mean loop flow velocity vK for the channel module, pressure in the filtration chamber pF and rotational speed of the filter disc nF in the rotating disc filter, and resulting values of the specific energy demand eF.

the average filtration pressure. At the same time, the filtrate flow rate increases nearly linearly with the loop flow rate · · 1.1 ), and an increase of the energy ( VF ~ V Sus input due to the loop flow rate results in a corresponding increase of the filtrate flow rate. According to eq. (7), the specific energy demand is therefore independent of the wall shear stress.

In the case of the rotating disc filter, it can be seen, that, in contrast to the channel module, the dependence of the specific energy demand on the pressure in the filtration chamber exhibits a distinct minimum. It occurs at the pressure in the filtration chamber, at which the transition of the local filtration conditions from the membrane controlled to the layer controlled regime is complete for the entire filter area.

It can be seen, that, at low values of the pressure in the filtration chamber pF, the specific energy demand strongly decreases with the pressure in the filtration chamber, but increases with the average wall shear stress (equivalent to the rotational speed of the filter disc). With increasing values of the average wall shear stress, the slope increases, and the decreasing section of the curve shifts towards higher values of the pressure in the filtration chamber. In this range of the pressure in the filtration chamber, the local filtration conditions for the entire filter area are in the membrane controlled regime. Thus, the local specific filtrate flow rate increases linearly with the local filtration pressure ΔpF. At very low values of the filtration pressure, the invariable energy input due to the wall shear stress of the rotating filter disc MF·2·π·nF is relatively large, while the filtrate flow rate is very small. According to eq. (8), the specific energy demand therefore goes to infinity with decreasing pressure in the filtration chamber.

At the same time, however, the local filtration pressure, and thus the local specific filtrate flow rate, decrease with increasing average wall shear stress (equivalent to the rotational speed of the filter disc), due to the hydrostatic pressure on the filtrate side, according to eq. (11). Thus, the

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dependence of the specific energy demand on the pressure in the filtration chamber exhibits a decreasing slope with increasing values of the average wall shear stress, and the decreasing section of the curve shifts towards higher values of the pressure in the filtration chamber.

At higher values of the pressure in the filtration chamber, the specific energy demand degressively decreases with the pressure in the filtration chamber, exhibits its minimum, and increases again. At high values of the pressure in the filtration chamber pF > 1.2 bar, the specific energy demand increases linearly with the pressure in the filtration chamber. With increasing values of the average wall shear stress (equivalent to the rotational speed of the filter disc), the slope decreases. In this range of the pressure in the filtration chamber, the local filtration conditions for the entire filter area are in the layer controlled regime. Thus, the local specific filtrate flow rate is independent of the pressure in the filtration chamber, and increases nearly linearly with the rotational speed · of the filter disc ( VF ~ n F1.1). At the same time, the energy input due to the loop flow increases linearly with the pressure in the filtration chamber. According to eq.

(8), the specific energy demand therefore increases linearly with the pressure in the filtration chamber. With increasing values of the average wall shear stress, the slope decreases.

Furthermore, the wall shear stress of the rotating filter disc strongly increases with the rotational speed of the filter disc (τW ~ n F1.8, according to eq. (13)). Thus, the energy input due to the wall shear stress of the rotating filter disc MF·2·π·nF strongly increases with the rotational speed of the filter disc. According to eq. (8), the specific energy demand therefore increases with the average wall shear stress.

4. Optimisation of the specific energy demand in dynamic surface filtration processes Modelling the dependence of the specific filtrate flow rate and the specific energy demand on the process parame-

ters for different dynamic surface filters and plant configurations enables the optimisation with respect to the specific energy demand. The potential for optimisation is demonstrated in the following example: An average specific filtrate flow rate of – vF = 2100 L/m2 h can be achieved using either the channel module at different values of the average filtration pressure – ΔpF and the mean loop flow velocity vK or the rotating disc filter at different values of the pressure in the filtration chamber pF and the rotational speed of the filter disc nF. The local filtration conditions can be either in the membrane or layer controlled regime. The different filters, plant configurations, and values of the process parameters are given in table 1 together with the resulting values of the specific energy demand.

It can be seen, that, for this example, the rotating disc filter at a pressure in the filtration chamber of pF = 1.0 bar and a rotational speed of the filter disc of nF = 1400 1/min yields the least specific energy demand of eF = 0.25 kWh/m3. The local filtration conditions are in the layer controlled regime. Choosing unfavourable filters, plant configurations, and values of the process parameters can result in a specific energy demand up to five times greater.

5. Summary A new method for the calculation of the average specific filtrate flow rate and the specific energy demand of dynamic surface filters and its application to the design and optimisation of dynamic surface filtration processes has been demonstrated. Using a channel module and a rotating disc filter as an example, it has been shown, that, by employing the new method, results for the specific filtrate flow rate can be transfered from one filter to another. Likewise, the process parameters to achieve a given average specific filtrate flow rate in a given filter can be determined. Furthermore, the specific energy demand for a given filter, plant configuration, and process parameters can be calculated. These calculations can be employed to determine the filter, plant configuration, and process parameters with the least specific energy demand to achieve a given average specific filtrate flow rate. The potential for optimisation has been demonstrated.

References [1] Altmann, J.: Partikelablagerung und Deckschichtbildung an überströmten Membranen.

University of Dresden, Diss., 2000.

[2] Schiele, B.: Untersuchungen zur Filtration feindisperser Suspensionen und zur Strömung im dynamischen Druckfilter. University of Stuttgart, Diss., 1978.

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Manufacturing, characterising and using innovative textile filter media A report from the 14th textile filter symposium H. Lyko * Textile filter media can be specifically designed with filtration properties customized to the relevant technical application and corresponding ambient conditions. In the opinion of Dr Ives-Simon Gloy, CEO of the Saxon Textile Research Institute (STFI), who were also the hosts, this benefit underlines the relevance of textile filters being used in the designing of living and working areas and for maintaining mobility. A total of 106 participants discussed new materials, fibres and filter media manufacturing methods, test methods and new simulation and modelling options as well as special filtration applications during the two-day seminar, which was held in Chemnitz. An accompanying exhibition that involved a total of 14 companies and institutes completed the event.

1 Introduction Filter media account for around 3.65% of the European nonwovens market [1] as well as around 10% of the global production volume of technical nonwovens. The latter figure was quoted by Dr. Ingo Mählmann, from Oerlikon Nonwovens GmbH, as part of his presentation (see Chapter 3). According to a market study carried out by Smithers Pira, an annual growth rate of 5.6% is expected for nonwoven filter media from 2015 until 2019 [2].

Oerlikon also anticipated even stronger growth beyond 2019 due to the above-average market developments in China and India. The multiplicity of air, gas and liquid filter applications has resulted in extremely high filter media diversification. Various manufacturing methods are available for this and reports covering the latest developments were given in various lectures. Filter testing, including the use of ISO16890 for testing ventilation filters, was another main topic. Filtration applications using different filter media in different industries as well as filter media development simulations were on the agenda on the second day of the event.

spondingly higher on the test duct. Topas has developed a mobile platform, which enables the aerosol to be redirected upwards.

The A2 fine dust, which is needed in a concentration of approx.

140 mg/m3, is dosed using a brush generator so that the constant dust dosage at different volumetric air flows can be set up via the transport speed. The various aerosols are applied at defined positions inside a large mixing chamber that is part of the test system, in order to realise uniform distribution. The fractional separation efficiency of the filters is ideally measured using two clean gas meters (one each on the filter‘s upstream and downstream sides).

The IPA conditioning cabinet is designed to produce the required

2 Testing and standardising Converting ventilation filter testing from the now invalid EN779 to the new ISO 16890 still involves test institutes, test system manufacturers and filter manufacturers. Even though the method for determining separation efficiencies with regard to the PM1, PM2.5 and PM10 particle fractions has already been specified (see [3] as well), filter energy classification procedures as well as those for designing filters according to DIN EN 16798-3 still have to be determined. Thorsten Stoffel, from Fläkt Group Germany, described them in a plenary address. The contents can be read in detail in [4].

Topas GmbH, being a supplier of air filter components and test stands, had to meet the challenges arising from the new standard with regard to the design of their test stands. Christian Wabnitz described the technical implementation with regard to the generation and uniform distribution of test aerosols from DEHS, KCl and A2 fine test dust, the aerosol sampling and analysing and conditioning the filters with isopropanol (IPA) as well as evaluating the final data. Implementing the KCl aerosol dosing to be used for determining the fractional efficiencies up to 10 μm (PM10) means an increased workload for test stand operators as the nozzles of the aerosol generators available on the market tend to clog and they have to be cleaned every 8 hours. The generator‘s outlet is at the bottom of the apparatus and it would have to be mounted corre* Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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Tab. 1: Proportions of different types of nonwovens used in filter media (production quantities of filter media in tons are about twice as high for liquid filters as for air/gas filter media) (Source: Mählmann lecture, Oerlikon Nonwovens)

volume of IPA vapour from a maximum of one litre of solvent and to simultaneously prevent condensation on the test piece.

IPA vapour leaking into the environment is impeded by using an automated safety design and an integrated rinsing cycle. The test procedure, data recording and evaluation are carried out automatically through the use of the appropriate software.

In his presentation Martin Schmidt, from Palas GmbH in Karlsruhe, did not refer to the testing of complete filter elements, but to filter media testing according to ISO 16890, which can be realised by using the MFP 3000 filter media test stand made by his company. It is also fitted with DEHS, salt (KCl and NaCl) aerosol generators and test dusts, but for correspondingly smaller quantities and volumetric air flows, which are adjusted to use a test medium area of 100 cm2.

A KCl generator for generating the appropriate volumetric flows is not described in the standard, so it was developed in-house.

The LSPG 16890 (Large Salt Particle Generator) aerosol generator provides KCl aerosol for a volumetric air flow in the 20 1,200 l/min range and ensures that at least 500 counter events occur in each size class that has to be measured in order to ensure that the fractional efficiencies are measured with sufficient accuracy. The aerosol generator nozzle is made from water-repellent Teflon in order to prevent the previously mentioned clogging. Schmidt presented measurement results from using latex standard particles and they showed that both the size resolution of the whitelight aerosol spectrometers used and the particle loss due to sedimentation in the duct (measured by taking measurements in the empty duct) meet the ISO 16890 requirements.

Dr Stefan Schumacher, from the Duisburg Institute for Environmental and Energy Technology (IUTA), studied the effects that the different methods used for discharging electret filters had on the collection efficiency. Electret filters contain quasi-permanent charges on the fibres, which, in addition to mechanical particle retention, also act by electrophoresis (attraction of oppositely charged particles to the medium) and dielectrophoresis (induction of dipoles in the particles that

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have to be separated). Specific unipolar charged aerosols were produced and channelled into the filter medium using a self-developed diffusion charger. This showed that charged particles can be separated more efficiently than uncharged particles, even though the difference between the positive and negative particle charges was rather small. As the electret effect also decreases with increasing particle loading, air humidity or solvents, many test standards need the filter media to be discharged or aged in order to obtain more realistic results. A change from discharging by impregnation in liquid IPA to discharging in IPA vapour was introduced with the change from EN 779 to ISO 16890. The three different media showed different separation efficiencies for soaked filter media as compared to media discharged using vapour. In addition to the question of whether soaking can lead to structural changes in a filter medium (the media feel softer after soaking) it also appears to be very important to ensure that the discharge has really been completed. An important application field for electret filters are indoor air purifiers, which are tested by using cigarette smoke to induce ageing.

A separate method was developed that is considered to be more realistic in addition to ageing in compliance with the applicable standard. The two ageing methods are described in [5].

Ralf Heidenreich, from the Institute for Air Handling and Refrigeration (ILK) in Dresden, reported on the performance testing of filtering separators used in production facilities, including ultra-fine aerosols. Their filter designs as well as the quantities, particle sizes and chemical properties of the dusts that have to be separated are as varied as the industrial processes in which they are produced.

Against the background of the amended Air Quality Control regulations and the expected tightening up of workplace limits, a test procedure has been developed within a BMWI project that enables emission values for the PM1, PM2.5 and PM10 particle fractions to be predicted and this will serve as the basis for a yet to be created test standard.

Dr Barbara Schimanz, from STFI, together with Dr Volker Bauer, from bg

filtration GmbH, jointly presented a project for the development of filter media with subsequent long-term testing of the material found on a drum filter used in an industrial application. Drum filters with high filter surface loads are used for filtering huge quantities of air, e.g. during the production of fibre materials. During the development of the filter medium, the focus was on an air permeability of above 700 l/(m2s) with a simultaneously high separation efficiency up to the PM2.5 range, a high dust storage capacity and good regenerability. The media should also be usable at temperatures up to 200°C and have a long service life when working with at a pressure difference of 100 Pa. Pile-fibre nonwovens were developed for this purpose and they were produced on a knitted mesh machine in accordance with the so-called Voltex process. This is one of several knitting processes that were developed and used in the Chemnitz textile region in the old East Germany. Pile-fibre nonwovens are „textile fabrics made from a fibrous weave with or without the use of a base material, and they consist of a fibre mesh side as well as a pile-fibre side in which the fibres are arranged so that they are virtually perpendicular to the fibre mesh layer“ (definition as per DIN 61211 [6]). Fig. 1 shows the structure of such a filter medium that is about 9 mm thick.

Various test media were produced from different base webs (nonwovens, fabrics as well as malivlies and Kunit nonwoven fabrics (see [6]) by combining them with different light-weight nonwovens into knitted meshes. After the media was characterised and the fractional separation efficiencies were determined at the ILK in Dresden, the two favoured variants, which had been produced using malivlies as the base web and a needle nonwoven as the pile layer, were tested on a drum filter test stand at bg filtration, one of the industrial partners, using wood chips and glass fibres over a long time period. The filter surface load was 27 – 42 m3/(m2 min), which is about 10 times higher than that of a bag filter. A continuous extraction system is used for the cleaning inside a drum filter, where the flow is from the inside to the outside.

