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Maschinen- und Anlagenbau

International R E P O R T Centralized Sewage Treatment

Dear reader,

– A Worldwide Solution? Today's situation of sewage treatment Already in 3800 BC, faeces together with wash water and storm water had been discharged from households in one channel. The most famous evidence for the old tradition of wastewater discharge is the "cloaca maxima" in Rome which was built in the 5th century BC. One has tried ever since then to dispose of this unpleasant material by discharging the wastewater. In contrast to the time of the Romans, the wastewater today contains much more nutrients and pollutants, due to the significantly higher population

density, which need to be separated in view of their harmful impact on the environment. We have therefore hold on to the old "Roman concept" of combined discharge of all water flows, completing it with a modern centralized sewage treatment plant.

The wastewater flows that are introduced into a centralized sewage treatment plant consist of: ● Faeces with a high organic carbon concentration ● Yellow water (urine) with a high nitrogen and frequently also medicine concentration ● Potable water for transportation of faeces

● Wash water from showers, washing machines, dishwashers ● Process and cleaning water from different industries ● Storm water (in combined systems) with greatly varying loads, dependent on the charge area With regard to the estimated 2.4 billion people (WHO) in Asia, Africa, South America but also Europe who are not having access to orderly sanitation facilities, the question arises whether the described way of wastewater treatment is the appropriate and useful method for all people or whether there could be found intelligent, reasonable and modern alternative concepts which do not require expensive sewer systems.

Content: Centralized Sewage Treatment

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Mechanical Preliminary Treatment with HUBER Machines

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There is only one name for grit washing: HUBER

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WAP/SL Screenings Wash Press – A Synonym For Best Results

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New: High Pressure Screenings Wash Press

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The Whole World Of Sludge Treatment

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HUBER Septic Sludge Treatment in Kuching/Sarawak

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KLEIN – The Sludge Treatment Specialist

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Sewage Sludge Screening Eliminates Operating Problems

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Low-Temperature Drying: KLEIN Recirculating Air Sludge Dryer

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Application of the CONTIFLOW® Sandfilter (CFSF)

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HUBER Service: A Customer Designed Product Product-Related Service to the Customer's Optimal Benefit

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RoK 1 Storm Screen Excels at Wigan, UK

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Please feel invited with this HUBER REPORT issue to visit our IFAT stand in hall A 2, No. 339/432, where we will of course present innovative products and provide according information. The IFAT is also a welcome opportunity for us to personally discuss your demands, requirements for new developments, product improvement and trends. We are especially looking forward to such exchange of information. The IFAT is certainly an international meeting point and t h e exhibition the world is looking at and visitors from all over the world will travel to. So we will have the chance to present ourselves to our international guests, too, and analyze their specific requirements to be able to develop and offer the suitable products individually tailored for each target country. The IFAT is in this sense an important event which gives us the possibility to question especially the export chances of our products, open up new ways and establish contacts. Though HUBER is meanwhile represented in 44 countries by subsidiaries, own and representative Roughly estimated, the costs for laying only one meter DN 800 sewer is exactly the same as for connecting one inhabitant to a decentralized sewage treatment plant (assumed 400 E per p.e.). In countries and areas where there is no orderly wastewater disposal existing today, new technologies are required which are able to improve fast, at low cost and efficiently the situation of the people living there and their environment. If the principles presented below are taken into account, the preferable solution seems to be decentralized sewage treatment, i.e. treatment of the wastewater at source.

offices, we have to be goal-directed orientating us to the very specific demand of the countries if we want to be successful there. We are already today realizing this by considering the individual conditions of different countries, developing products, systems and processes in close cooperation with universities in Germany which are especially suitable for export territories. This has also been considered with our products and ideas for decentralized wastewater treatment we will be presenting. They take up a trend which is increasingly developing especially in emerging countries. Decentralized sewage treatment allows for efficient wastewater conditioning at relatively low cost and for reuse of water resources. We would be very pleased to welcome you on our IFAT stand. You will find there a presentation of our new products and performances, especially in the field of service and industrial wastewater treatment. On the other hand, the information we will receive from you in personal discussions will help us to further improve new products and services. That is why we are especially looking forward to your visit! Yours sincerely,

Hans G. Huber

Direct benefit Design and construction of sewer systems usually takes up a time of several years. Since a centralized sewage treatment plant is naturally useless without the sewer system, the benefit starts to set in only after quite a time lag. Decentralized plants start cleaning the wastewater immediately after delivery, which takes only few weeks for standardized products. Such a construction provides a direct and immediate benefit. Reasonable costs with an immediate effect

To be continued on page 5


Mechanical Preliminary Tr

with HUBER Mach COARSE SCREEN: HUBER CLIMBMAX® Climbing Screen Bar spacing: Channel width: Channel depth:

FINE SCREEN: ROTAMAT® Micro Stra

100 - 10 mm 600 - 2500 mm up to 10 m

Separation of coarse material from big flows ● In front of sewage treatment plants to protect fine screens ● In front of pumping stations and intake structures as a protective system ● For screening of combined water in sewer systems

FINE SCREEN: ROTAMAT® Fine Screen Ro 1

Bar spacing: Channel width:

FINE SCREEN: ROTAMAT® Wedge Se

6 mm and 10 mm 600 - 3000 mm

Separation, washing, compacting and transport of screenings ● Combined in one unit ● High separation capacity ● Forced cleaning of the screen basket ● Well suitable for septic sludge treatment

FINE SCREEN: STEP SCREEN® Flexible Bar spacing: Channel width:

FINE SCREEN: ROTAMAT® Drum Filte 6 mm and 3 mm 500 - 2000 mm

Cost-effective separation and transport of screenings ● In front of sewage treatment plants ● Flexible installation possibilities ● Compact design ● Low head loss

FINE SCREEN: STEP SCREEN® Vertical Bar spacing: Channel width:

FINEST SCREEN: ROTAMAT® Membr 6 mm and 3 mm 600 - 2000 mm

Cost-effective separation and transport of screenings ● Flexible installation ● Compact design ● Deep channel installations ● High discharge height ● Low head loss

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reatment

SCREENING AND GRIT SEPARATION: ROTAMAT® Mini Complete Plant MiniCoP Throughput capacity: up to 5 l/sec Separation and compaction of screenings Separation of grit ● In front of small sewage treatment plants ● In front of pond plants and hydrophyte treatment plants

hines

● In front of hotel sewage treatment plants

SCREENING AND GRIT SEPARATION: ROTAMAT® Complete Plant Ro 5

ainer Ro 9 Bar spacing:

