Environmental Science & Engineering Magazine | April 2019

APRIL 2019 WWW.ESEMAG.COM @ESEMAG

10

Medicine Hat deploys permanent watermain leak detection system

20

Plant based micronutrients can effectively control WWTP odours

46

Will Bill C-69 improve how new projects are reviewed and approved?

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CONTENTS

April 2019 • Vol. 32 No. 2 • ISSN-0835-605X

Editor and Publisher STEVE DAVEY steve@esemag.com

Managing Editor PETER DAVEY peter@esemag.com

Sales Director PENNY DAVEY penny@esemag.com ales Representative DENISE SIMPSON S denise@esemag.com

Accounting SANDRA DAVEY sandra@esemag.com

6

Circulation Manager DARLANN PASSFIELD darlann@esemag.com Design & Production MIGUEL AGAWIN production@esemag.com

TECHNICAL ADVISORY BOARD Archis Ambulkar, OCT Water Quality Academy Gary Burrows, City of London Patrick Coleman, Black & Veatch Bill De Angelis, Metrolinx Mohammed Elenany, Urban Systems William Fernandes, City of Toronto Marie Meunier, John Meunier Inc., Québec Tony Petrucci, Stantec, Markham

Environmental Science & Engineering is a bi‑monthly business publication of Environmental Science & Engineering Publications Inc. An all Canadian publication, ES&E provides authoritative editorial coverage of Canada’s municipal and industrial environmental control systems and drinking water treatment and distribution.

Readers include consulting engineers, industrial plant managers and engineers, key municipal, provincial and federal environmental officials, water and wastewater plant operators and contractors.

Information contained in ES&E has been compiled from sources believed to be correct. ES&E cannot be responsible for the accuracy of articles or other editorial matter.

Articles in this magazine are intended to provide information rather than give legal or other professional advice. Articles being submitted for review should be emailed to steve@esemag.com.

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4 | April 2019

54

10 FEATURES 6 10 12 16 20 24 26 28 32 36 40 43 44 46 49 50 54 64

Regulations and testing are needed to fight ‘flushable’ wipes —Guest comment Medicine Hat deploys wide-scale watermain leak detection system Environmental isotopes help solve groundwater issues Municipalities wanted for new water loss testing project Plant based micronutrients can effectively control WWTP and other odours Health Canada introduces new guideline for lead in drinking water How to choose the correct metering pump Ex situ treatment approach for soil impacted with cyanides Using multiple lines of evidence helps in the study and remediation of PFAS How effective is direct horizontal-flow roughing filtration?

Deeper pond design improves sludge dewatering centrifuge performance Continuous monitoring of total inorganic nitrogen helps WWTP meet discharge limits Used shipping containers can house remote package water treatment plants Bill C-69 seeks to improve how new projects are reviewed and approved One man’s journey to help solve the global water and sanitation crisis Understanding how temperature and substrate influence wastewater nitrification Evolution of stormwater management technologies for urban applications Grinder design continues to evolve as wastewater streams change

DEPARTMENTS 57 60 65

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GUEST COMMENT mer is heated to a high temperature then extruded through small nozzles, while hot air is being blown.

The resulting product is a substrate that usually has a high wet-strength, because synthetic fibres retain their form, shape and strength in a moist state. This high wet strength is a desired outcome for wipe manufacturers, so the product will not fall apart during its life cycle.

A recent study looked at the physical and mechanical characteristics of non-flushable wipes, flushable wipes, and toilet papers, and found that flushable wipes are more similar to non-flushable wipes than they are to toilet paper. Flushable wipes are heavier, denser, thicker and have larger surface areas than toilet papers. Researchers found that under wet conditions, flushable wipes maintain most of their strength, as they are composed of synthetic fibres that retain their shape and strength.

Toilet paper loses on average 90% of its strength when wet, allowing it to disperse in toilets, plumbing systems and sewers. In contrast, flushable wipes only lose an average of 29% of their strength in wet conditions, meaning it takes much more force to break them down.

It is evident that wipes cause or contribute to pipe blockages and pump clogs, costing over $250 million per year to remove in Canada.

Regulations and testing are needed to fight ‘flushable’ wipes

By Barry Orr and Fatih Karadagli

W

astewater operators in Canada believe new flushability specifications will help reduce the cost and inconvenience to customers from blocked sewer pipes, and the impact to the environment from the flushing of inappropriate products down the toilet.

Currently, we should only be flushing the 3Ps (pee, poo and toilet paper).

The growth in the number of products labelled “flushable”, including wipes, has been a multi-million-dollar headache for water and wastewater utilities. In Canada, it is evident that wipes cause or contribute to pipe blockages and pump clogs. Removal of such materials from wastewater systems is costing Canadians over $250 million per year, according to the Municipal Enforcement Sewer Use Group (MESUG).

The wipe industry is represented by the Association of the Nonwoven Fabrics Industry (INDA) and the European Disposables and Nonwovens Associa6 | April 2019

tion (EDANA). INDA & EDANA developed guidelines and test methods to assess a wipe for its flushability.

Their Guidance Document (No. 4) serves as a platform to evaluate wipes.

However, many believe the pass/fail criteria of each test method potentially suits the interests of wipe manufacturers, while it fails to protect wastewater infrastructure, municipal funds, public health, and consumer interests.

WHAT ARE “FLUSHABLE” WIPES? Wipes are manufactured as nonwoven sheets of natural and manmade fibres such as cellulose, cotton, regenerated cellulose (rayon, lyocell), polyester, and high-density polyethylene (HDPE). They are marketed as either flushable, or non-flushable.

The fibres are mixed at various ratios through hydroentanglement, in which high speed jets of water strike a web of fibres so that they knot around one another. Or they are mixed when poly-

THE IMPACT OF FLUSHABLE WIPES Readers of ES&E magazine will already be familiar with the impact of flushable wipes on wastewater pumps, pipes and other infrastructure. Indeed, wastewater utilities from around the world have been reporting that wipes are responsible for most pipe blockages and pump clogs in sewer networks.

However, a growing concern is flushable wipes’ contribution to microplastic pollution, which threatens ecosystems and even human health. Microplastics/ microfibres are a source of contamination as they are carriers of chemical pollution (plasticizers and additives) also known as persistent organic pollutants (POP) that are adsorbed onto their surfaces.

These chemically polluted microplastics are then ingested by all types of organisms, such as crustaceans, fish, birds and ultimately, by humans via the food chain. Microplastics can increase the risk of cancer or disruptions to other systems like the endocrine system, leadcontinued overleaf…

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GUEST COMMENT ing to problems with sexual development and reproduction in animals and humans.

WHAT IS BEING DONE? Consumers assume that “flushable” products must have been tested rigorously for their compatibility with household plumbing and sewer systems. However, there is no standard definition of what is flushable, and no standard method to assess flushability.

Several organizations, such as INDA/ EDANA and the International Water Services Flushability Group (IWSFG) have developed test methods and technical specifications to define flushable products. They have proposed a slosh box disintegration test (SBDT) to evaluate disintegration of a wipe in water.

A slosh box is a framed-glass-box that rocks from one side to the other through a cam and lever mechanism. The purpose of this test is to assess the disintegration performance of a wipe material when it is subjected to hydraulic forces typically found in continuous flow conditions in small diameter (200 mm) sewer pipes.

These turbulent forces are equivalent to A slosh box disintegration testing station is used to evaluate disintegration of wipes in water. a Reynolds number of 20,000.

Table 1 compares experimental condiExperimental Requirement by Requirement by INDA/ tions and pass/fail criteria of the slosh-box Parameter IWSFG EDANA test procedure as proposed by IWSFG and

by INDA/EDANA. In parallel, INDA/ Sample A single sheet A single sheet EDANA’s test procedures are applicable only to wipes, while IWSFG’s test protoWater volume (L) 4 2 cols cover any product labeled “flushable”.

Mixing speed of SloshThis includes wipes, colostomy bags, and box (rotations per 18 26 toilet bowl cleaning brushes. minute) CONCLUSION Flushable wipes are not like toilet paper.

Their size, strength and material composition prevent them from breaking down in wastewater systems, and, even if they break down, they contribute to microplastic pollution in the environment.

Many feel that INDA/EDANA’s guidelines serve to protect the interests of wipe manufacturers, but fail to protect wastewater infrastructure, municipal funds, public health, and consumer interests.

Government regulations are needed urgently to define technical characteristics of flushable products. In this direction, IWSFG’s technical specifications and test methods clearly differentiate the products that are truly “flushable” 8 | April 2019

Mixing time (hours)

0.5

1

Expected ratio of disintegration to pass (% of initial dry mass)

95%

60%

Table 1. Comparison of experimental parameters, conditions, and pass/fail criterion of slosh box disintegration test as proposed by IWSFG (2018) and INDA/EDANA (2018).

from those that are not.

In light of these arguments and recent research findings, Fisheries and Oceans Canada have received a report from MESUG, stating the key reasons for why INDA/EDANA’s flushability guidelines are unacceptable by Canadian wastewater professionals.

Barry Orr is the spokesperson for Municipal Enforcement Sewer Use Group, and is with the City of London, Ontario.

Email: borr@london.ca Fatih Karadagli is an associate professor of environmental engineering at Sakarya University, Turkey. Email: fkaradagli@sakarya.edu.tr

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Medicine Hat deploys Canada’s first wide-scale wireless watermain leak detection system

By Alain Lalonde

F

amous for vast underground natural gas fields, Medicine Hat, Alberta also enjoys an ample aboveground water supply drawn from the South Saskatchewan River. However, water leaks and pipe failures compelled the city to seek an automated leak detection monitoring solution to cut water loss, avoid potential damage caused by pipe failures, and reduce unnecessary pipeline replacement costs.

Medicine Hat’s Environmental Utilities department maintains and operates the city’s 430 km water distribution system, serving more than 63,000 residents. It first tried to use portable leak detection equipment, relying on ground microphones and correlators to enable field crews to search for pipeline leaks.

However, the utility soon discovered that searching for leaks using this portable equipment required a considerable number of dedicated field staff, and an element of luck.

As a result, the utility used the portable leak detection equipment only when reacting to a pipe rupture to confirm that repair crews were digging in the right spot.

It then searched for a more advanced solution, delivering reliable and non-invasive monitoring of their trouble-prone older pipelines that also offered the least disruption to residents and businesses.

The EchoShore DX leak monitoring system is a permanent leak monitoring platform designed for water distribution mains. It features sophisticated acoustic sensors and proprietary processing algorithms to detect and pinpoint the source of faint noises emitted by pipeline leaks, long before they become detectable by conventional detection methods. Battery-powered monitoring “nodes” are built into fire hydrant pumper nozzle caps. They incorporate an ultra-sensitive acoustic sensor, enabling the system to identify and locate leaks by correlating, analyzing and comparing data from pairs of adjacent nodes.

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10 | April 2019

Battery-powered monitoring “nodes” are built into fire hydrant pumper nozzle caps.

professionals that actively monitor leak detection data and notify utility staff in the event of a probable leak on the network.

Supported by the LOC managed services, Medicine Hat’s water utility was alerted about potential pipeline leaks almost immediately after their new leak monitoring system became operational in early 2018. Monitoring 150 smart nodes installed within Medicine Hat’s pipeline system, Echologics technicians detected three separate locations identified with acoustic signatures consistent with pipeline leaks.

Two of the detected points of interest identified as potential leaks were confirmed with on-site inspections. The third acoustic point of interest turned out to be an anomaly that demonstrated the sensitivity and accuracy of the acoustic technology. Investigating field technicians discovered it was actually a pressure zone boundary valve that was partially open instead of firmly closed.

This caused a pressure leak into a lower pressure zone that had been hidden within the water distribution system for months. Pinpointing the problem and closing the valve eliminated pressure zone leak, decreased pumping effort and energy waste, and increased hydraulic integrity of the overall system.

Medicine Hat’s experience with the EchoShore-DX technology has resulted in plans to expand the city’s current leak detection coverage to include their entire metallic and asbestos cement water distribution pipe assets over the next three years. The city’s plans to install hundreds of additional nodes over a three-year period, making it the first Canadian city to monitor all of their pipe assets with a permanent leak detection technology.

The acoustic nodes in the EchoShore-DX system deployed in Medicine Hat are linked, using a Bell broadband wireless network. This is the first widescale wireless leak detection project of its kind in Canada. The secure wireless connectivity aids rapid deployment of the platform, enabling operators to perform a comprehensive system-wide leak detection correlation immediately upon initial system activation. Identifying and repairing existing leaks creates a highly accurate and reliable “acoustical baseline” for each monitoring zone that results in exceptionally high detection accuracy of any subsequent leaks that may develop in the future.

Medicine Hat opted for Echologics managed services from Mueller Water Products to support the system’s deployment and operation. The upgraded managed services include an Echologics Leak Alain Lalonde is Echologics Regional Operations Center (LOC). This is a spe- Manager for Mueller Water Products. cialized team of pipeline leak-detection Email: alalonde@echologics.com

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WATER Water (VSMOW). Isotopic concentrations are expressed as δ-values (del-values) in units of parts per thousand or per mil (‰).

Water molecules (H2O) consist of two elements: hydrogen (H) and oxygen (O).

Both oxygen and hydrogen have three isotopes: 16O, 17O, and 18O are oxygen isotopes, and 1H (protium), 2H (deuterium), and 3H (tritium) are hydrogen isotopes.

16 O, 17O, 18O, 1H, and 2H are stable isotopes; that is, their nucleus does not change. Tritium is a radiogenic isotope; its nucleus spontaneously decays (changes).

The stable isotopic ratios of water are affected by processes in the hydrologic cycle, giving water masses distinctive isotopic signatures that can be used to identify groundwater sources, evaluate Atmospheric testing of nuclear bombs during the 1950s and 1960s caused a dramatic increase in mixing of groundwaters, and as an inditritium concentrations in precipitation (and hence groundwater). cator of evaporation.

Evaporation, for example, preferentially removes water with lighter isotopes from the liquid. This results in vapour that is relatively enriched with lighter isotopes and residual liquid that is relatively enriched with heavier iso1 topes. When precipitation occurs from

By Fatemeh Vakili and Michael Sklash this vapour mass, the precipitation is relatively enriched with heavier isotopes, #702 edited by Steve and Sandra Banner: Water hen it comes to litigation, permit- result, isotopes of an element have dif- and the remaining vapour becomes relaEnvironmental isotopes solve tively enriched in lighter isotopes. atomichelp masses that,groundwater in turn, result issues ting, and evaluation of ground- ferent

By Fatemeh Vakili Sklash Since evaporation and condensation different physical behaviours. water remedial processes, the andinMichael rates arethe directly related to temperature, For example, most oxygen (O) atoms argument is strongest if multiWhen it comes to litigation, permitting, and evaluation of groundwater remedial processes, the above processes are also affected by 8 protons and that 8 neutrons ple lines of evidence that argument complement is strongest have if multiple lines of evidence complementin eachthe other are reported.

Duringthe the past environmental hydrogeology been used to conditions. Seasonal and longclimatic nucleus with aisotope resultant atomichasmass of routinely each other are reported. During past50 years, complement conclusions based on physical and chemical hydrogeology.

16 50 years, environmental isotope hydro- 16 ( O). However, about 0.2% of oxy- term temperature fluctuations can cause More recently, compound-specific (CSIA) has emerged as another line of significant spatial and temporal variageology has been used routinely to comgen atomsisotope have analysis 10 neutrons (18O, atomic evidence to identify the source of organic and inorganic contaminants or to assess plement conclusions based on physical mass = 18), and about 0.04% of oxygen tions in the isotopic concentrations in bioremediation of volatile organic compounds in the subsurface.

Most importantly, both and chemical hydrogeology.environmental isotopeatoms have 9andneutrons (17O, atomic Groundwater takes on the hydrogeology CSIA provide data that are mass independentprecipitation. of traditional physical and chemical=hydrogeology More recently, compound-specific 17). Waterarguments. molecules that contain the isotopic character of the average local preisotope analysis (CSIA) hasIsotopes emerged as heavier oxygen isotopes behave differ- cipitation. Sklash et al. (1986), for examin the water molecule another line of evidence toIsotopes identify in the hydrologic from those ple, used these differences to determine of anthe elementently are unique versions of an atomcycle (e.g., oxygen) that have the same number of protons (mass and electrons (mass =oxygen 0) but different numbers(more of neutronsthe (mass = 1). source of organic and inorganic con-= 1)with the light isotopes role ofAsgroundwater in surface water a result, isotopes of an element have different atomic masses that, in turn, result in different taminants or to assess bioremediation of discussion on this later). discharge for individual storm events. physical behaviours. volatile organic compounds in the subStable isotopes are reported as the On a longer time scale, stable isotopes For example, most oxygen atoms have 8two protons and 8abundant neutrons in the nucleus with surface. Most importantly, both environratio(O) (R) of the most isocan beaused to differentiate recharge from resultant atomic mass of 16 (16O). However, about 0.2% of oxygen atoms have 10 neutrons (18O, mental isotope hydrogeology and CSIA topes of anofelement (for is atomic precipitation atomic mass = 18), and about 0.04% oxygen atoms haveoxygen, 9 neutronsR (17O, mass = 17). during glacial times and provide data that are independent of tra-that the ratio of 18Ooxygen to 16Oisotopes [R=18behave O/16O]).