The maximum filter surface load, which can be reversibly cleaned with this system, was also determined. An energy calculator was also developed to determine the energy consumption of this type of drum filter under different operating conditions, as part of the research project. Accordingly, a drum filter for a volumetric air flow of 100,000 m3/h will only consume around 44% of the energy that a bag filter with jet pulse cleaning would need for handling the same quantity of air.

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SEFAR® PHARMA GMP Filter Media Solutions

Fig. 1: Non-woven pile fabric, produced by the Voltex process, refined surface (Image: STFI)

3 Fine-fibre technologies used in filter media Fine fibres play an important role in the separation of submicron particles with a tolerable pressure drop. Falling prices and the increased availability of fine fibre media can be attained through the use of more powerful production machines. Raphael Hermes, from Reifenhäuser Reicofil, presented the RF5 generation of systems for the production of spunbond nonwovens and meltblowns, which, in addition to generating a 35% increase in throughput, also feature up to 15% lower energy consumption when compared to predecessor machines. Using the meltblow process, Hermes explained how to increase stretching capability without causing instabilities in the yarn forming process such as shots (material accumulations created through filament tearing) or fibre fly. The most important issue is to avoid turbulences and excessive expansion of the free jet at the nozzle. This was realised through modifying the nozzle geometry and changing the air flow. It was also shown that the plant can be operated so that the distribution of the fibre diameters produced does not shift up to higher values despite the increase in throughput. The new meltblow plant now produces fibres with the same diameter distribution at a throughput rate of 70 kg/h/m as was realised by the previous system at 20 kg/h/m.

As reported by Dr Ingo Mählmann, vice-president at Oerlikon Nonwoven, filter media made from extruded thermoplastic polymers (meltblowns and spunbond nonwovens) are gaining in importance for use in air filtration systems at the expense of carded needle felts. Around half of all the media used in liquid filtration are meltblowns or spunbond nonwovens (see Table 1). Spunbond nonwovens are generally used to meet low to medium air and liquid filtration and meltblown requirements in high-performance air filtration. Media with higher surface weights are generally used for liquid filtration. The most commonly used polymers are PP (polypropylene), PET and PBT (polyethylene or polybutylene terephthalate). Oerlikon‘s innovations for manufacturing nonwovens include a revised extraction nozzle for the spunbond nonwoven machines, which reduces the compressed air level required for fibre stretching from about 3.5 to less than 1-bar. Considerable energy savings can be made through this. A redesigned forming zone improves the surface weight profile. With regard to the production of spunbond nonwovens, the company also has a wide range of options both for the production of bi-component fibres (some examples can be seen in Fig. 2) as well as a spinning package for mixed fibres. The latter enables fibres with different functionalities (i.e. titre, cross-sectional shape, polymer) to be combined in a single production step. With regard to the meltblow process, the design of the spinning head and process air nozzles

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Sefar AG Hinterbissaustrasse 12, CH-9410 Heiden Tel. +41 71 898 57 00, Fax +41 71 898 57 21 47 filtration@sefar.com, www.sefar.com

Highlights 2018

Tab. 2: Application areas for hot gas filter media (as per lecture given by T. Thiem, Norafin)

Fig. 2: Microscope images of various bi-component fibres (Image: Oerlikon Neumag)

has been improved in order to attain higher throughputs with reduced shot building tendency and improved nonwoven weight uniformity (reduced cloudiness). This was also realised through improved melt distribution and by using the same polymer residence time in the entire spinning package.

The distance from the delivery conveyor and its speed also determine the nonwoven properties in addition to the nozzle geometry, polymer throughput and air flow. With a multifunctional and WLAN controlled screen belt table, parameters such as fleece thickness and air permeability can be flexibly adjusted via the spinning height, the horizontal spinning position and the multisegmented and separately-adjustable

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intake boxes. In order to generate the electret effect for meltblowns, the company presented a highly flexible inline charging unit for the first time in 2017 and this is now fully integrated into the meltblown plant control system. It is possible to adapt the electrical charging to the application and material by varying the charging units.

Research has been ongoing for some time at the German Institutes for Textile and Fibre Materials (DITF) in Denkendorf, Germany, into the further development of melt spinning processes for the production of finer fibres. Ingo Windschiegl presented the developments over the last few years as well as the current state-of-the-art meltblow technology used for spinning poly-

propylene (PP). The results of the BMBF‘s joint NaBlo project (see [7]) and the work based on them were also presented.

The DTIF have a 500 mm wide meltblow unit that is used to study the effects of the polymer melt (material, throughput, melt temperature and melt viscosity), air temperature, velocity and airflow guidance as well as nozzle geometry and other parameters on the cross-sectional distribution of the fibres. The nozzles used in this system have a lower number of outlet holes than those used in commercial systems, which makes it possible to realise relatively high throughputs per nozzle using comparatively low quantities of polymer. Fig. 3 shows the plant‘s processing diagram. Heating the secondary air in the fibre stretching zone was introduced in the NaBlo project (nano-meltblown fibres for filter media) as an important element on the way to thinner fibres. Recent developments have involved the spin nozzle geometry and the properties of the polymer being used.

A spin nozzle with a diameter of 0.2 mm and an L/D ratio of 60 (L/D <15 in commercial systems) enables pre-orientation of the polymers to be used. Stiffening of the nozzle tip results in increased pressure stability and this makes higher polymer throughputs possible. The spin nozzle manufacturing process was developed in-house. PP variants were studied for use as spinning polymers as they make it possible for an increased mass flow to pass through the spin nozzle. Both the new commercial polymer and an experimental polymer from Borealis can be processed at a higher temperature (320° instead of 300°C), which will also increases the nozzle‘s throughput. All in all, these changes make it possible to attain a fibre fineness of around 0.4 μm.

By developing the smart-melamine polymer, the Thuringian Institute for Textile and Plastics Research has succeeded in producing a flame-resistant spunbond nonwoven from a thermosetting material.

Smart-melamine, which was presented by Yvonne Ewert, is an etherified melamine resin (MER = Melamine Etherified Resin) that is meltable and chemically and thermally cross-linked after nonwoven formation. This is realised by blowing in dry HCl gas and subsequent thermal treatment at 300°C. The material‘s flame-resistant effect comes from nitrogen being released at the start of combustion. The large-scale production of this nonwoven fabric, in which fibre fineness‘s of between 0.5 and 25 μm are possible, is carried out by an especially founded company called smartMELAMINE that is based in Slovenia and testing and marketing are undertaken by the German company, BinNova GmbH. Markus Langner, from BinNova, described

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into a Nomex spunlace for filtration up to 200°C and sintered metal nonwoven media and carbonised spunlace media with metal backing for high temperature applications. In the former, the change from needle felt to spunlace can increase the separation efficiency with less material being used. Nomex (m- / p-Aramid) is a proven flame-resistant material used for high-temperature dust extraction and its efficiency can be increased by using an equally flame-resistant meltblown with finer fibres. Metallic nonwovens can be produced by loading polymer fibre nonwovens with metal powders and subsequent sintering (see [8]). The first prototypes of combined carbonised spunbond fabric and a metallic support mesh proved to be highly efficient, temperature-stable and considerably more robust than a pure carbon fibre medium.

Fig. 3: Diagram of the plant used at DITF for further developing meltblow technology (Image: German Institute for Textile and Fibrous Materials, Denkendorf)

the media‘s properties for various applications. Media with fibre diameters of 0.5 - 10 μm and surface weights of 20 – 200 g/m2 were studied during the filtration process. Up to now, filter media have been produced up to the F8 performance class (according to the old EN779, 70% ePM1 or 80% ePM2.5, measured with DEHS), which, due to their lower densities, have a lower pressure drop than glass fibre media. Lamination on a spunbond or glass fibre material is recommended for foldable media. Flame-resistant filter media with a width of up to 2,400 mm should be available as from June 2018.

In 2005, Elmarco, a Czech company, presented the first largescale plant for the Nanospider nozzle-free electrospinning process, which coats large-format media with synthetic nanofibres. The original design of the transmitting electrode, which was a roll, has now been replaced by a wire, on which the spinning solution is spread by a carriage that moves along the wire. Dr Michal Vaniček showed the established process with wire electrodes running along both sides of the medium that has to be coated as well as a newly developed process based on a collector electrode designed as an endless strip. Motivation for the new development arose from the limitations imposed by the conventional process with regard to coating synthetic media with very low or no electrical conductivity. Due to the electrostatic properties of the substrate, the electric field between the electrodes located on opposite sides of the substrate is disrupted and the nanofibres formed at the transmitting electrode do not reach the substrate‘s surface. The new collector electrode, manufactured as an endless strip, consists of a special composite material that dissipates the charges accumulated on the substrate. This electrode design not only increases the variety of substrates that can be coated, it also shows that a higher coating uniformity can be realised than when using a collector electrode designed as a wire.

Tobias Thiem, from Norafin Industries, reported on recent developments in increasing the efficiency of hot gas filter media.

Table 2 gives an overview of hot gas filter media for use at different temperature levels. The existing options used to increase the efficiency of low-temperature filter media, such as the use of finer fibres, special fibre cross-sections, membranes or multi-layer media, are only of limited practicability with high-temperature media. The Norafin approaches include the use of waterjet bonded spunlace made from PolyPhenylene Sulphide (PPS) as an alternative to a needle felt made from the same polymer for the temperature range up to 190°C, the incorporation of a melamine meltblown

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4 Filter media processing and applications Ultrasonic applications are well-proven when filter media is assembled into ready-to-install filters. Thomas Fischer, from Herrmann Ultraschalltechnik, explained the ultrasound operating principle and showed his company‘s technology portfolio that covers the entire filter production process chain. Ultrasonics are used on an industrial scale for cutting, punching, embossing and

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Simulation and modelling

Fig. 4: Options for producing a light-emitting tissue by incorporating light-emitting PMMA fibres. Left image, UV light is only emitted at the cut ends of the fibres. Two images on the right, the fibres are coated with an acrylate in which microparticles are dispersed.

(Image: Deutsches Textilforschungsinstitut Nordwest, Krefeld)

welding filter media as well as for the connections between the filter media and the frames / housings. The advantage of using ultrasonics is the low energy input and the low stress on the materials being processed. The use of ultrasonics during the manufacturing of nonwovens has not yet been established, but it is being tested. One expects the thermo-mechanical bonding of nonwovens by ultrasonics to result in a higher strength from the mixed fibres. The fact that ultrasonic systems have neither heating up nor cooling down phases is also considered to be an advantage. Fischer showed microscope images of PP nonwovens that had been bonded by water jets, thermally or by ultrasonics, the latter by using an smooth or a contour roll. One could see that it was possible to identify differences in the included fibre structures and they still have to be evaluated. Ultrasonic bonding meets its physical limit at low surface weights. Another application that was discussed was the ultrasonic dewatering of a waterjet bonded nonwoven to relieve the load on the downstream drying section.

Dr Wolfgang Mölter-Siemens, from IUTA, reported on the re-entrainment phenomena found in compressed air filters, i.e. the carrying along of previously separated oil droplets by the air flow on the filter‘s clean gas side. This work was previously presented at the Palas Air Filtration Seminar 2017, which was covered in [5].

The development of light-emitting textile structures can solve a major problem with regard to the realisation of hybrid processes for particle filtration and simultaneous photocatalytic pollutant elimination: namely, to bring light into the more complex filter elements that cannot be illuminated from the outside by a single large light source mounted outside the filter apparatus. Dr Thomas Bahners, from the German Textile Research Institute 50

North-West in Krefeld, exhibited the options developed together with IUTA, the University of Duisburg-Essen and the Leibniz Institute for Surface Modification, for stimulating UV light emissions through the entire length of textile threads or fibres. Fibres emit light that has been guided into them, when total reflection in them is disrupted or completely eliminated, for example by strong bending, integration of scattering centres into the surface or roughening of a coating or the fibre‘s surface. Light-emitting fibres with coatings containing corundum and openmesh fabrics made from them as well as fabrics made from mechanically-roughened monofilaments made from polymethylmethacrylate (PMMA) were exhibited here. The degradation of IPA from air was tested in two different experimental setups, one was based on ISO 22197 (test standard for catalytically active ceramics that the flow passes over) and the other used a duct in which the medium was positioned like a house roof so that the contaminated air had to pass through the medium (IUTA setup). It was found that the degradation rates of the media that allowed the flow to pass through were similar to or slightly higher than those of the catalytic ceramics where the flow passes over them, but with energy consumptions reduced to about 40% of that of conventional systems. During the production of such light-emitting, flow-through media, it is fundamentally possible to implement the surface treatment of individual fibres or threads before they are integrated into a fabric or even to implement the surface modification on a finished fabric (see Fig. 4). Especially attractive in terms of energy consumption is the coupling of „internal lighting“ with a pollutant monitor in front of a filter: the light source is only turned on when the photocatalytic effect is really needed.

The random arrangement and orientation of separate fibres is an essential nonwoven property. Heterogeneities, which can also be expressed as cloudiness, also cause a heterogeneity of flow properties.

Dr Dietmar Hietel, from the Fraunhofer Institute for Industrial Mathematics (ITWM) in Kaiserslautern, works on the clarification of fibre structures by modelling the filament dynamics and the structure built by the fibres that are placed down on a transport belt according to the manufacturing parameters. The FIDYST simulation tool can be used to simulate the dynamics of a filament, e.g. in a spunbond nonwoven machine. Overlaying a large number of filaments creates the nonwoven structure, but this type of simulation is extremely complex. It is simplified by a stochastic substitute model that instead of simulating the dynamics of each individual filament on its way from the nozzle to its position, it simulates the image of the filament arriving in its position as a curve with a given stochasticity (see [9]).

Stochasticity is a measure used for the random proportion of filament positioning, i.e. the positioning probability of a filament in both coordinate directions on the positioning plane is subject to normal distribution. Distribution of the surface weight and also that of the local permeability of the unwoven results, but this depends on the stochasticity (calculated as the square of the noise level in relation to the throw distance). It is currently possible to assess the stochasticity range that would be needed for optimum surface coverage and it is also known that commercial nonwovens are not yet at their optimum level. However, there is currently no way to measure the noise level during fibre placement.