6 - 0.5 mm

Throughput capacity: up to 200 l/sec

Channel width:

300 / 400 / 500 / 700 mm

Separation, washing, compacting and transport of screenings

Separation, washing, compacting and transport of screenings

Separation, dewatering and transport of grit Separation and transport of grease

● Combined in one unit

● Turn-key system for mechanical preliminary treatment

● Excellent quality for low price ● For small and medium size sewage treatment plants

● With optional aeration ● Compact design ● Low expense for construction work

ection Screen Ro 2 Bar spacing: Channel width:

SCREENING AND GRIT SEPARATION: ROTAMAT® Complete Plant Ro 5 / K

6 - 0.5 mm 600 - 3000 mm

Throughput capacity: up to 160 l/sec Separation, washing, compacting and transport of screenings

Separation, washing, compacting and transport of screenings

Separation, dewatering and transport of grit

● Combined in one unit

Separation and transport of floating material

● Maximum separation capacities

● Turn-key system for mechanical preliminary treatment with minimum space demand

● Best suitable for grit-containing combined water

● Increased separation surface due to lamella units, but small dimensions

● Eliminates the necessity for preliminary clarification

● Low expense for construction work

er Screen Ro 13

SCREENING AND GRIT SEPARATION: ROTAMAT® Complete Plant Ro 5 / C Throughput capacity: up to 25 l/sec

Bar spacing: 6 - 0.5 mm Channel width: 600 - 3000 mm

Separation, washing, compacting and transport of screenings

Separation, washing, transport and compaction of screenings

Separation, dewatering and transport of grit ● Complete system for mechanical preliminary treatment with minimum space demand

● Especially suitable for in-line installations ● As a pre-treatment for grit washing

● Increased separation surface but small dimensions

● Compact design

● Low expense for construction work

● Completely encased system to eliminate spray water, aerosol, odors

GRIT SEPARATION: ROTAMAT® Circular Grit Trap HRSF

rane Screen Mesh size: Channel width:

1.0 - 0.2 mm 600 - 3000 mm

Throughput capacity: up to 125 l/sec Separation, dewatering and transport of grit Separation and transport of floating material

Separation, washing, transport and compaction of screenings

● Subsequent to screenings removal

● Especially suitable in front of membrane bioreactors

● Increased separation surface due to the separator cone, but small dimensions

● Removal of fibrous material and hairs

● With optional aeration ● Compact stainless steel design

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There is only one name for grit washing: HUBER The RoSF Grit Treatment Systems underline their leading position process technology and has become an essential component at the headworks! Combining reliable grit separation and upflow washing in the fluidized bed, the COANDA Grit Washing Plant offers the function of a grit classifier and at the same time reduces the organic material concentration in the grit to below 3%. Handling of up to 30 mm mineral grain size is no problem for the COANDA Grit Washing Plant and ensures the maximum yield of mineral fraction. Of course, the HUBER COANDA Grit Washing Plant, which had got a new outfit in 2000, has to gain acceptance in the market, competing against cheap would-be grit washing plants and copies. Fortunately, operators no longer seem to accept delivery of a "black box" which frequently turns out to be unable to achieve the required separation efficiency and guaranteed loss on ignition!

HUBER ROTAMAT“ COANDA Grit Washing Plant RoSF4 COANDA Grit Washing Plant Do you remember IFAT 1999? That was when we presented HUBER as the market leader with about 300 sold COANDA Grit Washing Plant units RoSF4. Now as the next IFAT is coming up, we can proudly report 600 worldwide COANDA Grit Washing Plant installations. This

high number of references proves impressively that the patented COANDA Grit Washing Plant is not only nationally but also internationally the state-of-the-art technology for washing of contaminated grit from sewage treatment plants! With an annual export share in excess of 50% the Grit Washing

Plant has been firmly established in Europe, USA and even Australia and sets also there the standards for grit washing, as it has done in Germany for years already. The COANDA Grit Washing Plant has been fully accepted by the relatively conservative mechanical wastewater treatment sector as a new innovative

Complete Grit Treatment Systems The situtation in Germany is as follows: Since introduction of a new regulation in 1993, any residential waste not complying with the criteria specified in this regulation have to be thermally pre-treated in a waste incineration plant. After expiry of a transitional period

until May 2005, the only waste allowed to landfills will be unreactive waste. The same time limit applies to untreated residential waste that has by now frequently been disposed to landfills, so that disposal costs for grit from sewer systems, sink pits and refuse will dramatically rise. By adding other process modules, the COANDA Grit Washing Plant can be completed to a full Grit Treatment System RoSF5, which typically consists of a feed arrangement and storage tank, coarse material separation and grit washing. The RoSF5 system ensures easy economical and ecological treatment of refuse grit, grit from sewer systems and sink pits and even highly contaminated oil grit. The first grit recycling system had been started up in 1995 already. Meanwhile, almost 50 installations with different components are operated all over Europe. Dependent on the specific requirements, the grit recycling plants are equipped with an optional separate water conditioning plant which ensures recovery of mineral material without any additional water demand. If you wish to obtain information where to find a near COANDA Grit Washing Plant or Grit Treatment System installation, contact us! By Wolfgang Branner

WAP/SL Screenings Wash Press – A Synonym For Best Results

New: High Pressure Screenings Wash Press

Measurements confirm the washout degree of >95%

- Washing of screenings and simultaneous dewatering with high pressure

One of the big water authorities in England had tested the WAP/SL for 6 months. The experienced results were deciding for the following framework agreement. The quality requirements for washed screenings are very high in England, demanding very good washout degrees and dry substance contents (DS). Both sizes together give a quality factor (QF) which explains the biological oxygen demand (BOD5) per g DS. A small QF stands for effective screenings washing (low BOD5) and high DS content. The QF required in England is

Some Test Results

< 20 mg BOD5 / g DS! But operational reliability and easy maintenance are just as important since

many sewage treatment plants in England are operated from telecontrol stations. Summary: The six months testing phase has impressively shown the innovative benefits of the WAP/SL. A) The very low QF in the washed screenings proves how intensive washing and pressing is by the WAP/SL. The QF reduction of > 95% related to screenings underlines that on the one hand plenty of carbon was washed back into the sewage treatment plant and on the other hand much less screenings had to be removed due to the increased DS. B) No great difficulties occurred during the full test period and no considerable wear was noticed despite continuous operation of the plant (24 h/d).