The in the today’s climate. For example, Crnokrak Water molecules contain the heavier differently hydrologic cycle from those withoxygen the light oxygen isotopes (more discussionofonathis later). (1991) used 18O concentrations to show ditional physical and chemical hydrogeisotopic concentration samology arguments. ple isas the reported relative to abundant a standard. deep (for overburden groundwater close Stable isotopes are reported ratio (R) of the two most isotopes ofthat an element 18 oxygen, R is the ratioFor of 18Ooxygen to 16O [R= O/16O]). The oxygen isotopic concentration of a sample isotopes, concentrations are to the lower Great Lakes recharged reported relative to a standard. For oxygen isotopes, concentrations are expressed as: ISOTOPES IN THE WATER isMOLECULE expressed as: during glacial (colder) times thousands Isotopes of an element are unique verof years ago, while the overlying ground- #$đ?‘‚đ?‘‚ / #.đ?‘‚đ?‘‚0%&'()* #$ − 17 Ă— 1000 ‰ sions of an atom (e.g., oxygen) that have δ đ?‘‚đ?‘‚%&'()* = ,-#$đ?‘‚đ?‘‚/ #.đ?‘‚đ?‘‚0 water closer to the surface is indicative %1&23&43 the same number of protons (mass = 1) of recent precipitation.

For oxygen isotopes in water, the standard is Vienna Standard and electrons (mass = 0) but different For oxygen isotopes in water,Mean theOcean stan-Water (VSMOW).

Tritium (3H) is a radiogenic isotope Isotopic concentrations are expressed as δ-values (del-values) in units of parts per thousand or numbers of neutrons (mass As a dard is Vienna Standard Mean Ocean continued overleaf‌ per= mil1). (‰).

Environmental isotopes help solve groundwater issues

W

12  |  April 2019

Water molecules (H2O) consist of two elements: hydrogen (H) and oxygen (O). Both oxygen 1 and hydrogen have three isotopes: 16O, 17O, and 18O are oxygen isotopes, and H (protium), 2HScience & Engineering Magazine Environmental (deuterium), and 3H (tritium) are hydrogen isotopes. 16O, 17O, 18O, 1H, and 2H are stable isotopes;

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Figure 1. Tritium concentrations in annual precipitation. All data are from International Atomic Energy Agency database (IAEA/WMO) (2006) / Global Network of Isotopes in Precipitation (The GNIP Database) and are accessible at: www.iaea.org/water.

of hydrogen with a half life of about 12.4 years. Tritium concentrations are reported as tritium units (TU) where 1TU is one tritium per 108 atoms of hydrogen. It is produced naturally in small but measurable concentrations. Atmospheric testing of nuclear bombs during the 1950s and 1960s caused a dramatic increase in tritium concentrations in precipitation (and hence groundwater).

Following the atmospheric test ban treaty in 1963, 3H in precipitation began to decline gradually (See Figure 1). Considering this factor and the half-life of 3H, one can estimate when the groundwater was recharged. If there is no tritium in the groundwater, it was recharged before 1950.

ISOTOPES IN CHEMICALS IN WATER Although most atoms have multiple isotopes, only a few are used in hydrogeology, including hydrogen (H), oxygen (O), nitrogen (N), carbon (C), chlorine (Cl), and sulphur (S). CSIA allows isotope analysis of elements within molecules, such as nitrogen isotopes for nitrate contamination issues, chlorine isotopes for trichloroethene (TCE) releases, and carbon isotopes for petroleum releases.

Chlorinated solvents are man-made products that may have distinctive isotopic signatures due to manufacturing processes or varying initial raw materials. Van Warmerdam et al. (1995) and Beneteau et al. (1999) used CSIA to analyze chlorinated solvents (including trichloroethylene [TCE], perchloroethylene 14 | April 2019

[PCE], and 1,1,1-trichloroethane [1,1,1TCA]) from various manufacturers and determined that these have distinctive isotopic signatures. These differences may be used to identify the source of a TCE release, for example, in the subsurface.

CSIA can also be useful in understanding the fate of the chlorinated solvents in groundwater. Since bacteria that degrade chlorinated solvents prefer to break chemical bonds between lighter isotopes, chlorinated solvents with heavier isotopes tend to remain in the groundwater as biodegradation progresses. At chlorinated solvent release sites where biodegradation is the remedial technique, CSIA measurements over time will help to assess the progress of bioremediation.

CASE STUDY Dragun Corporation recently consulted for a large dairy farm where the permitting required monitoring wells around the entire site to demonstrate that the dairy did not cause increases in nitrate concentration in groundwater leaving the site.

The regional (including upgradient) groundwater nitrate concentrations already greatly exceeded the drinking water criterion because of decades of regional chemical fertilizer use prior to development of the dairy. However, nitrate concentrations in groundwater at the designated upgradient monitoring well were lower than the drinking water criterion. The problem for the dairy was to determine why the upgradient mon-

itoring well did not reflect regional/ upgradient groundwater nitrate.

Dragun determined that the shallow groundwater around the dairy had δ2H and δ18O values that were consistent with those of the regional groundwater.

A massive spring storm event caused flooding in the area around the upgradient monitoring well during our investigation. Dragun submitted water samples from the flooded area (representing that precipitation event) and groundwater from the upgradient monitoring well for 2 H and 18O analysis.

These data indicated that the groundwater and storm isotopic values were different, and that the ponded surface water from the storm event had quickly infiltrated to the water table and isotopically altered the groundwater in the upgradient monitoring well (it had changed to the same value as the ponded water).

The infiltrating water not only changed the isotopic signature of the groundwater at the upgradient well, but it also diluted the nitrate concentration.

As mentioned earlier, it is useful to have multiple lines of evidence to prove a point. Dragun used high-resolution groundwater level monitoring that confirmed episodic mounding around the upgradient monitoring well and changes in the groundwater flow direction at the upgradient monitoring well. They also used CSIA for nitrate in the groundwater to identify areas where chemical fertilizers were responsible for the nitrate. The combined use of water isotopes, CSIA for nitrate, and high resolution groundwater level monitoring were instrumental in understanding the nitrate conditions and in obtaining a workable permit for the dairy.

When groundwater is impacted by anthropogenic sources, solutions depend on a thorough understanding of subsurface conditions. Using multiple lines of evidence, including environmental isotope hydrogeology and compound-specific isotope analysis, can greatly aid in reaching a solution sooner than later.

Fatemeh Vakili, PhD, and Michael Sklash, PhD, P.Eng., are with Dragun Corporation. Email: fvakili@dragun.com, msklash@dragun.com. References are available by request.

Environmental Science & Engineering Magazine

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WATER

Municipalities wanted for new water loss testing project

10

Night 1 Flow Night 2 Flow

8

1-hour Centralized Moving Average Recorded MNF

DMA Inflow (L/s)

6

By Fabian Papa and Bradley Jenks

4

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n recognition of the intrinsic connection between water supply and energy consumption, and more particularly the needless use of energy to pump water which is lost through leaks in municipal water distribution systems, a multi-year project has recently been initiated with the support of Ontario’s Independent Electricity Services Operator (IESO) Grid Innovation Fund.

This cross-sectoral collaboration which realizes broader energy efficiency gains by transcending typical municipal

Official Distributor

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jurisdictional boundaries is being led by HydraTek & Associates, in collaboration with the Ontario Clean Water Agency, the Ontario Water Works Association,

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municipalities with a cost-efficient method to measure minimum night flows (MNFs), being an indicator of leakage. It will also test whether the application of permanent pressure management systems to reduce leakage and, hence, pumping as well as other energy inputs, will yield sufficient benefits to warrant their implementation. Finally, it will provide valuable system performance information and drive awareness on leakage reduction practices and value.

The project will involve conducting field tests across 20 temporary district metered areas (DMAs) in various municipalities throughout Ontario. DMAs are segmented portions of a water distribution system isolated from other parts, so inflows and outflows can be accurately measured. In addition to receiving direct, accurate and reliable performance measurements of selected parts of their networks, participating municipalities will be able to compare how these performances compare amongst their peers and industry benchmarks.

MINIMUM NIGHT FLOW The concept behind MNF analysis is that the degree of leakage may be accurately determined when customer consumption is at a minimum. (See Figure 1) The flow into a DMA that is in excess of this legitimate consumption is leakage.

Of course, to estimate the leakage with reasonable accuracy, one must know the degree of consumption. This can be estimated based on minimum night factors as demand characteristics of residential customers are often quite consistent.

Another method to understand minimum night consumption is to have customer-level metering data at a suitable interval (e.g., one hour, preferably less) which is becoming increasingly available as municipalities migrate towards smart meters and automatic meter reading (AMR) and/or advanced metering infrastructure (AMI).

This project focuses primarily on residential areas so as to derive data and statistics that are directly comparable and can be used for benchmarking purposes.

As well, testing will be restricted to non-irrigation months (generally November to April) given that the impact of irrigation systems (which are often automated) on www.esemag.com @ESEMAG

demand patterns can be significant and in some cases can dwarf what would be a typical diurnal demand pattern.

The objective is to achieve the highest quality of data that can be used as a basis for meaningful comparison with other testing conducted in similar circumstances.

British engineer and water loss expert, Dewi Rogers, has worked in over 30 coun-

tries around the world. In the absence of direct customer meter readings (e.g., AMR or AMI) to compare DMA inflows to consumption for purposes of leakage estimation, he applies typical demand profiles derived from the monitoring of a large sample of customer meters. More particularly, he uses a minimum night factor which is defined as the lowest fraccontinued overleaf…

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tion of average consumption in a typical diurnal pattern. His assessment of thousands of residential properties across multiple countries shows that the results are surprisingly consistent.

Data collected from various Canadian utilities suggest a lower threshold in MNF relative to DMA size, representing well-performing DMAs. (See Figure 2) Results from this project will provide additional data to strengthen such benchmarking methods for use in the Canadian context, as well as the reliability in interpreting any individual results, including identifying poorly performing DMAs relative to their peers.

Apart from the MNF measurements under normal operating conditions, the project also involves testing the effectiveness of applying reduced pressures to the DMAs in respect of leakage reduction. That is, given that leakage is pressure-dependent, a reduction in pressure will result in a reduction in leakage. This project aims to seek the degree to which this can be achieved through direct and

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affordable measurements, such that reli- commonly referred to as pressure manable business cases for intervention can aged areas (PMAs), may be warranted. be developed.

If appropriate, permanent installations MOBILE TESTING UNIT While it is desirable to be able to meaof DMAs with pressure management,

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Environmental Science & Engineering Magazine

sure flows into a DMA on a permanent basis, the investment to do so is not trivial.

Mobile testing allows for a rather affordable means to obtain meaningful measurements. These can be used to help make informed decisions about where investment may be most cost-effectively directed. It also allows for a consistent means of measurement, which can be used to determine the degree of performance improvement realized by any system interventions to reduce leakage. It is important to note that IESO is expected to offer further incentive funding for those municipalities that demonstrate performance improvement.

The mobile unit consists of a flow meter, appropriately selected to be able to accurately and reliably measure MNF rates from rather small DMAs (or subsets thereof), an adjustable pressure reducing valve (PRV), and piping, ports, pressure gauges and related fittings.

In terms of its application, it is highly important that the hydraulic integrity of the DMA be established to ensure that no flow passes at any of the isolation valves which separate the DMA from the remainder of the network. This is accomplished by performing zero-pressure tests between the isolation valve and an adjacent valve. Although brief in duration, this requires careful planning and communication with affected customers. Flow into the mobile testing unit occurs through bypassing a closed isolation valve.

In earlier work, conducted by Ottawa over a decade ago, taps were installed within chambers on either side of isolation valves. This procedure is expected to be applicable to most of the testing sites in this program.

The mobile unit is specifically designed for accurate and reliable MNF measurement. Depending on the size of the DMA and its demand characteristics, it may not be suitable for use due to the hydraulic losses that would accompany higher velocities, particularly during the diurnal peak periods. For each temporary DMA, testing is planned to be conducted over a series of three to four night periods, from 12 a.m. to 6 a.m.

PARTICIPATING MUNICIPALITIES WANTED There is funding available to support www.esemag.com @ESEMAG

up to 20 testing locations. Participation involves in-kind contributions in the form of operator support in preparation for, and during, testing, as well as a modest financial contribution. Included with participation are two workshops.

One will be held prior to testing for general training to raise awareness and elevate understanding of water loss management. The second will be held after

testing is done to re-review the concepts from the first workshop as well as to review and interpret results of the testing.

Anyone interested in participating in the study, should contact the authors.

Fabian Papa and Bradley Jenks are with HydraTek & Associates (A Division of FP&P HydraTek Inc.). Email: f.papa@hydratek.com

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April 2019 | 19

WASTEWATER

Plant based micronutrients can effectively control WWTP and other odours

By Derk Maat

O

ffensive odours generated by landfills, wastewater treatment plants, transfer stations, food waste receptacles, garbage trucks, composting operations, sewer systems, pumping stations, stormwater ponds, combined sewer overflow facilities, canals, and agricultural operations are a challenge, especially in urban environments.

Measurement of offensive fugitive odours has grown into a significant business, spawning new innovative technology to address the problem. Drone-based sampling devices have now been developed to measure odours above and around industrial facilities.

There has been significant progress in measuring, quantifying and source identification of odours generating nuisance complaints. Regulatory agencies are now able to identify facilities and plants responsible for odour generation and force these facilities to deal with them.

ODOUR CONTROL TECHNOLOGIES Most of the new technology being developed is based on chemical breakdown of odours, using UV, carbon, ozone, and biological filtration. Other solutions include oxygenating and aerating solid and liquid waste collection basins to prevent septic conditions, which is an energy intensive practice. The least effective method is the use of chemical masking agents. These are often toxic and have human exposure restrictions.

Other initiatives and solutions have been based on the use of biocides to kill bacterial populations that are responsible for odour generation. Biocides currently in use consist of chlorine/quaternary ammonia, copper sulphate, and formaldehyde solutions which are highly toxic to the preferred beneficial bacteria and to the environment when discharged. These chemicals, when used as biocides, not only kill the offensive bacteria generating the odour, but also the bacteria responsi-

ble for treating the waste in composting or wastewater treatment operations.

Formaldehyde is used to kill odours in portable toilets. When the wastewater from these toilets is introduced into a municipal wastewater plant, it upsets and severely inhibits the biological processes in them, adversely affecting performance and effluent quality. Recovery time to rebuild bacterial populations can be weeks.

SELECTIVE BIOLOGICAL INHIBITION OF ODOUR PRODUCING BACTERIA A new biological and environmentally sustainable approach using plant based organic micronutrients has been developed over the last number of years to specifically stimulate aerobes and anaerobes and competitively inhibit the sulphur reducing and ammonia forming bacteria and enzymes.

The main active ingredients in the continued overleaf…

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Secondary Clarifier Improves settleability; Reduces scum; Reduces floating sludge

Reduces energy/oxygen demand; Reduces FOG, foam, scum Improves nitrification return activated sludge waste activated sludge Treated effluent Improves effluent quality

Aerobic Digester Holding Tank

Sludge Dewatering Reduces foam, FOG; Reduces energy/oxygen demand

Disposal of dewatered sludge Reduces odors

Removes odor; Reduces sludge volumes

Treated effluent discharged

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Anaerobic Digester

Reduces foam, odors, and H2S; Increases biogas production

20 | April 2019

Environmental Science & Engineering Magazine

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WASTEWATER

BIOLOGIC® Performance Improved Effluent Quality Performance Improvement

micronutrient solutions include plant sourced amino acids, vitamins and other plant based organic constituents and trace minerals. The micronutrient solution itself is biodegradable, as it is used up as food source by the beneficial bacteria found in organic waste streams.

These micronutrients, when added to liquid and solid organic waste streams, eliminate the formation of odours during the biological reactions that are responsible for organic waste degradation.

Research has shown that non sulphur reducing anaerobes and many different types of aerobes are stimulated by the plant based organic micronutrient catalyst to operate at much higher metabolic rates. Sulphur reducing anaerobes and ammonia generating enzymes are unable to utilize the specific micronutrients introduced into organic waste streams.

As a result, the microorganisms stimulated by the micronutrient solution outcompete the odour producing microbes for macronutrients. Competitive inhibition severely restricts the metabolic activity of odour producing microbes, which dramatically decreases the production of odorous gases.

The net impact is that odours are significantly reduced, but bacterial breakdown of the organic waste continues at an accelerated rate.

BENEFITS OF BIOLOGICAL INHIBITION OF ODOUR PRODUCING BACTERIA Biological inhibition of odour producing bacteria has been observed in sewer systems, wastewater plants, septic tanks, lagoons, composting facilities, stormwater retention ponds or combined sewer overflow ponds where the micronutrient solutions have been added. If micronutrient control of odour generation is implemented, there is no need to revert to aerating septic systems, tanks, lagoons or ponds, or treatment facilities to control and/or treat odours.

The advantages with biological source control of odours with micronutrients include: • Eliminates the need for significant infrastructure and space requirements to contain, control and treat odours.

• Eliminates 90% of the capital investment associated with odour control using 22 | April 2019

Performance improvement at a 6 MGD Activated Sludge wastewater treatment plant. *6 MGD Activated Sludge WWTP in North Carolina

chemical and/or biofilter infrastructure.

• Eliminates 90% of the energy demand associated with conventional odour control strategies and technologies, which reduces the overall carbon footprint.

The use of plant based organic micronutrients represents a near zero carbon footprint solution to eliminate odours. There is an immediate return on the investment for micronutrient usage as it replaces or eliminates the costly operation of biofilters, ozonation units, and carbon units.

TREATMENT OF AIRBORNE ODOROUS COMPOUNDS Plant based organic micronutrients can also be utilized in misting systems to treat odorous gases generated by nonpoint sources of odours in facility operations like transfer stations, landfills, garbage rooms in commercial facilities, wastewater plants, biosolids processing facilities, and organic material processing facilities like food production plants and/or pulp and paper mills.

Micronutrients can also be used to improve the capacity and performance of biofilters and wetscrubbers. Plant based micronutrients, when diluted in ratios varying from 100 – 1,000:1, react with airborne odour molecules in chemical oxidation reactions to render them odour free.