The GeoDict simulation tool was originally developed at Fraunhofer ITWM, but has been continuously further developed and marketed by Math2Market GmbH for some time now. As Dr Jürgen Becker explained, this simulation software can be used to simulate, analyse and optimise μm-scale filter structures from microscopic images as well as for modelling new materials without a real original. Becker also gave an example of new filter medium modelling without using a real template.

By simulating the multi-pass tests (oil filtration using ISO A2 fine test dust) the optimum distribution of two fibre types with a diameter ratio of 20:4 at a volume ratio of 60:40 should be found, which leads to the maximum particle absorption capacity during oil filtration at the same pressure drop (in the clean state) and same initial efficiency. The work is described in detail in [10]. Three fibre distribution F & S International Edition

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variants were considered, a homogeneous distribution, a linear increase in the concentration of thick fibres over the thickness of the medium as well as an exponential increase in the concentration of thick fibres over the thickness. Comparing the three media showed that the medium with the exponential distribution of the thick fibres has the longest service life and the highest dust storage capacity. The question arose during the discussion that followed as to how such a fibre distribution over the medium thickness could be practically implemented. According to Dr Hietel, the FIDYST simulation tool could help to limit the production parameters that would be effected.

Special filtration applications Membrane filter media, i.e. nonwovens on which ePTFE membranes are laminated, are regarded as being very efficient and easily cleanable filter media for use in industrial dust extraction systems. Dr Hans-Jörg Imminger, from BWF Tec GmbH & Co. KG, reported on the development of a new type of membrane which, when compared to others, is characterised by extremely strong fibrillation and a lower proportion of dense zones. This membrane, laminated onto a needle felt, was applied on a filter test stand that tested its capability with regard to fine dust retention. Fine dust was not previously considered for use with these dust extraction filters, because the emission limit value that has to be maintained is given as a gravimetric value. In this case, a zero gravimetric emission could be measured using the new medium with correspondingly low particle counts in the clean gas. Attention must be paid to possible leaks during the assembling of the filter media and their installation in order to realise such particle retention, even in a large-scale plant. By optimising the hoses, i.e. especially the sealing of the longitudinal seam and the filter system‘s operating mode, it was possible to almost achieve the zero emission state (as a gravimetric value) found in the laboratory during a measurement campaign that used various hoses over a period of around one year.

Gebr. Röders AG found another solution for fine dust separation in industrial dust extractors. As Uwe Schneider explained, ePTFE membranes have relatively low air permeability. In the filter medium exhibited by him, the fluoropolymer does not lie as a flat layer on the substructure, but rather it relocates on the filter medium‘s uppermost fibre layer. The effect of this coating, which can also be applied to various needle felt carriers, was demonstrated using a coated PolyEther Sulphone (PES) needle felt. An air permeability of 150 l/(dm2 min) was measured in laboratory tests and a clean gas concentration of 0.42 mg/m3 was determined in tests using fine dust that contained quartz. This means that the separation efficiency is somewhat lower than that of the membrane filter medium shown above, but lower filtration energy consumption is to be expected due to the higher air permeability. The fact that this filter medium actually acts as a surface filter and can therefore be easily cleaned off was proven by the data from an industrial application that uses super adsorber dust, in which conventional, uncoated nonwoven media had a service life of only two months. The coated material was still clean after 14 months of operation.

Antje Hesse, from K-Utec AG Salt Technologies, concluded the series of lectures with a project involving filter development for use in backfilling mining. In this project, empty mine tunnels were to be filled using backfilling, i.e. the solid material to be introduced is flushed in as a suspension and it hardens there. The excess liquid can be pumped out and reused. Backfilling media could be filter dusts from industrial dust extraction mixed with brine. The dewatering should take place via a structural textile barrier. The filter medium that will be used must produce a filtrate that is as clear as possible, be mechanically resistant to intermittent rinsing with varying quantities and must not become clogged under any circumstances, as backwashing or any other type of cleaning is not provided for. In the comparison between nonwoven and the spacer

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fabric, the nonwoven medium showed a better filtering effect than the pacer fabric with respect to particle sizes between a few micrometres and 2 mm, but the flow rate is too low. This was higher for a spacer fabric with a still adequate filtering effect. However, during the pilot phase it became apparent that a barrier structure with a framed filter surface over the entire duct height could not withstand the mechanical load of the suspension weight, which is why a hybrid structure was designed that has solid material in the lower section and filter meshes in the upper section.

Reference literature: [1] Sinowzik, L.: Nonwoven – The All-round Talent. F&S Global Guide of the Filtration and Separation Industry 2018-2020. 2018, ISBN 978-3-00-059320-8, pp. 182 – 189 [2] Smithers Pira Publications: The Future of Nonwovens for Filtration to 2019. www.smitherspira.com [3] Lyko, H., Stoffel, T.: Testing of air filters in compliance with the new ISO 16890.

F&S Global Guide of the Filtration and Separation Industry 2016-2018. 2016, pp. 215 − 220. ISBN 978-3-00-052832-3 [4] Stoffel, T.: Changes in energy classification of air filters and filter layout recommendations for HVAC units. F&S Global Guide of the Filtration and Separation Industry 2018-2020. 2018, pp. 190 – 195, ISBN 978-3-00-059320-8 [5] Lyko, H.: New Aspects Regarding the Testing of Air Filters – Report from the Palas Air filtration seminar. F&S International Edition. No. 18 (2018), pp. 64 – 66 [6] DIN 61211:2005-05: Auf Nähwirkanlagen hergestellte textile Flächengebilde – Technologische Einteilung, Begriffe [7] Batt., T: Entwicklung eines Meltblow-Verfahrens zur Herstellung thermoplastischer Feinstfaser-Vliesstoffe, Dissertation Universität Stuttgart. 2015 [8] Lyko, H.: Development, Production and Testing of Nonwovens for Filtration Use – Report from the 2017 Filtrex conference. F&S International Edition. No 18 (2018) pp. 47 – 53 [9] Klar, A.; Marheineke, N.; Wegener, R.: Hierarchy of mathematical models for production processes of technical textiles. ZAMM – Z. Angew. Math. Mech. 2009, 89 (12), S. 941–961 [10] Azimian, M.; Kühnle,C.; Wiegmann, A.: Design and Optimization of Fibrous Filter Media Using Lifetime Multipass Simulations. Chemical Engineering & Technology.

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The testing of air filters for use in general ventilation technology and as automotive cabin air filters A comparison of the developments in the field of particle filtration over the last 25 years F. Schmidt * Air filters are subjected to standardised tests agreed upon at national or international levels in order to demonstrate performance to the customers as well as for internal quality assurance purposes.

The fundamental meaning and purpose of standardisation is explained in a review article by Ripperger as “Standards are a means of standardising material and immaterial goods [1]. They also provide recognised solutions for recurring tasks.

One objective of standardisation is to promote national and international exchanges of goods and services”. The primary objective is not to represent “reality“, since standard-compliant filter testing serves only to evaluate a filter under comparable, i.e. reproducible, conditions. It is not possible to confirm the performance of filters in real operation (especially over their entire service life) based on these laboratory results. This requires additional tests with outdoor air. On the other hand, a standard-compliant measurement must not be completely isolated from the actual conditions in practical use, as new media * Prof. Dr.-Ing. Frank Schmidt University of Duisburg-Essen, Nanoparticle Process Technology (NPPT) Lotharstr. 1, MF 148, 47057 Duisburg, Germany Tel/Fax: +49 (0) 203 379-2780/4453 Email: frank.schmidt@uni-due.de

and filter elements are developed specifically with regard to the classification in the standard.

Direct comparisons of filter tests, run according to current standards and guidelines, to practical results have been the subject of several application-oriented research projects in recent years [8]. In some cases, large differences were found between the results of standard-compliant and practical measurements. In particular, the practical testing of vehicle cabin air filters revealed significantly lower collection efficiencies1 than could be expected from testing according to the standard. Some of these research results were also published in this journal [3]-[7].

Filter elements made of synthetic media are frequently used both in vehicle interiors and in general ventilation systems. The advantage of using synthetic media: Low pressure drop with high start-up fraction separation efficiency. Disadvantages: The electret properties degrade during operation. It was noticeable that filters made of synthetic media with electret properties are used in general ventilation technology as well as in vehicle interior filters, whereas the tests that conformed to the standards differ considerably. This is why the development of filter tests for both applications are reviewed in the following.

Fig. 1: Outdoor air filter test chambers for cabin air filters at IUTA

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1. Standardisation developments for cabin air filters The basis for today‘s testing of vehicle passenger compartment filters was laid with the draft version of DIN 71460 Part 1 [13] published in June 1993. This standard was developed by the Air Filter Testing Working Group appointed by the Motor Vehicle Standards Committee. An excerpt from the explanatory notes of the appendix: “The proposals submitted by the vehicle and filter manufacturers for the test methods described in this section instigated contrary discussions with regard to the individual test specifications”. Finally, the Fraunhofer Institute for Toxicology and Aerosol Research (Hannover) was commissioned to carry out basic studies.

The results led, amongst other things, to the determination of the test duct geometry (including the test specimen holder), selection of the SAE test dust (ISO 121031), the introduction of the test dust using a nozzle, the test channel arrangement and that the fractional separation efficiency is to be determined for particle diameters between 0.5 μm and 15 μm.

This draft has been replaced by DIN 71460-1: 2003-05 [14]. An electrostatic neutralisation of the test dusts was mentioned for the first time, although it was already prescribed according to ISO/TS

Fig. 2: DEHS efficiencies for new and isopropanol-treated (unloaded) filters

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Tab. 1: Minimum initial separation efficiency of filters in passenger cars and HGVs as per VDI 6032

dust should be used. The table is intended to “represent the state of the art for passenger cars and heavy goods vehicles” and it points out that “the filters for passenger cars and heavy goods vehicles are to be tested in compliance with DIN 71460-1 and those for use in buses in compliance with DIN EN 779”. “In practice, Class G4 filters are used in buses in accordance with DIN EN 779”. The significance of these standard-compliant measurements in real operation is illustrated by the following practical measurements of collection efficiency.

11155-1:2001 [16]. An excerpt from the introduction: “Various methods of neutralisation are still the subject of research and a general and internationally recognised method, [...] still does not yet exist.” Reference is made to the “high market acceptance“ of the standard and its “frequent use”. When compared with the original 1993 version, the innovations apply in particular to the testing of the new combination filters and the resulting need to keep the environmental conditions sufficiently stable. Even in the currently valid version of DIN 71460-1: 2006-04 [15] as opposed to ISO/ TS 11155-1 (Appendix D) no electrostatic neutralisation of the test dust is prescribed. The discharging of the filter medium isn’t required either. DIN 71460-1 therefore represents a special case, since Germany did not adopt the European or international standard ISO 11155-1: 2001-11 (which is currently still valid, last revision was in 2016), as is usual in almost all other technological sectors. Methods for discharging the test aerosol were previously proposed in 2001 in the normative appendix of the ISO/TS. The required minimum initial filter efficiency in passenger cars and trucks is listed in the VDI 6032: 2002 “Hygiene requirements for ventilation technology used in passenger transport vehicles” guideline [17] and in the current edition of VDI 6032-1: 2015 [18], (see Table 1). Testing in accordance with DIN 71460-1 should be carried out with a volumetric flow of 300 m3/ h and ISO A2 test

2. Practical measuring of the separation efficiency of cabin air filters using an outdoor air filter test bench The test stand (Fig. 1) consists of four separate test channels in compliance with DIN 71460 and this enables up to four filters to be continuously loaded over a period of several weeks. The test channels are housed in an air-conditioned container, which is located in the immediate vicinity of a busy road at a logistics site at the Institute for Energy and Environmental Technology (IUTA, Duisburg, Rheinhausen). The vehicle cabin air filters can be loaded with outdoor air or alternatively with soot / diesel soot.

The efficiency of the filters in their new condition and after aging using outdoor air was determined on the standard test bench with a DEHS test aerosol (usual for test of filters for ventilation and air-conditioning systems).

In Fig. 2, the average (5 test samples) DEHS efficiency (diethyl-hexyl sebacate) of unloaded combi-filters, both in their new condition and after electrostatic neutralisation with isopropanol (IPA), is shown. The fractional separation efficiencies were determined using a WELAS (Palas GmbH, Karlsruhe) particle measuring unit. The discharging of the filter element corresponded to the procedure according to DIN EN 779:2012 for determining the minimum efficiency.

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Fig. 3: DEHS efficiencies for cabin air filters both in their new condition and loaded with outdoor air

Fig. 3 shows the fractional separation efficiencies for filters that have been exposed to outdoor air for varying periods of time during the summer months. The average values and standard deviations are based on measurements taken from five aged test specimens. The measured fractional separation efficiencies were similar to those determined for the IPA-treated filter. Apparently the previous continuous flow over a period of three days had electrically neutralised the filters. The flow over a period of four weeks did not result in any improvement in efficiency due to particles that had already been separated.

Figure 4 shows the measurement results for filters downstream of a filter of filter class E10 in the sense of an absolute filter.

Merely the particle-free air passes through the filter. This way the filter is loaded with particles only to a very small extent.

It is therefore possible to differentiate as to whether the change in the separation characteristics is based exclusively on the loading of external air particles on the filter fibres or whether the loss of the filter‘s electret effect was caused by the temperature and humidity of the air flowing through the filter.

The results of the measurements after one, two and four weeks were within the range of the fractional separation efficiency that was determined using isopropanol-treatment. Only the curve for the shortest flow duration of three days (blue curve) is slightly above that of the isopropanol-treated filter. It appears that the filter still had not been completely electrostatically neutralised. The temperature range used during the four-week long flow period was between 12°C and 39°C and the humidity range between 25% and 96%. These boundary conditions led to the elimination of the filter‘s electret effect.

The “ageing” of the filters with outdoor air took place with a constant volume flow of 200 m³/h over 24 hours a day. Three days of continuous flow of outdoor air or “particle free” outdoor air correspond to four months of real driving at an assumed driving time of 1 h/day for 20 days/month.