The WAP/SL during its six months test operation

By Wolfgang Branner

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Conventional high pressure units often achieve only poor dry substance contents (DS) when processing municipal screenings without prior washing. The viscosity of faeces, grease and sludge, which are always contained in the screenings, does not allow built-up of higher pressure in the press (see fig. 1). It is absolutely necessary therefore to have the screenings washed before in order to achieve high DS contents. This conventional way of screenings treatment causes often very high investment, maintenance and spare parts costs. The new WAP high pressure wash press (/WAP/HP) is a successful symbiosis between the well-proven high pressure component of the ROTAMAT® wash press type

Ro4/HP and the WAP wash press. Screenings washing takes place in the wash zone, like in the WAP, which is located in the conveyor pipe. The washed screenings are then conveyed into the high pressure cone where intensive pressing takes place. The intelligent technique in the high pressure cone allows to react within seconds to possibly occurring material changes in the screenings, i.e. the machine operates permanently at the highest pressure in the press zone and achieves therefore continuously excellent DS contents between 50 and 60%, as the first reference plants show! By Wolfgang Branner

Fig. 1 left: screeings before washing; right: washed screeings


Continuation of page 1

Centralized Sewage Treatment – A Worldwide Solution? regularly and treated as shown in figure 1. In a following step, the effluent from the multi-chamber tank can additionally be treated by means of a simple biological system, such as rotating biological contactors. To collect the effluents of several tanks, such a system demands small channels, which are for example created with a plow. The sludge produced by this clarification process can be collected by trucks together with the faeces. Fine screening of wastewater

Fig. 1: Treatment concept for faeces from decentralized multi-compartment septic tanks and hygienic conditions, that do at Up to 90% of the investments for the Technical limitation complete sewage treatment facility In many areas of the world building this time not seem to have any chanare consumed by the sewer system of a sewer system is generally ce, due to financial reasons, to reach the standard of industrial nations. and have to be made during the con- impossible as We are rather sure to provide those struction phase but do not achieve countries the chance to make it even any benefit at that time. ● The load-bearing capacity of the better. foundation soil is insufficient or The investment and operational costs of decentralized plants, however, are low and calculable and directly coupled with the requested effect.

shows tectonic activity. ● The infrastructure of urban areas

Described below are some alternatives how to achieve a direct and sig-

Another treatment concept collects the wastewater from several dwelling units and separates the solids by means of a fine screen. A COD elimination of up to 60% can be achieved, which can be further improved by using additives. The residual material is composted or fermented, dependent on the amount. Of course, the screened wastewater can later be further clarified in a biological treatment stage without making fine screening superfluous. Integrated sanitation concepts Integrated sanitation concepts are concepts with nearly completely

of evolved mega cities is too dense. ● The individual households in

Autonomy

rural areas are too far apart. ● The falling slope is insufficient

Centralized sewage treatment enhances careless handling of the own wastewater, which results in ever rising expenses for wastewater that contains increasingly difficult to treat components. Decentralized systems prevent such carelessness, as the consequences of wrong handling have an immediate and directly visible effect for the operator.

The screened faeces are composted or fermented, whereas the yellow water is treated in a membrance activated sludge process together with the washing machine water and cleaning water. The clarified and disinfected wastewater is suitable to be used for irrigation. Such a concept saves a considerable amount of valuable potable water. Especially in countries where potable water recovery means a considerable technical and financial expense, any measure must be taken to use water as often as possible. Also other clarification concepts are conceivable, which could consists of SBBR fixed bed reactors, rotating biological contactors or chemicalphysical treatment and screening. The selection of the optimal process chain depends on the specific limiting conditions and requirements. Summary

the sewage treatment works. ● The solids concentration and thus viscosity of the waste water is too high to be flowable (caused by small wash water amounts and/or introduction of waste food). ● Extreme rain intensity occurs which cannot be handled (e.g.

Individual flow treatment

Individual flow treatment in decentralized systems is the reasonable alternative. Greywater can be conditioned to service water by means of relatively simple technical methods, faeces and kitchen waste can be used energetically and material recovered from industrial wastewater. Decentralized systems also provide the possibility to collect pollutants in a small and concentrated flow and treat this flow individually.

Faeces are collected together with yellow water and both separated by fine screening. As the contact time of both flows within the house installation is very short, the solids hardly dissolve in the liquid phase so that screening is efficiently separating faeces and yellow water. The ultrafiltrated greywater may be used as flush water for toilets. The application of vacuum toilets is also possible.

to transport the waste water to

monsoon).

In a sewer system, the described types of wastewater are combined, which makes their treatment expensive and complicated.

bacteria or viruses, it can be used in washing machines and as cleaning water.

A possibility for sewage treatment in such cases is provided by decentralized systems only.

Fig. 2: Diagram of an integrated sanitation concept nificant improvement for people and their environment by applying the concept of decentralized sewage treatment.

Septic sludge treatment Decentralized systems In view of all the reasons mentioned before, it is most useful to adjust our technologies such that they can be integrated into the concept of decentralized wastewater treatment. We are working hard to develop product designs which are able to give also those areas in the world a perspective for an environment worth living in and for clean potable water

In many countries the precondition for a short-term solution of the sewage problem is the specific collection of faeces and yellow water in multicompartment septic tanks. Such septic tanks with preceding percolation channels can be made even by the inhabitants themselves. The multi-chamber tanks retain the faeces, which represent the main load of dangerous germs and oxygenconsuming compounds. The retained faeces have to be pumped off Page 5

independent water supply and disposal within a sanitary unit. The water is treated and reused according to its pollution rate. Such concepts will hardly be applicable in newly industrializing and developing countries in the foreseeable future but rather in large hotels or industrial parks. The central point of the concept is separation of grey from black water, which can quite easily be achieved, even subsequently, by means of appropriate house lines. After preliminary clarification in a small screening plant the greywater from showers and wash-basins is fed into an ultrafiltration plant to remove hairs and grit. Since the water has then a low lye and surfactants concentration and does not contain any fungi,

Decentralized treatment of wastewater is in many cases – whether in Germany, Europe or newly industrializing and developing countries – an economical, ecologically reasonable or technically required measure. The systems and processes presented hereunder have been selected as examples and must individually be adjusted to the specific legal, financial and prevailing structural conditions. Whether municipal or industrial concepts for decentralized wastewater treatment – HUBER is a competent partner for any requirement. Additionally, customers can as always count on HUBER also if they need equipment for centralized sewage treatment plants. If you wish to obtain more detailed information about the HUBER concepts and products for decentralized sewage treatment, do not hesitate to contact us or visit the HUBER stand at IFAT 2002 in Munich (hall A2, stand 339). Hans Huber, Dr. Oliver Christ


The Whole World O Sludge Screening: ROTAMAT® Sludge Screening Plant RoS 1

The product: The Sludge Screening Plant serves for mechanical treatment of sludge, consisting in a ROTAMAT® Fine Screen or Micro Strainer installed in a tank. As the sludge flows into the tank and through the screen, any undesired material is separated. While a screw conveyor with integrated screenings press removes the separated screenings from the tank, they are dewatered and reduced in volume prior to being discharged into a skip. The complete clarification process takes place in a closed system, which eliminates odor annoyance. The screenings are additionally washed. The press liquor flows back into the wastewater stream, the obtained screenings are clean and suitable for disposal at landfills. The press liquor of the liquid phase with a high BOD load is passed on into the sewage treatment plant for further treatment.

