waterscapes, summer 2012

A technicAl publicAtion by the WAter Group of hDr SuMMer 2012

www.hdrinc.com

2Supporting Realistic Numeric Nutrient Criteria

9

7 Total Daily Maximum Loads:The Coming Wave of Regulation

Hexavalent Chromium, Perchlorate and Nitrosamines: New Challenges for Drinking Water Systems

165 The Biotic Ligand Model for Understanding Metals Effects

12

Management of Disruptive Aquatic Species in the Pacific Northwest

Invasive Quagga and Zebra Mussels

19 Microconstituents: An Overview

contents

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Water quality issues have always been a critical part of the permitting process that supports development of infrastructure projects completed for our nation’s municipalities (wastewater, drinking water) and industries along with watershed management efforts that address nonpoint and stormwater sources.

Recently there has been increased scrutiny by regulatory agencies and interested stakeholders on various water quality issues that are some of the more pressing water quality concerns in the country today.

HDR is involved in many of these emerging and challenging water quality issues around the country and has assisted our clients in navigating the water quality component of these permitting and watershed management projects in order to obtain fair but environmentally protective permits.

The water quality related articles in this edition of Waterscapes present HDR’s innovative efforts in addressing nutrient criteria and over-enrichment; metals bioavailability/effects; stormwater management and TMDLs; drinking water quality/treatment; invasive/disruptive species; and microconstituents. I hope you enjoy reading and gaining a better understanding of these topics presented in this issue.

Andrew J. Thuman, P.E.Vice President and Water Quality Planning Services Section Manager, Mahwah, N.J.

S U M M E R 2 0 1 2

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[ front cover photo ]

The James River near downtown Richmond, Va. HDR | HydroQual is involved in a study

of the James River to better understand the causes of nutrient-driven algal

blooms. The Virginia Department of Environmental Quality has requested the

study be conducted to see if a revision of its chlorophyll-a standards is necessary to help

reduce the algal bloom concerns.

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waterscapes | sUmmer 2012

[ surface water ]

NUtRieNtS have beeN ReCeiviNg much attention around the country from numerous stakeholders, including municipalities, private industry, state environmental agencies and the United States Environmental protection Agency (EpA).

This focus not only has been on the development of numeric nutrient criteria (nnc) to protect the nation’s surface waters from the effects of excessive nutrient enrichment, but also on the costs of treatment plant nutrient removal to meet these potentially very stringent nncs.

Although controlling nutrient loads to protect against excessive eutrophication impacts (e.g., algal blooms, low dissolved oxygen (Do), decreased transparency) are needed, the development of realistic nnc that are not overprotective and are based on site-specific considerations of the receiving water body needs to be considered.

HDR | HydroQual historically has been involved in nutrient-related water quality studies around the country. More recently, HDR has been conducting water quality modeling studies as part of nnc development to study the effects of nutrients on site-specific features of the water body.

What follows is a brief summary of nnc development in Florida and information from three projects.

NNC Developments in the State of Floridaover the past few years, the State of Florida has been the focus

of attention for the development of freshwater and marine nnc by both the EpA and the Florida Department of Environmental protection (FDEp).

FDEp currently is in the process of further implementing its narrative nutrient standard through continued rule development (chapters 62-302 and 62-303 F.A.c.) in response to the EpA’s development of nnc in lakes and flowing waters of Florida. FDEp’s goal in further interpreting its narrative nutrient criteria is “to manage nutrients in surface (and groundwater) at loadings or concentrations that result in protection and maintenance of healthy, well-balanced aquatic communities.”

The existing FDEp narrative standard (62-302.530 (47)(b), F.A.c.) further states that “in no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora and fauna.” Although the FDEp has proposed nnc in the state’s freshwaters, they are developing a process for implementing its narrative standard that considers biological effects as the ultimate indicator of nutrient effects. This process also would provide an approach for developing nnc based on site-specific water body characteristics.

In addition, the EpA currently is in the process of developing nnc for Florida bays and estuaries. The FDEp has provided significant information and data to support this effort in addition to its own development of estuarine total maximum daily loads (TMDLs).

In order to avoid implementing generic nnc for water bodies across the state, FDEp has encouraged scientists, water quality managers and engineers familiar with specific water bodies to compile and develop water body-specific information that can be used to develop more scientifically-based criteria for those individual water bodies.

currently HDR | HydroQual is working on two Florida projects where an effects-based nutrient criteria development approach is being used in the Escambia/pensacola Bay system and in the Econfina River near perry. The nutrient criteria development efforts are focused on the response variables (e.g., Do; seagrass light requirements; stream condition index (ScI)) for protecting the health of the water bodies, rather than solely relying on nutrient concentrations.

In addition, we also are involved in a study to assess the role of harmful algal blooms (HABs) in the development of chlorophyll-a criteria for the James River in Virginia. A summary of these ongoing efforts appears later in this article.

escambia/Pensacola bay tMDL & NNC (FL)

In Escambia/pensacola Bay, the nutrient criteria and TMDL development efforts we are involved in for a coalition of regulated entities include using an effects-based water quality modeling approach to relate nutrient loading to nutrient effects. The nutrient effects we are using include:• Assessing compliance with

existing and proposed marine Do standards• potential development of site-specific alternative criteria (SSAc)

for Do because bottom waters are affected by natural stratification processes and background oxygen demands

• Bottom light requirements to provide habitat necessary for seagrass survival and maintenanceThrough the use of an estuarine water quality model, acceptable

bay chlorophyll-a levels and ultimately protective nutrient loads will be developed that protect these nutrient effects endpoints

Andrew J. Thuman, P.E., Vice President and Water Quality Planning Services Section Manager, Mahwah, N.J.Thomas W. Gallagher, Water Resources Senior Engineer, Mahwah, N.J.James J. Fitzpatrick, Principal Engineer Water Quality SPA, Mahwah, N.J.

SupportinG

escambia/Pensacola bay tMDL Watershed that includes the panhandle section of Florida that extends into alabama.

2

(response variables). The cause-effect linkage between nutrient loading and nutrient effects was accomplished through the development of an estuary model that included a hydrodynamic model to represent tidal circulation in the bay system and a eutrophication model to link nutrient loads to nutrient effects.

In establishing the nutrient criteria endpoints, a determination of the spatial area (i.e., compliance zone), averaging period (i.e., annual or seasonal averages), and compliance frequency for applying the developed criteria also are important components of the criteria process.

To support development of the SSAc, along with using a reference condition approach and to assess background water quality, an estimated “natural background” model scenario (i.e., non-anthropogenic or no man-made sources) was completed for comparison to the existing conditions. The “natural background” projection scenario was developed assuming no point source discharges and conversion of agricultural, rangeland, urban and barren land uses to a forest land use.

This project is still on-going and – due to the significant efforts of the coalition and interested stakeholders – has developed such a good working relationship with the FDEp TMDL and water quality standards staff that the effort is being developed collaboratively with FDEp in coordination with the current EpA efforts in development marine nnc in the state of Florida.

econfina River Nutrient & DO SSaC (FL)

The Econfina River is an unimpacted water body near perry (panhandle East nutrient watershed region) that has been used as a reference site for the development of a Do SSAc and coastal chlorophyll-a target for the nutrient TMDL in the Fenholloway River.

This reference condition status is based on the Econfina River (WBID 3402) currently achieving its designated uses related to nutrients based on a land disturbance index (LDI) score of 1.14, which indicates that the site is absent of human influences and nutrient point sources.

FDEp also concluded that “…not only

are the nutrients concentrations reflective of minimally disturbed conditions, they are associated with biota demonstrated to be fully supportive of designated uses (i.e., healthy, well-balanced populations of aquatic organisms).” This healthy status is based on ScI data from 1996 to 1998 that resulted in an “excellent” status and ScI data from 2004 to 2008 that ranged from 40–59 (also representing healthy conditions in the river).

These ScI rankings indicate a long history of healthy biota in the river. Although the river has been determined to be healthy and used as a reference site, the river was considered impaired for total nitrogen (Tn) levels based on the recent EpA nnc for the panhandle East nutrient watershed region.

given this new proposed impairment

econfina River WbiDs and WQ stations

escambia/Pensacola bay direct runoff land use

status, HDR | HydroQual is involved in the on-going SSAc process, which is nearing completion. As opposed to the modeling-based approach used in Escambia-pensacola Bay, the nutrient SSAc for the Econfina River was based on historical monitoring data and statistical treatment of the data.

This was possible because the river had been determined to be healthy and that maintaining the historical nutrient concentrations was deemed protective of the designated uses. Additional data collection is underway to provide a dataset to develop the Do SSAc that will meet FDEp and EpA data collection and QA/Qc protocols.