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Fig. 4: DEHS efficiencies for cabin air filters both in their new condition and loaded with “particle free” outdoor air

Four weeks corresponds to nearly three years of service life, a period during which a filter replacement should normally have already taken place in the vehicle. The test procedure and the results are described in detail in [4] and [6].

3. Filter standardisation development for general ventilation filters DIN EN 779: 1994-09 [20], which is a translation of EN 779: 1993, forms the basis for determining the filter efficiency of “Particle air filters for use in general ventilation technology”. This European standard replaces the German standard, DIN 24185 Part 1 and 2. “The essential change concerns the filter classes“. The designations of the filter classes were changed and the associated final pressure differences were redefined; the specifications for the test setup, dust and evaluation correspond to those of DIN 24185-1. Technical Committee 195 from the European Committee for Standardisation (CEN) was responsible at the international level for “Air filters for use in general ventilation technology” This version has been replaced by DIN EN 779: 2003-05 [21]. National interests were taken care by the General Air Technology department of the Mechanical Engineering Standards Committee (NAM) within DIN. The problem of the degraded electret effect of some filters is mentioned for the first time in the appendix: “Certain types of filter media use electrostatic effects in order to realise high efficiencies at low pressure differences. Exposure to some types of air pollutants, e.g. combustion aerosols or oil mists, might neutralise such charges, resulting in reduced filter efficiency. It is important for filter users to be aware of the possibility of performance degradation caused by charge losses of the filter media during operation.”

Filter media discharging is specified in appendix A (normative), whereby different types of discharging by isopropanol, diesel soot, surface-active substances in

water etc., are permitted as long as they fully discharge the filter medium. The “IPA immersion bath“ for filter media is described in detail. However, the results of the efficiency measurements after discharging are not included in the classification. Only the following note is given: “Therefore, the test results do not provide a basis for predicting the operating efficiency or the service life. Charge losses in the filter medium and the stripping away of particles or fibres can also affect the efficiency.”

Furthermore, the discharging of the DEHS test aerosol is also discussed, even if the charge state, i.e. the number of charges per particle, cannot be compared with that of the test dust dispersed by a brush generator.

In this context, the introduction of the minimum efficiency and the normative definition of the IPA immersion bath for discharging the filter media were the main changes to DIN EN 779: 2012 [22], which had once again led to heated discussions in advance. It was found that the result of this test after the discharging of a filter made of synthetic media decided on the filter class.

The new test standard ISO 16890 “Air filters for general ventilation” [23] replaced DIN EN 779: 2012, which was previously valid in Europe. The most important changes are explained in [2]. Even if the test methods were changed once again, the comparative measurements are basically the same as those used in other tests according to the standard. The suitability of the performance data from filters determined in the laboratory to real use must be questioned again, whereas the new approach is certainly promising. However, problems for the laboratories carrying out the tests also arise during implementation.

A discharging chamber with high safety requirements, which is now mandatory, is needed to discharge the entire filter. The recently introduced test with KCl aerosol especially for the super-micron size range must also prove itself in everyday laboratory use.

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Relevant in this context are the VDI 3803 Part 4 and VDI 6022 guidelines. VDI 3803 also deals with the type of testing and classifying of air filters and it also refers to DIN EN 779 for fine dust filters.

“The VDI 6022 guideline was initially published in 1998 with the aim of countering the public discussion about illnesses caused by air conditioning systems. The version from 1998 focused on being a guideline that covered the maintenance of ventilation systems based on DIN 1946 Part 2” [9]. The guideline was extended in 2006 to include aspects of planning and construction of air conditioning systems, and the experience gained from hygiene inspections. “The amended European standardisation principles were taken into consideration in the 2011 edition [24]” [9].

Fig. 5: F7 pocket filter (synthetic-fibres with electret effect), left: efficiencies after loading with outdoor air, right: pressure drop as a function of the separated dust masses divided by filter area

4. Efficiency measurements of general ventilation filters used in ventilation systems at the University of Duisburg-Essen (ageing with outdoor air) Pocket filters made from synthetic or glass-fibre media were exposed to outdoor air or recirculating air in regular ventilation system operations at the University of Duisburg-Essen and were removed at frequent intervals in order to subject these filters, which had aged during real operation, to a DEHS efficiency measurement (Di-Ethyl-Hexyl-Sebacat) in a standard test bench. Filter pressure drops and efficiencies after ageing/loading with outdoor air were determined and compared with those of the standard-compliant filter test.

The test procedure and the results are described in detail in [3] and [5].

The determined retentions (corresponding to the time intervals given in the legends) are shown in the left-hand diagrams in Figs. 5 and 6 and the associated pressure drops as a function of the separated dust masses relative to the filter area are shown in the right-hand diagrams.

Fig. 6: F7 pocket filter (glass-fibre), left: efficiencies after loading with outdoor air, right: pressure drop as a function of the separated dust masses divided by filter area

the filtration efficiency resulting from the deposited particles can be seen. It remains at the same low level. The separated masses depicted in the legend as well as the pressure drops are the average values of the three filters. The pressure drop data for the three filters was plotted separately in the right diagram starting from a value of 95 Pa at 3,400 m3/ h in the initial condition (scattering over three filters is approx. ± 1 Pa). One can see that the separated masses on the three filters were very different.

This is probably due to an uneven inflow situation for the three filters inside the filter

Fig. 5 shows the results for an F7 pocket filter made of synthetic fibres. Three of the sixteen filters that were applied in the first of two filter stages were investigated.

These filters were exposed directly to the outdoor air without any pre-filtration. The fractional separation efficiency is shown as the average value of the three filters in the diagram on the left. The separation efficiency had decreased significantly after 3.5 months due to the degraded electret effect. A further degradation can be seen after a total operating period of 8 months.

Even after 18 months no improvement of

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stage. During the 18 months of use, the maximum pressure drop increased from 95 Pa to approx. 120 Pa for one of the filters. When exposed to the test dust ASHRAE according to DIN EN 779, the maximum pressure drop is 450 Pa. This final pressure drop value was not reached in any case.

The results for the F7 pocket filter made from glass-fibres are shown in Fig. 6. In this case, all four filters applied in the second filtering stage of a small ventilation system were examined. G4 filters were used in the first filter stage. These F7 filters were therefore exposed to pre-filtered outdoor air. They were used in the ventilation system for a period of 21 months. A slightly better separation efficiency appears to have been realised after 21 months whereas the fractional separation efficiencies up to a period of use of 16 months can hardly be differentiated from each other. The pressure drop at 3,400 m3/h, which averaged 102 Pa (± 2 Pa) over the four filters in the initial condition, averaged 132 Pa after 21 months. The masses separated individually on the filters scatter significantly less than those of the filters shown in Fig. 5. This indicates a more uniform inflow. The separated masses are significantly lower than in the previous case study due to the pre-filtration.

5. Conclusion Filter media with electret properties are frequently used as cabin air filters and general ventilation filters. The change in filter efficiency with increasing loading or longer service life is mainly affected by the degraded electret effect and less by the improved mechanical separation with an increasing amount of dust being stored.

If the vehicle passenger compartment filters are loaded with A2 test dust and the efficiency is also determined using A2 test dust as stipulated in DIN 71460-1, then this results in high separation efficiencies that could not be confirmed after the ageing with outdoor air. The degrading electret effect is affected by the particle size distribution and the high electrically charged state of the applied A2 aerosol. Significantly lower efficiencies are measured if the separation efficiencies are determined using DEHS droplets.

If cabin air filters are classified using the same classification system that is used for filters in the area of general ventilation and air-conditioning technology, they are classified in filter classes M5 or M6. The isopropanol-treated and therefore electrically neutral filters show efficiencies that can be rated as minimum efficiencies that can occur during service life, depending on the period of time that the filters are in use.

From a scientific point of view, there is no reason why the central points of the filter test (test aerosol and discharging the filter medium to determine the minimum efficiency) do not concur for both application areas “vehicles” and “ventilation technology”.

The “high market acceptance” argument, which is used as justification for the special German solution, is not very convincing. Even more so against the background of some advertising statements made by automobile manufacturers and manufactures of cabin air filters, e.g. the article from 21.04.16 [10]: The cabin air filter will ensure that “the interior of your Mercedes Benz” is “100 per cent free of fine dust“. This statement was immediately withdrawn with regard to the health-relevant fine dust as being “simply wrong“.

The “PR-Desaster vom Feinsten” article can still be viewed online.

Similar tenor: from Spiegel-online “Die luftigen Versprechen der Automobilhersteller” [11]. From a current article in avr-online [12]: “The filter consists of four biocide and nanosilver filter layers that are ion-free and they provide almost 100 per cent protection against fine dust and allergens as well as protection against harmful gases and unpleasant odours”.

Pocket filters for general ventilations systems made from synthetic or glass-fibre media were loaded with particles from the outdoor air during operation in a ventilation system and then tested

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in compliance with the standard. This approach seems to be much better suited to obtain results for the actual filter efficiencies during real operation and over their entire service life when compared directly with measurements made in accordance with DIN EN 779.

However, the ageing test showed that determining the minimum efficiency in EN 779: 2012 was an important first step.

The extent to which the modified test methods and the evaluation of the air filter elements using PM1, PM2.5 and PM10 fine dust classes in accordance with ISO 16890 “Air filters for use in general ventilation system technology” result in better concurrence between the laboratory results and those found in practice, will also be studied in a new research project. The filter elements were again installed in ventilation systems and subjected to efficiency measurements made at pre-determined times. These results were then compared with the standard-compliant procedure according to DIN EN ISO 16890.

Acknowledgement: The IGF project 19095 N of the “Forschungsvereinigung Luft- und Trocknungstechnik (FLT)” is funded by Federal Ministry of Economics and Energy through the AiF as part of the promotion of the joint industrial research programme, which is based on a decision taken by the German Bundestag.

Literature: [1] Ripperger, S.: Sinn und Zweck der Normung und Standardisierung auf dem Gebiet der Separationstechnik, Filtrieren und Separieren 25 (2011) Nr. 2 [2] Lyko, H.; Stoffel, T.: Die neue ISO 16890 zur Prüfung von Luftfiltern; F & S Filtrieren und Separieren 29 (2015) Nr. 6, S. 382 - 384 [3] Schmidt, F.; Engelke, T.; Breidenbach, A.; Däuber, E.: Die Effizienz und der Druckverlust von Filtern für raumlufttechnische Anlagen - Labortests mit den Prüfstäuben ASHRAE und A2 im Vergleich mit Filtern aus realen Anlagen, Filtrieren und Separieren, 3 (2017), 164-171 [4] Schmidt, F.; Breidenbach, A.; Engelke, T.: Die Effizienz von Kfz-Innenraumfiltern bei zunehmender Beladung mit Außenluft (Teil 1: Ermittlung der Leistungsdaten bei der Partikelabscheidung), Filtrieren und Separieren, 1 (2017), 13-16 [5] Schmidt, F.; Breidenbach, A.; Engelke, T.; Däuber, E.: Die Effizienz von Filtern für raumlufttechnische Anlagen bei zunehmender Beladung, Gefahrstoffe – Reinhaltung der Luft, 76(3) (2016), 92-96 [6] Schmidt, F., Breidenbach, A.: Vergleichende Prüfung von Kfz-Innenraumfiltern, F&S Global Guide of the Filtration and Separation Industry (2012-2014), 256-262; ISBN: 978-3-00-037568-2 [7] Breidenbach, A.; Schmidt, F.; Finger, H.; Haep, S.: Prüfung von Kfz-Innenraumfiltern – Dieselruß als Prüf- und Beladungsaerosol, Gefahrstoffe – Reinhaltung der Luft, 69(5) (2009), 189-193 [8] http://www.iuta.de/index.php?article_id=662&clang=0 [9] www.vdi.de [10] http://www.zeit.de/2016/16/daimler-feinstaub-filter-pr [11] http://www.spiegel.de/auto/aktuell/innenraumfilter-die-luftigen-versprechen-derautohersteller-a-1094348.html [12] http://www.avronline.de/neuer+kfz+innenraumfilter+micronair+blue+schuetzt+ zuverlaessig+vor+feinstaub+ und+allergenen.173176.htm#.WoazznwiGpo [13] DIN 71460-1: 1993 “Luftfilter für Kraftfahrzeuginnenräume - Teil 1: Prüfverfahren für die Partikelfiltration“, Beuth Verlag GmbH, Berlin [14] DIN 71460-1: 2003 “Luftfilter für Kraftfahrzeuginnenräume - Teil 1: Prüfverfahren für die Partikelfiltration“, Beuth Verlag GmbH, Berlin [15] DIN 71460-1: 2006 “Luftfilter für Kraftfahrzeuginnenräume - Teil 1: Prüfverfahren für die Partikelfiltration“, Beuth Verlag GmbH, Berlin [16] ISO/ TS 11155-1: 2001-11 “Straßenfahrzeuge- Luftfilter für den FahrzeuginnenraumPrüfverfahren für die Partikelfiltration“ [17] VDI 6032: 2002 Blatt 1: “Lufttechnik, Luftqualität in FahrzeugenHygieneanforderungen an die Lüftungstechnik, Beuth- Verlag, Berlin [18] VDI 6032: 2015 Blatt 1: “Hygiene-Anforderungen an die Lüftungstechnik in Fahrzeugen zur Personenbeförderung“; Beuth- Verlag, Berlin [20] DIN EN 779: 1994 “Partikel- Luftfilter für die allgemeine RaumlufttechnikAnforderungen, Prüfung, Kennzeichnung“, Beuth Verlag GmbH, Berlin [21] DIN EN 779: 2003-05 “Partikel- Luftfilter für die allgemeine Raumlufttechnik “, Beuth Verlag GmbH, Berlin [22] DIN EN 779: 2012 “Partikel- Luftfilter für die allgemeine Raumlufttechnik- Bestimmung der Filterleistung; Deutsche Fassung der EN 779:2002“, Beuth Verlag GmbH, Berlin [23] DIN EN ISO 16890:2017-08 Blatt 1-4 “Luftfilter für die allgemeine Raumlufttechnik“, Beuth Verlag GmbH, Berlin [24] VDI 6022: 2011 Blatt 1 “Raumlufttechnik, Raumluftqualität- Hygieneanforderungen an Raumlufttechnische 1

Editor’s note: The terms “efficiency” and “separation efficiency” are used in this article for the particle retention percentage achieved by the filter media, which depends on the particle size. Therefore the efficiency corresponds to the “fractional separation efficiency” that is also mentioned. The various standards discussed here are not uniform in their use of terminology.