The sturdy and efficient Sludge Screening Plant achieves without problems a maximum throughput capacity in excess of 300 m3/h and is available with 3 to 12 mm bar spacing. The plant has well proven its capability in numerous installations, even with grit and stones, and is the best-selling machine of its type worldwide.

Some of the benefits: ● High separation efficiency ● Low head loss ● Screening, transport and dewatering combined in one unit ● Sturdy, low-maintenance stainless steel design

Sludge Thickening: ROTAMAT® Screw Thickener RoS 2

The product: ROTAMAT®

The Screw Thickener serves for thickening of different types of municipal sludge and separation of fibers in industrial applications. After addition of polymer, the sludge flows into the wedge wire drum of the Screw Thickener where it is pre-dewatered. The high degree of admission of the drum prevents re-dilution of the thickened sludge. The free water passes through the wedge wire into the outer wall of the thickener from where it is discharged by gravity. The polypropylene brushes mounted on the screw flights clean the wedge wire from inside. The time-controlled spray nozzle system ensures a free filtrate outlet. The thick sludge is by pump delivered to further treatment. An intermediate storage tank for the thick sludge provides also in this section for a closed integrated system.

With the three available different model sizes, capacities of up to 100 m3/h can be achieved with one unit.

Some of the benefits: ● Compact and closed design, minimum space demand ● Inclined installation with discharge on top ● Controllable solids concentration between 5 % and 12 % DR ● Corrosion and wear resistant stainless steel construction ● Flexibly applicable, also as a mobile unit

Sludge Screening: STRAINPRESS® SP

The product: STRAINPRESS®

The is a horizontal pipeshaped continuous coarse material separator which consists of inlet and driving zone, screening and press zone and finally a discharge section with pressure cone and pressure cone adjusting system. Feeding is by a pump which presses the medium through the screening zone and forwards it via the outlet pipe to further process steps. The coarse material retained on the screen surface is transported to the press zone by the screw which serves as a removal unit. In the press zone, the material is dewatered to spadable condition prior to being discharged. The motor speed, screen perforation and geometrical design of the discharge section can be adjusted to all different media. The coarse material is separated continuously under pressure, periodical cleaning of the screening zone by backwashing is not required. Screening is achieved with 0.35 to 10 mm perforation.

Sludge Th Dra

Some of the benefits:

The product:

● Continuous sludge screening

The KLEIN Drain Belt excels for its simple process, easy operability and minimum wear. The sludge is fed onto the filter belt which rotates at approx. 15 m/min and separates by gravity the water previously set free by flocculation. Separation is assisted by pillow blocks which repeatedly restack the filter cake and create in this way new drainage ways for the free water. Hardly any mechanical stress is exerted on the sludge as it is transported on the filter belt, which results also in a low polymer consumption.

● Coarse material dewatering and solids removal combined in one unit ● Retrofitting into pipe lines is possible without additional storage tanks and conveying units as the STRAINPRESS® is a closed system (in-line installation with minimum space demand). ● Self-cleaning screen surface and readjustable sieve cleaning screw ● Reliable operation and constant dewatering results due to automatic performance control and pressure cone adjusting mechanism

The belt velocity can be controlled by frequency converter and can be adjusted to suit specific requirements. Filtrate is used for belt cleaning. The KLEIN Drain Belt achieves without problems throughput capacities of up to 80 m3/h per unit and has a patented forcedguided belt so that any belt drift is definitely avoided.

Sludge Dewatering: ROTAMAT® Screw Press RoS 3

The product:

With the three available different model sizes, capacities of up to 20 m3/h can be achieved

ROTAMAT®

The Screw Press serves for sludge dewatering and solids separation of small flow rates and has well proven its capability for many years, especially in paper and food industries. The Screw Press excels for its closed design and easy operability. Its very low connect load makes it one of the most economical machines for sludge treatment on small sewage treatment plants. The sludge is fed directly into the screen basket, from where the screw conveyor transports the material at low speed (approx. 2 - 3 rpm) towards the discharge on top of the plant. While the decreasing screw pitch and drum diameter continuously increase the pressure on the sludge, a pneumatic cylinder on the discharge controls the counter pressure and thus the dewatering efficiency of the Screw Press. The wedge wire cylinder is cleaned by a washing system which can be operated with used water. The small wedge wire spacing guarantees an excellent filtrate quality.

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Some of the benefits: ● Compact and closed design, minimum space demand ● High efficiency despite low operating and maintenance costs and reduced operator attention ● Fully automatic continuous operation requires only minimal attendance ● Best quality for low price ● Corrosion and wear resistant stainless steel construction ● Flexibly applicable, also as a mobile unit

Sludge De Boge

The product: The KLEIN Belt Filter Press is one of the bestselling sludge dewatering machines worldwide. The first KLEIN belt press had been developed in 1960 and was continuously further developed and optimized. The latest development is the KLEIN Bogenpress which consists of four dewatering zones: 1. High-performance predewatering zone: The sludge that has been conditioned with polymer is thickened under gravity. Additional pillow blocks repeatedly restack the filter cake to achieve a rapid solid/liquids separation. More than 50 % of the water contained in the sludge is separated in this zone. 2. Wedge zone: In this predewatering zone the filter belts slowly converge like a wedge and ensure in this way a very gentle and regular build-up of pressure in the filter cake. 3. Curve zone: The filter cake, which is lying between the two filter belts, passes over a perforated curved plate, the radius of which is decreasing over its length to achieve a regular and continuous pressure increase, which is slow and gentle enough to compact


Of Sludge Treatment

hickening: ain Belt DB

The KLEIN Drain Belt can be combined with the KLEIN Bogenpress to achieve an improved Bogenpress capacity of up to 80 m3/h, with the same base area and only one-time addition of polymer.