The micronutrient solutions contain no masking agents except in some cases where a tracer fragrance is required.

Also, they do not contain any bacteria or enzymes that may be subject to regulatory restrictions, or any minerals in concentrations harmful to the environment.

When added to the waste streams they inhibit the formation of hydrogen sulphide, ammonia, trimethylamine, methyl mercaptans, and other non-identified sulphur reduced organic compounds.

Sci-Corp has carried out a controlled

laboratory study to measure the effec19 tiveness of these micronutrient products when added to decaying organic waste.

Two reactors with an enclosed head space, a control and a test reactor, were set up containing 1 kg each of decaying food waste. The test reactor was treated with a one time 5 ml dose of Biologic SRC. The reactors were equipped with sampling ports to sample headspace gases and were incubated at a temperature of 30°C to represent warm weather conditions. The reactors were sampled every 12 hours over a five day period. Air bag samples were sent to a certified laboratory and analysed by gas chromatography mass spectrometry for the four compounds listed above. The reactors were also subjected to a simple olfactory test by the technician.

The control sample was characterized by a highly putrefied odour. The treated sample was free of any objectionable odours.

The laboratory tests confirmed that a one-time dose was effective over a five day time period to suppress the generation of odorous gases by 70% – 85% from organic waste incubated at a temperature of 30°C. These results have significant implications for the source mitigation of odours from green bins, composters, transfer stations, landfills and wastewater treatment facilities. Further testing has confirmed that solid organic waste degradation rates were increased by up to 65% under laboratory and field conditions.

MISTING/SPRAYING APPLICATIONS Air misting in a hog slaughterhouse barn and in hog rearing facilities resulted in 85% – 90% reduction in H₂S/ ammonia concentrations in the atmosphere. Air misting in poultry barns has

Environmental Science & Engineering Magazine

shown similar results. Commercial misting applications in garbage rooms of stores and institutions achieved similar reductions.

Misting applications in municipal solid waste (MSW) transfer stations, landfill sites, tipping floor and pits in a MSW incineration plant, and chicken-rendering plants have all resulted in dramatic odour reduction and elimination of neighbouring odour complaints. Industrial misting applications of the micronutrient solutions in tannery facilities and sludge processing facilities also resulted in significant odour reductions.

Misting into biofilters improves the performance of biofilms and also complexes odour molecules into non odour generating compounds.

Table 1. Results of micronutrient application to WWTP influents.

nutrient products are manufactured and of beneficial biodegradation mechasold by Scicorp International Corp. They nisms represents an alternative innovahave been tested and certified non-toxic tive but proven environmentally sustainby a leading toxicity laboratory (TOX able approach.

WASTEWATER TREATMENT Monitor/BSR, Inc. Illinois U.S). They PLANT APPLICATIONS are also certified within the Ecologo/UL Derk Z. Maat, M.Eng., P.Eng., is with Maat Environmental Engineering. Email When applied in wastewater plants for program. odour control, the micronutrients were In conclusion, the use of micronutri- derk@maatenv.com also able to improve wastewater treat- ent solutions for odour source control ment performance and reduce operat- and odour abatement and stimulation Waste Water products plus NMac 4.65 x 4.65.pdf 1 1/24/2018 7:37:09 AM ing costs. The typical addition rates for odour control in wastewater plants range from 1 ppm (domestic wastewater) to 10 ppm (industrial wastewater).

Pumps for all your waste water challenges Application to biosolids processing plants at 50 ppm to 2% TSS sludge mix Thickened Sludge  Bio-mass  Thin Sludge tures also reduced odours by 80%. Appli Dewatered Sludge  Activated Sludge  Lime Milk cation in wastewater treatment plant  Auxiliary Flocculents  Combined Sewage  Flotation Sludge influents by direct injection has also resulted in dramatic reduction in ambient CLASSIC TORNADO® T1 air H₂S reductions, as illustrated in Table 1.

Rotary Lobe Lagoon and combined sewer overflow Pumps pond surface spray applications have eliminated odour generation and odour complaints from lagoons containing NEMO® Progressing effluent from ethanol plants, paper mills, N.Mac™ Twin Cavity Pumps septic tank sludges, hog manure, and Shaft Grinders cherry processing facilities, ranging in Full Service-in-Place volume from 500 m3 to 45,000 m3.

(FSIP®) Pumps Inoculation of 2% solids sludges from paper mills and wastewater plants prior TORNADO® T2 NEMO® Mini Rotary Lobe Pumps Metering Pump to dewatering has reduced odours 80% – 90% and eliminated the need for large biofilters, scrubbers and contaminated air treatment facilities by reducing and/ or eliminating the generation of odours NETZSCH Canada, Inc. at source.

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April 2019 | 23

WATER

Health Canada sets new guideline for lead in drinking water

Estimated Daily Intake (μg Pb/kg-body weight per day)

H

ealth Canada recently published revised guidelines concerning lead in Canadian drinking water. The most significant change is the reduction of the maximum allowable concentration (MAC) of lead in drinking water from 0.01 mg/L (set in 1992) to 0.005 mg/L. According to the agency, since the phase-out of leaded gasoline and the reduction of airborne lead pollution, food and drinking water are the primary sources of lead exposure to adults.

However, even at low concentrations, lead causes negative health effects, with infants and children the most sensitive to its harmful effects.

Health Canada’s lower MAC of lead is based on recent research that indicates that lead can have harmful effects at extremely low levels, according to the Canadian Water and Wastewater Association (CWWA). At 0.005 mg/L, Canada now has one of the lowest targets for lead in the world.

The CWWA said it fully supports the revised drinking water guidelines and the goal of eventually eliminating all lead from drinking water. To help municipal water professionals speak to the new drinking water guidelines, it has put together a fact sheet and speaking notes containing helpful information about lead in drinking water. To view the fact sheet visit: www. cwwa.ca.

However, Health Canada's guidelines are not regulations and it is up to Canadian provinces and territories to determine how, and if, they will adopt the lower levels for lead.

According to the CWWA, water that is treated and distributed in municipal systems is generally lead-free. However, drinking water can come into contact with lead in the “service lines”, which are the pipes that connect each property to the water main. Lead can also be found in household plumbing materials, such as lead pipes, brass fixtures and lead soldering.

While Canadian municipalities began phasing out the use of lead in “service lines” to properties in the 1960s, the National Plumbing Code permitted the use of lead until 1975 and lead solder until 1986. Restrictions on lead content in brass fittings are much more recent, with the newest definitions set in 2013.

The average dietary intake of lead (µg/kg body weight/day) by Canadians of all ages has decreased approximately eight-fold between 1981 and 2000. However, there is no known level of lead exposure that is considered safe. Graphic Credit: Health Canada

Health Canada said simple actions to reduce exposure to lead from household drinking water includes: • If water has been siting for several hours, flush out pipes before consuming the water.

REMOVING LEAD FROM DRINKING WATER According to the CWWA, the first goal is to eliminate lead • Clean taps monthly and check tap aerators for debris. from water systems by removing and replacing lead service • Replace brass faucets and valves with fittings that are certilines. Communities across Canada have endeavoured to stra- fied to the standard on low lead content. tegically replace lead service lines at appropriate opportunities • As a temporary solution, a household tap water filter, which is NSF International Certified, can effectively remove lead such as during road reconstruction.

While this replacement process can be expensive and take from water. many years, the CWWA said that communities are making great progress through these efforts and continue to iden- For more information on lead in drinking water, including tify and remove any remaining lead service lines from their public awareness and outreach information, visit municipal systems. A less expensive, but still effective alterna- www.cwwa.ca and tive to replacement, is to line the interior of service lines with www.canada.ca/en/health-canada. a material that blocks the lead from entering the water supply.

24 | April 2019

Environmental Science & Engineering Magazine

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PUMPS

How to choose the correct metering pump technology for your application

By Andrew Snyder

S

pecifying the proper chemical metering pump for an application can be simplified by acquiring all application parameters. It is important to take into account such factors as the fluid to be pumped, the output volume required, and the pressure which the pump will be working against in the system. Once these are taken into consideration, the information will guide the engineer or end user in selecting the best pump option to ensure optimal performance.

Peristaltic metering pumps have been widely accepted as the preferred technology in many applications, including municipal drinking water and wastewater treatment, food and beverage processing, commercial swimming pool and aquatics water sanitation, and many others.

These types of applications use chemicals which off gas and calcify. When diaphragm pumps are used, this can cause vapour locking as well as clogged valves.

Peristaltic pumps are not affected by gas, air bubbles or particulates, as they allow bubbles and particles to simply move through the system.

staltic tube could be replaced as infrequently as once per year, depending on the system conditions. This leads to minimal down time at the plant and allows an operator’s time to be spent on other equipment needs and day to day operations, thus cutting costs.

An additional advantage of peristaltic pumps is that they perform well against limited pressure. They will not lose output rate versus pressure, whereas, diaphragm units do require the use of a Blue-White Industries' Three Pro Series Pumps backpressure valve. The smooth feed of have been designed for many applications, peristaltic metering pumps also elimiincluding water and wastewater treatment. nates the need for a pulsation dampener, leading to further cost savings.

One disadvantage of peristaltic pumps Also, peristaltic units do not require regular maintenance other than pump can be pumping against high pressures. tube replacement due to wear. Diaphragm As the pressure increases in a system, pumps, on the other hand, require ongo- tube life decreases. This is due to the ing maintenance as valves must be regu- increase in pressure which increases the force on the walls of the rubber tubing. larly cleaned.

The estimated life of the peristaltic pump tube can be determined when all Andrew Snyder is with Blue-White application parameters are known. This Industries. For more information, allows operators to implement a regular email: sales@blue-white.com, or visit maintenance schedule which can increase www.blue-white.com efficiency and prove to be cost-effective.

Diaphragm pumps typically require weekly maintenance, whereas a peri-

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REMEDIATION

Ex situ treatment approach used for soil impacted with cyanides

The ex situ chemical oxidation remedial program involved using two cement mixer trucks with a capacity of 9 m3 each.

By Viktor Kopetskyy and Jim Phimister

F

rom 2000 until 2007, numerous environmental investigations, including Phase One and Two environmental site assessments, subsurface investigation and monitoring programs, have been conducted at a former industrial facility in Guelph, Ontario. Two separate areas of soil impacted with cyanides, approximately 30 m2 and 400 m2, respectively, were identified within the footprint of the former industrial building, housing electroplating operations.

Depth of the impacted soil ranged from the surface to 6.1 metres below ground surface (mbgs), with irregular distribution of concentrations throughout the depth. The range of free cyanide (CN-) concentrations was between 233 µg/g and 237,000 µg/g. Soil stratigraphy at the property consists mainly of fill material comprised of a mixture of silty sand and silty clay, ranging from 2.4 mbgs to 5.5 mbgs and underlain by native silty sand.

28 | April 2019

REMEDIAL METHODOLOGY For many years, the most effective methods to treat industrial wastewater containing cyanides were oxidation with sodium hypochlorite (concentrated waste solutions from electroplating baths) or filtration through ion-exchanging resins/ membranes (rinse water with low cyanide concentrations). Due to relatively high cyanide concentrations in soil, the oxidation method of remedial treatment is preferable. However, the heterogenic nature of the mixture of the impacted soil and reagents makes the efficacy of the oxidation process questionable, due to slow transportation rates of reagents to heterogenic surfaces of soil particles.

Therefore, a key element of the remedial strategy was to create a quasi-homogeneous reactive volume of the impacted soil and reagents. It was achieved by mixing water with the impacted soil to create a water suspension (slurry) of soil particles with sorbed cyanides.

CYANIDE OXIDATION PROCESS Alkaline chlorination is the most economical and controllable method to remove cyanides from wastewater. Chlorine may be added either as a free gas (either chlorine or chlorine dioxide) or as bleach (sodium/calcium hypochlorite).

Cyanide waste treatment is usually a two-stage process. Sodium hydroxide is added to provide the high alkaline environment required for the oxidation. The initial reaction between chlorine and cyanide is the formation of cyanogen chloride. However, in the high alkaline environment, carbonates and ammonia can be produced as the result of the reaction.

The initial oxidation to cyanogen chloride is slow below pH 8.0. Above 8.5, the reaction goes to completion in less than 30 minutes, even faster as the pH is raised. Cyanogen chloride is volatile and odorous. When airborne it is a lachrymator and special safety precautions are required for anyone in the area. Since the

Environmental Science & Engineering Magazine

cyanogen chloride becomes more soluble and less volatile as the pH increases and the rate of conversion to cyanate dramatically increases with the pH, the first stage of oxidation is usually conducted at pH 11.

The second stage of oxidation (conversion of cyanate to carbon dioxide and nitrogen) is also pH dependent. At pH 8.5, the reaction is usually complete in 10 minutes and, at pH 10, the reaction usually requires 40 minutes. The recommended rate of chemicals is 6.82 kg of chlorine and 5.21 kg of sodium hydroxide per one kilogram of free cyanide. Even though the reaction may appear to be a two-step process and the rate of the reaction at the second stage is slow under the first stage reaction conditions, cyanate is converted to carbon dioxide/carbonates and nitrogen/ ammonia at the elevated pH values of the first stage reaction.

Stoichiometric requirements of chlorine show that 40% of the total demand would be consumed in step one and 60% in step two. In reality, it has been

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Drawing No. 3 – Remedial System Layout

shown that 70% – 80% of the total chlorine demand will be consumed in step one. Therefore, a significant portion of the cyanate has been oxidized to the final products in step one. Also, waste-

water treatment experience shows that the actual amount of chlorine consumed by the reaction may be as much as 200% of the theoretical amount. continued overleaf…

April 2019 | 29

REMEDIATION If insufficient chlorine is added to the first stage, free cyanide will exit and in the second stage with the reduced pH, cyanogen chloride will evolve from the solution. To ensure complete oxidation of cyanide, adequate mixing is extremely important. The tank should have a mixing rate of 2.5 to 3.0 turnovers per minute. Poor mixing may produce isolated pockets where the solution alkalinity has been decreased, and noxious cyanogen chloride gas will evolve. The reaction is controlled with pH and oxidation-reduction potential (ORP).

A test pit was conducted in the vicinity of a previous borehole where a soil sample with the elevated cyanide concentration was recovered. The concrete foundation was cut and the impacted soil to a depth of 3.2 mbgs was excavated and stockpiled.

The stratigraphy of the soil underneath the concrete slab generally consisted of grey to brown sand and gravel, with some cobbles underlain by sand to silty sand fill to a depth of 3.2 mbgs. Fill, in turn, was underlain by brown silty sand with trace clay to the termination depth of the test pit.

To stabilize pH of the excavated soil, the stockpile was sprayed with lime soluREMEDIAL ACTION PLAN tion and covered with tarpaulin.

The remedial action plan to address Two portable cement mixers with a the identified cyanide exceedances of capacity of two and four cubic feet, respecthe applicable standards (Ontario Min- tively, were set up at the site (with reguistry of the Environment, Conservation lar and advanced design of mixing partiand Parks (MECP) Table 4 Stratified Site tions), along with a power generator and a

tion process were evaluated during the treatment: • Mixer type (A – advanced design of mixing partitions, B – regular design).

• Treatment (retention) period (30, 60, 90 and 120 min).

• Reagent rate (100%, 150%, 300% and 400% of calculated stoichiometric amount).

OPERATION RESULTS Based on the results of the field pilot test, a full-scale ex situ chemical oxidation remedial program for cyanide impacted soil at the site was designed and conducted from November 2008 to January 2009.

In October 2008, previously delineated areas of cyanide and copper impacted soil in the eastern (Area A) and northern (Area B) portions of the former manufacturing building were excavated to a depth of approximately 5.5 and 1.3 mbgs. Prior to the excavation, overlaying concrete slab in the area was removed and conIf insufficient chlorine is added to the first crete fragments were stockpiled at the site.

In November 2008, prior to commencstage, free cyanide will exit and in the ing the remediation program, the excasecond stage with the reduced pH, cyanogen vated soil was screened to remove boulders and cobbles and was organized into chloride will evolve from the solution. three stockpiles according to the estimated level of contamination. These stockpiles were located in the central portion of the concrete slab of the former manufacturing building and were covered with tarpauCondition Standards in a Potable Ground drum with water for the reagent solution lin. An approximate soil volume in these Water Condition) consisted of the follow- preparation. The following reagents were stockpiles was estimated as 950, 380 and ing steps: added to the mixers during the treatment: 380 cubic metres, respectively.

• Lateral and vertical delineation of the 12% sodium hypochlorite, 30% caustic For confirmation purposes, represenidentified cyanide impacted soil. soda and detergent solution to improve tative composite soil samples were col• Excavation of the impacted soil, fol- desorption rate of cyanide particles. lected from different areas of the stocklowed by segregation of soil, stones, boulThe process was controlled by mea- piles. Thirteen collected soil samples ders and debris using a trommel. suring ORP and pH before, during and were submitted to an accredited labora• Preparation of water slurry with the upon completion of the chemical reac- tory for analysis of free cyanide. impacted soil (loading to a cement mixer tion. Ambient air and soil vapours in the All of the analyzed soil samples truck with a loader and a conveyor, mix- recovered samples were measured using exceeded the applicable MECP standards ing with water). a VRAE PGM-7800 gas monitor and a for free cyanide. Based on the analytical • Chemical oxidation of the slurry (load- portable Gastec pump with Gastec tubes results, the identified free cyanide concening reagents, mixing).

1G12LL calibrated for hydrogen cyanide. trations in the soil in Stockpile 1 exceeded • Solidification by adding cement pow- Hydrogen cyanide vapours measured the applicable standard for free cyanide for der to the slurry upon completion of the during the field pilot test, both in the surface soil by approximately two times. reaction and discharge at the site. excavated soil and in the test pit, as well However, they were within the standard as the ambient air, were non-detectable. for subsurface soil.