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James River 2012Site: JMS75Source: P. Bukaveckas, VCU

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While the James River Estuary does not suffer from low levels of Do usually associated with nutrient over-enrichment or eutrophication, it does suffer from the occurrence of HABs both in the freshwater and saline portions of the river.

In the upper James River, the HAB of concern is Microcystis aeruginosa, a cyanobacteria or blue-green algae. M. aeruginosa is of particular concern because it can produce microcystin, a known cyanotoxin. The World Health organization (WHo) guidelines and risk levels for microcystin-LR are 1 μg/L for drinking water and a concentration of 4 μg/L – representing a low risk for recreational contact – and 20 μg/L for moderate risk.

In the U.S., the State of Vermont uses a tiered approach which requires a beach to close if there is the visible presence of a cyanobacterial scum. Beaches re-open if no visible scum is present and the concentration of microcystin-LR is 6 μg/L or less.

To date, observed concentrations of microcystin in the upper freshwater James River Estuary have been less than 4 μg/L, which exceeds the WHo guidance for drinking water, but presents only a low risk for recreational contact.

In the lower saline portion of the estuary, there are a number of HAB bloomers. The most prevalent of these is Cochlodinium polykrikoides, a toxic dinoflagellate. Blooms of these organisms have become

more prevalent in the James River over the past several years. During a massive bloom of C. polykrikoides that occurred during the summer of 2007, bioassays determined that C. polykrikoides exerted a lethal affect on juvenile fish and shellfish, causing 100 percent mortality of juvenile fish (Cyprinodon variegates or sheepshead minnows) in less than 24 hours and 20 percent mortality in juvenile American oysters (~21 mm Crassostrea virginica) within 72 hours.

HDR | HydroQual is part of a consultant team that includes the Virginia Institute of Marine Science and HAB experts from old Dominion University, Virginia commonwealth University and the University of north carolina that will develop watershed, hydrodynamic, conventional and HAB-specific eutrophication models for the Virginia Department of Environmental Quality (VADEQ).

These models will permit the VADEQ to develop new chlorophyll-a standards for the James River Estuary and to develop nutrient loading targets necessary to achieve these standards. This VADEQ project is driven by the desire to revise the chlorophyll-a standards currently used in the James River as part of the chesapeake Bay TMDL and the subsequent James River Tributary Strategy that developed nutrient load allocations for sources within the watershed.

The chlorophyll-a standard revision is focused on the consideration of algal blooms (species type, location, duration)

Chlorophyll-a and microcystin concentration levels in the James River

for better representing the effects of nutrient loading in the river.

SummaryThese projects demonstrate different

methods that may be suitable for determining nnc and also the concerns related to HABs. The modeling approaches explicitly link cause and effect (i.e., nutrient causal parameters to nutrient response parameters) through the water quality modeling framework, and the data approach uses a historical assessment of river health (i.e., LDI and ScI scores) to determine the nutrient concentrations that are protective of this healthy designation.

Both approaches have data needs, and selection of one approach over the other is more influenced on whether nnc development needs to be determined based on nutrient effects variables (i.e., model-based) or whether the health status is known (i.e., data-based).

It is also important in these analyses to view the development of nutrient criteria in a historical perspective to account for local hydrology effects on nutrient loading along with the spatial area and time period for applying the criteria. This could involve developing a protective nutrient load that represents a compliance frequency (e.g., 95th, 99th percentile load) that allows regulatory agencies to establish compliance with the criteria each year but also allows the magnitude, duration and frequency aspects of water quality standards to be addressed.

There is no one solution to developing nutrient criteria due to the varied effects of nutrient loading that are unlike criteria development for other parameters (e.g., copper toxicity that follows a strong dose-response relationship). Building in site-specific water body conditions ultimately provides more scientifically-based criteria that are protective of the environment and allows the implementation of cost-effective nutrient control strategies.

For additional information about this article, please contact Andrew Thuman at [email protected] , Thomas Gallagher at [email protected], or James Fitzpatrick at [email protected] .

4

[ surface water ]

ThE BioTic LigAnd ModEL For unDerStAnDinG MetAlS effectS

The Biotic Ligand Model (BLM) developed by HDR | HydroQual is an easy-to-use computer program that helps dischargers and regulators determine realistic metals criteria for use in determining discharge limits.

The toxicity of metals to aquatic organisms can be influenced by water quality factors such as organic matter, pH, hardness and alkalinity. These factors can vary from one site to another, and this variation can result in large changes in metal toxicity. Regulatory approaches for metals need to be able to consider these variations. If not, criteria designed to be protective at the most sensitive sites would be overprotective elsewhere.

The current regulatory approach for most metals considers hardness but does not consider a wide variety of other water quality factors. When hardness alone is considered, metals criteria are often in the low parts per billion. For example, the chronic criteria for copper can range from 3 to 30 µg/L.

Background concentrations for metals in the absence of any anthropogenic sources are often in similar range of concentrations. For example, a review of background copper concentrations excluding anthropogenic sources showed average concentrations by state range from 5 to 50 µg/L.

Approaches for developing metals criteria, or for determining compliance with criteria, do not usually distinguish background metals concentrations and metals in a discharge.

currently there are over 7,000 sites listed on the 303d list as impaired for metals other than mercury, and over 30 percent are due to copper when impairment is assessed on the basis of a hardness-based criterion. given that the hardness-based water quality criterion does not consider many factors that influence copper toxicity, it is possible

that many of these sites are listed because the water quality criterion is overprotective and not due to any actual impairment.

HDR | HydroQual developed the BLM to provide a predictive tool that considers other water quality factors, such as pH and organic matter, which can affect metal toxicity to aquatic organisms. The BLM is based on a mechanistic framework that considers how water quality affects both the chemistry of the metal, as well as the physiological responses of aquatic organisms to metals.

For example, the presence of natural organic matter in receiving water can bind metals, thereby reducing metal bioavailability and toxicity. The BLM predicts that a water quality criterion value for copper can be higher when there is natural organic matter (measured as dissolved organic carbon, or Doc) compared with the hardness equation (Figure 1).

criteria values calculated with the BLM can be higher, but still meet all the intended levels of protection of aquatic

Robert Santore, Section Manager, Environmental Chemistry, East Syracuse, N.Y.Adam Ryan, Ph.D., Senior Project Scientist, East Syracuse, N.Y.Paul Paquin, Senior Project Manager, Mahwah, N.J.

Figure 1 - Comparison of acute copper water quality criteria (continuous maximum concentra-tion, or CMC) using the traditional hardness equation (dashed yellow line) and the biotic Ligand Model (“bLM”; orange lines). the two methods produce similar values over a wide range of hard-ness values when dissolved organic carbon is low.

CMC by Hardness Equation

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organisms in the environment as set out in the guidelines developed by the United States Environmental protection Agency (EpA). As a result, the BLM was adopted by the EpA in the latest update to the copper criteria.

application to Surface WatersWastewater from municipal water

treatment plants frequently contain metals in excess of criteria values. For cases where existing water quality criteria are overprotective, the EpA has allowed dischargers to develop a site-specific criterion using the Water Effect Ratio (WER) approach.

Developing a WER requires a discharger to collect samples from its site and perform toxicity tests in site water and a reference water to demonstrate that toxicity is lower in waters from the site. comparison of site-specific criteria for copper at a number of discharge sites in pennsylvania and new Jersey showed that criteria values based on the hardness-equation were typically overprotective (Figure 2 – light orange bars).

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has been shown to protect against copper toxicity, and this effect can be predicted with the BLM. In the absence of a BLM approach for copper in marine waters, the current criterion value is a constant value of 3.1 µg/L and does not consider any bioavailability effects. This value is frequently exceeded

in estuaries and harbors. The marine BLM will consider local conditions, including organic matter, pH and salinity to provide a site-specific criterion that is protective to sensitive aquatic marine life, but not overly protective.

In addition to freshwater and saltwater BLMs for copper, we have been actively developing BLM versions for other metals, including aluminum, cadmium, cobalt, nickel, lead, silver and zinc, and have been applying these models at sites in the U.S. and the European Union.

Sediments

HDR | HydroQual has several efforts underway to extend the applicability of the BLM to other environmental exposure scenarios, such as soils and sediments. Since soils and sediment frequently include exposure to numerous metals, for application in these scenarios the BLM needs to simultaneously consider the effects of multiple metals.