Some of the benefits: ● Reduced mechanical stress minimizes polymer consumption ● Clear filtrate due to gentle flock treatment ● High separation efficiency: approx. 98 %

Sludge Thickening: Twin Belt TB

Sludge Thickening: ROTAMAT® Disc Thickener RoS 2 S

The product:

Some of the benefits:

The KLEIN Twin Belts are based on the same process technology as the KLEIN Drain Belts and excel also for their simplicity, easy operability and minimum wear. In contrast to the Drain Belt, the KLEIN Twin Belt consists of two filter belts with separate drives, which are arranged one above the other. The upper filter belt is running at increased speed and the KLEIN Twin Belt is able to virtually double the throughput compared to that of the Drain Belt.

● Reduced mechanical stress minimizes polymer consumption ● Clear filtrate due to gentle sludge treatment ● High separation efficiency: approx. 98 %

The belt velocity can be controlled by means of a frequency converter to suit individual requirements. Filtrate is used for belt cleaning.

The product: ROTAMAT®

The Disc Thickener is an inclined, slowly rotating filter disc construction. The filtration unit consists in a circular micro filter with constant mesh. The filter disc is selfsealing and installed into a closed stainless steel tank, it divides the tank into a thickening and a filtrate collection zone. The preflocculated sludge flows from the reaction tank onto the filter disc surface. The slightly flocculated sludge settles on the filter, the filtrate water is collected in the filtrate collection zone and leaves the tank through the outlet. An additional scraping device is fitted to the disc surface to support discharge. The inclined arrangement of the entire system ensures that only highly thickened solids are discharged as thick sludge.

The KLEIN Twin Belt achieves without problems a capacity of up to 150 m3/h per unit and has also the patented forced-guided belt which prevents any belt drift.

The standard conception is for cleaning with filtrate. As a result of this system, the solids load in the filtrate is extremely low.

Some of the benefits: ● Sludge volume reduction by up to 90% of the initial volume ● Reliable, compact and closed complete system ● Adjustable and controllable high sludge outlet concentration ● Clean filtrate – Minimized return load onto the sewage treatment plant ● Long life and corrosion-resistance ● Minimal mechanical stress on the sludge flock reduces polymer consumption

Cleaning of the filter disc is discontinuous by means of a spray nozzle bar, which guarantees that no solids will be washed into the filtrate. Such discontinuous cleaning leads to enormous water savings, permanent operation of the cleaning system is unnecessary.

ewatering: enpress BS

the sludge to such an extent that it can be exposed to highest pressures in the following shear and press zone. 4. Shear and press zone: Several press rolls (6 - 10) intensify the pressure on the cake continuously as their diameter is decreasing and exert a shearing effect on the sludge due to the permanent change of direction. The Bogenpress is applicable for throughputs up to 25 m3/h, and for up to 100 m3/h when combined with the BS Combi unit (with preceding Drain Belt).

Some of the benefits: ● High efficiency ● Economical unit, high quality standard ● Any machine components in contact with the medium are of stainless steel ● Oversized, trebly sealed self-aligning roller bearings

Sludge Dewatering: ROTAMAT® Centrifuge RoD

The product:

The available centrifuge sizes cover throughput capacities from 8.0 to 50.0 m3/h.

ROTAMAT®

Decanter Centrifuges are a new development of HUBER Technology. They are preferably designed for high-performance dewatering of municipal sewage sludge but are also suitable for industrial applications. The high-quality stainless steel rotors allow for a slim and yet sturdy design with a reduced weight of the rotating mass compared to conventional designs. Components which are exposed to increased wear are equipped with a high-quality and easy to replace wear protection. The drum and screw conveyor bearings have been designed for a long life and minimum maintenance.

Some of the benefits: ● Corrosion and wear resistant stainless steel design ● Frame and cover with integrated noise protection ● Well-proven hydraulic worm drive ● Flexibly applicable, also as a mobile unit ● Fully automatic operation requiring only minimum operator attention ● Maximum operational reliability due to on-line control of machine parameters

The frame and machine cover are noise protecting. The main drive arrangement provides for space-saving and flexible installation, which makes the machine especially suitable for mobile installations.

Sludge Drying: Recirculation Air Sludge Dryer

The product: The KLEIN Recirculation Air Sludge Dryer is a cost-effective and technologically simple evaporative dryer operating at low temperatures. Additional process stages are not required, especially vapor and exhaust air treatment are unnecessary (dust, odor and pollutants). Dust production is extremely reduced as no mechanical stress is exerted on the sludge during the drying process so that measures or devices for explosion protection are not required. The Recirculation Air Sludge Dryer is a modular design, one module being sufficient for up to 750 kg/h vaporization capacity, which corresponds to approx. 120,000 p.e. The energy required is 0.3 - 1 kWh/kgH2O, dependent on the climatic conditions. The KLEIN Recirculation Air Sludge Dryer can be operated with different types of alternative energy, such as any type of exhaust air, solar energy or simply fuel. Especially solar energy is of significant importance with regard to energysaving operation.

Page 7

The Sludge Dryer is made of stainless steel, due to condensation. Energy supply is automatically controlled on the basis of the ambient and exhaust air moisture and temperature. KLEIN Recirculation Air Sludge Dryers operate automatically and require only minimal attendance.

Some of the benefits: ● Energy-saving evaporative drying ● Use of available exhaust heat ● Modular design for easy system expansion ● No vapor and exhaust air treatment required due to low temperatures


HUBER Septic Sludge Treatment in Kuching/Sarawak Kuching with 350,000 inhabitants, is located on Borneo, Malaysia, about 200 km north of the equator. The city uses mainly the system of cesspools to which the individual households are connected.

ge treatment plant which was finally put into operation in March 2000 and has been working without problems since that time. The HUBER ROTAMAT® products supplied contributed a lot to the

which it is fed into the ROTAMAT® Sludge Dewatering Plant by adding coagulant agent. Most of the solids are separated from the sewage/sludge mixture by this two-stage treatment system which is a mere mechanical system. The two treatment stages achieve a reduction of the COD concentration by up to 90% and of the phosphorus concentration by approx. 80%. These results allow problem-free treatment of the sludge in a conventional subsequent biological treatment stage.