FIELD PILOT TEST A factorial experiment was designed Soil samples collected from Stockpiles Prior to the implementation of the and implemented during the field pilot 2 and 3 exceeded the applicable Table 4 remedial action plan, a field pilot test was test to evaluate optimal technological standards for free cyanide for both surconducted at the site to evaluate the effi- parameters for the oxidation process. The face and subsurface soil by over three cacy of the proposed remedial approach. following factors controlling the oxida- times. Therefore, the ex situ chemical oxi30 | April 2019

Environmental Science & Engineering Magazine

dation program was conducted on the soil recovered from Stockpiles 2 and 3. Upon completion of the remedial program, the excavated soil from Stockpile 1 was used for backfilling of the remedial excavation below a depth of 1.5 mbgs (criteria for stratified condition).

REMEDIATION STATION LAYOUT The ex situ chemical oxidation remedial program was implemented using a trommel, two cement mixer trucks with a capacity of 9 m3 each, a mobile conveyer for loading soil and cement into mixers, a power generator to supply power to the conveyor, a large excavator, a skid steer loader, a stainless steel utility pump with the associated hosing for transferring chemicals to a cement mixer, and two plastic holding tanks for water. The program included the following stages: • Pumping water into the cement mixers.

• Loading the water-filled cement mixers with the cyanide impacted soils from Stockpiles 2 and 3.

• Adding sodium hydroxide and sodium

hypochlorite to the mix of water and soil.

• Mixing of the resulting slurry from 30 to 45 minutes.

• Adding cement to the treated slurry after the completion of the oxidation process to produce un-shrinkable fill.

• Placement of un-shrinkable fill at the site.

produce un-shrinkable fill varied from 200 to 280 kg per mixer truck load. A treatment period was initially set up as 45 minutes, and then was adjusted to 30 minutes, based on the field observations.

SOIL CHEMICAL ANALYSIS A total of 41 soil samples of pretreated and treated soil were submitted CONCLUSIONS to an accredited laboratory for analyses.

The ex situ chemical oxidation pro- This included free cyanide (29 samples), gram of the cyanide impacted soil was pH (four samples), free cyanide and pH conducted from November 20, 2008 to (three samples), free and total cyanides January 13, 2009. Field measurements (four samples), free/total cyanides and during the remediation program were pH (one sample). Selected samples were conducted using a portable meter HI analyzed for pH to confirm the required 9025 for measuring pH and ORP in the conditions for oxidation of the cyanide treated soil, and VRAE PGM-7800 gas impacted soil. All soil samples analyzed monitor for measuring hydrogen cya- for free cyanide were within the MECP Table 4 standard for surface soil. nide vapours in the ambient air.

In total, 105 mixer truck loads or 1,345 tonnes of cyanide impacted soil Viktor Kopetskyy, PhD, P.Eng., is were treated with chemicals. 16,082.5 kg with Soil Engineers Ltd. Email: of 25% sodium hydroxide and 15,444 kg vkopet1661@rogers.com. Jim Phimister, of 12% sodium hypochlorite were used. P.Eng., P.Geo., was formerly with Cement adding to the treated soil to Barenco Inc.

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REMEDIATION

A lot can be learned from samples of PFAS in the soil, sediment and water taken on-site.

Using multiple lines of evidence helps in the study and remediation of PFAS

By Stefano Marconetto

I

nvestigating and remediating soil and groundwater impacted by per-and polyfluoroalkyl substances, collectively known as PFAS, is a particularly challenging puzzle. Conventional techniques tend not to be very effective, calling for a multiple lines of evidence (MLE) approach.

Over the past 50 years, thousands of PFAS have been developed for different applications. Each has its own chemical and physical properties, which affect the way it migrates and is distributed in soil, sediment and water.

The huge range of PFAS-containing products, such as firefighting foam, carpets, waxes and breathable outerwear, and their use in several industrial processes, mean different dispersal patterns.

Firefighting foams may spread PFAS into soil and sediment as well as surface and groundwater. Industrial uses may result in leaks, spills, air, wastewater or waste discharges, and PFAS from consumer 32 | April 2019

products may end up in landfill leachate.

PFAS may be spread far from point of origin by wind, sediment or water without breaking down.

Their persistence, wide use in many products, long-standing utilization of over half a century, and their long-range atmospheric transport and deposition mean that they can be almost anywhere.

It is important to separate the effects of these background concentrations from those of the PFAS specific to the site being investigated.

These factors make PFAS a good example of a particularly challenging class of compounds to study and to remediate. The MLE approach used for PFAS is practical, customizable and scalable, and can be designed to fit the objectives and complexity of the project at hand.

The MLE approach can be used on a wide range of PFAS-impacted sites. Its purpose is to determine the source(s) through fingerprinting the range of PFAS that are

found. This approach also helps separate PFAS impacts that are specific to the site, and those that come from off-site sources or background concentrations. This is particularly important, since PFAS have dispersed widely into the environment.

Golder’s MLE approach involves four steps: 1. Analyze PFAS present on the site – Even though PFAS are almost ubiquitous in the environment, their composition and release mechanisms are often different, depending on the source. This fact means we can learn a lot from samples of PFAS in the soil, sediment and water taken from the site. This includes studying the concentrations in the source zones, as well as along the primary flow paths, and how the composition stays the same or evolves along them.

Many site investigators consider their work to be complete if they assess the concentrations for the few PFAS that are currently being regulated. We find that we gain valuable insights from a more comprehensive approach. This includes studying the relative concentrations of all of the PFAS being analyzed, typically 10 to 30, depending on the laboratory and the site being analyzed.

Some of those insights come from producing radial or “star” plots for each sample, so that the concentration of each PFAS is represented by an arm of the star. When each star is placed on a map of the site to indicate where the sample was taken, it is easy to see whether the proportions of each PFAS are the same throughout the site.

If there are differences, it may indicate that some impacts are from different sources or may suggest preferential transport/partitioning of some PFAS versus others, based on chain length or other properties.

Radial plots, positioned on a site map, help with the fingerprinting process to determine the origin and cause, as well as with fate and transport assessment.

We also find that these maps are readily understood by stakeholders, including property owners and political leaders. Therefore, they form a valuable tool for gaining support for site management and remediation. continued overleaf…

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REMEDIATION

Film manufacturing facility

Fire-fighting training area

Landfill

Radar plots can be used to display relative PFAS concentrations at any sampling location and can assist with the identification and characterization of multiple PFAS sources and plumes. This example shows distinct PFAS signatures for three different sources.

FilmFilm manufacturing manufacturing facility facility training training area area Landfill Landfill Radar plots canfacility be Fire-fighting usedFire-fighting to Fire-fighting display relative PFASarea concentrations Film manufacturing training Landfill at any sampling location and can assist with

identification and characterization of multiple sources and plumes. This example shows distinct PFAS Film the manufacturing facility Fire-fighting training area PFAS Landfill

three 2.signatures Determinefor the totaldifferent mass of sources.

PFAS on the site and analyTherefore, we use chromatograms of the PFAS analysis to sis of its signature – While the radial plots provide part of the assess the linear versus branches ratio for selected PFAS. This, answer, the MLE approach means going broader. This is partly along with the other analytical tools in the MLE toolbox, helps because of the limitations of current commercial laboratories us distinguish sources, and understand the PFAS transport in analyzing PFAS. Most laboratories are only able to test for and fate pattern. about 30 PFAS, out of well over 3,000 that have been devel4. Analyze the general chemistry of the site – A fourth oped over the past 50 years. aspect of our MLE approach is to take a broader look at the This means that much of the PFAS chemistry on any given site’s chemistry. We find that this often provides insights into RadarRadar plotsRadar plots can be can used be tobe display to display relative relative PFAS PFAS concentrations concentrations at anyatsampling anyatsampling location location and can andassist assist with with with can used to display relative concentrations anybox. sampling location and can assist site isplots still aused frustratingly large andPFAS impenetrable black We thecan way PFAS will behave. This stage includes studying the pH, the identification the identification and can characterization andbecharacterization of multiple of multiple PFAS PFAS sources sources and plumes. and plumes.

This example This example shows distinct distinct PFAS PFAS PFAS the identification and of multiple PFAS sources and plumes.

Thisshows example shows distinct Radar plots usedcharacterization to display relative PFAS concentrations at any sampling location and can assist with are not able to analyze all the compounds that may be present, specific conductivity, dissolved oxygen, temperature, oxidasignatures signatures foridentification three for three different different sources. signatures for three different sources. the andsources. characterization of multiple PFAS sources and plumes. This example shows distinct PFAS including some compounds (precursors) that over time could tion-reduction potential, as well as analyzing other contamisignatures for three different sources. biotransform into the PFAS that are being regulated. nants that may be present.

However, what we can do is assess the total PFAS mass at The MLE and the number of lines of evidence used is cusany given location. This not only provides insights into the tomizable to site characteristics and project objectives. The use size of the contamination problem, but the analysis of its sig- of all of these tools may not be required in every PFAS site nature also helps us gain insights into whether specific PFAS characterization. However, we find that it is important to keep precursors are present. This becomes a valuable line of evi- in mind all of the available tools in our toolbox, so they can be dence for characterization of PFAS impacts and fingerprinting. used when needed.

3. Study PFAS linear and branched isomer composition – We find that this MLE approach to PFAS site characterizaGoing beyond the study of PFAS concentrations and mass, our tion has helped us understand the sources, transport and fate of MLE approach can include analysis of their chemical structure. this class of compounds, which are a class that is coming under Some PFAS compounds have a linear molecule. Others have a increasing regulatory scrutiny and public concern. Furtherbranched molecule that looks like a letter “L” or a “T”. It’s the more, the multiple lines of evidence approach provides robust same compound, but with different variants. Each variant has data that can be relied upon to design remediation strategies. its own properties and so may behave differently in the environment. This includes how easily the compound migrates by Stefano Marconetto, MSc, P.Eng., is with Golder. Email: stefano_marconetto@golder.com means of air dispersal, groundwater or surface water.

In certain circumstances, additional lines of evidence such as the use of TOP Assay results, branched vs. linear isomer compositions and local geochemistry can assist with In certain In certain circumstances, circumstances, additional additional lines of lines evidence of evidence such theas use theBy ofuse TOP Assay TOPofaAssay results, results, branched branched vs. vs. linear isomer isomer compositions and local and local geochemistry geochemistry can assist can assist with with with In certain circumstances, additional lines ofsuch evidence such as theofuse TOP Assay results, branched vs. linear isomer compositions andcan local geochemistry canfollow-up assist distinguishing PFAS sources and assessing fate and as transport. providing better understanding oflinear the PFAS issues atcompositions theresults, site, this approach help tolinear better scope In certain circumstances, additional lines of evidence such as the use of TOP Assay branched vs. isomer compositio distinguishing distinguishing PFAS PFAS sources sources and assessing and assessing fate and fate transport. and transport.

By providing By providing a better a better understanding understanding of the of PFAS the PFAS issues issues at the at site, the this site, approach this approach can help can to help better to better scope scope follow-up follow-up distinguishing PFAS sources and assessing fate and transport.

By providing a better understanding of the PFAS issues at the site, this approach can help to better scope follow-up investigations, monitoring programs, risk assessments, risk management or remediation. distinguishing PFAS sources and assessing fate and transport.

By providing a better understanding of the PFAS issues at the site, investigations, investigations, monitoring monitoring programs, programs, risk assessments, risk assessments, risk management risk management or remediation. or remediation. investigations, monitoring programs, risk assessments, risk management or remediation.

investigations, monitoring programs, risk assessments, risk management or remediation.

34 | April 2019

Environmental Science & Engineering Magazine

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WATER

Determining the effectiveness of direct horizontal-flow roughing filtration

By Jahangir Chowdhury

F

iltration is the most common treatment process used in all water treatment plants to remove suspended particles and pathogens. A roughing filter uses media that is more than 2 mm in diameter. These can be of horizontal-flow, up-flow or down-flow.

Horizontal-flow roughing filtration (HRF) for pre-treatment has been applied successfully in many facilities for raw water of medium to low turbidity. The main characteristics of the process are its horizontal flow direction and three to four gravel packs, ranging from coarse to fine grain. HRF technique is a natural purification process and no chemicals are necessary.

Installation of such filters requires only local resources such as construction material and manpower. Furthermore, no mechanical parts are required to operate or clean the filters.

Due to high deposits storage capacity and considerably longer service period, the HRF became a promising alternative pretreatment method prior to slow sand filters (SSF) and rapid sand filters (RSF).

Its horizontal-flow direction allows construction of shallow and structurally simple filters.

However, at high raw water turbidity (> 200 NTU) or relatively high filtration rates (> 1 m/h), the turbidity removal efficiency and filter run length of HRF

HRF acts as a multistore sedimentation tank

drop drastically. Consequently, it needs a large surface area. Removal of sludge by flushing remains critical where there is organic matter in raw water.

Collected silt in many cases is sticky, and is difficult to flush out. This makes HRF technology unattractive for application in semi-urban and urban areas.

Therefore, further modification of HRF was carried out to overcome these drawbacks.

To overcome some of HRF’s limitations and to allow higher filtration rates and longer filter run time, application of a coagulant to the influent water before HRF is an interesting process modification. This new process modification is called direct horizontal-flow roughing filtration (DHRF). Investigation shows that the size of DHRF can be reduced substantially and hence capital cost may be lowered.

The feasibility of DHRF, so far, has proved to be an attractive and promising pretreatment process at bench scale.

Its application on full plant scale prior to SSF and RSF in semi-urban areas and the small towns of developing countries needs to be investigated. The construction cost of DHRF was estimated to be about two times lower than a conventional flocculation-sedimentation system.

Accumulation of solids on the upper collector surface

MAIN FEATURES Direct horizontal-flow roughing filtration is a promising pretreatment process with an appropriate level of technology.

The filter bed is composed of a simple box filled with gravel of different sizes varying from coarse (20 mm) to fine (5 mm) over two to three compartments in the direction of flow. The compartments at the inlet and outlet site of the filter box establish an even flow distribution and maintain a certain water level across the filter bed.

The total length of the filter bed ranges from 9 m to 12 m. Height is limited to 1.5 m to allow comfortable manual cleaning. The width of the filter box depends on the filter capacity and normally varies from 2 m to 5 m.

Water flows in a horizontal direction through the filter bed. Treated water is collected by an outlet chamber and then discharged over a weir. The bulk of solid matter is retained in the filter bed.

With progressive accumulation of solid matter in the media filter, efficiency decreases, so periodic cleaning must be done. After several months or years of service, periodic cleaning may not be sufficient to reestablish filter efficiency.

Therefore, filter media must be manually removed, washed and replaced.

Drift of separated solids to the filter bottom

Figure 1. Particle removal mechanisms in direct horizontal-flow roughing filtration (HRF).

36 | April 2019

Environmental Science & Engineering Magazine

REMOVAL MECHANISMS With respect to the removal mechanism of the first coarse grain (~ 20 mm diameter) compartment of DHRF, several researchers have reported that sedimentation is the main removal process and in-pore flocculation also plays an important role. The filter acts as a multiple-plate settler and provides a very large net surface area on which sludge may accumulate.

Sludge accumulates on top of grains and grows into dome-shaped aggregates with advanced filtration time. The size and shape of the heaps formed is controlled by their slope stability. Some of the small heaps drift toward the filter bottom.

This drifting partly regenerates the filter efficiency of the upper filter layer, but gradually clogs the filter bed from the bottom.

Besides the vertical downwards drift of the sludge there is also a horizontal drift in the direction of flow. This drifting process is advantageous as the removal capacity of the upper layers is restored to

The feasibility of DHRF, so far, has proved to be an attractive and promising pretreatment process at bench scale.

a certain extent. (See Figure 1) Preliminary studies on the removal mechanism of the subsequent compartment with medium size grains (~ 8 mm diameter) showed characteristics similar to deep-bed filtration. It can be said to act as a number of vertical filtration layers perpendicular to the flow direction.

In the first coarse compartment, the turbidity decreases gradually along the length, in a pattern similar to the particle removal pattern in a sedimentation basin. In the finer media compartment, a progressive clogging front is developed with filter run time, which is assumed to be similar to vertical deep bed filtration.

EXPERIMENTAL RESULTS Six filter runs under different process conditions were considered. Performance of the first and second compartments is shown in Figure 2. Experimental data used in this Figure have been calculated as weighted average value during the "working stage" of the filter.

The bigger size particles present in the influent are settled by sedimentation (as in settling basin) in the first compartment of DHRF. Influent of the second compartment (i.e., effluent of the first compartment) consists of particles of comparatively smaller size and of less continued overleaf…

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April 2019 | 37

WATER

Initial Turbidity = 400 FNU)

Initial Turbidity = 200 FNU)

100

Remaining Concentration (%)

100

Remaining Concentration (%)

settling velocities.

However, due to higher head loss (~ 3 cm/m compared to 1 mm/m in the first compartment) results in higher G – value and in-pore flocculation, the particles may subsequently grow in size again in the second compartment.

The earlier breakthrough with higher filtration rates and influent turbidity occurs because of higher shear stresses, which cause particle dislodgement. The increase of influent turbidity provides a higher concentration of particles, which contributes to higher floc formation.

The pore size or the storage capacity of the filter reduces faster. Therefore, after a certain filter run time, the particles move horizontally with the bulk of the flow instead of settling. This causes an early breakthrough.

Although the breakthrough or filter run time reduces tremendously with increasing filtration rates, the cumulative specific deposits value was found to be nearly the same.