Application of the BLM to sediment exposures has been shown to identify when metals are toxic to sediment organisms, and is typically more accurate than other sediment guidelines. For example, application of the sediment BLM to samples affected by mining activity was able to identify effects from a combination of cadmium, lead and zinc that correctly identified which samples had toxic effects to benthic invertebrates (Figure 4).

The use of the BLM in understanding ecological risk due to metals in the

Both the WER and BLM approaches resulted in similar values and both methods produced criteria that were significantly higher than the hardness equation (Figure 2 – dark gray and dark orange bars). However, the BLM can produce these results with much less cost and effort than a WER study, since no biological testing is required.

Although the EpA has currently adopted the BLM for setting criteria for copper in freshwater, there are many other BLM development efforts underway. The BLM has been shown to be predictive of copper toxicity to sensitive marine invertebrates such as the blue mussel (Mytilus) as part of an ongoing effort to derive a BLM approach for copper in marine and estuarine saltwaters (Figure 3).

For these marine organisms, the presence of natural organic matter

Figure 2 - the ePa has allowed dischargers to generate site-specific adjustments to water quality criteria using the Water effect Ratio approach (WeR).

environment provides a much more accurate assessment compared to the more conservative screening guidelines such as the Threshold Effect concentration/probable Effect concentration (TEcs/pEcs).

Summary and ConclusionsThe BLM can be used to help

determine how local conditions affect metal toxicity and to derive suitably protective discharge limits with much lower cost and effort compared with other approaches. HDR | HydroQual has been actively developing the BLM approach for an expanding list of metals and currently have versions for aluminum, cadmium, cobalt, copper, nickel, lead, silver and zinc.

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Figure 3 - We are currently developing a ma-rine approach for a copper bLM, by consider-ing the protective effects of DOC to copper toxicity for sensitive marine invertebrates such as Mytilus (blue mussels).

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HDR | HydroQual also has been developing the model to consider additional exposure scenarios such as soils and sediments, and in doing so have extended the approach to consider simultaneous effects from multiple metals. The BLM represents the current state-of-the-science for understanding ecological risk due to metals in the environment, and can be used to develop scientifically-defensible regulatory approaches in a cost-effective and efficient manner.

For more information about this article, please contact Robert Santore at [email protected], Adam Ryan at [email protected], or Paul Paquin at [email protected] .

Figure 4 - the bLM also has been used to consider the effects of multiple metals to sediment-dwelling organisms, and is useful for assessing ecological risks that might result from metal contaminated sediments.

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WATERScApES | SUMMER 20126

[ surface water ]

OUR NatiON’S WateRS – the rivers, streams, brooks, creeks, ponds, lakes, estuaries, lagoons, oceans – all are supposed to support fishing and swimming.

That is what congress said when passing the clean Water Act in 1977. That is what it said when it amended the clean Water Act in 1987 to regulate non-point source discharges.

Yet many of these waters, called receiving waters by the United States Environmental protection Agency (EpA), are impaired.

They have too much nitrate, phosphates sediment, bacteria, toxic metals, toxic pesticides, trash or other constituents to fully support wildlife, fisheries or recreational swimming.

A provision in the clean Water Act, under section 303, is called the Total Maximum Daily Load, or TMDL. This provision requires the EpA to issue TMDL limits to all dischargers should a receiving water remain impaired.

What this MeansThe act requires all discharges to be permitted under the national

pollutant Discharge Elimination System (npDES) program.Under this npDES program, no point source can discharge without

a permit. The permit limits the amount of pollutants that can be discharged based on a variety of considerations – water quality objectives in the receiving water, technology limitations – as well as some practical considerations.

For non-point source discharges, the act sets an initial standard to limit discharges of pollutants to the maximum extent possible using Best Management practices (BMps). As time goes on, if increasing levels of controls do not improve water quality, then the non-point source permits may include numerical effluent limits or prescriptive controls.

This is where the TMDLs come in. non-point sources – including stormwater – have been regulated under npDES using BMps to a maximum extent practicable standard for 20 years.

Many waters are still impaired. The EpA and the states are moving forward by adopting TMDLs in many receiving waters. once adopted, each category of dischargers in that receiving water will have a daily maximum load of pollutants that they are allowed to discharge. This is a numerical effluent limit that will apply to stormwater as well as traditional point sources.

By Richard Haimann, P.E., National Technical Advisor – Stormwater, Long Beach, Calif.

ToTAL MAXIMUM DAILY LoADS: THE coMIng

WAVE OF REGULATION

1972Federal Water

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1977Clean Water Act (CWA)

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1999Water Keeper

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Permits tightened

2003Phase II MS4

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Permits tightened

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Numerical E�uent Limits

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Permits tightened

1999-2011TMDL adoption accelerates

Stormwater key focus

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once adopted, TMDLs will be provisions in the npDES permits. There will be phase-in periods written into the TMDLs that give dischargers time to finance, plan, design and construct the water quality controls needed to achieve their TMDLs, but there still will be strict compliance deadlines.

This is one of the most significant changes happening in the water resources field in the United States. Stormwater clients, who traditionally needed hydrologic modeling, design and construction support for drainage projects, now need a much broader range of services to help them comply with ever-tightening npDES requirements driven by TMDLs.

Who is affected?Everyone! Wastewater agencies, cities, counties, departments of

transportation, federal facilities, industrial operations, construction contractors, and confined animal feeding operations. The only significant exemption is general agriculture.

HDR has developed a national stormwater practice that has stormwater quality specialists in all areas of the business. HDR professionals can help cities negotiate an npDES permit and implement a compliance program, or assist dischargers develop site-specific criteria and third party TMDLs, to helping a project incorporate Low Impact Development (LID) or other stormwater quality controls during its design.

HDR also has worked on projects to help clients:•comply with construction stormwater requirements•Design and build treatment systems for dry or wet weather storm

flows•Meet permit requirements through testing sample storm flows•Meet a permit requirement to help clients evaluate pollutant

trading schemes within a watershed• Form stormwater utilities

This is a business that will not stay as is. As TMDLs are adopted, it will become necessary for cities and counties to collect dry weather urban runoff and stormwater in substantially greater quantities than they do today.

They will have to decide what they can do with this water – treat and discharge, infiltrate into ground water basins, capture and store

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for later use, restore ecosystems. This is bringing our public works clients, who typically had to manage street drainage, into the water agencies arena.

Stormwater – which once was managed as a nuisance and drained to the creek, lake or ocean as quickly as possible – now is being viewed as a potential resource, primarily because the cost of capturing and treating this water makes it too valuable to simply waste to the storm drain.

Potential Market SizeWhen the metals TMDL were adopted in the Los Angeles River

in the early 2000s, two studies conducted at local universities evaluated the potential cost of complying.

one assumed full capture and advanced treatment of enough water to achieve the TMDL. It estimated total capital costs on the order of $284 billion.

trend toward integrated Water Management

SustainableSupply Options

ImprovedWastewaterTreatment

GreywaterRecycled Water

DemandManagement

IntegratedWater Cycle

ManagementStormwater

Capture & Use

RainwaterCapture & Use

ReducedSewer

Over�ows

Stormwater QualityImprovement

HydrologicManagement/Flood Control

Potable Water Wastewater

Stormwater

Another assumed that the TMDL could be achieved with widespread implementation of LID, infiltration basins, retention basins and constructed wetlands. It estimated capital costs of $44 billion.

This is a wide range, and there is significant uncertainty as to what level of capture and treatment will be needed to achieve the TMDL. nevertheless, taking these types of values and extrapolating them to impaired waters across the country, the stormwater compliance market could become as large as $200 billion per year – a figure in the same neighborhood as the wastewater market.

HDR has built a team with substantial experience in water quality modeling, TMDL implementation planning, TMDL development, site specific criteria development, low impact development planning and design, npDES permit negotiations, stormwater npDES program implementation, stormwater monitoring program management, BMp design and wet weather treatment system design to help entities of all sizes.

For more information about this article, please contact Richard Haimann at [email protected] .

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[ drinking water ]

DRiNkiNg WateR QUaLitY is closely regulated under provisions of the Safe Drinking Water Act (SDWA) by the United States Environmental protection Agency (EpA). over the years the EpA has established standards for over 90 contaminants in drinking water. Utilities must comply with these standards on a daily basis to protect public health and produce aesthetically- acceptable water.

Yet the regulatory environment is not static. Research continues to identify contaminants that may pose a risk to public health when present in drinking water. Advocacy groups bring pressure on regulators to set standards for contaminants of concern to their group.

overall, the definition of what constitutes safe drinking water continues to be refined over time. The reality is that in the future utilities will have to meet more standards and that existing standards are likely to get more stringent. This article provides information on three contaminants which will pose new challenges for utilities in the future.

hexavalent Chromium historyHexavalent chromium first came to

the general public’s attention in the early 2000s due to the popularity of the movie Erin Brockovich. In this movie industrial contamination of drinking water with high levels of hexavalent chromium was thought to cause the ill health of the residents of a small california community.