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Sensor technology used in air and gas filtration – main topic at the 9th IUTA filtration day H. Lyko * The practical implementation of the so-called Industry 4.0 in filtration systems also needs the required data to be continuously available together with the required accuracy. This means that the digital networking of a filtration system with a higher-level platform starts with integrating the sensors needed to monitor the most important parameters.

These are the inflow velocity or the volumetric flow as well as the pressure drop in the filter and the concentrations of the contaminants to be separated. Recent developments in sensor technology, especially those for detecting and determining the concentrations of gaseous or particulate air pollutants, formed the main focus of the filtration day, which was held at the Duisburg Institute for Environmental and Energy Technology (IUTA) in November 2017. A record number of 175 participants for this annual event demonstrated the importance of this topic as well as of other current research topics underway at the Institute that involve air and compressed air filtration.

Developments in sensor technology A rapidly growing market for gas and particle measuring sensors can be seen along with increasing awareness of the effects of air pollution on health as well as the need for stricter air quality requirements. Dr Christof Asbach, IUTA, pointed this out in his introduction to the topic, which was based on the trend in a number of scientific publications covering sensor development, whereby particle sensor technology still lags significantly behind gas sensor technology. Overall, the air quality monitoring market is expected to grow by 8.5% p.a. from US $ 3.75 billion in 2016 to US $ 5.64 billion in 2021.

Sensors with different functionalities and qualities are available for a unit price of less than US $10 on the internet. Fine dust measuring in the ambient air takes place not only at the regional, national or European networked measuring sites, but also as part of the ‘Citizen science’ projects, where interested citizens can collect measurement data and upload it to internet platforms that have been created specifically for this purpose. One example of this is the luftdaten.info project that is helping Baden-Württemberg to expand the existing measuring network, which is very patchy in some regions, that belongs to the State Institute for the Environment, Measurements and Nature Conservation.

The results of a study into how the “official” air quality measurements compare with those carried out by the project participants are available in the form of a master’s thesis by M. Blon, which was completed at the Esslingen University of Applies Sciences /1/. Fig. 1 shows the sensor for which a purchasing list and the assembly instructions are available on the website. * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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The initial application for sensors integrated in filter systems is found in vehicles, where the air quality measured at the fan is used to automatically switch its operation from supply air to recirculation air. Top-quality room air cleaners have VOC and particle sensors and their data is used to control the devices. The use of these sensors in buildings is the next stage in their development and is described below in the SENSIndoor project report.

Quality monitoring in compressed air networks presents a special challenge, as the availability of sensors for monitoring the corresponding operating pressures, especially those for monitoring oil vapour concentrations, is currently very limited.

Well-proven gas detectors and recent developments The detection of gases and water vapour (as relative humidity) is an integral part of the monitoring process for indoor air quality used in general ventilation technology (humidity, CO2 and VOC) as well as in the monitoring of production areas (additional toxic or combustible gases). Prof. Dr Klaus Schierbaum, from the Institute for Experimental Physics of Condensed Matter at Heinrich-HeineUniversity (HHU) Düsseldorf, gave an overview of the various established technologies used for gas detection as well as some new developments that are on the threshold of market introduction.

Established technologies include the electrochemical determination of CO, nitrogen oxides and other gases, the detection of combustible gases using semiconductor technology, the use of Non-Dispersive InfraRed sensors (NDIR) for determining CO2, the capacitive measurement of air humidity and determining the presence of explosive gases through the use of pellistors. Electrochemical sensors measure the current generated by the reaction of

the gas (analyte) that is found with an electrolyte. The current strength in analyte is in the 100 nA/ppm range. Selective electrochemical sensors are available for a large number of analytes and the need for further development lies in optimising the electrodes (catalytically active electrodes) and impeding electrolyte evaporation (this determines the service life).

With semiconductor gas sensors, the gas components being detected encounter a heated sensitive layer of a metal oxide.

Oxygen molecules from the ambient air are adsorbed on this surface and this creates oxygen ions that react with the gas that is being detected. The interfacial reaction of these gas components can be measured as a change in the electrode current. The trend with semiconductor sensors is towards smaller elements with lower power requirements.

With NDIR sensors, the gas to be measured enters a sample chamber and it is then irradiated by an IR light source.

An IR detector measures the adsorption of specific infra-red light wavelengths by certain gas components. Modern NDIR sensors are also becoming smaller through the use of light-emitting diodes and more sensitive through the use of improved photodetectors.

Capacitive humidity sensors use the change in the capacity of a capacitor or a capacitor system that is induced by humidity. They are now available as polymer-based sensors for use in mass market applications.

Pellistors consist of an inert oxide pellet that is coated with an active catalytic layer. A heating wire runs through the inside of the oxide and the oxide helps it to heat up to several 100°C. All of the combustible gases that are present on the surface of the oxide pellet are oxidised by the adsorbed oxygen. The released heat is then measured as the change in resistance

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Fig.1: Fine dust measuring sensor used in the luftdaten.info citizen science project

of the heating wire relative to a reference element not touched by the gas. The trend here is also towards smaller elements.

Size is an essential criterion for futureoriented sensors, because, on the one hand, small elements can be more easily integrated into existing systems, e.g. including filters, and on the other hand size is also associated with reduced material consumption, which - if the manufacturing process has been adequately developed – should also bring down the price.

Under the direction of the Fraunhofer Institute for Microelectronic Circuits and Systems, Duisburg, the EFRE’s FunALD (Functional ultra-thin materials through Atomic Layer Deposition for the next generation of nanosystem technology, see www.leitmarktagentur.nrw) project, which is currently underway thanks to a subsidy of 1.5 million euros. The project involves the Prof. Schierbaum Institute in Düsseldorf, IUTA, Ruhr University Bochum and ExTox-Gasmesssysteme GmbH. This project aims to develop the material base for compact, intelligent and cost-effective sensors to be used for various measuring tasks.

With the production of Plasma Electrochemical Oxidation (PEO) sensors, in which a highly porous oxide surface is created from a metal such as titanium, it has already been possible to develop marketable sensors that function at room temperature and work with different measured variables that depend on the gas that has to be detected. Electrical quantities such as impedance, current or voltage or the reaction heat can be measured as the gas concentration mass, depending on the sensor electronics being used. These sensors are commercially available for humidity, CO, NO2 and H2. This makes it possible to detect hydrogen as a caloric measurement at the lower explosion limit.

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Fig. 2: Gas detector, based on the arc discharge principle (Image: Institute for Physical Chemistry at HHU Düsseldorf)

Under the direction of Prof. Andreas Schütze, a cost-effective sensor for the continuous monitoring of indoor air was developed at Saarland University, together with cooperation partners, as part of the three-year SENSIndoor EU project, which was completed at the end of 2016. The sensor detects specific organic substances in this concentration range whose limit or reference values are in the lower ppb range. For example, one such toxic gas is formaldehyde. VOC sensors available on the market detect total VOCs in the ppm range and are therefore not sensitive nor selective enough. The newly developed sensor, which was presented by Dr Tilman Sauerwald, consists of semiconductor material (metal oxide) whose sensitivity is specifically increased by operation within a controlled temperature cycle (see /2/ as well). The semiconductor material adsorbs more oxygen at high temperatures than it does at low temperatures.

If a sudden drop in temperature occurs then the oxygen distribution will initially be higher than the equilibrium value associated with the low temperature and it will only degrade slowly until equilibrium is reached. If another gas hits the surface in this state then more oxygen ions will be available for the reaction than there were in the equilibrium state and the sensor’s sensitivity will increase. An increase in sensitivity by a factor of 700 was measured for ethanol. The temperature cycle is just one module within the sensor development. Other developments that increase sensitivity include the manufacturing process of the semiconductor layer by laser deposition (PLD stands for Pulsed Laser Deposition), with which the metal oxide can be deposited as nanoparticles with a very large surface on the heatable substrate, and the development of micro pre-concentrators, with which

gas molecules occurring in extremely low concentrations are “collected” before they are fed to the sensor. Details about the specific developments and all of the publications can be found at the project’s website (www.sensindoor.eu).

During the filtration day it was also mentioned that benzene can be detected in front of a more complex background matrix with a measurement error of 1 - 2 ppb. The price of a sensor (for detecting a gas) and including the electronics should be around 100 euros. The SENSIndoor project received the Nanofy! award as best project at the EuroNanoForum 2017 that was held in Malta.

The development of a sensor for an intelligent gas filter to be used in passenger compartment protective ventilation systems that will indicate, when the filter’s capacity to absorb harmful gases has been used up, is the objective of the ZIM BESMART project, which is being developed by Hauser Umwelt-Service GmbH &Co., KG, Krefeld, in conjunction with IUTA and the Institute for Physical Chemistry at HHU Düsseldorf. Prof. Hans Bettermann, from Düsseldorf University, explained the principle of arc discharge by gas molecules and the analysis of the resulting light spectrums implemented in this project (Fig. 2).

Recent dust sensor developments Top-quality scientific equipment for measuring particle concentrations and particle size distributions are available from various suppliers and they provide important scientific services, especially when it comes to the efficiency testing of filter media and filters in test stands. As Dr. Christof Asbach, from IUTA, explained that particle measuring instruments of

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Tab. 1: Overview of the available dust sensors (Source: C. Asbach, IUTA)

this kind are unsuitable for continuously collecting data about the particle separation quality in every filter system, if only because of their price (approx. 2,000 to 50,000 euros). Not all of the information provided by such devices is really needed to monitor the state of a filter or the air quality. On the other hand, small, lightweight and battery-powered dust sensors are available for significantly less money. (see Table 1). They are based on the photometry or nephelometry principle. The air sample is irradiated with light and the resulting scattered light is detected as electrical voltage and converted into a concentration. This conversion requires assumptions about particle shape and distribution, refractive index and particle density (if not available), which might result in systematic inaccuracies. The SDS001 device mentioned in Table 1 is the dust sensor used in the luftdaten.info project (Fig. 1). The Alphasense spectrometer is somewhat more expensive (approx.

400 euros) and complex and it provides a concentrations number as well as a size distribution (Table 1). Asbach summarised what these inexpensive dust sensors can achieve, whether they can be calibrated or not as well as where they can be used meaningfully and his summary was based on the results of measurements carried out at IUTA and the data published in the

reference literature (/3/, /4/, /5/ and /6/).

One expects to see a linear characteristic curve (curve of the measured voltage over the particle concentration) within the usable measuring range from dust sensors working in accordance with the photometer or nephelometer principles.

Dependencies on the particle type and size became clear when the results obtained using this type of sensor were correlated with the concentrations determined by a scientific instrument (e.g. an SMPS as in /4/). This was also proven in comparative measurements made with a Sharp sensor in the IUTA laboratory using various aerosols (NaCl, DEHS and cigarette smoke).

The comparison of different sensors of the same type using the same aerosol (Corena oil) produced a relatively good match. It is accepted by all the publications mentioned that these sensors are expected to be less accurate than scientific instruments. The effect of the air humidity proved to be the main source of error. (see /3/ as well).

However, they were found to be suitable for analysing the distribution and identifying “hot spots” when used in comprehensive air quality measuring systems, for monitoring the consistency of an aerosol used in the laboratory, for monitoring filter ageing from cigarette smoke and – most important with regard to integrating them into filter systems – for controlling filtra-

Fig.3: Design, filter assignments and airflow inside a safety cabinet (see Table.1) (Image: IUTA)

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tion applications. Operation within the concentration limits of a sensor’s linear measuring range is assumed here.

Velocimetry in low-turbulence air flows The protection of people and material in safety cabinets is based on two principles: air pollution control through the use of appropriate filters and the generation and continuous upkeep of defined air flow velocities for a low-turbulence displacement flow through the work areas (downflow, see Fig. 3).

Dr Siegfried Opiolka, from IUTA, reported on the development of an ultrasonic sensor that makes continuous and spatially resolved monitoring of air velocity in safety cabinets possible. Ultrasonic measuring has the fundamental advantage that the sensors do not have to be installed in the middle of a flow and therefore they do not disturb it. The operation of safety cabinets was previously monitored through annual inspections and occasional spot measurements using hot-wire anemometry or differential pressure measuring. A pair of ultrasonic transducers was used here for measuring the flow whereby one of the transducers emitted a directional component with the flowing medium and the other emitted in the opposite direction. The flow velocity ensured a relative shift in the echo times and this time difference served as measure for the velocity. In order to measure the downflow as shown in the side view in Fig. 3, both of the ultrasonic transducers in the pair must be mounted opposite each other on the front and rear walls but at different heights. The ultrasonic signal’s transit time difference is in the nanoseconds range in this slow air flow application.

Time-to-digital converters were used to convert extremely short time intervals in the ns range and below into digital outputs as well as signal amplifiers were used to construct a circuit with 4 pairs of ultrasonic converters evenly distributed over the width of the safety cabinet and this was tested against hot-wire anemometers. The new measuring device proved satisfactory

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with a measuring range of 0.2 to 1 m/s, a resolution < 0.01 m/s and sufficient accuracy. Work processes in the cabinet remained undisturbed, but obstacles could well interfere with the measuring.

The sensors are small, easy to clean and are resistant against common disinfectants. This enables continuous and spatially resolved measuring and creeping to occur and local flow changes can be detected more quickly.