The accumulation of deposits for var-

80 60 40

V = 7 m/h

20

80 60 40 v = 7 m/h

20

V = 3 m/h

0

0.0

1.0

V = 3 m/h

2.0

3.0

0

4.0

Filter Length (m)

0.0

1.0

2.0

3.0

4.0

Filter Length (m)

Figure 2. Turbidity profile along filter length.

ious filtration rates and influent turbidity show that approximately the same amount of deposits accumulate (~ 25 g/l in first and ~ 11 g/l in second compartment) in the pores of the grains before breakthrough.

Head loss increases with filter run time.

However, its development in the first compartment is negligible and, in the sec-

ond compartment, it is of minor importance for filter operation as it will only be within a few centimetres.

MODELLING THE FIRST COMPARTMENT In this model, plain sedimentation is the main process mechanism in the gravel bed of the first coarse compart-

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Environmental Science & Engineering Magazine

ment of DHRF. The filter bed acts as a multiple plate settler. The model applies sedimentation theories from a multiple plate settler system. To determine the removal efficiency of the filter, the results of quiescent column settling tests are incorporated in the model.

The assumption of the model is that the total volume of the model settler is equal to that of the first filter compartment. The thickness of the settler plates and the spaces between the plates are equal to the average grain size dg and the initial porosity ε₀ of the filter respectively.

as sedimentation, as in the case of the first compartment. Deep bed filtration is assumed in the second approach. A combination of sedimentation and deep bed filtration is considered in the third approach.

According to the optimization of parameters of the first and second compartment of DHRF, a tentative design guideline for initial turbidity ranges from 200 NTU to 400 NTU at the influent of the first compartment.

tion-sedimentation process and be used before the slow and rapid sand filtration.

The dominant particle removal mechanism in the first compartment of DHRF with coarse grain (~ 20 mm diameter) is sedimentation, while in the second compartment with medium sized grains (~ 8 mm diameter) it is deep bed filtration.

As filtration has much higher particle removal efficiency than sedimentation, the removal efficiency of the second compartment is higher (~ 96 %) than the first (~ 75 %) for the same filter CONCLUSIONS dimensions.

The process modification done on For filter runs with medium (200 HRF by adding coagulant prior to fil- FNU) and highly (400 FNU) turbid water MODELLING THE SECOND COMPARTMENT tration has proved to yield good efflu- and filtration rate varying from 3 m/h to A mathematical model was developed ent quality with longer run time. Higher 7 m/h, the optimum filter length for the to assess the main process mechanisms filtration rates (3 m/h – 5 m/h) can be first compartment is determined to be and to predict the removal efficiency applied in DHRF compared to HRF (0.5 4 m and for the second compartment is 2 m to 3 m. along the filter length of the second com- m/h – 1 m/h).

Because of the relatively low construcpartment of DHRF with medium sized grain (~ 8 mm diameter). In the model, tion and operation cost, DHRF could be Jahangir Chowdhury, MScEng, three different approaches are made to an appropriate pretreatment technology. P.Eng., is with Aecom. Email: assess the dominant process mechanism. Findings also indicate that it has good jahangir.chowdhury@aecom.com The first approach treats the process potential to substitute for the floccula-

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April 2019 | 39

BIOSOLIDS

Deeper pond design improves sludge centrifuge performance

By Frank Scriver

L

iquid pond depth has been proven to have a significant impact on solid-bowl decanter centrifuge dewatering performance. Since the adaptation of this dewatering technology for municipal biosolids, scroll design advancements have allowed decanter centrifuges to operate with deeper liquid ponds, resulting in increased performance.

The original solid-bowl decanter centrifuge design was modeled after the principle of a rectangular gravity clarifier. The primary difference between the two is that instead of the solids settling under the normal force of gravity (1g), the entire clarifier is wrapped around an axis of rotation and spun at 2,700 – 5,000 rpm. This results in g-forces in excess of 3,000.

Major components of the gravity clarifier are also found in the decanter centrifuge. These are the inlet (feed tube), settling zone (cylindrical section), settled solids removal device (scroll), clarified liquid discharge (centrate discharge), solids dewatering beach (conical section), and solids discharge.

This original design worked well for separating discreet particles such as crystals or mine tailings and to a certain extent, primary solids from municipal treatment plants. As more facilities added secondary treatment processes, solids became finer with more amorphous characteristics. These solids did not allow free water to drain and needed to be compressed to force the free water from the voids.

By attaching a vertical plate to the scroll body at the transition point from the cylindrical to the conical section, a barrier (dam) is created that prevents liquid from passing to the solids discharge of the centrifuge. This vertical plate, referred to as a “barrier disc”, “baffle disc (BD)” or “dip weir”, depending on the manufacturer, is of a slightly smaller diameter than the inside diameter of the centrifuge bowl, leaving a small gap 40 | April 2019

configuration. The disc creates a dam that allows the elevation of the liquid pond surface to be above the elevation of the solids discharge. The deeper the liquid pond, the higher the hydrostatic pressure and subsequently the greater the compressive force acting on the solids. This results in an increased dewatered cake solids concentration.

Approximately 2/3 of the total power demand is used to accelerate the product to operating speed of the centrifuge.

This power is converted into rotational or kinetic energy. The separated phases maintain their angular momentum when being discharged from the centrifuge. This force acts in the opposite direction of the bowl rotation. Specific energy demand is the amount of energy required to accelerate the bowl to maintain a set operating speed.

To increase the depth of the liquid pond, the centrate discharge radius is decreased (brought closer to the axis of rotation).

Reduction in the discharge radius has a direct impact on the angular momentum, resulting in a reduction of the specific energy demand of the centrifuge.

The original solid-bowl decanter centrifuge design was modeled after the principle of a rectangular gravity clarifier.

between the plate and the bowl wall.

Settled solids collect on the inside surface of the cylindrical section of the bowl and are transported to the solids discharge by the scroll conveyor. During conveyance, they are compressed under their own weight and the hydrostatic pressure of the liquid phase acting upon them. Compression of the solids closes the voids and drives out free water.

Prior to entering the conical section and leaving the centrifuge through the solids discharge ports, compressed solids pass through the gap between the disc and the bowl. It is at this point that the solids are at their maximum dryness.

Using a baffle disc or dip weir allows the centrifuge to operate in a “deep pond”

SUPER-DEEP POND The depth of the liquid pond is limited by the inside surface of the bowl wall and the outside diameter of the body of the solids removal scroll inside of the bowl. In order to maintain high settling efficiency in the centrifuge, the surface of the liquid pond must remain quiescent. Any contact between the pond surface and scroll body would create turbulence along the length of the scroll body and inhibit settling.

Increasing the diameter of the centrifuge bowl also increases the overall size of the centrifuge, and in almost all cases is not a cost-effective solution. The diameter of the scroll body can be reduced.

However, this affects the structural integrity of the scroll at the risk of increasing

Environmental Science & Engineering Magazine

By replacing the solid scroll body with a tubular space frame the pool depth can be increased significantly without affecting the structural integrity. The open scroll design allows the centrifuge to operate in “super-deep pond” mode as the pond surface is actually inside of the tubular space frame members.

vibration levels.

The third alternative is the elimination of the solid scroll body altogether.

By replacing the solid scroll body with a tubular space frame, pool depth can be increased significantly without affecting structural integrity. The open scroll design allows the centrifuge to operate in “super-deep pond” mode, as the pond surface is actually inside of the tubular space frame members. The only limitation of the pond depth is the outer diameter of the scroll bearing housing.

Solid scroll body designs incorporate a chamber used to accelerate the axially flowing feed prior to introduction into the bowl. In addition to acceleration, this feed zone changes the direction of the feed from axial to tangential

through a series of openings in the scroll body called feed ports. The combination of acceleration and change of direction subjects flocculated feed to a significant shear force. This damages the flocs formed prior to introduction to the feed zone, resulting in the need for a higher polymer dose to produce more rigid flocs. Open-scroll body designs eliminate the feed zone and introduce the feed directly on the moving layer on the surface of the liquid pond.

Due to the small diameter of the super-deep pond and resulting low circumferential speed of the pond surface, shear forces are a fraction of those developed in conventional feed zones. The result is reduced polymer consumption.

EFFECT ON PERFORMANCE Full-scale testing was performed at three wastewater treatment plants (WWTP) to compare the super-deep pond design to the deep-pond design. All three plants used activated sludge treatment. Two utilized anaerobic digestion for stabilization, while the third aerobically stabilized its sludge.

Testing was conducted using centrifuges of the same size (bowl diameter, length, drive system and controls). One unit was fitted with a deep-pond configuration and the other with a super-deep pond configuration.

SUMMARY OF PERFORMANCE DATA Average results for all three WWTP continued overleaf…

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April 2019 | 41

BIOSOLIDS operating G-force of the centrifuge.

Liquid pond depth is calculated by subtracting the solids discharge diameter from the bowl diameter. Standard G-volume calculations do not take into consideration that the majority of manufacturers are now using deep pond technology. In other words, the presence of a baffle disc or dip weir is not represented in this calculation.

The difference in pond depth is significant when calculating using the centrate discharge diameter. While current CENTRIFUGE SIZING AND COMPARISON G-volume calculations calculate some Since there are many different man- volume in the conical section, in reality ufacturers of centrifuges and most of the conical section is full of dewatered these use different bowl geometry, it is solids that have been extruded through difficult to compare one to the other in the gap between the disc and the bowl. order to determine what throughput a The cone, therefore, does not contribute at all to the suspension volume. given centrifuge will handle.

While G-volume is a widely accepted For many years, G-volume has been widely accepted as a value for comparing method of comparing the capacity of one make and model to another. As the one centrifuge to another, it does not name implies, G-volume is the product of accurately represent centrifuge designs the calculated suspension volume (cylin- currently being used for dewatering drical section + conical section) and the municipal biosolids. In addition, it does

tests show a 15% – 25% reduction in specific energy consumption between the deep-pond and super-deep pond designs.

An average increase in dewatered cake concentration between 1% and 2% total solids was observed between the deeppond and super-deep pond designs. A reduction in polymer consumption of between 2 kg and 4 kg active/tonne of dry solids was observed to meet the same dewatered cake concentration.

42 | April 2019

not take into consideration the impact that deep pond and super deep pond technologies have on performance and operating costs.

Calculating G-volume using the suspension volume of the cylindrical section with the centrate discharge diameter provides a more representative comparison.

In addition, a comparison of the ratio of the centrate discharge diameter to the inside diameter of the bowl allows for evaluating the pond depth and its impact on performance.

Frank Scriver is with Flottweg Separation Technology. Email: fscriver@flottweg.net

Environmental Science & Engineering Magazine

WASTEWATER

Continuous monitoring of total inorganic nitrogen helps WWTP meet discharge limits

A

fter years of significant population growth and increases in daily flows, two wastewater treatment facilities’ land application discharge permits were modified, requiring a new limit of 10 mg/L total inorganic nitrogen (TIN). Treated effluent from these facilities is used for golf course irrigation.

The plants faced the possibility of a significant capital investment in order to meet an 18-month compliance schedule. As such, their operations staff went to work trying to identify an operating strategy that could achieve discharge requirements without an expensive engineering solution.

The initial strategy was to create an anoxic zone by maintaining low dissolved oxygen (DO) in the first pass of the twopass aeration tank by cycling blowers on and off, allowing denitrification to occur in the settled biomass. Some denitrification did occur, but a TIN of 10 mg/L in composited effluent could not always be achieved.

In order to dial in the optimum operating strategy and to identify times and conditions of underperformance, a more thorough evaluation was required. The primary goal was to determine nitrate levels in and after the anoxic zones to ensure appropriate denitrification had taken place in the process. An IQ SensorNet (IQSN) 2020 XT monitoring and control system from YSI, a Xylem brand, was installed to monitor critical parameters in real time.

This provided a modular plug-and-play system to continuously monitor ammonium, nitrate, dissolved oxygen, pH and oxidation-reduction potential (ORP) in the oxic and anoxic zones, using a single networked monitoring system. The probes used for monitoring included the TriOxmatic (dissolved oxygen), Sensolyt (pH and ORP) and VARiON ion selective electrode (ISE) sensor (ammonium and nitrate).

treatment process in certain locations within the facility to be sure that the overall process was helping meet the new TIN compliance parameters. The IQSN system was redeployed to assess the result and determine if additional improvements to provide internal mixed liquor recirculation were required. It determined that both facilities had seen a TIN level of 10 mg/L, which is well within the new guidelines.

What the plant operators did not expect to find were the other efficiencies gained with the continuous monitoring system. Over the course of the assessment, they were also able to see the real-time data obtained from the IQSN system for nitrate, DO, NH4, pH and ORP. This data provided great visibility into the biological health of the plant.

YSI is represented in Ontario by SPD Sales Ltd. For more information: email: cosentino.f@spdsales.com

A BALANCING ACT The real-time monitoring data showed that the on-off operating strategy was able to meet target compliance concentrations intermittently, but it was a balancing act. During periods in which ammonium concentrations were lowest, nitrate concentrations were higher. This indicated that more time was required for denitrification. If insufficient time was provided for nitrification, ammonium would spike and nitrate would be lower. The online monitoring demonstrated clearly and quickly that meeting the new requirements was going to require more than a change in operating strategy.

The next step was to design and build anoxic zones to provide a more reliable and consistent solution for the denitrification process. Needs were identified, a plan was drawn up and the renovations were implemented. The upgrades included installing a wooden baffle and a floating downdraft mixer, in addition to removing some diffusers in the first pass.

Once the renovations were done and the anoxic zones were integrated into the plant flow, there was a need to monitor the www.esemag.com @ESEMAG

April 2019 | 43

WATER

Used shipping containers can house remotely located package water treatment plants

By Robert Abernethy

R

emote communities face unique challenges. Their partial or full isolation due to geographic accessibility and separation from the electrical and natural gas network make providing efficient, high quality water treatment expensive and difficult.

According to a 2006 Statistics Canada Census, there are 292 remote aboriginal and non-aboriginal communities and commercial outposts in Canada, with a total population of almost 200,000. Yellowknife, Whitehorse and the Magdalene Islands account for about 28% of this total.

The common characteristics of remote communities, such as limited/seasonal road access, shortage of services, small populations and limited education, mean many share a similar plight in terms of the ability to provide safe drinking water. It is expensive and complex, with no one-size-fits-all solution.

Some of these communities are unfortunate examples of water infrastructure planning not taking into account these restrictions. Too often, the result is

Top: 3D digital rendering of an example interior of a WaterShed package water treatment plant.

Right: A completed WaterShed beginning the first overland part of its journey from Ontario to Newfoundland.

poorly functioning multi-million-dollar water treatment systems.

Physical considerations, such as road access, weather, distance from the near-

est urban centre, have considerable influence on the cost of equipment and materials. Rarely can the equipment, materials, engineering know-how and construction

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44 | April 2019

Environmental Science & Engineering Magazine

crews be sourced locally.

Upgrading such water treatment plants is expensive and communities with small populations often do not have the funds to handle the extra costs for even basic, conventional water treatment. Should a community seek alternative disinfection methods and multi-barrier approaches, the cost is even more prohibitive. Even if capital costs are scraped together, the ongoing operating expense may be the undoing of the project.

Another issue, particularly in First Nations communities who receive top-ofthe-line water infrastructure, may be the availability of trained operators to successfully operate and maintain the system.

ADDRESSING THE SITUATION A relatively inexpensive source of ready-made infrastructure is recycled shipping containers. They have found second lives as schools, hydroponic greenhouses, store fronts and alternative housing. Costing $1,000 – $5,000, these containers have been tested in water treatment, and provide an affordable, durable and pragmatic approach to hosting package water treatment plants (PWPs).

PWPs can be ideal for remote locations, as they address many challenges: • They are transportable, allowing them to be designed and built off-site, reducing the need for multiple expensive shipments of materials and equipment.

• They reduce reliance on local engineer-

www.esemag.com @ESEMAG

ing services and personnel, as they are largely pre-calibrated before shipping.

• The “plug-and-play” capabilities require little to no infrastructure modifications.

Once in place, they can be “plugged” into the community’s local power supply and water infrastructure.

• Financial risk is minimized, as there is a fixed, firm cost prior to delivery.

By simplifying infrastructure, PWPs are often substantially more affordable than conventional water treatment solutions. This, along with their versatility, makes them an ideal treatment solution.

dosing and monitoring technology with the Sunnyside system to inject stabilized hydrogen peroxide to mitigate the formation of chlorinated DBPs and provide an effective and long-lasting disinfection residual in distribution.

Upon confirmation that the dosing and monitoring technology was working, the next stage of the pilot was to provide a custom, pre-built filtration system contained within SanEcoTec’s PWP. WaterShed was attached to the existing treatment facility, further enhancing system performance.

After implementation there was an immediate 70%+ reduction in DBPs, bringing the water quality to within Health Canada Guidelines. Sunnyside reduced the volume of treated water being used to flush the system by up to 50%. The distribution network remained substantially free of debris and biofilm buildup, as well as E. coli and total coliforms. This resulted in no more boil-water advisories.

The total system cost over 50% less than proposed conventional water treatment systems and effectively overcame many of the traditional obstacles found in a “remote” community.

®

CASE STUDY Sunnyside, Newfoundland, has a population of less than 400 people, with fewer than 300 dwellings. The debris and minerals in its source water interacted negatively with chlorine disinfection, creating high-levels of potentially harmful disinfection by-products (DBPs) and unpleasant taste and smell in the drinking water. Sunnyside was concerned with the health effects of these DBPs and the frequency of boil-water advisories.

SanEcoTec was approved by the province’s Department of Municipal Affairs and Environment (MAE) to conduct a pilot in Sunnyside, using its AVIVE drinking water treatment technology.