In December 2010 the advocacy group Environmental Working Group, published a non-peer reviewed report that claimed that “hexavalent chromium, the carcinogenic Erin Brockovich chemical” was found in tap water of 89 percent of the cities sampled by their study.

While such sensationalized publicity does little to protect human health, recent studies by the national Toxicology program concluded that ingestion of hexavalent chromium at concentrations several orders of magnitude greater than that typically found in water caused cancer in laboratory rats.

In response to these findings, the EpA is considering a revision to the current standard for chromium in drinking water. The revision could include setting a hexavalent chromium-specific regulation and modifying the existing total chromium maximum contaminant level (McL) of 100 ug/L.

Any regulatory action by the EpA likely won’t take place for several years. Independent of EpA action, in 2011 the State of california established a public Health goal (pHg) for hexavalent chromium of 0.02 ug/L. Using its pHg as a point of departure, california is in the process of establishing a state-specific standard for hexavalent chromium.

Chemistry, Occurrence and health effects

chromium is the 21st-most abundant element in the earth’s crust and is widely present in water. Industrial use of chromium, particularly for electroplating and alloying metals, is widespread. Hence, there are many opportunities – both natural and manmade – for chromium to enter water supplies.

once in water, chromium can be present in two forms – trivalent chromium (cr(III)) and hexavalent chromium (cr(VI)). Like most metals, the form of chromium present in water is determined by a complex set of chemical and physical reactions. The sum of hexavalent and trivalent concentrations is termed total chromium and serves as the basis of current regulation.

The health effects of the two forms of chromium are different. Unlike hexavalent chromium, trivalent chromium is a micronutrient and consumption of small amounts – ranging between 0.2 µg/day and 35 µg/day, depending on age and sex – is necessary for good health.

Much of the current debate regarding regulation of hexavalent chromium revolves around chromium’s ability to revert between the non-toxic trivalent and the possibly toxic hexavalent forms.

treatment Optionscurrently no utility in the United States

operates a full-scale treatment system for the removal of cr(VI) from drinking water. The Water Research Foundation sponsored research (Low Level Hexavalent chromium Treatment options: Bench – Scale Evaluation, Brandhuber et al. 2004), identified several technologies that are capable of treating cr(VI).

These include reverse osmosis membranes, strong base anion exchange, weak base anion exchange and reduction/precipitation/filtration (RpF). This research also established the possibility of formation of cr(VI) in distribution systems due to the oxidation of cr(III) in the presence of residual disinfectant. Table 1 summarizes possible treatment options for hexavalent chromium and their limitations.

neW chAllenGeS for Drinking Water SySteMSBy Philip Brandhuber, Ph.D., Project Manager, Denver

hExAvALEnT chroMiuM, PErchLorATE And niTrosAMinEs:

9www.hdrinc.com


hDR’s involvementThis summer, in cooperation with the

Water Research Foundation, Louisville Water company and four other utilities, HDR is undertaking the new research project, Sources, Fate and Treatment of Hexavalent chromium. Due to be completed in 2014, the project objective is to better understand the options available to utilities for the treatment of hexavalent chromium.

Perchlorate historyperchlorate first came to the public’s

attention in the late 1990s with the unintentional release of large quantities of perchlorate into Lake Mead as the result of perchlorate manufacturing activities in nevada.

Because of the importance of Lake Mead and the colorado River as a drinking water supply, the health risk posed by perchlorate received considerable regulatory

agency and media attention. Aggressive remediation at the nevada manufacturing sites has since virtually eliminated the discharge of perchlorate to Lake Mead.

However, subsequent investigations found that human exposure to perchlorate is far more widespread than originally thought. In addition to its occasional presence in drinking water, studies have found trace concentrations of perchlorate in breast milk, cow’s milk and leafy vegetables. Studies documenting the presence of perchlorate in human urine indicate widespread exposure to perchlorate from food and water.

In 2006 the EpA established the maximum allowable daily dose for perchlorate, termed the reference dose (RfD), of 0.0007 mg/kg/day. In 2009 the EpA published a non-enforceable Interim Health Advisory of 15 µg/L for perchlorate in drinking water.

In February 2011 the EpA announced

it will formally regulate perchlorate in drinking water. The agency is scheduled to propose a perchlorate McL in 2013, with the final McL promulgated by late 2014 or early 2015. A number of states already have set local regulations for perchlorate.


perchlorate (clo4-) is an anion and the

most oxidized form of chlorine (+7 valance state). Despite its high oxidation state, perchlorate is relatively stable and mobile in aquatic environments.

Salts of perchlorate are used in a number of applications, including its use as an oxidizer in solid rocket fuel and as a component of fireworks, pyrotechnics, flares and explosives.

perchlorate also has been identified in chilean nitrate fertilizers. Though uncommon, perchlorate has been found to naturally occur in soils of arid and semi-arid climates.

An analysis of occurrence data collected by the EpA and state agencies concluded the occurrence of perchlorate in drinking water is widespread but at very low concentrations (A Review of perchlorate occurrence in public Drinking Water Systems, Brandhuber et al. 2009).

This study also concluded that perchlorate has been detected in drinking water in at least 26 states and puerto Rico, as well as in approximately five percent of the nation’s large public water systems.

perchlorate is classified as a goitrogen. goitrogens adversely affect human health by interfering with normal iodine uptake by the thyroid gland.

While chronic exposure to trace concentrations of perchlorate does not directly result in adverse health effects, it may indirectly impact health by upsetting hormonal processes regulating developmental or normal bodily functions. pregnant women, infants, children and people with iodine-deficient diets or pre-existing thyroid deficiencies may be more sensitive to the presence of perchlorate than the general population.

treatment OptionsThere are several advanced treatment

table 1 - hexavalent Chromium treatment Options

10

options that are effective for the treatment of perchlorate, including:• Single use ion exchange • Regenerable anion exchange• Reverse osmosis• Biological reduction

To date, single pass and regenerable ion exchange have been the treatment of choice for perchlorate in drinking water systems. While effective in removing perchlorate, membrane systems are typically more costly to operate than ion exchange-based systems.

The use of biological treatment, which has been found to be cost-effective for the environmental remediation of perchlorate, has been limited due to regulatory agency reluctance to permit biological treatment of drinking water systems.

The advantages and disadvantages of perchlorate treatment technologies are presented in Table 2.

hDR’s involvementHDR has been involved in perchlorate

occurrence analysis and regulatory development. HDR also has recently completed a design/build of a single- use perchlorate treatment system in pomona, calif.

Nitrosamines historyUnlike hexavalent chromium and

perchlorate, nitrosamines have received little media attention. Yet their potential regulation could have a significant impact on the drinking water industry.

As a chemical family, nitrosamines were identified over a century ago and their carcinogenicity is well-established. only in the late 1980s, with the advent of sensitive analytic techniques, were compounds from this family of contaminants detected in drinking water.

Initially nitrosamine contamination of drinking water was solely thought to be the result of industrial pollution. But additional research found that nitrosamines can be formed by certain water treatment processes.

Similar to hexavalent chromium and perchlorate, there are currently no enforceable national standards for nitrosamines in drinking water. At the state level, california has established notification levels of 10 ng/L for three nitrosamines:•n-nitrosodimethylamine (nDMA)•n-nitrosodi-n-propylamine (nDpA) •n-nitrosodiethylamine (nDEA)

The EpA is likely to proceed with the regulation of nitrosamines at a national level. A decision to start the formal regulatory process is anticipated later this year. A proposed regulation is possible in 2014.


nitrosamines are aromatic (ring shaped) or aliphatic (straight chained) nitrogen containing molecules that have undergone nitrosation to form compounds that include nitroso (R-n=o) functional groups.

numerous nitrosamine compounds

can be formed, but nDMA (c2H6n2o) is the compound most commonly found in drinking water. The pathway for the formation of nDMA is not completely understood, but dimethylamine (DMA) appears to be the most important precursor to the formation of nDMA.