Reference literature: /1/ M. Blon: Untersuchungen zur Messung von Feinstaub – Das Citizen Science Projekt luftdaten.info; Masterarbeit Hochschule Esslingen, 2017 /2/ A: Schütze, T. Baur, M. Leidinger, W. Reimringer, R. Jung, T. Conrad, T. Sauerwald: Highly Sensitive and Selective VOC Sensor Systems Based on Semiconductor Gas Sensors: How to?, Environments 2017, 4, 20; doi:10.3390/environments4010020 /3/ Landesanstalt für Umwelt, Messungen und Naturschutz Baden-Württemberg (LUBW): Messungen mit dem Feinstaubsensor SDS011 – Ein Vergleich mit einem eignungsgeprüften Feinstaubanalysator, Juni 2017, s. www.lubw.de /4/ Y. Wang, J. Li, q. Zhang, J. Jiang, Pr. Biswas: Laboratory Evaluation and calibration of Three

Low-Cost Particle Sensors for Particulate Matter Measurement; Aerosol Science and Technology 49, 11, 2015, 1063-1077, DOI: 10.1080/02786826.2015.1100710 /5/ S. Sousan, K. Koehler, G. Thomas, J.H. Park, M. Hillman, A. Halterman, T.A. Peters: Intercomparison of low-cost sensors for measuring the mass concentration of occupational aerosols; Aerosol Science and Technology 50, 5, 2016, 462-473, DOI: 10.1080/02786826.2016.1162901 /6/ L. Crilley, M. Shaw, R.Pound, L.J. Kramer, R. Price, S. Young, A.C.Lewis, F.D,Pope: Evaluation of a lowcost optical particle counter (Alphasense OPC-N2) for ambient air monitoring, Atmos. Meas. Tech. Discuss.

2017 https://doi.org/10.5194/amt-2017-308

Fine dust monitoring developments Report from the “PM2.5 monitoring – What’s Next?” network meeting H. Lyko * The monitoring of PM2.5 fine dust concentrations is now standard practice at public measuring stations in Germany, even though it is usually just the PM10 values that are published on the websites belonging to the Federal Environment Agency and the regional offices. The 39th German Federal Immissions Protection Act [1]) from 2010 stipulated a PM2.5-limit value that must be complied with as from January 1, 2015. At network meeting 2018 hosted by Palas GmbH, who are also suppliers of particle measuring devices used for fine dust monitoring, the question: “What comes next?” was in the focus. The broad spectrum of topics included ongoing discussions about the current fine dust pollution found in metropolitan areas and its effects on human health, about the current measurement technology being used up to the consideration of fine dust found in the workplace, at airports and in automotive engineering, with the latter ranging beyond exhaust gases. The event was moderated by Prof. Achim Dittler, head of the Gas Particle Systems working group at the Karlsruhe Institute of Technology (KIT), and he also gave the introductory lecture.

Fine dust facts and public perception The grade of public’s perception of fine dust as a health hazard does not necessarily correlate with the actual situation, as Prof. Dittler pointed out in the context of a historical study of actual air pollution and the assessment of air quality in the media, which was based on living conditions and other events. The positive perception of smoking chimneys being a sign of productivity and prosperity was permanently demolished by serious smog events in London in 1952 and in the Ruhr in 1962.

As early as the 1980s, the years with the most frequently published statements on air pollutants coincided with steadily reduced pollutant concentrations when compared to previous years – only to be almost forgotten by the media because of the Chernobyl disaster [2]. For example, the current perception of how good or bad the air quality actually is has sadly * Dr.-Ing. Hildegard Lyko Dortmund, Germany, mlyko@t-online.de

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led to Stuttgart, the state capital of BadenWürttemberg, becoming famous throughout Germany as being a city polluted with fine dust. This was triggered by fine dust alarms being declared several times a

year due to the limit value for PM10 being exceeded at the Neckartor measuring station. Air quality has shown an upward trend in recent years, as the air pollutant concentrations in Stuttgart outlined in

Fig. 1: Air quality development in Stuttgart between 1986 and 2017 at the Stuttgart centre (Schwabenzentrum) measuring station. (Source: Environmental Protection Office, Stuttgart: www.stadtklima-stuttgart.de)

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Fig. 1 show [Prof. Dittler presented the dustfall development as a bar graph (see grey curve in Fig. 1)]. The current limit and target values for air pollutants set out in the 39th German Federal Immissions Protection Act can be found in Table 1.

The measuring station looked at in Fig.1 is the cleanest in the greater Stuttgart area, whilst the Neckartor station has the highest number of days when the PM10 limit was exceeded, even though the trend is clearly downwards. In the “rankings list” of the German measuring stations with the most days on which the PM10 limit value of 50 μg/m3 was exceeded in 2018, the Stuttgart Neckartor station is ranked 9th in the list with 20 days exceeding the limit (status on 06.11.2018, www.umweltbundesamt.de). Places 1 - 3 with 33, 29 and 27 days when the limit was exceeded on the mentioned date are filled by measuring stations in the capital Berlin and 4th place was taken by the Lower Rhine town of Niederzier, which has a brown coal mine located in its immediate vicinity. Dittler pointed out that the Neckartor measuring station did not meet the requirements for a sampling station, i.e. that there is a free air flow in an arc of at least 180° or 270°.

He presented SEM images and analyses of dust samples taken from window sills directly next to the measuring station. The particle analysis showed a median value x50.3 of 25.5 μm and a proportion of around 60% that has to be counted as being part of the PM10 fraction, as the remainder were coarser. The magnetic particles proportion of around 5 - 8% was attributed to brake dust. It was also pointed out that the fine dust pollution in the underground subway stations was significantly higher than that found in the above-ground hotspots.

With fine dust monitoring, the tendency is towards covering larger areas with a large number of measuring points, mainly through implementing the measuring through the use of simple sensors by interested ordinary people as part of the so-called “citizen science projects”.

The measurement results are published at: www.luftdaten.info (see Fig. 2). Overall, it is hoped that this will provide a more comprehensive picture that can be differentiated through the causes of air pollution.

domestic combustion processes. Vehicle traffic has the highest share at over 20% in countries such as Germany, Great Britain or the USA [3]. In Aachen, due to its valley location and its frequent weather inversions and industrial effects from Belgium (the wind from the west is the most frequent wind direction), similar conditions prevail as in Stuttgart, but the Aachen conditions are not published as often (nationwide). The statistical lifetime reduction caused by air pollution in 2000 was >12 months, which is above the German average of around 10 months.

The HumTec City 2020+ interdisciplinary research project was carried out in the Aachen model region in order to evaluate environmental medicine, produce details about existing risk and derive limit values.

Fine dust samples were analysed with regard to PM10 and PM2.5 concentrations as well as their chemical compositions at three different measuring stations, one on

a busy road, one on the outskirts of the city and one in a rural environment in the Eifel.

The third pillar of the project was the clarification of the toxicological mechanism of action of the fine dust components. The particles were extracted from the collecting filters, suspended in high-purity water and then brought into contact with various human cells. The toxicological study procedures and their results are published in [4]. When the fine dust samples from the three different measuring stations were compared, it was noticed that the PM2.5 / PM10 ratios increased as the distance from busy locations grew. Whereas inorganic particles predominated in the city centre, out in the countryside there was a mixture of organic (including fungal spores) and inorganic substances. The widespread opinion that sports activities such as jogging are healthier in the countryside than in the city was not confirmed by Dr Michael. The number of measuring stations

Fig. 2: Visualisation of the fine dust values uploaded as citizen measurements at www.luftdaten. info (example taken from October 2018)

Health effects caused by fine dust According to estimates from the World Health Organization (WHO), around 4.2 million premature deaths can be traced back to air pollution. Dr Sabrina Michael from the German Federal Railway Authority quoted this when she spoke about her research activities at RWTH Aachen into the health effects of air pollutants. In many countries the main sources of air pollutants are power generators and

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Fig. 3: Display of the PM1, PM2.5, PM4 and PM10 fine dust fraction concentrations recorded with Fidas

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Tab. 1: Limit and target values for air pollutants as per 39th German Federal Immissions Protection Act

involved in the study was considered to be too small for a comprehensive assessment of health risks caused by fine dust.

Practice and regulations covering the measuring of fine dust in the outside air With their Fidas system, Palas now has three different versions of the measuring system that is certified for the continuous monitoring of PM2.5 and PM10 concentrations in the outdoor air at public measuring stations. Dr Frederik Weis reviewed the lengthy suitability testing of this system, which is capable of displaying all of the fine dust fractions simultaneously (see Fig. 3). The advantage over gravimetric fine dust analysis using a collecting filter is, in addition to the reduced workload, continuous measuring with high temporal resolution, which also makes it possible to assign specific parameters to the

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total temporal concentration.Thus specific time-limited air pollution control measures may be accordingly adjusted whenever necessary. Each of the three Fidas systems with activated and deactivated drying sections were operated in parallel on the summit of the Puy de Dôme volcano in the French Massif Central as part of the ACTRIS EU research infrastructure that monitors aerosols, clouds and gaseous air pollutants. Cloud droplets and the effects of moisture on particle growth can be identified by comparing particle number concentrations and size distributions.

A question about including the PM1 fraction in the measurement programme was raised during the current discussion. The focus also included the so-called ultrafine particles. They are dusts, fumes and mists comprised of particles with diameters of less than 100 nm. They can be measured using the U-range system, which is Fidas

combined with a nanoparticle counter.

A practical field of application is analysing particle emissions from airport operations, as aircraft engines are known to be the source of particles of this size (see [5] as well).

The British company, Air Monitors UK, is a private company that operates around 80% of the public air quality monitoring stations in the UK on behalf of the UK Government. Jim Mills, their CEO, reported on his experience with the collecting and processing of data from around 145 Fidas devices, nearly 300 conventional measuring stations and an additional 600 locations, where so-called low-cost sensors provided the data. Mills described the loss of particles that are not deposited on the collecting filter, for various reasons due to the wind or because they are volatile substances, as a major difficulty in gravimetric dust analysing as well as the amount of work involved and the lower accuracy obtained. Consequently, other systems for determining the mass concentrations were installed in the network in addition to the optical spectrometer. The Beta Attenuation Monitor (BAM) process and the Tapered Element Oscillating Microbalance (TEOM) process were used together with a measuring system that recorded the filter dynamics (FDMS = Filter Dynamics Measurement System).

The absorption of beta radiation by the particles collected on a quartz filter is measured by the BAM process. The process is relatively simple and inexpensive, but it generates measurement errors as it also absorbs moisture and uses relatively loud pumps with high power consumptions.

The TEOM process uses a microbalance to directly measure the particle mass on the filter. Particle loss due to volatile particles is also possible here. The system also needs a sturdy platform, a heater for the incoming air to prevent moisture precipitation on the filter and an air-conditioned cubicle. The time-dependent loss caused by volatile particles can be quantified or offset by combining the system with a measuring system that records the filter dynamics (FDMS). On balance, TEOS / FDMS has become a “technical monster” (according to Mills) that delivers precise values, but is unsuitable for use as a mass instrument in a large network. When the overall costs were compared, Fidas scored best due to the fact that it did not require any operating resources (filters) and it consumed less energy. Since June 2018 the “London hyperlocal air quality network” project has been running in London under the aegis of the Environmental Defence Fund Europe with participation

by Air Monitors, Google Earth Outreach, Cambridge Environmental Research Consultants, University of Cambridge, the

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National Physical Laboratory and King’s College, London. Air Monitors’ participation involves a total of 100 stationary multi-parameter measurement devices (AQmesh PODS) and two cars from Google’s “Street view” fleet that are equipped with measuring devices to provide the mobile air quality data. However, due to the particle dynamics, it is not possible to record the PM10 values using a system that is moved around due to it being installed inside a car. More data will also be collected from citizens under the ‘Sense my street’ project, partly using the portable Fidas Frog system.

Aircraft are not the only sources of fine dust or ultra-fine dust found at airports.

Running the entire structure of an airport represents a multitude of emission sources, which are evaluated according to different standards and compliance with the maximum workplace concentrations is important for the large number of employees working in different parts of the airport.

Emanuel Fleuti, head of the environmental protection department at Flughafen Zürich AG (at Zurich airport), listed the various regulations and standards that must be considered at an airport with regard to air quality. Almost all of the emission sources at an airport are regulated, with the exception of the smaller auxiliary power units. The International Civil Aviation Organisation (ICAO) considers the emissions that occur at an airport and distinguishes between aircraft emissions, emissions resulting from the handling of aircraft on the ground, emissions resulting from the airport infrastructure and stationary sources at an airport as well as vehicle emissions in its “Airport air quality” manual (Document-No. 9889, see [6]).

Standards that regulate the emission of pollutants exist for each of these different emission source groups. Devices that are not specific to airports (vehicles, energy production and heating incinerators, etc.) are subject to the directives applicable to these sectors issued by the EU or national legislators. The EU Directive and national occupational health and safety guidelines must always be complied with in areas where people work. Furthermore, the air quality guidelines also apply to all outdoor areas as they do to everywhere else, for example in Germany the 39th German Federal Immissions Protection Act Current applications of various fine dust sensors Apart from the fact that it would simply be too expensive to increase the density of public measuring stations equipped with technical equipment that meets today’s standards, the need for a nationwide and denser measuring network, which can also

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Fig. 4: SDS 011 fine dust sensor made by NOVA Fitness (Image: IUTA).

Fig. 5: Summary of measurement results obtained with Nova Fitness’s low-cost SDS011 fine dust sensor when compared to the MPG II reference collector (Image: IUTA).

be used for the temporal identification of air polluters, can be met in two ways.

One way is to use so-called low-cost sensors, which can be installed and distributed throughout the region and the other way is to use mobile measuring instruments. Dr Matthias Kaul, from the Bergische Universität in Wuppertal, studied the application possibilities of Fidas Fly, from Palas, as a mobile system for use in Wuppertal. This small sensor also has a GPS module included in its low weight.

However, it does not have a drying unit, which makes measuring in high humidities more difficult. Transporting the measuring unit in a backpack on foot or by bicycle enables flexible fine dust collection to be implemented even in places that are difficult to access. Temporary sources of fine dust, such as daylight construction sites, can also be reliably recorded. An elec-

tric car was chosen as the third transport option. However, it should be noted here that isokinetic sampling is not possible if the measuring instrument is moving considerably faster than the ambient air that has to be analysed. It is also possible to record concentration profiles above normal heights by installing the measuring device in a drone. This type of mobile measurement requires personnel, but can be carried out with just a few, higher quality instruments that will provide more reliable results, even though the results would not be recorded simultaneously.