Robert Abernethy, P.Eng, MBA, Initially, SanEcoTec upgraded the exist- is with SanEcoTec Ltd. Email: ing water treatment plant, ensuring that robert.abernethy@sanecotec.com MAE-required chlorine contact times were met. Then, they integrated their

®

April 2019 | 45

REGULATION

Early and effective consultation with stakeholders is one of the key aspects of the proposed legislation. Courtesy of Golder

Bill C-69 seeks to improve how new projects are reviewed, approved

By Jill Baker

T

here has been a lot of controversy around Bill C-69, the proposed “Impact Assessment Act” (IAA), which seeks to overhaul the way major projects, including mines and pipelines, are reviewed and approved in Canada. The new legislation is intended to replace the Canadian Environmental Assessment Act (CEAA, 2012).

The Senate began a nine-city tour to consult Canadians on Bill C-69 on April 8. While there are still many questions around the final form of the legislation, what we have seen so far seems to include many steps in the right direction, including: • Early, meaningful and sustained engagement with stakeholders, communities and Indigenous people.

• More transparency about the review process and expectations.

• A more comprehensive approach to assessments, looking beyond environment impacts.

46 | April 2019

EARLY PLANNING PHASE INVOLVES THE FEDERAL GOVERNMENT AT THE START One of the major changes is the addition of a 180-day “early planning phase,” in which federal government representatives get involved in the planning right from the start, so they can guide the process and help move it along towards an outcome that works for all concerned. This includes meaningful dialogue with the local community and Indigenous people.

This new phase supports what many proponents have known all along, that projects are most likely to succeed, without being tangled up in legal proceedings, bad publicity and community opposition, if they engage effectively with stakeholders and affected parties early in the process. The proponent may be working with members of the community for the duration of the project, which may span 30 to 40 years. So, it only makes sense to start relationships off on the right foot.

Early engagement makes it possible

to find out about community concerns, while the project design may still be flexible, and can be changed to satisfy those concerns. It is this openness to concerns and ideas that helps make engagement meaningful, as communities may have a true opportunity to influence project designs. Having a meaningful and sincere engagement process helps with the legitimacy of the process, which can lead to more local support. It is also possible, based on the feedback, to design the project in a way that helps the community indirectly, such as by helping set up locally-owned businesses to supply products or services to the project.

The benefits of early planning are nothing new. What’s different about the IAA is the expectation that government will be involved from the beginning, and the nature and timeliness of that involvement.

At the end of the early planning phase, the government is required to produce a number of documents, which create a road map for the impact assessment process going forward. These include tailored impact statement guidelines, impact assessment coordination, indigenous engagement and partnership plan, public participation and permitting plans. These documents form one of the little-recognized benefits of the proposed legislation, more certainty in the planning process, due to government authorship and involvement.

Detailed impact statement guidelines can provide clarity on impact statement effort and may reduce information requests later. Various coordination, engagement and partnership plans should provide clarity on how stakeholders will work together and how communities can be meaningfully involved. The indigenous engagement plan and partnership plan may reduce uncertainty around legal requirements related to consultation.

Finally, early engagement and issue identification could reduce the risk of unknown issues arising later in the process.

GOING BEYOND ENVIRONMENTAL ISSUES TOWARDS SUSTAINABILITY A second key aspect of the IAA is that it broadens the review process from a focus mainly on environmental issues to considering a wider range of factors

continued overleaf…

Environmental Science & Engineering Magazine

30th

www.esemag.com

2018

January/February 2014 | 45

REGULATION that encompass “sustainability.” These include the social, health and economic impacts of the proposed project. While some may see this as being too much to expect from a proponent to consider, it is already included in several provincial and territorial legislative requirements in Canada. So, it is not a new idea to be more comprehensive in the review scope. It is just new at the federal level.

Further to this, the IAA emphasizes the importance of focusing on not just the mitigation of potential negative impacts, but also giving serious attention to the potential positive benefits of projects. If done well, the sustainability assessment will look to the long-term goal of creating communities that can thrive beyond the life of the project.

Taking this more comprehensive approach will bring Canada in line with the impact assessment review processes followed in many other parts of the world, which formally incorporate economic, social and health factors. While environmental considerations are critical to address, often projects come up against opposition, due to the inadequate attention given to the social issues that communities care about. This has not necessarily been any fault of the proponents but rather due to a significant gap in the requirements in law. The IAA will rectify these gaps with the proposed sustainability approach.

It sounds like a lot more work for proponents, so why should they welcome such change? It may come down to good business practice. Proponents of large infrastructure projects, which the IAA will likely affect the most, should have a business interest in developing constructive, collaborative relationships with the communities that they are moving into, especially if they plan to be there for decades. Through their projects, they have the potential to assist in community development, and not just economically.

They have the potential to help contribute to the growth and development of healthy communities, if done right. This begins with early, meaningful engagement on the issues that people care about.

Therefore, a review that is comprehensive, allowing for dialogue on issues of social, health, economic concerns and opportunities, in addition to the usual 48 | April 2019

The IAA seeks to overhaul the way major projects, including pipelines, are reviewed and approved.

discussions on environment, may be of benefit over the long term. And again, it is important to point out that the proposed IAA requires and encourages the assessment of the positive gains of a proposed project. This new information will be taken into consideration by decision makers when weighing the pros and cons of a project. It will affect the “public interest” test which is now acknowledged as a point of contemplation by the government in deciding upon approvals.

The inclusion of social, health and economic aspects points to the integrated nature of many development issues, and why it makes sense to include these considerations in the scope of assessment.

For example, while potential impacts to a river are identified as an environmental issue, they may also be an economic issue if people in the area depend on fish from that river as part of their food supply. It can be a social issue too, if fishing is part of their spiritual life or community recreation.

In practice, it is often difficult to separate social issues from economic. In many jurisdictions around the world and in Canada, the regulations talk about “socio-economic” factors. This helps with sustainability in two ways. One is the context around global sustainability, the wise use of resources, and the accepted definition of “allowing current generations to meet their needs while not interfering with future generations to meet their needs.” But it goes further, into

the ability of the project to sustain itself, given a good level of acceptance and support from the people being affected by it, so that they will allow it to continue.

For example, a project that relies only on a “fly-in-fly-out” workforce may not be as sustainable as one that hires local people and trains them for the work available, with chances for advancement, as well as becoming a reliable customer for local businesses. With the emphasis that the IAA places on sustainability, it is companies that reach out to communities early for discussion, and work with them to build socio-economic sustainability into the project, that are the most likely to be successful.

The benefit to project proponents is that these broader considerations of social, economic and health factors can build public trust and support for the project.

Ultimately the changes to CEAA, 2012 are aimed at creating a good planning process. Good environmental and social impact analysis is about good planning and having a well-informed process that is inclusive, with meaningful engagement, the inclusion of rigorous science and traditional knowledge, and decisions that are transparent and timely.

The views presented here are those of the author and do not represent those of Golder.

Jill Baker is with Golder and is the past Executive Director of the International Association for Impact Assessment (IAIA). Email: jill_baker@golder.com

Environmental Science & Engineering Magazine

GUEST COMMENT

My journey to help solve the global water and sanitation crisis

By Tony Petrucci

C

an you imagine a world where everyone has access to clean drinking water and proper sanitation?

It’s not an impossible vision. Last year’s World Toilet Day was on November 19. It may sound funny, but clean water is no joke. And neither is the fact that 2.1 billion people currently don’t have access to safe, reliable water. Even more – 4.5 billion – don’t have access to improved sanitation.

I’d like to tell you about my work with Water For People (WFP), a global nonprofit organization, and why I’m so passionate about trying to help solve the global water and sanitation crisis.

My introduction to the organization’s water, sanitation and hygiene program began with a presentation I attended during the 2004 Water Environment Federation’s Annual Technical Exhibition and Conference in Chicago. Steve Werner was the Executive Director of WFP at the time. He had one slide in his presentation that had the face of a child disappearing every 15 seconds to represent the number of children that are dying because of the global water and sanitation crisis, specifically from waterborne diseases.

I believe everyone should have access to safe drinking water and proper sanitation. It is a basic human right. For all of us that are more fortunate and have the means to help, we have a moral obligation to help our global brothers and sisters.

For that reason, I have helped with fundraising efforts and awareness-building campaigns to support Water For People Canada’s program work in nine countries. The work, which impacts more than four million people, involves delivering safe water, improved sanitation, and hygiene education services, in cooperation with community members, governments and other like-minded Non-Governmental Organizations.

I am also on my second tour of duty on www.esemag.com @ESEMAG

Tony Petrucci (left) and ES&E Magazine’s Penny Davey (right) on their visit to Chaqui Kjocha, Bolivia, in 2008.

the Water For People Canada Board and currently serve as President. Our goal is to substantially increase our annual revenues to impact as many people as possible. We want to reach every school, clinic and family in the countries and communities where we work, and at a scale where we can reach “Everyone Forever”.

My most memorable volunteering experience came during a visit to Bolivia in 2008 to see the water and sanitation work in person. I will never forget the appreciation from families for WFP’s assistance. Community leaders were so proud to secure the necessary funding and technical support to give their children the opportunity for a healthy and bright future.

That experience inspired me to continue to work hard here in Canada to raise awareness of the global water and sanitation crisis, and still inspires me today. This cause means so much to me, because it reflects the industry I work in.

Last year, volunteers from Stantec stepped up to the challenge in 20 offices,

and raised more than $15,000 through employee giving and local fundraising efforts in each office. Every dollar raised to support WFP’s water and sanitation work results in a 5-to-1 economic impact for those communities.

Special thanks to Julie Kauffman at WFP for her efforts in helping us launch our employee giving campaign. I’d also like to pass along my deepest appreciation to Stantec volunteers, WFP volunteers, and WFP – Canada volunteers, as well as to our industry partners that supported our fundraising and awareness-building activities.

Please help celebrate World Toilet Day 2019 by helping Water For People, Water For People – Canada, or other likeminded NGOs in their efforts to make sure safe drinking water and adequate sanitation reach Everyone Forever.

Tony Petrucci is with Stantec and is President, Water For People Canada.

Email: tony.petrucci@stantec.com and visit: www.waterforpeople.org April 2019 | 49

WASTEWATER

Understanding how temperature and substrate influence wastewater nitrification

By Nick Szoke

G

ood science dictates that the protection of aquatic life needs to consider the most sensitive life stages of all species at risk. As such, depending on the aquatic life diversity and species present in the receiving water body, monthly or seasonal maximum ammonia loading and/or concentration limits are commonly set by the regulatory authority.

Low limits are typically set for spring conditions, the most sensitive time of the year, to protect fish during spawning and recently hatched fish. This also tends to correspond to the spring freshet that results in cold extraneous surface water entering a sewer system, depressing the influent water temperature and diluting the constituent concentrations. Cold dilute influent creates a challenge for operators trying to maintain the level of nitrification required to meet low NH3 effluent limits during this period.

Wastewater nitrification is a two-step process that requires an aerobic environment and sufficient alkalinity to support the growth of chemoautotrophic nitrifier populations. It is important to note

that total ammonia nitrogen (TAN) is the sum of un-ionized ammonia (NH3) plus ammonium (NH4+). Total nitrite nitrogen (TNN) is the sum of nitrite (NO2ˉ) and nitrous acid (HNO2ˉ). This clarification is very important since the equilibriums between NH3 ←→ NH4+ and NO2ˉ ←→ HNO2ˉ are a function of temperature and pH. Un-ionized ammonia (NH3), often referred to as free ammonia (FA), is a form toxic to aquatic life if present in large enough concentrations. Moreover, HNO2, often referred to as free nitrous acid (FNA), is highly toxic to living organisms in very small quantities. NH4+ is the fraction of TAN used by ammonia-oxidizing bacteria (AOB) to convert it to nitrite (NO2ˉ).

The process of nitritation (NH4+ → NO2ˉ) consumes alkalinity, which can drive down pH and increase the concentration HNO2ˉ in the process to a point that can inhibit the nitrification process.

This is a self-limiting process, if alkalinity is in short supply. In some cases, it is possible to nitrify in low pH environments (above 6.5), if sufficient alkalinity

exists, because the environment acts as a natural selector and changes the bacterial community structure. Essentially, this is survival of the fittest.

A rapid drop in pH will result in a very harsh condition, since there is inadequate time for the community to adapt and acclimate to the new environment.

For normal conditions, it is important to keep pH above 7.0 and in the optimal range of 7.5 to 8.5 pH units. Nitrite-oxidizing bacteria (NOB) convert NO2ˉto nitrate (NO3ˉ) but consume alkalinity to a much smaller degree.

There are many different biological nutrient removal (BNR) processes that include nitrification (Johannesburg, Bardenpho, Step-feed, Westside, Modified Ludzack-Ettinger, University of Cape Town, etc.) with or without denitrification and phosphorus (chemical or biological) removal. The BNR treatment process normally includes a secondary clarifier, which is a critical unit operation in an activated sludge (AS) process. The AS BNR process will be configured differently (i.e., aerobic, anoxic, and anaerobic zones) depending on the treatment

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50 | April 2019

Environmental Science & Engineering Magazine

process employed to achieve the desired effluent quality.

Denitrification requires an anoxic zone (oxygen only in the form of NOx), while biological phosphorus removal requires an anaerobic zone (devoid of all forms of oxygen) and a source of volatile fatty acids (VFA). Chemical phosphorus removal via a metal salt can be done by adding the chemical prior to the primary or secondary clarifiers, but can reduce the pH of the wastewater stream.

Biological nitrification is performed by two chemoautotrophic nitrifying microorganisms in sequence, AOB then NOB. The anabolic and catabolic processes of AOBs and NOBs are influenced by a host of factors: Growth rate (µmax) and solids retention time (SRT); decay rate (b); half saturation (Ks – also referred to as affinity); substrate concentrations (NH3, NO2, HNO2, O2, alkalinity, P, etc.); temperature (T) and Arrhenius (Ѳ); pH; alkalinity in the form of CO2; oxygen concentration; C/N/P ratio; microbial community composition; light; inhibitory or toxic compounds; hydraulic retention time (HRT) and process configuration.

Temperature influence on the nitrification processes is an important factor in the design and operation of a BNR treatment process. In an AS process, the influence of temperature on process kinetics can be expressed by the following equation: Rate adjustment coefficient, kT = k20 ∙ Ѳ(T-20) Where: • k20 is the reaction rate at a reference temperature of 20°C • Ѳ is the temperature Arrhenius activity coefficient (unitless) • T is temperature (°C) The maximum specific growth rate of nitrifiers (µmax) and maximum decay rate (bmax) combine together to establish the net growth rate of nitrifiers (µnet) at a reference temperature of 20°C. • µnet = (µmax,20 ∙ Ѳµ(T-20)) – (bmax,20 ∙ Ѳb(T-20)) Since nitrification is a two-step process, the kinetic rates influenced must be adjusted independently to properly simulate the biochemical conversion of ammonium to nitrite, and from nitrite to nitrate. The difference in growth rates and environmental conditions can result in nitrite accumulation in the system and prevent full nitrification from occurring. This condition is referred to as nitrite-lock and requires a closer inspection of the cause (e.g., low pH, low DO, low alkalinity, temperature, startup lag, etc.) to properly address the situation.

• AOB, µAOB,max,20 = 0.90 (d-1), ѲAOB,µ = 1.072, KAOB,s = 0.70 (mg/L-N), bAOB,max,20 = 0.15 (d-1), ѲAOB,b = 1.029 • NOB, µNOB,max,20 = 0.70 (d-1), ѲNOB,µ = 1.060, KNOB,s = 0.10 (mg/L-N), bNOB,max,20 = 0.15 (d-1), ѲNOB,b = 1.029

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continued overleaf…

Temperature influence on the nitrification processes is an important factor.

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April 2019 | 51

WASTEWATER The following provides an example calculation to illustrate the impact of cold influent on the nitrification process.

A summer influent can have a temperature of 20°C, while influent temperatures can be depressed to 8°C during the spring freshet if too much extraneous flow enters the sewer system.

• µnet, AOB, 20°C = (0.9 ∙ 1.072(20-20)) – (0.15 ∙ 1.029(20-20)) = 0.75 d-1

• µnet, AOB, 8°C = (0.9 ∙ 1.072(8-20)) – (0.15 ∙ 1.029(8-20)) = 0.28 d-1 The above calculation highlights that it takes 2.6 times longer to grow AOBs in a colder environment.

The half saturation constant (Ks) used in switching functions is based on an empirical Monod type relationship to adjust the growth response based on substrate (S) concentration, as given below.

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• µactual = µnet [S/(S+Ks)] Assuming no TAN limitation, nitrification requires an aerobic environment (i.e., DO ≥ 2 mg/L) with sufficient alkalinity to sustain the biochemical process. To account for more than one limiting substrate (e.g., oxygen, alkalinity, nutrients), switch functions for each substrate [S/(Ks + S)] are multiplied together to account for the synergistic effect on growth rate. Specifically, as the substrate concentration decreases, the growth rate decreases, and becomes very pronounced below the Ks value.

Dilution of influent due to extraneous inflow into the sewer system can negatively impact the nitrifier biomass that can be grown in the bioreactors due to the diminished growth rate. A higher concentration at the start of the bioreactor, the faster the kinetics. Starting at a lower initial concentration near the Ks value will significantly hinder the growth rate.

The aerobic solids retention time (SRTa) required to grow nitrifiers is the inverse of the actual growth rate, SRTa = 1/µactual. Factoring in the reduction in nitrifier growth due to colder influent and the dilute substrate concentration from extraneous inflows, a longer SRT is required to achieve the desired degree of nitrification to meet effluent ammonia requirements. Simply put, a longer SRT will result in more solids inventory and higher mixed liquor suspended solids (MLSS) in the bioreactors.

Too high a MLSS in the bioreactors can exceed the safe solids loading rate (SLR) of the final clarifiers and cause non-compliance with final effluent requirements. There is also the risk of possible failure of the nitrification process due to an abrupt change like washout (i.e., SRTa below 1/µactual) and the inability to achieve the final effluent ammonia concentrations due to the loss of nitrifier mass.