Even if the pathway for nDMA formation is not completely understood, its formation in drinking water systems has been associated with certain conditions, including:

• In the source water – presence of DMA from environmental

pollution – presence of wastewater derived amines– presence of soluble microbial products

from biological wastewater treatment • In the plant

– Use of certain polyelectrolytes such as poly–DADMAc

– Use of certain ion exchange resins– Use of chloramination for disinfection

or disinfectant residual formation The occurrence of nDMA in drinking

water appears to be fairly widespread. nationwide sampling of drinking water systems mandated by the EpA concluded

TEchnoLogy oPErATing PrinciPLE AdvAnTAgE disAdvAnTAgE

single use Anion Exchange

perchlorate ion exchanges with chloride ion on resin. Resin has high capacity for perchlorate.no regeneration of resin is required.

no perchlorate containing liquid residual stream requiring disposal.Resin may last a year or more prior to replacement.

High cost of resin. possibility of resin fouling and premature perchlorate breakthrough.possible accumulation of radionuclides on resin.

regenerable Anion Exchange

perchlorate ion exchanges with chloride ion on resin.Resin is periodically regenerated with sodium chloride.

Lower resin cost.Simultaneous nitrate removal is possible.

Requires disposal of high TDS and perchlorate liquid residual stream.

reverse osmosisMembrane provides a physical barrier preventing passage of perchlorate.

capable of simultaneous removal of many contaminants.

High cost. Water loss.Requires disposal of perchlorate containing liquid residual stream.

Biological reduction Microorganisms reduce perchlorate to chloride.

perchlorate is destroyed by chemical reduction to chloride. Lack of regulatory acceptance.

table 2 - Perchlorate treatment Options

C

C

C

C

NN N O

NDMA

Nitrostation

(continued on back page)

11www.hdrinc.com



[ drinking water ]

WhiLe iNvaSive QUagga aND zebRa mussel species (Dreissena bugensis, Dreissena polymorpha) have impacted drinking water supply infrastructure in Eastern and northeastern water bodies for a number of years, these invasive species have only in the past several years been transported to Western and Southwestern waters (including Texas).

now both water and power utilities across the West and Southwest are dealing with the invasion of these mussel species. Figure 1 shows a USgS map of the spread of invasive mussels across the country.

native to Eastern Europe, including the Black, Azov and caspian seas, the zebra mussel (Dreissena polymorpha) spread through Western Europe in the 19th century as canals and inland waterways were connected to facilitate trade. The species was believed to have been introduced to north America in 1985 or 1986 by the release of mussel larvae in ship ballast water.

Zebra mussels were first documented in Lake St. clair in 1988. The first quagga mussel (Dreissena bugensis), a cousin to the zebra mussel, was found in Lake Erie in 1989. However, it was not identified as a separate species until 1991. The mussels species look similar to one another as shown in Figure 2.

Quagga and zebra mussels are considered adults when they reach sexual maturity, which in north America is within the first year of life. once established in a water body, these mussels multiply rapidly, with the growth rate of larvae and veligers dependent mainly on temperature and chlorophyll-a concentration.

Unlike native mussels, which burrow in sand or gravel, zebra and quagga mussels spend their adult lives attached to hard substrates that can include rocks, logs, aquatic plants and the shells of native mussels, as well as man-made structures of plastic, wood, concrete, fiberglass and iron.

The ability to attach to these various substrates, along with the species’ high fecundity and passively dispersed planktonic veliger larval stage, have allowed zebra and quagga mussels to significantly change ecosystem trophic dynamics and spread rapidly throughout freshwater ecosystems.

Mussels are filter feeders with multiple food sources, including micro-algae, micro-invertebrates, bacteria, detritus and other organic materials. Large colonies of mussels have been shown to remove a large portion of the phytoplankton from the water.

This results in clearer water (increase in Secchi depth) where light penetrates to greater depth. When algae is present, algae blooms have increased significantly and have occurred at greater depths in lakes and reservoirs. Increased algae growth can lead to increased instances of taste and odor events in drinking water sources.

Invasive mussels have demonstrated a high tolerance to many environmental and water quality factors that enhances the species survival in north American waters. Factors affecting mussel colonization potential are shown in Table 1 (as presented by o’neill, 1996). Established colonies of mussels naturally disperse within a body of water or downstream into other streams, rivers or lakes. For mussels to move upstream in a watershed or cross watershed boundaries to new water bodies requires an external method of transport.

Mussels are most frequently transported by humans with any activity that moves water (which can contain veligers) or submerged objects (which can be fouled by juvenile or adult mussels). commercial and recreational boats and trailers are assumed to be the major mechanism for moving mussels between watersheds.

Disruptive Aquaticinvasive Quagga and Zebra MusselsBy Sarah Clark, P.E., Senior Project Manager, Denver

WATERScApES | SUMMER 201212

impacts to Water Systems

Mussels can quickly colonize submerged water system infrastructure causing significant impacts on the operations of water systems. The adverse financial and

operational effects of zebra and quagga mussels on water supply facilities in the U.S. have been well-documented since the early 1990s.

Mussels can infest many water supply system components, including intake systems, transmission lines, treatment facilities and any other components upstream of disinfectant chemical addition. Adverse effects of mussel attachment to water supply system components include:• Loss of hydraulic capacity due to colonization inside pipes

(up to 6 feet of macrofouling) as illustrated in Figure 3 on the following page

•obstruction of valves and gates which limit operation• Blockage of screens and trash racks which limits flow• Increased corrosion of steel and cast iron pipes due to bacterial

growth around byssal threads•Accumulation of shells and detritus in water supply facilities•creation of taste and odor problems due to accumulation of

decaying detritus

Mussel ControlA wide variety of mussel control methods have been considered,

evaluated and used by water and power utilities. Each method tends to focus on preventing settlement in critical locations, preventing attachment to critical substrates, or causing mussel mortality.

Some methods are best applied to organisms in a specific stage in the mussel lifecycle. The veliger or planktonic stage, for example, is easier to kill with an oxidant than an adult mussel which is protected by a shell. Table 2 on the following page summarizes the many

Species

Figure 1 - 1 USgS 2012 Map of Mussel Distribution in the United States

Figure 2 - zebra and Quagga Mussel Physical Characteristics

control methods discussed in the mussel literature. Research into many of these methods is on-going. The Bureau

of Reclamation has been testing foul/release coatings over the past several years in the reservoirs on the lower colorado River,

Across the nation the alarming spread of zebra and quagga mussels, as well as increases in the frequency and severity of harmful algal blooms in drinking water sources, have caused increasing concern about the disruptive impacts that aquatic species can have on drinking water utilities.

hDr has been tracking developments associated with disruptive aquatic species closely. the two articles included here are a result of these continuing efforts.

Sits flat on ventral sideTriangular in shapecolor patterns vary

Will not sit flat on ventral sideRounder in shapeDarker concentric rings on shellpale in color near the hinge

13www.hdrinc.com


so information is still forthcoming on coatings that work the best in various circumstances. Emerging technologies such as the bacteriological agent Zequanox have recently been approved by the EpA for full-scale testing.

All of these results are being watched carefully by HDR and by those systems that expect mussel controls in the near future may be needed.

Response to Spread of Mussels

Efforts to coordinate the response to the spread of mussels into the western U.S. are led by the Aquatic nuisance Species (AnS) Task Force, an intergovernmental organization dedicated to preventing and controlling aquatic nuisance species. The AnS Task Force coordinates the efforts of multiple agencies through focused regional panels.

The Western Regional panel, a coalition of federal and state agencies, has established a Quagga/Zebra Mussel Action plan with several major elements that are currently being implemented by State AnS programs throughout the West.• prevention of the spread of mussels through the development

and implementation of mandatory boat inspection programs•Development of risk assessment methods to determine water

bodies at risk• Expansion of early detection monitoring programs

• containment and control of existing populations of mussels• coordinating consistent outreach and education of the public References1. o’neill, charles R. Jr. Zebra Mussel Impacts and control. cornell

cooperative Extension Information Bulletin 238, 1996.2. Aquatic nuisance Species Task Force information may be found

at: http://www.anstaskforce.gov/default.phpw

For more information about this article, please contact Sarah Clark at [email protected] .

kEy PArAMETErs coLoniZATion PoTEnTiAL

Water Quality variable high Moderate Low very Low

Salinity (ppt) 0.1 1–4 4–10 10–35

calcium (mg/L) 25–>125 20–25 9–20 <9

Total Hardness (mg caco3/L) 90–125 45–90 25–45 <25

pH 7.5–8.7 7.2–7.5 8.7–9.0

6.5–7.2 9.0

<6.5 >9

Water Temperature (oc) 18–25 16–18 25–28

9–15 28–30

<8 >30

Turbidity (cm Secchi disk) 40–200 20–40 10–20 200–250

<10 >250

Dissolved oxygen (ppm) 8–10 6–8 4–6 <4

Water Velocity (m/sec) 0.1–1.0 0.09–0.11.0–1.25

0.075–0.091.25–1.5

<0.075>1.5

conductivity (uS/cm) 83–>110 37–82 22–36 <22

Reference: O’Neill, Zebra Mussel Impacts and Control, 1996.

table 1 - Physio-Chemical Factors effecting invasive Mussel Colonization Potential

Figure 3 - impact of mussel infestation on hydraulic capacity of full pipe

45

40

35

30

25

20

15

10

20 40 60 80 100 120

PErc

EnT

oF

iniT

iAL

cAPA

ciTy

PiPE diAMETEr (in)

assumptions:• Fixed head• 6” infestation depth•Hazen Williams c factors

– 130 initial– 60 post infestation

14

TEch

no

Log

y

sPEciFic METhod PurPosE TArgET

AgE EFFiciEncy conTAcT TiME coMMEnTs

Biol

ogic

al

Bacterial Exposure Mortality All >95% 6 hours

proven mortality – Regulatory approval for open water application (not drinking water). Several treatments required.

predation Reduce biomass All Low not applicable not effective in producing mortality.