A major disadvantage of these inexpensive sensors is their measuring inaccuracy in high humidities. On the other hand, the Institute for Environmental and Energy Technology (IUTA) in Duisburg, considers the use of such sensors for determining workplace concentrations to be far

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more promising because the humidity in many workplaces is relatively low and it is not subject to major fluctuations. Dr Stefan Schumacher compared the results obtained from such indoor sensors against those obtained when using a top-quality aerosol spectrometer and a reference dust collector. A test stand was set up at the Institute for Hazardous Substance Research (IGF) in Dortmund for this purpose and various test aerosols were fed in through a 20 m long tunnel under controlled conditions and into a test chamber with a volume of 24 m3. In the chamber, the size-dependent mass concentrations resulting from the supply of 4 different dust types (2 x CaCO3, different size distributions, ground shale and glass beads) were measured simultaneously using a total of four different spectrometers, three inexpensive photometers and the MPG II reference collector. All of the specific measuring equipment that was used and the results obtained are described in detail in [7]. Comparing the scientific instruments against the PG II reference collector showed good PM4 fraction correlations from all of the spectrometers. The inexpensive sensors produced PM2.5 and PM10 concentrations that were comparable with those from the reference collector. There were also good linear correlations with the MPG II results as well as stronger scatters in the PM10 fraction. The SDS011 sensor

made by Nova Fitness produced a very good PM10 correlation up to a concentration of about 2 mg/m3 and an excellent linear correlation for PM2.5 (see Figs. 4 and 5). Further studies using different aerosols are still being planned.

Concepts for fine dust reduction in inner cities The filter manufacturer Mann+Hummel is considering how to reduce traffic-related fine dust concentrations in urban centres independently of the drive technology used in motorised vehicles. Dr Christoph Schultz pointed out that only about 15% of traffic-related fine dust is released into the environment through engine exhaust gases. Other important sources are brake disc abrasions, tyre abrasions and the dust stirred up by traffic. These fine dust particles will be tackled using specially-developed brake dust filters, air filter systems mounted on or in vehicles and stationary air filter columns installed at the roadside. F&S 4/2018 (Page 294) has already reported on the air filter columns that are to be positioned along the roadside at the Neckartor in Stuttgart. The brake dust filters will be mounted directly on each of a vehicle’s brake discs and they will be designed so that their service life corresponds approximately to that of the service intervals for the brake linings. The

vehicle air filters will be available in two versions for roof or underbody mounting and they are intended for use in inner-city traffic, i.e. preferably in buses, delivery vans, etc. You can see prototypes of brake dust filters and air filter systems mounted on vehicles if you visit Youtube on the internet.

Reference literature: [1] Neununddreißigste Verordnung zur Durchführung des Bundes-Immissionsschutzgesetzes (Verordnung über Luftqualitätsstandards und Emissionshöchstmengen – 39. BImSchV) vom 2. August 2010, zuletzt geändert am 18. Juli 2018 [2] Kepplinger, M.: Künstliche Horizonte – Folgen, Darstellung und Akzeptanz von Technik in der Bundesrepublik, Campus Verlag 1989 [3] Lelieveld, j.; Evans, J.S.; Fnais, M.; Giannadaki, D.; Pozzer, A.: The contribution of outdoor air pollution sources to premature mortality on a global scale, Nature 525 (2015), S. 367-371, DOI: 10.138/ nature15371 [4] Michael, S.; Montag, M.; Dott, W.: Pro-inflammatory effects and oxidative stress in lung macrophages and epithelial cells induced by ambient particulate matter, Envrionmental Pollution 183 (2013), S. 19-29 [5] Lyko, H.: Europäische Normungsarbeit und Praxis der Luftqualitätsmessung und -bewertung Bericht vom VDI-Expertenforum Feinstaub. F&S Filtrieren und Separieren 6 (2018), S. 413-417 (in diesem Heft) [6] International Civil Aviation Organization (ICAO) Dox 9889 (2011): Airport Air Quality Manual, s. www.icao.int [7] Asbach, C.; Hellack, B.; Schumacher, S. et al.: Anwendungsmöglichkeiten und Grenzen kostengünstiger Feinstaubsensoren. Gefahrstoffe – Reinhaltung der Luft 78 (2018) Nr. 6, 242-250

Dedusting technology for organic dusts with reliable containment Th. Schwalbe * Containment includes a number of technical measures to protect processes against inadmissible, harmful leakage.

Dedusting filter technology plays an important and complex intermediate part in reaching these protection objectives.

Besides leakage in the feeding and removal of process materials, process dedusting represents the largest material loss and is therefore in the focus of critical observation by producers of harmful agents. Containment dedusting filters by TRM Filter combine filter system designs that are adapted to the risk involved with the possibility of lifelong upgrading, thus ensuring that operators make the right decision even in changing risk assessment situations.

In the European judicial enforcement area there are two different triggers for the containment protection of systems for organic powders. On the one hand, intermediate products are preventively processed under containment conditions according to the REACH directive of the EU * Dr. Thomas Schwalbe Business Development Manager TRM Filter d.o.o.

Weitzesweg 16 E 61118 Bad Vilbel, Germany

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(Registration, Evaluation, Authorisation and Restriction of Chemicals), regardless of their toxicity level. On the other hand, pharmaceutical companies know the toxicological effects and side effects of their active ingredients and identify accurate threshold values for the load on ambient air of plants and for the deposit of materials on surfaces as reference values in the context of product carryover.

While the REACH directive primarily – although not exclusively – refers to the portfolio of products that have not had

any noticeable toxicological effects for a longer period of time, this is very different for active ingredients. Not only are their effects and side effects known; some new-generation active ingredients have much greater effects and side effects than established, commonly prescribed active ingredients. For instance, the strictest demands on breathing air quality of employees in pharmaceutical production – OEL (Occupational Exposure Level) – are made for cytostatic agents. Here, OELs are below 0.1 μg/m³ – more than a thousand

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reliably protected dedusting filter systems for appropriate protection. For highly active pharmaceutical active ingredients (HPAPI), reaching the envisaged level of protection is much more complicated: Operators, plant constructors and dedusting filter suppliers have to team up to coordinate all specific requirements.

Appropriate suction and disposal

Fig. 1: ECR filter system

times less than the level of low-toxicity substances. Patents have recently been expiring for some of these substances.

Generics are being produced i.a. in India.

China is preparing to start manufacturing these substances. The situation calls for

Fig. 2: Bag with cover

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In many cases, after the feeding and the removal of production materials, the filtration of process dusts represents the third-largest mass flow across process borders. During the processing of intermediate products of relatively low added value, the stronger and therefore efficient suction of the powdery goods clearly promotes working hygiene and workspace protection. This primarily concerns the rigorous containment according to ECHA (European Chemicals Agency) guidelines in “open” isolators (strategy 3). Suction point design is particularly important. The situation is different for closed process workflows (strategy 4) and the majority of pharmaceutical applications. Here, it is the objective to suction off exactly that dust which is not processed by the technical design of value-adding process steps.

With a given layout of suction points, the adjustment of the suction power becomes a significant parameter for the optimisation of the application technology of a product in an automated process. Powders that do not become waste throughout suction do not pose any occupational hygiene risk and therefore do not have to be retained in the filter’s containment in the first place.

Rigorous containment – reliable, easy and simple with standard systems TRM Filter meets the requirements of the rigorous containment of dedusting filter systems by offering the ECH product lines for local dedusting of mostly individual processing plants in solids handling and ECR products for the dedusting of greater process airflows. Both product lines can be upgraded throughout their entire process lifecycle. At all handling steps, both product lines reach containment objectives measured with regard to residual leakage, thus offering design reliability of the dedusting function even with progressively increasing hygienic assessment quality of the dedusted processes and process substances.

Boost the security level: Upgradeable dedusting filter systems In the basic Enduro configuration, the ECH and ECR systems (Figure 1) include a cleanable primary filter step and a secondary filter step H13. The dust cleaned off the primary filter step is collected in a dust collector box. As an option, the systems can be equipped with integrated fans. They are available as powder-coated steel systems or as stainless steel systems.

These systems offer great benefits. They can be upgraded throughout their entire lifecycle and adapted to changing occupational hygiene standards, especially with regard to REACH.

Fig. 3: Bag-in/bag-out filter exchange

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Easy handling of dedusting of less toxic dusts In compliance with ECHA strategy recommendations with regard to the rigorous containment in open isolators (strategy 3), TRM Filter recommends the Novento configuration for ECH and ECR models. This configuration ensures the protection of all ways of handling dedusting filter systems by using simple designs of protective film technologies. The dust is collected in a container whose inlay bag is closed by a lid for disposal (Figure 2). The occasional exchange of both filter elements is carried out using the bag-in/bag-out technique (Figure 3). The lifecycle of the cleanable primary filter is up to three years, depending on the dust load.

The dedusting of pharmaceutical dusts of medium toxicity (OEL > 10 μg/m³) up to OEB 3 and the rigorous containment in isolators with closed handling (strategy 4) according to ECHA is possible with the Practico configuration of TRM Filter’s ECH and ECR product lines. This configuration closes and protects all ways of handling of the dedusting filter system with simple designs of protective film technologies. The dust is collected in the safe bag (Figure 4) which is detached without being opened and sealed on both sides.

Fig. 4: Safe bag dust collection

Accurate suction thanks to controlled airflow For the dedusting of pharmaceutical dusts of high toxicity (OEL > 1 μg/m³) up to OEB 4 (including) and if there are specific, weightier reasons with regard to strategy 4 (rigorous containment in isolators with closed handling according to ECHA), the Optimo configuration of the ECH and ECR systems offers an increased level of protection. Dust cleaned off the filter is collected in compartments of endless film (Figure 5) closed at both ends. The dust deposit on the filter elements can be immobilised before their exchange. The dedusting airflow inside the Optimo is measured and controlled. The amount of dust can be weighed.

For the dedusting of very toxic dusts (OEL<1 μg/m³) from OEB 5 onward, customer-specific systems are built on the basis of the Maximo configuration. Aside from the secondary containment of dust collection in a glove box, the systems offer widespread precautions for dust immobilisation and cleaning preparation. These dedusting systems are configured and validated in close cooperation with system integrators and operators.

Fig. 5: Dust collection in continuous film IMPRINT Publishing house: VDL-Verlag GmbH Verlag & DienstLeistungen Address: F&S - Filtrieren und Separieren VDL-Verlag GmbH Verlag & DienstLeistungen Heinrich-Heine-Straße 5 63322 Rödermark / Germany Phone: +49 (0) 6074 92 08 80 Fax: + 49 (0) 6074 9 33 34 e-mail: evdl@vdl-verlag.de www.fs-journal.de

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Editor: Prof. Dr.-Ing. Siegfried Ripperger Birkenstraße 1a 67724 Gonbach / Germany Phone: +49 (0) 6302 57 07 Fax: +49 (0) 6302 57 08 e-mail: SRipperger@t-online.de Dipl.-Ing. Jakob Barth Kaiserslautern / Germany jakob.barth@mv.uni-kl.de Publisher: Eckhard von der Lühe

Reliable and comprehensive protection for the containment of toxic substances The ECH and ECR dedusting filter systems by TRM Filter offer comprehensive protection with regard to the rigorous containment of substances in all ways of handling during proper operation.

In addition, the systems themselves remain closed off from their environment even in the event of explosions. Environmental contamination is therefore ruled out. The systems can be upgraded throughout their entire lifecycle at the described protection levels. They thus offer the possibility of making reliable decisions for investments in dedusting technology against the backdrop of evolving toxicological process risk evaluation.

Advertising department: Eckhard von der Lühe Phone: +49 (0) 6074 92 08 80 Fax: + 49 (0) 6074 9 33 34 e-mail: evdl@vdl-verlag.de

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International Sales Manager: Margot Görzel Phone: +49 (0) 6196 65 32 11 e-mail: fs-journal@mgocommunications.de

F & S - International Edition is a special edition of the trade magazine F & S - Filtrieren und Separieren published in Germany.