Maintaining a larger inventory of AS in the final clarifier to support nitrification can, in certain cases, cause bulking or rising sludge to occur. This is due to the fact that the sludge age or mean cell residence time (MCRT), which is different than the SRTa, can change in the community structure (i.e., fair excessive filamentous growth) and/or cause the

Environmental Science & Engineering Magazine

final clarifier to behave as a bioreactor, resulting in denitrification and the formation of nitrogen gas bubbles. As such, bulking or rising sludge can cause a deterioration in final effluent quality. Incomplete denitrification in mainstream process during stressed conditions resulting from cold dilute flows can also lead to rising sludge in the final clarifiers.

Stantec has designed and upgraded BNR wastewater treatment plants across North America to meet the challenging conditions associated with cold weather nitrification. As flows and loads increase to these northern wastewater treatment plants, the demands placed on the nitrification process will increase. The design and operation of the nitrification process in a BNR system requires careful attention to several parameters and environmental conditions. Simply increasing

the SRTa to compensate for cold dilute inflows can lead to other undesirable conditions if the system was not sized to handle the seasonal episodes of cold dilute flows.

A high sludge volume index (SVI) is an indicator that the capacity of the treatment process is showing signs of stress, and a good indicator for a call to action. A review of the treatment pro-

cess capacity will help to identify modifications needed to successfully achieve ammonia effluent compliance requirements during this challenging period.

Nick Szoke is with Stantec. Email: nick.szoke@stantec.com

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A sludge separation test cylinder. Longer SRTs will result in more solids inventory and higher mixed liquor suspended solids. www.esemag.com @ESEMAG

www.xypex.com April 2019 | 53

STORMWATER

evolution of stormwater management technologies for urban applications

T

echnology can be transformative, as it was when Blackberry introduced the first generation “Smartphone” that allowed email to be used on a handheld device. But since then, each new development has been evolutionary, as handheld devices became accepted to the point where they are now a business essential that we think little about. However, Blackberry, who once defined this market, is now reduced to a historical footnote on the product development path.

We can think of stormwater management in much the same way as smartphone technology. When the concept of underground water storage was introduced as a commercial solution, this was transformative. Now, large catchment areas such as parking lots have their water controlled in an effective way, so much so that we give little thought to the inconvenience of surface water as it is quickly dispatched to the nether world of the sewer system.

Much the same way as we view the inconvenience of a malfunctioning app on a phone, we now view excess surface water the same way, as it is simply not encountered often enough to seriously think about it.

Today, with an increased focus on stormwater overwhelming storm sewer systems, governments have changed building codes to push this responsibility back on property owners, builders, developers and, ultimately, on architects and engineers. The efficiency of water management systems is at the forefront of every new development and many retrofit developments, as the increased stormwater volumes need to be managed in an efficient manner.

Ponds, cisterns, and arch and crate systems offer benefits for different applications and should be considered accordingly. Concerns about geology, topography, loading and historical events are all important deciding factors when choosing the most cost-effective one.

Ponds have been used for centuries.

They are relatively low cost to construct and have a certain bucolic esthetic that can be used if the space required is avail54 | April 2019

The ACO StormBrixx® crate system offers efficient use of underground space with extreme void ratios of up to 97%. Its modular “building block” nature allows for irregular shape tanks to be formed.

able. Ponds can add to park-like settings which communities can be built around.

Unfortunately, this is where the benefits stop, mostly due to high land costs. Ponds are an inefficient use of land mass that developers are loathe to give up for loss of revenue generating property. Significant risks in terms of public safety from drowning or unsafe outdoor skating rinks raise additional community concerns.

As witnessed in a few high-profile cases in western Canada, the impact of non-native invasive species such as coy fish and reptiles can have an impact on local environments, with many direct and indirect implications. Infrequent but costly maintenance is also a factor when considering ponds as overgrowth and silt buildup from airborne dust and debris can reduce the effective volume. Lastly, the holding of water for release to storm systems presents issues with solar warming that causes further issues downstream. Ponds may also become an undesired mosquito breeding ground.

Cisterns have been used for centuries to collect stormwater for reuse in agriculture and grey water applications. This practice has seen a recent resurgence,

in an attempt to reduce dependence on municipal treated water. However, unless this is incorporated as part of a new development design, the high cost of retrofit for existing developments precludes this from being a mainstream application.

Other than for large infrastructure municipal applications, extreme landscaping depth limitations or significant volume requirements, the high initial costs limit this method’s viability for all but a few select applications that can support those costs and the associated civil engineering that accompanies it.

Prefabricated arch systems were a significant evolution in suburban and urban water management programs as the water management tank could be buried, similar to a cistern, but with a cost closer to a pond style system, allowing for the best of both worlds. The low initial cost combined with quick installation, limited equipment and civil involvement is why this is the standard for stormwater management for parking lots in many North American cities. It is also a common application for large new commercial developments where roof water must be mitigated.

Environmental Science & Engineering Magazine

As accepted as arch systems are, they face challenges for contractors and engineers due to the large excavation area they consume, large foot print, the limited configurations, and the relatively low void space of expensive clear crushed stone required to make up the tank volume. This restricts the ability to be used in a retrofit application or in urban environments where space is at a premium.

The arch system performs well in an infiltration application and can be used as a detention tank, but the complexity of sealing the arch and stone combination limits this application. Lastly, the reduced ability for inspection and maintenance limits the system to basic functionality.

The next evolution of stormwater tanks is the crate style system. This method combines all of the functionality of an arch system with a high void compact structure, that is ideal for both new development as well as retrofit applications. These plastic molded elements feature high strength to weight ratio for ease of construction with no civil requirement due to the pre-engineered nature of the product.

The ACO StormBrixx® crate system was developed in Europe to deal with centuries old stormwater issues. It offers efficient use of underground space with extreme void ratios of up to 97%. This high void ratio limits excavation costs and also eliminates the need for expensive clear crushed stone as this does not make up part of the tank volume.

Its modular “building block” nature allows for irregular shape tanks to be formed that are ideal for geographically challenged retrofit applications. Being modular also allows for smaller tanks to be placed closer to source points of stormwater, further reducing underground piping and manifolds to create simple and cost-efficient infiltration or detention tanks.

Lastly, the open interior ”grid” type architecture of these systems and the purposely designed inside ”boulevards” allows for multiple port options and complete access for inspection and maintenance.

Furthermore, the design life span of theses systems is 50 – 60 years, making them long-term solutions for their intended applications.

The high initial cost of crate systems is often seen as a downside, especially when compared to arch-style systems. However, reduced excavation, limited stone requirement and extremely fast installation times can mean crate systems actually offer the lowest installed “cost per cubic metre” of storage.

The benefits of a crate style system were demonstrated at a recent project in Milton, Ontario, when site plan approvals of a subdivision were submitted. The town required the stormwater tank to be moved further away from existing dwellings. This led to a challenge for the designer, as they had to overcome the site constraints where this tank could be located. Traditional stormwater tanks

would not be able to satisfy the volumes required in the given space.

ACO StormBrixx was selected as it was able to satisfy the space/volume requirement. The contractors gained approval for its use, as an irregular shaped tank would fit within the available space, providing a cost-effective and much quicker installation than traditional systems.

The advantages of the open cell structure further satisfied requirements for inspection and cleaning. To make use of this advantage, 12 StormBrixx inspection ports were placed around the tank to provide access for future inspections and maintenance, ensuring trouble-free operations for years to come.

Other factors to be taken into account were the type, size and frequency of static or live loads, type of top cover and backfill material, underground water levels, depth of underground infrastructure, and surface deflections under design live load.

Surface deflection is a particular design consideration, even though the specified tank may not collapse under the design load. Excessive deflections can lead to deterioration of the paved surface on top of the tank. This becomes quickly apparent, especially in cold climate areas as the seasonal temperature cycle will accelerate surface failures.

For more information, email: dinu.filip@aco.com, or visit www.acocan.ca

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April 2019 | 55

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PRODUCT & SERVICE SHOWCASE TURBO BLOWER

Aerzen Turbo G5 Plus is the most compact and efficient turbo in its class. It features AERZEN airfoil bearings with double coating and the new multilevel frequency converter technology, which reduces the heat loss in the motor to a minimum and, consequently, improves total efficiency significantly.

Aerzen Canada T: 450-424-3966 E : sales-ca@aerzen.com W: www.aerzen.ca

DIAPHRAGM METERING PUMPS

Chem-Pro® MC-2 and MC-3 Diaphragm Metering Pumps are built to meet the exacting demands of municipal water and wastewater treatment applications.

Chem-Pro units will handle pressures to 12 bar (175 PSI); and feed demands to 153 LPH (40 GPH); Turndown ratio is 200:1. Chem-Pro® M is fitted with the exclusive Dia-Flex® single layer diaphragm for optimum performance.

Blue-White Industries T: 714-893-8529 F: 714-894-9492 E: sales@blue-white.com W: www.blue-white.com

ALL NEW ULTIMATE CHEMICAL FEED SENSOR

The ProSeries-M® MS-6 Chemical Feed Sensor accurately measures chemical feed of dosing pumps. MS-6 provides the

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widest flow range on the market, from 10 to 10,000 ml/min, and has a pressure drop of less than 1 PSI. The affordable MS-6 sensor can be used for a variety of applications: flow verification, chemical metering, fluid metering, leak detection, ultra-pure water, and polymer feed.

Blue-White Industries T: 714-893-8529 F: 714-894-9492 E: sales@blue-white.com W: www.blue-white.com

ROAD MAINTENANCE

Consider a proactive approach to road maintenance this year. Many municipalities and private companies are utilizing Denso’s polymer modified–bitumen asphalt joint tapes to prevent water infiltration at joints.

DensoBand and Denso Reinstatement Tape provide a permanent, flexible barrier between hot asphalt and steel, concrete and existing asphalt. Great for bridges, railway crossings and utility cuts.

Contact Denso for more information.

Denso North America T: 416-291-3435 E: sales@densona-ca.com W: www.densona.com

MULTIPROBES FOR THE FIELD TECHNICIAN

The Manta family offers multiprobes, an integrated package, a rugged construction with anti-corrosive housings and sensors, and an industry-leading 3 year warranty.

Simple usage allows one touch and automatic data capture, fast and easy calibration. Applications include lakes, rivers, estuaries, process waters, wastewater, and more.

GENEQ Inc. T: 800-463-4363 E: info@geneq.com W : www. geneq.com

FIBERGLASS FLUMES

Hoskin Scientific offers a full line of standard fiberglass flumes, such as Parshall Flumes, Palmer Bowlus Flumes, H Flumes, Trapezoidal Flumes, along with countless custom structures used for open channel flow measurement.

Hoskin Scientific E: salesb@hoskin.ca, Burlington, ON E: salesv@hoskin.ca, Burnaby, BC E: salesm@hoskin.ca, Montreal, QC W: www.hoskin.ca

IN-CHANNEL ULTRA-FINE SCREEN

The HUBER Drum Screen LIQUID poses an interesting alternative to primary clarifiers for several reasons. LIQUID has better removal rates than clarifiers, but with a smaller footprint. It also provides better process control in surge events, with more reliable operation.

Finally, LIQUID has lower investment costs relative to primary clarifiers.

HUBER Technology T: 704-990-2053 F: 704-949-1020 E: huber@hhusa.net W: www.huber-technology.com

April 2019 | 57

PRODUCT & SERVICE SHOWCASE

STORM DRAIN CATCH PIT INSERT

The LittaTrap is a low-cost, innovative technology that prevents plastic and trash from reaching our waterways.

Designed to be easily retrofitted into new and existing stormwater drains, the LittaTrap is installed inside storm drains and, when it rains, catches plastic and trash before it can reach our streams, rivers and oceans.

Imbrium Systems T: 800-565-4801 E: info@imbriumsystems.com W: www.imbriumsystems.com

OGS/HYDRODYNAMIC SEPARATOR

The new Stormceptor® EF is an oil grit separator (OGS)/hydrodynamic separator that effectively targets sediment (TSS), free oils, gross pollutants and other pollutants that attach to particles, such as nutrients and metals.

The Stormceptor EF has been verified through the ISO 14034 Environmental Management – Environmental Technology Verification (ETV).

Imbrium Systems T: 800-565-4801 E: info@imbriumsystems.com W: www.imbriumsystems.com

58 | April 2019

MANHOLE SYSTEM

The Muffin Monster® Manhole is a pre-fabricated manhole system with a Muffin Monster sewage grinder and is fully assembled and ready to install. This fiberglass manhole is an excellent solution when a sewage grinder is needed but space is limited. Installation is easy – just dig down to the sewer line, create a concrete pad and tie in the sewer lines.

JWC Environmental T: 800-331-2777 E: jwce@jwce.com W: www.jwce.com/product/muffinmonster-manhole/

WASH PRESS

JWC Environmental’s new Monster Wash Press leads the industry in the management of headworks screenings. It features a Muffin Monster® grinder to pre-condition rags and trash within screenings before they enter the patented wash zones. This promotes removal of soft organics and fecal matter from the screened debris. JWC has also improved key maintenance items like a removable screen and wash nozzles and top down access to the auger press.

JWC Environmental T: 800-331-2777 E: jwce@jwce.com W: www.jwce.com/product/monsterwash-press/

WATERTIGHT DOORS

Huber, a proven German manufacturer, now provides watertight doors that allow safe access to tanks for construction and/or maintenance. Doors can be provided as round or rectangular for installation onto existing concrete surfaces or cast-in-place in new concrete.

They can handle heads up to 30 m and hold pressure in seating and unseating directions. Huber’s watertight doors can greatly reduce construction and maintenance costs and dramatically improve safety/access.

Pro Aqua T: 647-923-8244 E: aron@proaquasales.com W: www.proaquasales.com

HYPERBOLOID MIXERS

Invent Environment is the manufacturer of hyperboloid mixers which have revolutionized anoxic and swing zone mixing. Invent provides low-shear, efficient mixers with no submerged motors or gear boxes for easy access for maintenance. They have now released the Hyperclassic Mixer Evo 7 which has increased the number of motion fins and adjusted the geometry of the mixer to maximize mixer efficiency, reducing operation costs even further.

Pro Aqua T: 647-923-8244 E: aron@proaquasales.com W: www.proaquasales.com Environmental Science & Engineering Magazine

MEMBRANE BIOREACTOR SYSTEM

The enhanced TITAN MBR™ Membrane BioReactor System is the market’s most operator-friendly MBR, delivering the best operator experience with a streamlined pre-packaged design, high-performance flat-sheet membranes and intuitive graphical touchscreen PLC controls and smart automation features. Tailored to your specific permit requirements, the system can achieve high effluent quality, including for water reuse and Title 22 approval.

Smith & Loveless T: 800-898-9122 F: 913-888-2173 E: answers@smithandloveless.com W: www.smithandloveless.com

GRIT REMOVAL SYSTEMS

PISTA® Forced Vortex Grit Removal Systems utilize advanced hydraulic baffle technology to provide the finest grit removal across all flows, including 95% removal efficiency for grit down to 100 microns. PISTA systems integrate specially-designed inlet and outlet flumes, circular flat-floor chambers and integrated flow control baffles to create the forced hydraulic action that maximizes grit capture.

Smith & Loveless T: 800-898-9122 F: 913-888-2173 E: answers@smithandloveless.com W: www.smithandloveless.com

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SYSTEM SOLUTION FOR HDPE PIPE

The industry’s first-ever Installation-Ready™ plain end and grooved technology for high-density polyethylene (HDPE) eliminates the need to fuse.

Victaulic’s system solution for HDPE pipe saves time with no heating or cooling pipe ends, no fusion equipment, and rain or shine installation.

Victaulic T: 905-884-7444 W: www.victaulic.com

DISPOSABLE GROUNDWATER FILTERS

Waterra has expanded its product range of PES Inline Disposable Filters to now include pore sizes: 0.2 micron, 0.45 micron, 1.2 micron and 5 micron. These capsule filters are available in two size formats: a 300 cm² surface area version and a 600 cm² surface area version for higher turbidity samples.

Waterra Pumps T: 905-238-5242 F: 905-238-5704 E: sales@waterra.com W: www.waterra.com

HS-2 OIL/WATER INTERFACE SENSORS

Waterra HS-2 Oil/Water Interface Sensors represent some of the most advanced technology available today for hydrocarbon product

layer measurement. To define the product layer, these devices utilize a proprietary ultrasonic sensor which is more sensitive in a broader range of hydrocarbon products than conventional optical systems. These quality sensors are now also available with Kynar (PVDF) jacketed tapes.

Waterra Pumps T: 905-238-5242 F: 905-238-5704 E: sales@waterra.com W: www.waterra.com

RUGGED AND RELIABLE PERISTALTIC PUMP

The Spectra Field-Pro is the most popular peristaltic pump that Waterra has sold. The FieldPro combines the MasterFlex Easy-Load II pump head with a powerful motor and power supply in a rugged aluminum case. It will work all day on a full charge, and includes a 12 Ah AGM battery, smart charger and storage compartment – everything you need in a portable peristaltic pump.

Waterra Pumps T: 905-238-5242 F: 905-238-5704 E: sales@waterra.com W: www.waterra.com

ADVANCED AND PORTABLE WATER LEVEL INDICATOR

Waterra’s WS-2 Water Level Sensors are advanced products that utilize advanced electronic technology. The WS-2 features an innovative design as well as compactness, portability and reliability – all at a competitive price. WS-2 tapes are available with Kynar (PVDF) or polyethylene jackets and graduated in imperial or metric units.