Spawning Inhibition Limit Spread Veligers 95–100% 2–4 hours Emerging – Awaiting regulatory and technological

advances. only proven in lab setting.

Aco

usti

c

cavitation Mortality Veliger/Juvenile nA < 60 seconds Emerging – Awaiting technological advances. Effectiveness

is reduced in high flows.

Sound Treatment Limit Spread Juveniles 90% 4–12 minutes Emerging – Awating technological advances. Does not

produce mortality.

Vibration prevent Attachment Mortality

Veliger/Juvenile 100% nA

Emerging – Awaiting technological advances. only applicable for locations with structures that can be subjected to vibration.

chem

ical

oxi

dant

s

chlorine Mortality Various 100% 2 hours Implementable at full scale. not viable for open water system due to EpA regulations. can produce DBp’s.

ozone Mortality All 100% 5 hours Implementable at full scale. Difficult to maintain oxidant dose.

potassium permanganate Sodium permanganate

prevent Attachment Mortality All 90–100% 48 hours Implementable at full scale. Must have high continuous

dosage for mussel mortality.

Hydrogen peroxide Mortality Veliger/

Juvenile 100% 6 hours Implementable at full scale. High doses required.

chem

ical

non

oxid

ants

Activated Starch Mortality Veligers 100% 0–72 hours Emerging – Awaiting regulatory and technological

advances. not proven in open water system.

Aluminum Sulfate

prevent Attachment Mortality All 50–100% 24 hours Implementable. High concentrations are needed. High

solids loadings result.

chloride Salts Mortality Veliger/Juvenile 95–100% 6 hours Implementable. Very high doses required.

copper Ions prevent Attachment Mortality Veligers 100% 24 hours proven – Requires regulatory approval. causes skin

irritation, regulatory restrictions. Tested at dose of 5 mg/L.

potassium Salts Mortality Adults 95-100% 48 hours Implementable but irritating to humans.

organic Molluscicides

prevent Attachment Mortality Various 95–100% 48 hours

Few are implementable for water supply facilities. Difficult to handle (corrosive), regulatory restrictions for water supply facilities.

Elec

tric

al

cathodic protection System

prevent Attachment Adults 75% Immediate Implementable. not effective in producing mortality.

plasma Spark System

prevent Attachment Mortality Juvenile 90–100% Several weeks proven – Awaiting technological advances. Designed for

pipes; difficult to implement.

pulse power Electric Field

prevent Attachment Mortality Juvenile 80–90% Seconds Emerging - Awaiting technological advances. High voltages

required.

Phys

ical

permeable Barrier Limit Spread All Unproven Immediate Implementable for full scale. navigational/migrational

restrictions.

Mechanical cleaning

prevent Attachment Mortality

Juvenile/Adult 95% Immediate Implementable. Must periodically repeat process.

Mechanical Filtration

Limit Spread; Mortality All 95% Immediate proven – Awaiting technological advances for full scale.

Typically designed for confined area, not open water use.

Light Sources Limit Spread Juvenile 0–50% Several hours Implementable. Effectiveness is very limited.

UV Radiation Limit Spread Mortality All 100% 4 minutes– 4 hours

proven – Awaiting technological advances for full scale. High intensities are required.

Infiltration Intake System Limit Spread All 100% n/A Implementable, but may require replacing intake facilities.

table 2 - Mussel Control Options for Drinking Water Facilities 15www.hdrinc.com


FiNDiNg eFFeCtive MethODS for preventing the disruptive impacts that a wide range of aquatic species can have on drinking water supplies is an ongoing challenge throughout the water industry.

In recent years drinking water providers in the coastal pacific northwest Region have experienced numerous events associated with algal blooms, zooplankton populations and the appearance of invasive aquatic species that have had debilitating effects, including:• Loss of water production capability – clogging of screens or filters

in utility treatment works•Health or regulatory concerns – associated with excretions, lysis,

or by-product formation when species are exposed to treatment processes or chemical oxidants

•Aesthetic issues – tastes and odors•customer service – associated with end uses such as clogging of

meters, point of use filters, or adverse effects on commercial or industrial processesYet management of aquatic species often requires intensive

monitoring and specialized knowledge on an organism-by-organism basis that simply is not available or affordable. As such, it is critically important that drinking water providers develop improved understanding of these issues and have access to resources for effective monitoring and prevention.

Sponsored by the Water Research Foundation under its Tailored collaboration program, HDR has teamed with three of the largest drinking water providers in the pacific northwest region to address challenges associated with disruptive aquatic species in a collaborative effort.

With HDR in the role of principal investigator, Tacoma Water, Seattle public Utilities (SpU), and the city of Everett are currently

PAcific NorthweStBy Matt McFadden, P.E., Bellevue, Wash.

[ drinking water ]

established aquatic species such as periphytic blue-green algae can cause taste and odor issues

established aquatic species such as periphytic blue-green algae can cause taste and odor issues

Management of disruptive Aquatic species in the

undertaking this broad-based study, Management of Disruptive Aquatic Species in Pacific Northwest Drinking Water Supplies, to develop a practical informational resource for regional utilities facing similar challenges.

The study includes collecting data and information from utilities throughout the pacific northwest region, and identifying solutions and best practices, through detailed case studies at each of the utilities comprising the project team, to the unique challenges faced by drinking water providers. Key study goals include:• Evaluating and prioritizing risk associated with invasive

aquatic species•Developing tools to help predict species occurrences in source

waters, especially established disruptive algal and zooplankton species

•Developing an understanding of factors that drive species occurrence

•Developing practical guidelines for streamlined and effective monitoring strategies

• providing practical guidelines for preventing and remediating the impacts of disruptive species on drinking water suppliesAn important result of the early stages of this research has been

the development of a tool to identify and prioritize risks associated with potentially invasive species that could have disruptive impacts. In collaboration with the participating utilities, HDR developed a prototype tool that guides the user through a qualitative risk assessment.

The spreadsheet-based tool is designed around a scoring system that accounts for both the probability of establishment and the severity of potential impacts associated with organisms of concern. The tool addresses invasive species on an organism by organism basis. This produces a risk score which is used to rank the organisms evaluated by level of risk.

This ranking system provides guidance, tailored to a utility’s unique source water ecology and operations, to help prioritize and guide implementation of monitoring and prevention efforts for invasive aquatic species.

The tool, because it must address the unique characteristics of

16

each organism, relies on literature review to characterize a globally realized niche associated with each organism, and assess whether the utility’s unique watershed and source water ecology is compatible with that niche.

Values for physical requirements (e.g., range of conditions for temperature, substrate), chemical requirements (e.g., range of conditions for pH, nutrients), and biological requirements (e.g., adequate food source for zooplankton) are gleaned from literature. The spreadsheet tool facilitates execution of this comparative analysis. Because of the reliance on literature, a library/data organization feature is included in the tool.

A second portion of the probability analysis is scoring vector intensity to assess the likelihood of the organism’s arrival in the area. A set of anthropomorphic vectors are identified for scoring based on a utility-specific review of activities in the watershed such as logging, fishing, sampling, camping, recreation and fire fighting.

The strength of these vectors is based on the likelihood that it would be a means of transport and establishment for the

organism being evaluated. The probability scoring system also includes elements to account for uncertainty associated with each vector.

In addition to evaluating the probability of an invasive species establishment, the tool incorporates an evaluation of the potential severity of impact. The severity of impact score is based on understanding of the organism’s potential impacts and judgment scoring based on utility experience.