The totally closed design of all HUBER plants minimizes annoying odors. The special climatic conditions required modification of individual plant components. The control

easy to apply, and has been applied, to other processes as well (e.g. treatment of manure from animal farms etc.), we received an extraordinarily positive feedback from many inte-

Details of mechanical treatment: The septic sludge is delivered by tankers to three parallel installations of Sludge Acceptance Plants Ro3.3 with integrated grit trap and stored in the following intermediate storage tank, from where four parallel Sludge Dewatering Plants RoS3, size 2, are fed, adding polymer. The total plant is designed for a capacity of 350 m3/day. Map of Sarawak The septic sludge settles in the cesspools while the supernatant liquor is discharged through a sewer system directly into the recipient. Since they did not have an evacuation concept for the 77,000 cesspools in Kuching until a few months ago,

short construction time and efficient and trouble-free treatment of the septic sludge. The ROTAMAT® machines handle the major part of mechanical treatment. Main part of the plant are the wellproven HUBER ROTAMAT® Slud-

Inside the Ro3.3 the sludge flows through the integrated ROTAMAT® Fine Screen Ro1 which is a well-proven screen that is ideal for this application due to its wear-resistant and sturdy design.

Tanker delivering septic sludge into the HUBER ROTAMAT® Sludge Acceptance Plant Ro 3.3 panels for example were equipped with cooling systems to ensure problem-free plant operation in such a dry area. This is another project which proves impressively that

rested customers already within the first months after plant start-up. Similar plants will soon be realized in cooperation with our partners in Malaysia and will certainly under-

After removal of the coarse material (> 10 mm) the sludge flows into the integrated grit trap which separates gravel and grit particles.

After mechanical treatment the sludge is pumped into storage tanks which have stirrers integrated to produce a homogeneous sludge that is suitable for dewatering.

Complete plant model overflow of the pools was inevitable and the septic sludge made its way directly into the recipient, which led to significant hygienic and health problems for the population living on the Kuching river. To manage the problem, they began in 1998 to plan a central septic slud-

ge Acceptance Plant Ro3 and Sludge Dewatering Plant RoS3. The septic sludge is delivered by tankers and fed into the Sludge Acceptance Plant. The integrated Fine Screen Ro1 removes the coarse material which is discharged into an intermediate storage tank, from

Polymer is added and the septic sludge pumped into the Sludge Dewatering Plant RoS3. A slowly rotating conveying and compacting screw (1-8 rpm) integrated in the RoS3 removes the sludge that has been separated by a wedge wire drum and dewaters it in the course of the process. Due to this principle of slow rotation the forces acting on the structure are considerably reduced and a special foundation or support is unnecessary. Also wear of the machine is reduced to a minimum and maintenance work virtually eliminated. The energy demand is very low (approx. 2 kW per main drive per machine).

Complete mechanical preliminary treatment: removal of screenings and grit by the HUBER ROTAMAT® plant HUBER is able to supply high-efficiency plants at a competitive price. Since this technology is furthermore

line the capability and adjustability of the well-proven HUBER technology. By Franz Heindl

The results are impressive: Sewage sludge with an average solids concentration of 3% is dewatered to a DS concentration of approx. 40%. The removal rate in the filtrate water lies at approx. 95% and can be increased to up to 99% by using a filtrate return pump.

HUBER ROTAMAT® Sludge Acceptance Plant with integrated grit separation

As the dewatering rate is high, addition of lime after the dewatering plant can be minimized and is only required for disinfection. Page 8

Sludge dewatering up to 40 % DS with HUBER ROTAMAT® RoS3


The Sludge Treatment Specialist – Innovative Technology from the leading specialist – The first belt filter press was developed by KLEIN, Niederfischbach in 1960. Whereas sewage sludge had before been "dewatered" mainly by storing the sludge for weeks on sludge drying beds, the new development provided for the first time the possibility to dewater sewage sludge in a continuous process to obtain spadeable and transportable material. The new belt filter press began its immediate triumphant progress at first in Germany and later all over the world. KLEIN has continuously developed the system from the once simple and low-performance machines to high-efficiency systems which could assure their position on the market against other systems, such as centrifuge, screw press and chamber filter press, and are still in a leading position in a lot of countries. Belt filter presses are today available from numerous suppliers worldwide, which are finally all based on the original from KLEIN. Nevertheless, KLEIN is still the leading

supplier with more than 4000 units sold worldwide. In 1985 a new idea was borne: KLEIN established a sludge thickening machine for biological excess sludge. Since the amount of light excess sludge with a low solids concentration was rising as biological treatment methods were improved, KLEIN engineers developed the predewatering drum of their belt filter press to a special reactor for such difficult to thicken light-weight excess sludge. That development was revolutionary. The special reactor was a conical basket covered by a filter cloth that rotated over the longitudinal axis at approx. 10 rpm and separated the water set free by prior flocculation. It was in this way possible to continuously thicken biological excess sludge from approx. 0.5% DS to 5-7% and reduce the volume to less than 10%. 1000 m3 excess sludge left approx. 10 m3 which required further treatment. This system once developed and established by KLEIN is today state-

of-the-art technology and it is impossible to imagine sludge treatment today without this system. The sieve drums were meanwhile replaced by high-performance belt thickeners which are able to thicken up to 150 m3/h excess sludge. With more than 800 sludge thickening units sold, KLEIN is ahead of the field also on this sector. In 1990 KLEIN put the so-called "Air-O-Dry" process on the market. This cost-effective and technically simple drying process for sewage sludge is especially designed for small and medium-size sewage treatment plants. Compared to other known thermal systems the Air-ODry process offers special advantages as it operates in the low-temperature range, which ensures especially economical, eco-friendly and reliable treatment of municipal and industrial sewage sludge. The process is an open process which uses the moisture absorption potential of the ambient air and is able to ensure economical operation under cold or

Fig. 2: HUBER-KLEIN Belt Filter Press for sludge dewatering moist weather conditions by recirculation of air. As the temperature of the drying air is low (approx. 40°C), no detrimental vapors are produced and the exhaust air can be discharged without additional treatment. The KLEIN Air-O-Dry system dries pre-dewatered sludge from belt filter presses, centrifuges or chamber filter presses to up to 90% DS. Drying is managed by easy-to-operate belt conveyor dryers that require

only minimum maintenance. Their energy demand is only half the consumption of thermal dryers. With nearly 20 sludge drying units sold to municipal and industrial sewage treatment plants KLEIN is among the leading suppliers also in this field. HUBER will continue to be innovative on the KLEIN products. By Manfred Dörner

Sewage Sludge Screening Eliminates Operating Problems Untreated screenings in the primary sludge at the STW Berlin-Waßmannsdorf caused tremendous operating problems, which could completely be eliminated by screening the primary sludge with the STRAINPRESS®. The continuous coarse material separator is an enclosed air-tight in-line system integrated in a suction pipe line that separates coarse material from the liquid and dewaters and discharges it in one operation. The STW Waßmannsdorf has been upgraded to handle a future flow of 230,000 m3/day instead of the current 140,000 m3/day. Four traveling screens were installed in the STW’s

inlet but the 8 mm perforated plate segments were not able to prevent fibrous material like hair from passing into and settling in the preliminary and secondary clarification units. As part of the mixed sludge they clogged the heat exchangers and settled on the inflow edge of the plates in front of the sludge digestor. As a result, each of the four heat exchangers had to be opened and cleaned once a week, which is difficult, time-consuming and offensive smelling work. Installation of two SP4 STRAINPRESS® units eliminated the difficulties and the previously installed Mono Munchers were no longer needed.