Waterra Pumps T: 905-238-5242 F: 905-238-5704 E: sales@waterra.com W: www.waterra.com

April 2019 | 59

ES&E NEWS BC TOWN EXPLORES OPTIONS TO CUT MANGANESE LEVELS IN DRINKING WATER

While low levels of manganese have few known effects on human health, at concentrations exceeding 0.15 mg/L, the The British Columbia town of Osoyoos mineral stains plumbing fixtures and has been adding chlorine to several of its laundry and causes undesirable tastes in water supply wells to dissolve manganese water. Osoyoos officials said they were ahead of concerns that Health Canada advised that a new federal maximum may revise acceptable levels for the min- allowable concentration for manganese eral in drinking water later this year. could be .12 parts per million. The town’s

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current affected wells sit at about .135 parts per million.

A report by True Consulting Ltd. said the town’s manganese particles settle in reservoirs and coat the walls of the distribution piping, creating an environment for bacterial growth that gets stirred up when the system is drained or flushed.

In a memo to municipal officials from Osoyoos director of Operational Services, Jim Dinwoodie, it was noted that the elevated levels of manganese in the water supply make it necessary to remove the manganese prior to treatment with chlorine. In 2014, Osoyoos piloted a new manganese removal technology at two of its six approved wells, which did successfully eliminate manganese from the water sampled.

True Consulting Ltd. suggested options for the development of a water treatment program for Osoyoos. They involve treating certain wells at a centralized treatment facility ($12 million) or converting the water supply to surface water obtained directly from Osoyoos Lake ($24 million).

Its report also states that BC’s Interior Health Authority has concerns about the town’s number of positive coliform tests, which have also prompted Osoyoos Public Works to flush the system and treat with chlorine.

NIAGARA-ON-THE-LAKE RAMPS UP DECOMMISSIONING OF OLD TREATMENT FACILITY, SEWAGE LAGOONS

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60 | April 2019

With the Ontario city of Niagara-onthe-Lake set to open its new $51.4-million plant wastewater treatment facility, municipal officials have set aside $12 million in their latest budget as they weigh options around the decommissioning and remediation of the city’s old treatment plant and open-water sewage lagoons.

In December of 2018, the city completed an environmental assessment to determine the preferred alternative for decommissioning of the existing Niagaraon-the-Lake wastewater treatment plant.

Niagara-on-the-Lake’s director of Water and Wastewater Services, Joe Tonellato, recently told the city’s Committee of the Whole that the preferred option for lagoon decommissioning is to create a

Environmental Science & Engineering Magazine

ES&E NEWS new riverine wetland. “We’re basically filling in the lagoons, putting the creek back, essentially allowing for natural flooding of the area,” he said, noting that they have approval from Parks Canada after a yearlong process.

The Harmony Residents Group has been pushing for years to have the sewage lagoons left untouched to gradually settle as natural wetlands. The group also wishes to see the main building on the property retained and reused as space for administration offices, an outdoor education centre, parking and other visitor facilities.

Regional officials, however, have long held the view that the lagoons cannot simply be left to revert into a wetland, as the discontinuation of water inflows from an operating treatment plant would see them effectively dry up and expose contaminated hot spots.

ALBERTA ENVIRONMENT MINISTER ORDERS STAGED CLEANUP OF FORMER WOOD TREATMENT SITE

Alberta Environment Minister Shannon Phillips issued a ministerial order that requires a nine-step remediation process to take place over the next nine months at a former Domtar wood processing site in northeast Edmonton, where a number of contaminants still remain on the property.

The order was issued in response to recommendations from the Alberta Environmental Appeals Board, and follows a recent provincial open house where local residents addressed health concerns raised in a new health assessment report prepared for the province by Hemmera Envirochem Inc. Provincially-conducted surface and sub-surface testing at the former wood treatment site over the last year involved more than 1,000 sample locations with 1,457 specimens analyzed. Results indicated that 183 samples exceeded human health guidelines for dioxins and furans located on fenced-off areas of the property.

The wood preserving plant operated from 1924 to 1987.

A developer named Cherokee Canada has started turning the old Domtar site into a new residential community but www.esemag.com @ESEMAG

legal proceedings have halted the project. Prior to the new ministerial order, the company had recently won an appeal over enforcement orders that called for mass remediation on the property.

The Alberta Environment and Parks health assessment report raised eyebrows over its findings of higher cancer rates for three types of cancer in residents of neighbourhoods surrounding the former Domtar site. Rates were slightly higher in these neighbourhoods compared to the rest of the province for existing cases of lung cancer, breast cancer, and uterine cancer. For example, officials say six to 14 cases of lung cancer would be typically expected; however,

the neighbourhoods in question have 22 cases.

Many other factors could contribute to an increased risk of cancer, including medical history, certain medication usage and tobacco use, and the report does not draw clear links to the site’s contaminants.

FIRST NATIONS DRINKING WATER ADVISORY UPDATES

Long-term drinking water advisories at three separate First Nations reserves were lifted in February, including one that had been in place for 18 years, the

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April 2019 | 61

ES&E NEWS Canadian government announced. and upgrades to the community's water Long-term water advisories, which treatment plant and distribution system. take effect if concerns have been present Also, North Spirit Lake received operafor more than one year, have been lifted tional support from the Keewaytinook at two Ontario reserves where water and Okimakanak Water and Wastewater wastewater facility upgrades occurred, Operations Hub. including the Northwest Angle No. 37 The advisory for the Northwest Angle reserve at Windigo Island and North No. 37 First Nations at Windigo Island Spirit Lake in the north of the province. had been in place since February 2015.

The third long-term advisory was lifted Treatment technology upgrades were in Saskatchewan for the Nekaneet First completed as interim solutions at its water Nations, where similar treatment facility treatment plant to restore safe drinking upgrades took place. water. The federal government says it’s The advisory for the North Spirit Lake working to advance a long-term solution First Nations in northern Ontario had that will meet the safe drinking water been in place since the summer of 2001. needs of the community for the next 20 It was recently lifted for the population years.

In Saskatchewan, operational improveof about 263 residents following repairs

ments and repairs to the community's water treatment plant and distribution system have ended a long-term water advisory that had been in effect since October 26, 2017.

Three short-term water advisories were also lifted over the last month. At Deer Lake First Nation, and Webequie First Nation, both in Ontario, water main repair ended those advisories, while a new pipe ended an advisory at the Star Blanket Cree Nation in Saskatchewan.

As of mid-March, 59 long-term drinking water advisories for public systems on reserve were in effect, but are expected to be cut to 35 by the end of 2019. By March of 2021 the federal government aims to have ended all long-term drinking water advisories on public systems financially supported by Indigenous Services Canada.

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62 | April 2019

A ban on single-use plastics passed first reading through an NDP Private Member’s Bill in the Ontario Legislature in mid-March.

Ian Arthur, MPP for Kingston and the Islands, and NDP critic for the environment and sustainability, introduced Bill 82, Single-Use Plastics Ban Act, 2019, on March 18, as an attempt to amend the Resource Recovery and Circular Economy Act, 2016.

As Arthur introduced his bill at Queen’s Park, he said the Act should be amended “to include a plan that identifies measurable targets and sets out timelines for the immediate reduction and eventual elimination of the distribution and supply of single-use plastics in Ontario and that requires the immediate elimination of certain single-use plastics.”

The bill calls for the immediate elimination of the following single-use plastic items: plastic straws and drink stirrers; expanded polystyrene foam food and beverage containers; plastic bags; items made from oxo-degradable or oxo-fragmentable plastics; disposable coffee cups; and plastic water bottles intended for single use.

Oxo-degradable plastics, as opposed to biodegradable plastics, are convenEnvironmental Science & Engineering Magazine

ES&E NEWS tional plastic materials with artificial additives that do not biodegrade but merely fragment into small pieces.

Arthur’s Private Member’s Bill follows immediately on the heels of a provincial waste discussion paper published earlier this month by the Ontario Ministry of the Environment, Conservation and Parks. The paper states that almost 10,000 tonnes of plastic debris enter the Great Lakes each year and more than 80% of litter collected during volunteer cleanups along the shorelines of the Great Lakes is plastic.

Following Arthur’s Private Member’s Bill, the Canadian Plastics Industry Association released a statement on single-use plastics. The association noted that “single-use plastic bans are not the answer but rather managing them at their end of life is.” The association goes on to say that scientific and economic studies demonstrate that in most cases plastic packaging, plastic shopping bags and some single-use plastics are a better environmental choice when managed properly.

Bill 82, Single-Use Plastics Ban Act, 2019, will next head to the committee level for study.

Yellowknife River pipeline that carries water from Pumphouse 2 at the river, through Yellowknife Bay, to Pumphouse 1 in the city, is “reaching the end of its useful life”, so the city needed to either replace the pipeline or use Yellowknife Bay as an alternate water source. Prior to 1968, Yellowknife obtained its drinking water from the bay, which is connected to Great Slave Lake, but the city switched it water source to the Yellowknife River in 1969 over concerns about arsenic contamination from the Giant and Con mines.

The Aecom report stated that, while water treatment options exist to remove arsenic from Yellowknife Bay, processes such as reverse osmosis would not be feasible because of residuals disposal issues and high operation and maintenance costs.

“An adsorptive media system would provide some removal of arsenic, but may have difficulty removing enough arsenic to meet drinking water quality guidelines at some of the high arsenic concentrations estimated to occur during upset conditions,” stated the report.

Yellowknife is still looking to come up

with about $9 million for its share of the water line replacement project, which has become a challenging task as it looks to make its new municipal aquatic centre vision – which could reach $50 million – a reality.

“Because of climate change, extreme weather events are becoming more severe and more frequent, and they are doing more damage and [costing] more money,” said federal Minister of Public Safety, Ralph Goodale, regarding the funding announcement. “By investing in infrastructure that protects our neighborhoods, businesses and families, we are building communities that will be resilient to future natural disasters and prosperous for generations to come,” he added.

FEDERAL INVESTMENT IN YELLOWKNIFE DRINKING WATER PIPE UPGRADE

The federal government is contributing $25.8 million from its Disaster Mitigation and Adaptation Fund towards the replacement of a submerged, aging drinking water pipeline in the Yellowknife River.

Most communities in the Northwest Territories are near water, with some designated as flood zones. In Yellowknife’s case, the new upgrades are aimed at increasing the capacity for flood water retention and will better protect the community drinking water supply during times of extreme weather. The changes will also help reduce greenhouse gas emissions from water line replacement and system operation.

The new 8.5-km drinking water line also means that Yellowknife can avoid drawing water from the region of a nearby, toxic former gold mine.

A 2017 report prepared by engineering firm Aecom found that the current www.esemag.com @ESEMAG

April 2019 | 63

WASTEWATER

Grinder design continues to evolve as wastewater streams change

E

ver since the development of activated sludge processes in the early 20th century, wastewater engineers have had to contend with debris getting into them. Unwanted materials cause pump clogging, fouling of thickening technologies like centrifuges, and potential damage to a variety of critical treatment equipment. To combat this, engineers began to deploy reduction and removal equipment into sludge systems, including additional screening and single shaft comminutors.

In the early 1970s, the two-shafted grinder was introduced to the market and has been a fixture in wastewater treatment plant sludge systems ever since. The slow speed but extremely high torque operation of a two-shafted grinder proved itself as a reliable solution to shred the toughest solids and make the life of a wastewater operator much easier.

The industry has seen significant changes since the 1970s but the need for grinders has persisted and evolved. JWC Environmental started offering twoshafted grinding more than 45 years ago with its Muffin Monster grinders. Kevin Bates, their director of product management and marketing, was recently asked several questions about the use of grinder technology in the wastewater industry.

1. Why were grinders first used with a treatment plant’s sewage sludge system?

The number one reason grinders have become a staple in treatment plants around the world is their ability to protect sludge pumping equipment. Due to the viscous nature of sewage sludge, there are a variety of pumping technologies that are typically employed to move thickened materials.

Some of these, like progressive cavity and rotary lobe pumps, rely on elements with very close tolerances. These pumps can easily be damaged by harder debris, and fouled by rags or other stringy materials. Grinders are used to simply shred the materials small enough, so that the 64 | April 2019

(Top) Introduced during WEFTEC 18, the Channel Monster® FLEX grinder offers a modular and adaptive architecture. (Right) Grinders are are routinely used to protect WWTP centrifuges and heat exchangers from debris.

pumps can do their job efficiently.

2. What has changed with how grinders are used in sewage sludge systems?

While protecting pumps still remains the top application, the sophistication of biosolids processing in treatment plants has evolved significantly over the last 45 years. This has exposed new areas where grinders are needed to help overall plant efficiency. They are routinely used to protect centrifuges and heat exchangers from debris that can put them out of commission. The cost of a grinder is very small, compared to a significant repair on a centrifuge.

3. With the increase in primary treatment, especially headworks fine screening, isn’t there less debris in sewage sludge today?

Some of the largest items that would have historically been found in a plant’s treatment systems are now pulled out at the headworks. That said, smaller debris still makes its way into a plant and into digestion systems. This can include hair, smaller wipes materials, and other inorganics. Additionally, there are secondary sources like trucked-in septage or sludge from other facilities that can introduce

additional trash. This small debris can come together in digesters and form hair balls, wipes ropes and other tougher solid masses. When sludge is drawn off the bottom of digesters or through a recirculation loop, the solids will quickly shut down pumps.

4. What has changed in sludge grinder technology?

One new advancement from JWC Environmental has been its Wipes Ready technology for Muffin Monster two-shafted grinders. This technology includes new serrated cutters which are specifically designed to handle disposable wipes. The Wipes Ready cutter first saw success in protecting lift station pumps within collection system networks where the wipes problems are the worst. More recently treatment plants have been using the technology for their inline Muffin Monster sludge grinders.

Users are reporting even better performance in cutting through rags and hair within recirculation loops and waste activated sludge pipelines.

5. Are there any important design considerations in two-shafted grinders?

Rugged construction and a history

Environmental Science & Engineering Magazine

of reliable performance are paramount in selecting a two-shafted grinder. Like everything else in a treatment plant, they are working in a harsh and often hazardous environment. If a grinder needs frequent attention, it is not only burdening a plant’s maintenance staff, it is also exposing them unnecessarily to bio-waste and other hazards.

There are various design concepts for two-shafted grinders on the market today that have real trade-offs engineers must consider. One is to only support the twin shafts at the top end of the grinder. This is done by eliminating the bottom bearings and seals and allowing the shaft ends to float in the pipeline.

The concept of this approach is that by eliminating the bottom seals they don’t have to survive submerged in the sludge.

This design without seals will of course lower the cost of the grinder.

Unfortunately, with support at only one end, the two shafts are allowed to flex as solids pass through them which can lead to failure of the top seals and even-

www.esemag.com @ESEMAG

tually the shafts. JWC’s Muffin Monsters always provide top and bottom tungsten carbide seals, which rigidly control the shafts to deal with the loading of tough solids and reversals.

6. What are the maintenance considerations for two-shafted grinders in sludge?

In general, the application of grinders within sludge systems is not extremely difficult compared to other areas in wastewater where they are used. This means that maintenance should only be an inspection to verify everything is working as intended. For in-pipeline type grinders used in sludge systems, the operator should be able to inspect the cutter condition while the cutter stack stays within grinder housing. This is achieved using inspection ports designed in the grinder housing.

Operators can avoid the time and potential complexity of lifting the heavy cutter stack out of grinder housing.

Ideally, inspections should only be required on an annual basis. There are

some grinders which require lubrication oil changes every three months to protect the bearings or to clean out debris traps. Unfortunately, if frequent tasks like lubrication are required, they are often neglected, leading to premature failure of the grinder.

For more information, contact Kevin Bates, JWC Environmental. Email: kevinb@jwce.com JWC is represented in Ontario by ACGEnvirocan. For more information, email: sales@envirocan.ca

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April 2019 | 65

LEADERS IN INNOVATION AND SUSTAINABILITY REVOL MIXING

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PRIMARY TREATMENT • Complete line of fine screening equipment • Self-cleaning perforated plate screens • FlexRake® front-raked fine screens • FlexRake® front-raked bar screens • FlexRake® Low Flow • Self-Cleaning trashracks • Muffin Monster® grinder (for sludge, scum, septage, screenings & wastewater) • Channel Monster® grinder for pump stations and sewage treatment plant headworks • Honey Monster® septage receiving station • Auger Monster® fine screen system • Monster® fine screen & band screen perforated plate fine screens with 2, 3 & 6mm perforations • Screenings washer/compactors • Rotating drum screens (down to 2mm perfs) • Raptor screenings washer press • Grit removal • Rotary drum screens SECONDARY TREATMENT • AquaNereda® Activated Granular Sludge Technology • Aqua-Jet® direct drive floating aerator • Aqua DDM mechanical floating mixer • Fine bubble aeration systems using membrane or ceramic diffusers with gas cleaning systems • Stainless steel coarse bubble aeration systems • Multi stage activated biological process (MSABP) • Two & three rotary lobe P/D blowers • Centrifugal multistage blowers • Hybrid screw/lobe compressors • Floating diversion curtains (for aerated lagoons, activated sludge systems & clear wells) • Subsurface jet aeration/mixing systems • Spiraflo & Spiravac peripheral feed clarifiers • Closed loop reactor oxidation ditch systems • Rotary brush aerators • High efficiency single stage integrally geared blowers • Direct drive turbo type blowers • Aeration system controls & instrumentation • Chain & flight clarifier systems & components (plastic, cast iron or stainless steel) • Half bridge, centre feed, circular clarifiers • Spiral blade clarifiers TERTIARY TREATMENT • AquaDisk® - cloth media tertiary filter • AquaDiamond® tertiary cloth media for traveling bridge filters • Filter Underdrain Systems HIGH EFFICIENCY MIXING TECHNOLOGY • High Performance Centrifugal Dispersing Impeller (HPCDI™) mixers

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