Utilities are asked to score potential impact severity based on metrics tailored to their own operational procedures and challenges. Typical drinking water utility scoring metrics include:•Disruption of drinking water production• Treatment or distribution system

equipment damage•complaints about taste and odor•Health or regulatory impact (algal toxins

or increased disinfection byproducts)• Ecological disruption and damage to

the watershedoverall risk scores are the product of

normalized probability and severity scores. The overall score for each organism is used

to generate a utility-specific, ranked list of prioritized organisms of concern. A sample ranked list, and a plot of ranked organisms plotted on a probability/severity matrix, are shown in Table 1.

organism-specific data collected during the evaluations are also summarized in tables and data sheets to be used by each utility to provide an informational resource to provide staff with identification, monitoring and prevention field guidance.

If addressing risk associated with establishment of an invasive species is an established part of a utility’s watershed management or monitoring program, it frequently is the responsibility of a small group of staff who also are faced with the daunting challenge of managing recurring disruptions caused by established or emerging aquatic species.

Because of the wide variety of unique aquatic organisms – and because predicting or managing the disruptive impacts associated with a given organism are likely to be highly organism-specific – staff are confronted with an array of disparate responsibilities that require streamlining.

As a result, prioritization of monitoring efforts and establishing best practices for data analysis and predictive capability are central themes in each of the three utility case studies forming the core of the collaborative research project.

Seattle Public UtilitiesWith separate water sources on both the

Tolt River and cedar River systems, SpU has experienced historical drinking water quality and production issues associated with an assortment of disruptive aquatic species both indigenous and invasive.

At Lake Youngs, a storage reservoir on the unfiltered cedar River System supply, periphytic blue-green algae and spring diatom blooms have caused taste and odor problems since the early 1990s. Implementation of ozonation has helped mitigate taste and odor issues caused by these algae, yet SpU has experienced increased ozone demand caused by the green algae Sphaerocystis.

The diatom Tabellaria associated with these spring blooms has caused clogging of customer taps and complaints from

table 1 – invasive Species Risk tool Output Rankings

scorE codEDidymo 4.51 D

Eurasian Water Milfoil 4.03 E

Quagga Mussel 4.01 Q

Zebra Mussel 3.98 Z

parasitic copepod 3.44 p

new Zealand Mudsnail 3.21 nZ

Whirling Disease 3.01 WD

Asian clam 2.99 A

Hydrilla 2.98 H

Bryozoan 2.97 B

White Water Lily 2.43 W

nutria 2.01 n

impa

ct

Very High

High p Q,Z D

Moderate B E

Low A,c WD nZ H

Very Low n

Very Low Low Moderate High Very High

Probability of invasion

17www.hdrinc.com


industrial facilities using large amounts of water. Zooplankton population increases, typically following diatom blooms, also have led to screen clogging complaints.

In the past few years SpU has identified several new algal species at Lake Youngs. While many of these emergent species have not been disruptive, a bloom of a microfilamentous species of the diatom Cyclotella in 2008 (Figure 1), never before seen at Lake Youngs, resulted in clogging of treatment facility instrumentation and fish screens.

The case study is focusing on refining data collection and monitoring efforts, as well as developing data analysis and data storage practices that will increase the effectiveness of SpU’s efforts to predict the occurrences of these species and streamline. The applicability and value of using available computer models also is being assessed. Approximately 20 years of monitoring data from the two watersheds currently are being evaluated.

City of everettAt the city’s water filtration plant on

Lake chaplain, periodic episodes of population increase of the Cladoceran zooplankton Holopedium gibberum (H. gibberum) have caused disruption to drinking water production due to filter clogging.

H. gibberum develops a gelatinous sheath several millimeters in diameter around its body to ward off predators (Figure 2). When H. gibberum enters the treatment plant, the gelatinous

sheaths accumulate on media filter surfaces that causes severe blinding and reduces filter run times by several hours.

numerous factors, including irregular changes in population abundance, diurnal migrations within the water column and indiscriminate feeding habits, make prediction of these disruptive occurrences a continuing challenge for treatment plant personnel.

The case study is focusing on statistical analysis of monitoring data toward the goal of developing a population model to predict H. gibberum occurrences. In addition, a variety of pre-treatment technologies to remove H. gibberum from plant raw water are being evaluated.

tacoma WaterTacoma Water, the sponsor of the study, is particularly concerned

with anticipating the occurrence of aquatic species within the context of change.

The disruptive blue-green algal species Aphanothece, which causes filter blinding due to mucilaginous sheaths that bind colonies together, was identified at potentially problematic levels at their unfiltered primary source at the Eagle gorge Reservoir on the green River.

This occurrence and the presence of numerous other potentially disruptive species within the Eagle gorge Reservoir raises serious concerns regarding future operations of a new filter plant at this supply, which is planned to come on-line in either 2014 or 2015. In addition, changes to the Howard Hanson Dam facility are being implemented by the U.S. Army corps of Engineers.

The need to understand what disruptive species pose substantial risk for future operations, and how they will be distributed within the reservoir under future conditions, is of paramount importance as Tacoma Water implements major operational changes. The case study is focusing on the identification of established disruptive aquatic species in the reservoir, and extrapolating from existing data how changes to the dam and reservoir operations could change the distribution of these species.

In addition, the impact on species distribution that discharge from the dam and travel through a three-mile reach of river leading to the treatment plant intake is being evaluated. A goal of these evaluations is to develop targeted monitoring strategies and to develop a rational basis for continuing data analysis to help predict the occurrence of disruptive species moving forward through the planned changes.

HDR and its study partners are performing regional outreach through this project by conducting a survey of regional utilities, encouraging follow-on data-sharing among participating utilities, and holding a regional workshop to share case study and survey results.

A focus of the workshop will be actively encouraging communication and increasing knowledge throughout the region, ultimately creating an environment where co-operative efforts among utilities and existing agencies to address disruptive species management is fostered.

When completed, it is hoped that the region-specific results of this project will benefit surface water utilities in different regions by providing a template for development of their own regional efforts.

For more information about this article, please contact Matthew McFadden at [email protected] .

Figure 1 - Microfilamentous diatom, Cyclotella, which forms mats that can cause severe clogging of filters and screens

Figure 2 - the zooplankton Holopedium gibberum devel-ops a gelatinous sheath that can cause filter clogging

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[ drinking water ]

MORe aND MORe the public, stakeholders and clients are inquiring about the occurrence of microconstituents such as EDcs (endocrine disrupting compounds) and the potential impacts of exposure on humans and wildlife.

They also are increasingly concerned about the occurrence, impact and control of other groups of contaminants known as compounds of potential concern (cpcs), compounds of emerging concerns (cEcs), pharmaceutical and personal care products (ppcps), and various other terms and acronyms currently being used by professional organizations serving the engineering and sciences communities.

cpcs, cEcs, EDcs, and ppcps collectively are called “microconstituents.”

The primary objectives of drinking and wastewater treatment are to protect human health and promote economic vitality while minimizing adverse environmental impacts caused by the use of water. Water reuse for irrigation purposes impacts human health and wildlife as well.

The extent and seriousness of the problems posed by microconstituents is unknown, although environmental concerns are likely to exceed human health concerns. A majority of the concerns surrounding microconstituents to date have focused on the impacts to human

heath and wildlife. However, recent research indicates microconstituents may have an impact on the aquatic environment and the growth of plant life.

While there is plenty of uncertainty regarding the risk of microconstituents, utilities will face questions from customers and possible action by regulators. The regulatory framework for drinking water falls under the Safe Drinking Water Act (SDWA), while wastewater discharge is regulated under the clean Water Act (cWA).

Reuse activities are regulated at the state level, often by combining features of both the SDWA and cWA. compliance with the SDWA and cWA is overseen by the

By Marie-Laure Pellegrin, Senior

Water/Wastewater Engineer, Tampa

A n o v E r v i E W

19www.hdrinc.com


United States Environmental protection Agency (EpA) and commonly enforced by state and local health departments or natural resource divisions. The EpA generally sets water treatment or wastewater discharge standards based on human health effects or environmental impacts.

The EpA established the Endocrine Disruptor Screening and Testing Advisory committee (EDSTAc) in 1996 to oversee the Endocrine Disruptor Screening program (EDSp), which has validated numerous assays and considered approximately 53,000 compounds for endocrine disrupting effects.

In 2009, EDSp identified 75 of these compounds as the first to be evaluated by a two-tier screening process. State efforts have focused on monitoring of microconstituents. california and oregon have led the way and their actions can provide utilities with guidance on which contaminants are being monitored. no unified national regulatory response to

the presence of microconstituents currently exists.

There are five removal pathways of

microconstituents through wastewater treatment plants: biodegradation,

photodegradation, selective ion removal (reverse osmosis (Ro)), sorption and stripping. The two primary pathways are biodegradation and sorption.