The STRAINPRESS® is a horizontal pipe-shaped machine for continuous separation of solids from sewage sludge, which consists of an inlet and drive zone, screening zone, integrated press zone and discharge area with a pneumatic pressureregulating cone. The liquid is pressed or sucked through the screening zone. The coarse material retained on the screen surface is transported to the press zone by the horizontally movable screw. Slowly increasing compression compacts the coarse material to a plug. The press filtrate and the filtrate from the screening zone are passed through an outlet pipe for additional wastewater treat-

Clogged channels in the heat exchangers ment processes. Remote water supply for screen cleaning is not required. The total mixed sludge is screened immediately before the heat exchangers. The fibrous material and hair are separated from the sludge flow and compacted. 60 m3/hour of mixed sludge are fed into the STRAINPRESS® by gravity or vacuum forced through the machine by pumps behind the coarse materi-

Coarse Material Separator STRAINPRESS® Page 9

al separators. The inlet concentration of the primary sludge is between 2 and 3% DR. Approximately 1 ton/day of screenings with roughly a 42% DR are separated as compacted screenings. Tests have shown that the efficiency of the STRAINPRESS® is excellent. Since the start-up in April 2000, the heat exchangers have not needed any maintenance. By Martin Stumpmeier


Low-Temperature Drying: KLEIN Recirculating Air Sludge Dryer 1. SUMMARY Disposal of sludge from sewage treatment plants and production processes has become an expensive problem for a lot of plant operators. An important step towards reduced disposal costs is maximum reduction of the sewage sludge volume. To achieve this, sludge from a conventional mechanical sludge dewatering process is dried afterwards. Conventional thermal drying plants are operated at temperatures over 100° C, which requires appropriate equipment and safety engineering and available qualified staff. Alternative simple but efficient drying methods have been developed which work at temperatures far below 100° C and are economical, safe and eco-friendly. Among them are solar drying systems and low-temperature dryers, such as the KLEIN Belt Dryer. The KLEIN Air-O-Dry-System uses the water absorbing potential of ambient air for drying of municipal and industrial sludge and products. The system offers a capacity of 50 – 750 kg/h vaporication capacity with an energy demand of 0.3 – 1 kWh/kg water. The dry material produced at low energy and purchase cost is available for many ways of utilization and disposal. 2. INTRODUCTION Different drying methods for sludge from sewage treatment plants or industrial production processes have existed since many years which dry the sludge to a small residual water content. Such processes are: ● Drying processes operated at over 100° C ● Drying processes operated at temperatures far below 100° C.

All those processes have the same purpose: ● Reduction of sludge volume to minimize disposal costs,

● Stabilization of the sludge for long-term storage, ● Increases usability of the sludge for advanced thermal utilization processes or other ways of disposal. Processes using high temperatures (> 100° C) ● Demand appropriate material suitable for high temperatures, ● Require qualified staff that is permanently available (shift work), ● Burden the environment and workplace due to the high tempratures and produce polluted exhaust air and vapors.

ge drying system to make drying more independent from ambient influences. This system was for the first time realized in 1998.

3. PLANTS FOR LOW TEMPERATURE DRYING Belt dryers for ambient recirculating air drying are equipped with two or more belts which are positioned one

are probes to measure the introduced ambient air temperature to be able to determine the quantity of heat required for drying. Depending on the weather conditions there are two different operation modes applied: ● Low-temperature drying: Drying with ambient air only ● Recirculating air drying: Drying by recirculating drying air During ambient air drying the recir-

● Easy operation (no additional staff qualification required), ● Reduced plant technology and safety engineering owing to the low temperatures, ● High operational reliability ● Low temperature that makes exhaust air treatment unnecessary and does not produce condensate which would have to be returned into the sewage treatment plant, ● Product-protecting operation, ● Possibility to use exhaust heat from other processes to save primary energy, ● No lengthy start-up and closedown processes that need attention. Low-temperature drying in a belt dryer was investigated in the eighties and realized for the first time in 1989. The advantages and disadvantages could soon be experienced and were considered when manufacturing follow-up units. The low temperature process was further developed to the ambient recirculating air slud-

NOVELTY: The right use of solar energy Fully automatic state-of-the-art solar drying, easy to operate, offering up to 90 % dewatering efficiency. As fossil fuels are limited, the use of renewable sources of energy such as solar energy is inevitable. KLEIN offers therefore its recirculating air dryer as an option with solar panels for ambient air heating. The panels are attached on the dryer sides to minimize the additional space demand but maximize energy saving.

The dry material produced (with 80 to more than 90% solids concentration) can be stored outdoors over a longer period without finding any

Fig. 1: Diagram of a two-stage ambient recirculating air dryer with gas burner





 

The advantage is the high drying efficiency and minimum space demand. Drying processes which operate at low temperatures are solar drying processes and low-temperature drying in a belt dryer. They excel for their:

able to evaporate water amounts of 100 to 750 kg/h and achieve a final solids concentration of 90%. Bigger amounts of water can be handled by installing multi-line plants. Another option is partial drying to a solids concentration between 30 and 85%, as required.

  exhaust air  dewatered sewage sludge  breaking device  fresh air  fuel  dried sewage sludge



above the other and use ambient air as transport medium for the water to be evaporated and the necessary drying energy (indirect process). The ambient recirculating air drying system can be used for municipal or industrial sewage sludge and for products that need a drying temperature far below 100°C. It is necessary to break up and pelletize the dewatered material to ensure efficient low-temperature drying to ● Generate a big surface for discharge of the water into the drying air. ● Achieve sufficient permeability of the sludge layer on the dryer belts to ensure a sufficient amount of fresh drying air is brought into contact with the particles.

culation system is closed and the ventilators draw the maximal amount of air through the dryer, along the distributed sewage sludge, to achieve the required water evaporation. When the weather conditions or time of day do no longer allow such operation, the ventilators are throttled, the additional air supply openings closed and the recirculation system opened. The amount of fresh air flowing into the dryer is much smaller then and is heated prior to being mixed with the recirculating air. The low-temperature drying units that have been installed by now are

fungal infestation, odors or increased moisture.