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Centrifugation f g - Keyy Technology h l gy for f solid/liquid/liquid l d/l q d/l q d separation p · Air Quality l y Controll & Aerosols l · Dewatering g off Concentrates and Tailings g - Large g Scale Duties in the Mining g Industryy · Digitalization g of Centrifuges g - Helpful p or senseless? · Enhancing g Filter Media Performance during g Industrial Gas Filtration · Low-cost p porous ceramic filters for p potential microfiltration and ultrafiltration applications pp · New developments p in woven wire filtration media: 3D high g p perfomance filter cloth; Woven wire mesh combinations in solid-liquid q separation p · Ceramic membrane system y for drinking g water application pp operating p g with high g flux · Antifouling gg grafting g of nanofiltration membranes: new insights g into membrane fouling g mechanisms · Cleanable filter media g go close to zero emission · In-situ cleaning gp process of chamber filter p presses with sensor-controlled and demand-oriented automation · Influencing gp parameters to improve p the regeneration g efficiencyy of backwashing g filters · Investigation g about cohesion and adhesion in backwashing g filtration based on p penetrometryy and tension tests · Maximising g comfort and minimising gp pollutant exposure p in the vehicle cabin using g the ventilation system y · A novel coating gp process for p particle binding g to textile interface for improved p antimicrobial performance p · Smart air filtration, air filters go g digital g - Chances and risks of new roads to market · Separation p of crude oil from crude oil contaminated water using g biowaste-waste p polythene y composite p · New p pilot for sludge g electrofiltration and electrodewatering g · Welstrat: An innovative filter media for hot air filter application pp · Improved p fouling g resistance of ceramic membranes using g organic/inorganic g g modification for water purificati p on · Measurement of the PM2.5 oil concentration in water-oil miscible metal working g fluid droplet p emissions and a new aerosol g generator for high g oil-water-droplet p concentrations · Enhancing g bubble-point p testing g capabilities p on wire meshes byy numerical analysis y · Investigation g of regeneration g stabilityy of p pulse-jet j regenerated g filter media under laboratoryy test conditions · Low concentration SO2 purification p p performance of different amine-modified p porous materials · Effect of the temperature p on the degradation g of p polyphe yp nylene y sulfide non-woven bag-filter g media byy NO2 g gas with a continuous-flow exposure p method · Performance of adsorption p system y for water desalination using g metal organic g framework · Pressure drop p evolution during g dust loading g of hollow-fiber membranes · HETA smart filtration 4.0 · Improving p g depth-filter p media using g a new multi-scale appro pp ach · Improving p g the p performance of direct contactt membrane distillation utilizing g spacer-filled p channel · The influence of bimodal p particle systems y on filter cake structures using g micro tomography g p y · About dynamic y modeling g and process simulation of solid bowl centrifuges p g · Round robin test to evaluate the test method according g to ISO 16890 - Air filters for g general ventilation · Developing p g a tester for automated in-line filter testing g · Bagasse g extracts fractionation byy combination of membrane and chromatographic g p technologies g · A setup p for measuring g passenger p g car brake dust particles p emissions · Numerical and experimental p investigations g on loading-dependent g p p particle deposition p in electret filter media · Washing gp performance p prediction off horizontal vacuum belt filters for different wash modes · Deodorizing g filters containing g visible light g p photocatalysts y for air purifiers · Automatic water disposal p for heavyy dutyy and industrial applications pp - removal of hydrocarbons y to ensure environmental p protection · A new set-up p for characterisation off p particle collection efficiencyy on elastic single g fibres · Experimental p characterization of p particle structure re-arrangement g and detachment from a steel fiber exposed p to hot air flow · Generation and characterisation off reactive/inert particle p aerosols · Back cleanable air filter elements for critical dust systems y - US HEPA, IFA H and EN1822 HEP PA · A comparative p investigation g of soluble filter cakes upon p contact with liquid q droplets p · VisionAir Clean for clean room air change g rate optimization p · Experimental p studyy on the p preparation p of ceramic fiber filter elementt for hot g gas filtration · Hydrodynamic y y Influences in Dissolved Air Flotation · Reducing gp pressure drop p of coalescence filtration media byy p patterned modification of wettabilityy · Methods to increase the filtration p performance of metal woven wire cloths · Performance of two online p particulate matter measurement principles p p in a fertilizer industrial prilling p g tower · Filtering g of high g solids concentration media using g complex p p powerful to the flow · Some aspects p of application pp nanostructured filter media in air and water filtration · The effect of membrane structure p prepared p from carboxymethyl y y cellulose and cellulose nanofibrils for filtration and biochromatograph g p ic separation p · Feedbacks on p performance tests with Filtralite® media compared p to conventional media filters at p pilot scale · A p probabilistic-statistical model of change g in p particle size distribution in fine filters · Investigating g g the cleaning g efficiencyy of filters clogged gg with metallic nanoparticles p · Co Combined p porous mesh metals for filters and capillary p y fencing g devices · Geometrical model of the p porous structure of the permeable p material and the new experimental p method off determinig d g its structural characteristics · Interaction between p polysaccharide y and p protein on membrane foulingcaused g byy microbial metabolite · Effect of ethanol concentration on n filter cake characteristics in microfiltration of ye y ast suspension p · Powder sampling p g with a p pressure p portt on the high g p pressure natural g gas filter for differential p pressure g gauge g · Cha aracterization of an electrostaticallyy charged g water spray p y for reducing g fine dust emissions · Experiments p on the rearrangement g behaviour of dust in wall flow filters · Two yyears of filter testing g experiences p according g to new ISO 16890 · HEPA/ULPA filter leak testing g for production p control using g solid PSL (Polystyrene-Latex) ( y y ) aerosol · Experimental p methods in i dust emission p prediction · Bionics in application pp : Superhydrophobic p y p functional textiles for the removal of oil contamination from water · Simulation and experiments p on the ca ake formation in dust filtration with fabric filters · Influence of the deliquescence q and efflorescence off hygroscopic yg p salt particles p on the performance p of surface filters · A susta sustainable, modular and lean solution for p pocket filter assemblyy · Flow through g randomly-oriented y fibrous filters · Numerical and experimental p investigation g of filter cake formation during g solid-liquid q separation p byy resolved CFD-DEM coupling p g · A new methodology gy for continuous scanning g of p particle aerodynamic y diameter and application pp to filtration p performance assessment of a room air p purifier · Advances in p plasma deposition p of functional nanocoatings g for filtration applications pp · Efficiencyy of collection of p particulate matter and maximum p pressure drop p of p precoating g · Cost and energy gy saving g through g automatic backwash filter in PE production p · Cabin air quality q y and energy gy savings g in electric vehicles byy using g a smart filtration system y · Characterization of p performance relevant media p properties p in oil mist filtration · Dynamic y simulation of mechanical dewatering g of compressible p cake in decanter centrifuges g · Sustainable p production in the metal industryy - Separation p off ® valuable components p from acidic effluents · Recent developments p in industrial wastewater treatment byy aerobic and anaerobic Membrane Bioreactors · Sinterflo FMC ((fibre metal composite) p ) - Development p and application pp · A New PM2.5 Assessment for a Gas-Liquid q Cross-Flow Arrayy System y as Dust Separa p tor · Computer-aided p studyy of the diesel-water separation p efficiencyy of screen meshes · Applied pp colloidal aggregation: gg g Separation p of fine p polymer y p particles from dilute suspensions p byy magnetic g seeded filtration ((Microplastics) p ) · Fractionation of ultrafine p particles byy size and density: y evaluation of separation p efficiencyy byy UV-VIS spect p rometryy · Automation of particle p classification in a tubular centrifuge g based on a dynamic y short-cut p process model · Monitoring g technique q for mechanical expression p using g electrokinetic response p caused byy liquid q flow through g filter cake · Simulation of solid p particle separation p in self-cleaning g filter with dynamic y filtration · Application pp of antifouling g filter media based on nanofibres in liquid q filtration · Pre-filter design g of high g efficient multilayer y filter media for p pulse cleanable filter cartridges g for challenging g g atmospheric p conditions · Test of cabin g gas filters · New test method for bag g house filters · CORES -Vacuum drum filter for highly g y corrosive media · Controlling g specific p p properties p of p paper p wet laids for air filtration byy means of hydro-entanglement y g t · Simulation Based Analysis y of the Multi-Stage g Filter Cake Washing g · Augmented g filter media development p byy virtual p prototype yp op ptimization · New Flexible Ceramic Filter Media for Microfiltration · Design g of a multi-purpose p p fuel filter sytem y to better understand the challenges g of biodiesel filtration · Technical extraction of EPS from Streptococcus p thermophilus p byy dynamic y cross-flow filtration on a pilot p scale · Modeling g the dynamics y of filtration processes p under variable flow conditions · smartMELAMINE® - The firstt melamine meltblown nonwoven · Determining g the filtration p properties p of different p protein crystals y in the centrifugal g field using low volume samples p · Optimization p of g gas input p t in aqueous q two-phase p flotation ((ATPF)) for enzyme y p purification · New Development p in Bag g Filtration · Benefits of single g p photometer technology gy in an automated filter tester · The influence of slip p flow on Filtration simulations on the nano scale · High g speed p laser drilling g of p precise micro and nano holes in metallic surface filters · Bio-inspired p separation p - Formulation of an innovation model and ideation tool to boost innovation in the sector of separation p technology gy · Filtration p performance of PAN fiber p produced byy centrifugal g spinning p g using g DMSO and DMF as solvent · Performance of Nanofiber Filters and HEPA in the collection of nanoparticle p for air filtration · A methodology gy for estimating g water droplet p sizes and predicting p g filter performance p in diesel fuel and lube oil applications pp · Filter cloths: Bluetes anti-abrasion resin · Network model of p porous media - Review of old ideas with new methods · Fractionating g of finest p particles using g the crossflow filtration · Bekaert Bekipor p ® Metal Fiber Media Filtration Solutions for Hydraulics y · High-pressure g p operation p of spiral p wound membrane elements: The relevant aspect p of p permeate channel fluid dynamics y · Best Practice for Liquidq Liquid q separation p with cartridge g coalescers · Effect of aeration on hollow fiber microfiltration characteristics of activated sludge g · Filtration modeling g and simulation with GeoDict, from filter media to filter element · Identification of fiber characteristics of a filter media based on artificial intelligence g ((AI)) with GeoDict · Comparison p of different discharg ging g methods and test aerosols for measuring g the efficiencyy of electret filters · Assessment of commercial cartridge g filters for usage g in low-cost household water treatmentt systems y · FILOS - Module I: The novel software for the reliable analysis y of filtration test data and suspension p characterization including g washing g and deliquoring q g of filter cakes · FILOS - Module II: The novel software for the reliable selection, performance p prediction p and optimization p of filters for the cake forming g filtration of suspensions p · CENTRISTAR - A novel software for filter centrifuges g · Benefits of filter presses with artificial intelligence p g ((AI)) support pp in the chemical and mining g industries · Heat exchange g simulation for single g HF membrane module using g CFD modeling g · The effectt of p particle sedimentation on the p performance of p pressure filters · Collection efficiencyy of a bag g after 3 yyears of use in a bag g filter · The Krauss-Maffei Peeler centrifuge g with pneumatic cake discharge p g · Development p and p performance test of MIL-88 based filter structure using g electrophoretic p deposition p · Experimental p studyy of the separation p degradation g of dyes y using g composite p p photocatalytic y membrane treatment · Novel sintered metal filter elements: Performance evaluation in biomass gasification g conditions · A flexible approach pp for meso-scale filtration modelling g based on Open-Source p CFD · Influence of fiber size distribution on the p permeabilityy of fibrous filters · Production and characterization of filter media obtained byy electrospinning p g for applications pp in air filtration · Assessment of filter media p properties p for automatic selff-cleaning g filters · Development p of microfiltration membranes of biodegradable g biomass p plastics with the aid of surfactants and their application pp to depth p filtration · Associating g filters by series for optimizing p g the retention capacity p y off nanoparticles p · Sludge g solids concentration: Which are the limits? · Simultaneous dust and noxious gas g separation p in an entrained-flow adsorber on surface filters · Filter testing g regarding g g separation p efficiencyy in terms of airborne fungal g spores p · Droplet p size measurement of cutting g fluid aerosols · Aspec p ts of air filter testing: g dust loading g · Proof-of-concept pt of a newlyy developed p device for the coupled p g generation and separation p of crystalline y p particles · Energy gy reducing gp polymeric y filtration mesh · Influence of oil droplet p size distribution on the fouling g mechanisms of UF/MF membranes during g filtration of oil nano-emulsions · Whyy dewaterabiltyy of sewage g sludge g occurs upstreamp a model to q quantifyy the effects · Low p pressure drop p media for A+ filters · Investigation g of filter cake characteristics regarding g gp particle shape p and wettabilityy · Process simulation and characterization of nonwoven inhomogeneities g and their negative g effect on filtration due to local flow rate heterogeneities g · 0.45 micron g grade microfiltration composites p for solid liquid q separation p · Measurement of the p porosityy of spherical p p particle deposit p formed byy filtration: Discussion on the Peclet number; effect · Combinatorial optimization p of double-layered y filtration media for higher g p performance · Multipore p ™: The state-of-the-art wire mesh · Air separation p from a hydraulic y tank using g special p meshes · Understanding g the role off cake structure in the filtration of needle-like crystals y in the p pharmaceutical industryy · Behavior of metallic filters used to p protect HEPA filters in case of vapor p release · Evaluation of process p strategies g to homogenize g the lautering g filter cake structure and enhance wort production p · Investigation g of the Filtration Kinetics of Depth p Filter considering g Tomographic g p Data · Exentis Group p AG: Industrialized Additive Manufacturing g · New approaches pp for p phosphate p recoveryy applying pp y g iron hydroxide y containing g material in adapted p sorption p processe · Testing p g the efficiencyy of p process filtration of viruses in g gases with p protein nanoparticle p surrogates g ·Ap probability and statistical model of p particle separation p in hydrocyclones y y · New synthetic y nano-aerosol for accelerated realistic ageing g g of air filters · Optimizing p g spunbond p nonwovens for filter media production p using g a novel approach pp of machine learning g and fiber/fluid simulations · Separation p and dewatering g of biological g microparticles p from low concentrated suspensions p byy using g the energy gy efficient thin film filtration · Microsand cross flow filtration in cooling g towers water circuit - a sustainable approach pp for hvac systems y · Size characterization of p plastic microparticles p · Modelling g off the mechanical aging g g behaviour of PLA-based nonwovens and monofilaments under filter application-relevant pp conditions · Clarification of low concentrated microalgae g suspensions p byy decanter centrifuge g · Environmental issues of waste tire recycle y system y · Filtered dryy stack tailings: g The 'state of p play' y for high g capacity p y tailings g filter p plants · The effect off normal load on the shear yyield stress of suspensions p · New p physical y p principle p of dilution system y for crankcase ventilation filter testing g · Filter media testing g in accordance with ISO 16890 · A multi-scale studyy of the p permeabilityy of compressed p nonwoven filter media · Measuring g the maximum p pore size of a filter, choosing g the most statisticallyy robustt parameter · Flow resistance evaluation through p g nonwoven filter media · Experimental p assessment of deposition p of synthetic y fibrous dust within the ductwork of residential ventilation ® systems y · Measuring g PM2.5 for cleanable filter media in ISO 11057 or ASTM D6830 tests using g an optical p aerosol spectrometer p Promo LED · Pore Size of the Spunlaced p Nonwovens and Optimization p of the Parameters for Air Filtration Application pp · Characterisation of micron p pore size filter media comparison p of methods ·Predicting g collision efficiencies of colloidal nanoparticles p in single g spherical p and fibrous collectors: A numerical study · Tackling urgent water related p problems in the mining g industryy using g membrane processes · Filters with low tortuosity produced in a roll to roll process…

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