There have been studies to evaluate the removal or transformation of microconstituents by biological treatment, disinfection and the advanced oxidation processes (Aop). chloramine and UV disinfection processes are not viable removal barriers.

Activated sludge treatment can be effective in removing microconstituents. However, to achieve good removal of most target compounds, a more advanced treatment barrier such as Ro or Aop might be necessary. Ro membranes typically achieve the following:• Excellent removal (>90 percent) of

pesticides, industrial chemicals and steroid hormones

•good removal of metals (70-90 percent)•good to excellent removal of

organometallics• poor to low (<20 percent or 20-40

percent, respectively) removal of some inorganicsWhile Ro is a highly effective barrier, it

should also be noted that all membrane systems have some degree of “leakage” through fractured glue-lines, o-ring failures or other physical limitations. consequently,

many experts in the industry support the use of an advanced oxidation process following Ro to address removal of trace organics.

Aop appears to be evolving into two different approaches: UV/peroxide and ozone/peroxide. ozone with peroxide has some advantages over the UV-H2o2 process because it provides more oxidation potential; however, in general, UV-H2o2 is understood to be more cost-effective.

Understanding the effectiveness of different wastewater treatment technologies is crucial for understanding human and wildlife health impacts that occur from exposure to water reuse. pathogen reduction and microbial limits

continue to be the major objective of regulations, while chemical pollutants in treated municipal wastewater have not been targeted by state regulations for reclaimed water.

There is ongoing research, but much is unknown about the effects on animals and humans exposed to reuse water from microconstituents that pass unmeasured through wastewater treatment facilities not yet designed to deal with them. It is essential to educate the end user of reuse water about proper uses and potential hazards.

If the public understands the effects of these contaminants and where and how these contaminants originate, a decrease in the contaminants could potentially evolve. one example of an educational program is that of King county (Wash.) which has a web page dedicated to educating the public on endocrine disrupting chemicals.

Research currently is being conducted by many agencies, including WERF, WaterRF and the WateReuse Foundation (WRF), to assess methods for monitoring and removal of microconstituents. The EpA also has adopted a multi-year plan from 2000-12 to further assess these contaminants.

Each research group is still trying to understand the toxicological implications of these compounds and how utilities can relay useful information to the public on this topic. The work of these research and regulatory entities will help:• provide understanding of the impacts

of microconstituents to people, vegetation and wildlife exposed to these contaminants

• Set a priority for regulating contaminant levels

• Establish the effectiveness of conventional and advanced treatment technologiesThe topic of microconstitutents remains

an important issue. To best serve everyone, it is vital to understand the following key issues:

Common Microconstituents1. Endocrine disrupting compounds (EDcs)

20

2. pharmaceuticals and personal care products (ppcps)

the Concerns1. More sophisticated measurement

methodologies have allowed detection of microconstituents at very small concentrations, but they have been in our waterways for longer than we have known how to detect them

2. EDcs are considered a global environmental concern since they are an exogenous substance or mixture that alters the function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, or its progeny, or (sub)populations

3. In addition to antibiotics and steroids, over 100 individual ppcps have been identified in environmental samples and drinking water

4. potential impacts to humans, the environment and ecology are not entirely known and additional research is still required

5. Many existing treatment facilities are not yet equipped with a means for treating these microconstituents

Regulatory ResponseThe primary action taken by the EpA

in response to EDcs/ppcps was the establishment in 1996 of the EDSTAc to oversee the Endocrine Disruptor Screening program (EDSp). EDSp has validated numerous assays and considered approximately 53,000 compounds for endocrine disrupting effects. In 2009, 75 of these compounds were the first to be evaluated by a two-tier screening process.

State efforts have focused on monitoring of EDcs/ppcps. Two states have led this effort – california and oregon. In california, reuse systems are required to perform an additional monitoring program for EDc/ppcps when practicing groundwater recharge. The specifics of the program are subject to negotiation with the california Department of public Health.

public pressure in oregon resulted in passage of Senate Bill 737 in 2007 requiring

the Department of Environmental Quality to develop a list of priority persistent bioaccumulative toxics (p3 List). In 2009, the final p3 list was published indentifying 69 “Tier 1” persistent pollutants and 49 “Tier 2” legacy pollutants.

Microconstituents RemovalThe EpA published a literature review

in August 2010 discussing the removal of microconstituents through different types of processes. The EpA also released a database with all the microconstituent removal efficiencies for different compounds moving through different processes. The database can be accessed at http://water.epa.gov/scitech/swguidance/ppcp/results.cfm.

In general, an increase in Solids Retention Time (SRT) enhanced the removal of the majority of the monitored microconstituents. The SRT required to achieve consistent removal above 80 percent is compound specific with many of the target compounds well-removed by activated sludge processes with SRTs of 5 to 15 days. Activated sludge treatment can be effective in removing microconstituents. However, to achieve good removal of most target compounds, a second treatment barrier might be necessary.

Biological systems (suspended growth or attached growth) are fairly efficient at removing most of the compounds. Membrane bioreactors do not appear to remove microconstituents to a significantly higher degree than conventional activated sludge systems. A one-stage disinfection system, such as chlorination or UV, provides mixed results and is not as efficient. combined disinfection technologies such as ozonation and hydrogen peroxide improve removal efficiencies drastically.

reverse osmosis removes almost all compounds to high-level efficiencies depending on the size, polarity and solubility of each compound. While Ro is a highly-effective barrier, some organics pass through the membrane. It also should be noted that all membrane systems have some degree of “leakage” through fractured

glue-lines, o-ring failures or other physical limitations. For these reasons, many experts in the industry support the use of advanced oxidation following Ro to address removal of trace organics.

Advanced treatment processes used to remove organic compounds rely primarily on sorption, physical separation, oxidation and biodegradation. Treatment efficiency is dependent on the structure and properties of the target chemical, water quality and the operational conditions of the treatment process employed. The pH of the water affects the ionization state of organic chemicals, which, in turn, impacts contaminant removal.

AoP is presently a best practice requirement to address trace organics. They appear to be evolving into two different approaches. The first involves UV/peroxide. The second involves ozone/peroxide. While some in the industry refer to advanced oxidation as a process used for destruction of chemicals, complete mineralization of the chemical is not achieved for the entire list of microconstituents. In many cases, partial decomposition of a non-biodegradable organic contaminant can lead to biodegradable intermediates which, in some cases, could be or form byproducts.

What’s Next?Microconstituents in biosolids have

received significant attention by the scientific and regulatory community for many years. To date, most research has suggested that the risks to human health and the environment are minimal.

However, there are still significant concerns by the scientific community and the general public that there is a lack of sufficient data to accurately assess the potential impacts of these chemicals.

For more information about this article, please contact Marie-Laure Pellegrin at [email protected] .

www.hdrinc.com

[ drinking water ]

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that nDMA was detected in approximately 24.6 percent of the 1,071 systems tested. nDMA is classified by the EpA as a probable human carcinogen. A lifetime exposure to concentrations as low as a few parts per trillion (ng/L) in water is thought to increase the risk of developing cancer.

Yet any regulation of nDMA is complicated by the fact that the body naturally produces nDMA and many foods - including milk, bacon and beer contain nDMA concentrations that are many orders of magnitude greater than in drinking water. Hence, any future nDMA regulations will need to take into account that the contribution drinking water makes to nDMA exposure is probably small compared to other exposure pathways.

treatment Options once formed, nDMA is relatively difficult to treat. Reverse osmosis membranes are marginally effective but are unlikely to be capable of

treatment to low part per trillion levels. Advanced oxidation processes, including ultraviolet light/peroxide or ultraviolet light/ozone, are required for effective treatment. It may be necessary to combine advanced oxidation with membrane treatment to obtain treated water nDMA concentrations at the low part per trillion level.

preventing the formation of nDMA through the control of nDMA precursors appears to be a more cost-effective treatment strategy than treatment after formation. ongoing research has found that ozone, chlorine or chlorine dioxide, used as a preoxidant, may be effective in destroying nDMA precursors, thereby preventing the formation of nDMA.

However, each of these approaches requires balancing the formation of other disinfection by-products created by these oxidants against possible formation of nDMA. Simply put, the control of nDMA in drinking water systems will be difficult.

hDR’s involvementHDR has been closely monitoring nDMA regulatory development. HDR also participated in the design of a combined membrane and UV/

peroxide system treating nDMA in groundwater recharge at the West Basin Municipal Water District in california.

For more information about this article, please contact Phil Brandhuber at [email protected] .

(continued from page 11)

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