Utilization of exhaust heat Belt dryers with low-temperature drying offer the advantage that lowtemperature exhaust air can be used for drying.

Exhaust heat has usually a temperature of 60 to 90° and is either exhaust air or cooling water and offers for conventional drying plants only a limited potential for utilization.

The sludge particles are fed onto a belt in the dryer and evenly distributed. During drying the particles rest on the belt without undergoing any mechanical stress. Such gentle treatment prevents further breakup of particles and eliminates thus the risk that particles are discharged or dust is produced during drying. Low-temperature drying uses the capability of absorbing water of ambient air for the drying process. The process is therefore rather vaporization than evaporation of water.

The belt dryers are additionally equipped with burners to heat the drying air to achieve a constantly high drying result. The fuel used for the dryers is natural gas, digester gas, liquid gas or oil. Since the energy demand for drying depends not only on the amount of water to be evaporated but also on the moisture of the ambient air, there Page 10

Fig. 2: Two-stage ambient recirculating air dryer of a municipal sewage treatment plant


Application of the CONTIFLOW® Sandfilter (CFSF) Hans Huber AG manufactures under license of Parkson Corporation the CONTIFLOW® Sandfilter CFSF which has proven its benefits in hundreds of filter plants and various fields of application. Filtration technology is typically used for separation of material from various media. Physical separation of suspended material in wastewater treatment is typically combined

with physical-chemical and/or biological elimination mechanisms. Table 1 shows several filtration technologies. The most common fields of application of the CONTIFLOW® Sandfilter are wastewater treatment, water treatment and recycling in the following branches: Paper and pulp industry, food industry, chemical industry, iron and

Filtration Technology •

1

2

3

Granular filtration: Surface filtration, filter layer height up to 30 cm

Application •

suspended solids > 10 µm •

Volume filtration: Filter layer height >= 1m

Cloth filtration

Elimination of

Chemical-physical effect due to precipitation and

steel industry, mining, surface treatment industry, municipal water works and sewage treatment works. The CONTIFLOW® Sandfilter can be used for the following applications: ● As an intermediate treatment stage in the process chain to obtain wastewater that contains as little solid material as possible, e.g. prior to activated carbon absorption, ion exchanger or membrane filtration. ● As a final treatment stage to reduce the concentration of suspended material. ● As a biological intensified filtration for advanced elimination of organic substances or denitrification.

Fig. 1: Continuous contact filtration ● For elimination of substances, organic pollutants and refractory material which are difficult to eliminate biologically by using adsorptive substances, such as powders combined with coagulant agents. The CONTIFLOW® Sandfilter is a continuously backwashed sand filter. Costs

for additional wash water and sludge liquor tanks are eliminated. Also the measuring and automatic control devices are simple compared with discontinuous systems. By Dieter Hilligard

floccation •

Biological effect

Elimination of suspended solids > 10µm Chemical-physical effect due to precipitation and floccation

Membrane filtration, e.g.

Separation of

Reverse osmosis

Ion, molecules

Membrane filtration

Micro filtration

Macro molecules and colloides

Macro molecules, colloides and technical emulsions

Table 1: Filtration technologies and their application in wastewater treatment

Fig. 2: Recycling of water

HUBER Service: A Customer Designed Product Product-Related Service to the Customer's Optimal Benefit Competence and Efficiency · Reliability and Quality Since the ever tightening drinking and wastewater market today has become a playground for a multitude of machine and plant manufacturers, it is getting increasingly difficult for customers to make a buying decision as frequently offers differ completley, especially in terms of prices and „promised performances.” Supply of high-quality technology at favorable price is one important thing, but lasting aftersales-service is of at least the same importance! An increasing number of customers, espacially operating staff of drinking and wastewater plants, confirm the high priority of a reliable and long-term service for purchased machines! The HUBER business unit „Service” is especially concerned about such important immediate and long-term service by offering an extensive program together with a competent and highly motivated team! Page 11


RoK1 Storm Screen Excels at Wigan, UK RoK 1 Storm Screen during trials channel fabricated from GRP panels. From the channel, the spill from the screen and the continuation flow were directed to separate chambers containing frameworks for the installation of 6 mm mesh sacks. The continuation/spill flow split was regulated by means of a slide valve in the continuation flow outlet pipework. Flowmeters are also installed in both the spill and continuation flow returns to the inlet works.

Screening of up to 10 m3/s combined water with 6 mm perforated plate

It is no secret that the most sophisticated testing of storm screens in the country, if not the world, is conducted at North West Water's Wigan WWTW, as part of the research program of UKWIR CSO Research Group. The ROTAMAT RoK1 Storm

Screen, which is now operational extensively throughout the UK, took to the CSO test facility for its own trial evaluation. Briefly, the set up at Wigan is as follows: Raw sewage, having been elevated by the works inlet

screw pumps, is intercepted upstream of the works inlet screens and routed through large bore pipework, incorporating regulating valves and an induction flowmeter, to test facility. The RoK1 Storm Screen was installed on a side weir within a

The construction of the screen is extremely simple and robust, consisting of a half cylinder of 6 mm perforated stainless steel, in which a transport auger with a continuous brush fixed to the trailing edge of the flight is located. The auger is driven by an explosion proof submersible motor/gearbox, and the flights transport screenings captured on the perforated plate to the downstream end of the screen, where the perforations give way to a solid plate. Screenings were returned, by means of the screenings discharge mechanism, back to the continuation flow.

For the duration of the trial, the RoK1 Storm Screen was operated in automatic mode, i.e. running intermittently from the commencement of a spill, with the ability of switching automatically to continuous operation under maximum hydraulic/screenings loading conditions. Tests were undertaken with incoming flows set at 30, 45, 60 and 100 l/s, each with continuation/spill flow splits of 0.1, 0.2, 0.4 and 0.6. A final conclusion, wholly based on the results from the trial, was quickly reached. In terms of total solids, the RoK1 improved the solids retention of a CSO with a high sided weir by approximately 10-20% over that achievable without a screen. However, more importantly when related to the NRA AMP2 (1993) requirement, "in terms of gross solids (greater than 6 mm in two dimensions) the RoK1 allowed none to pass to spill".

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International Report, issue 2002, english  

International Huber Report