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PURPOSE

BACKGROUND

WITNESSES

The Water Resources & Environment Subcommittee is scheduled to meet on April 13, 2005, at 10:00 AM, in Room 2167 of the Rayburn House Office Building, to receive testimony on wastewater blending at wastewater treatment plants during peak wet weather flow conditions. Testimony is expected from State and local government officials, as well as environmental health science experts and advocates for environmental groups and municipalities.

Municipal wastewater collection systems collect domestic sewage and other wastewater from homes and other buildings and convey it to wastewater treatment plants for proper treatment and disposal. These collection systems and treatment facilities are an extensive, valuable, and complex part of the nation’s infrastructure. The collection and treatment of domestic sewage and other wastewater is vital to public health and the protection of the environment. To achieve these benefits, a wastewater treatment system must be adequately designed to handle the volume of wastewater it receives, and function properly.

Under the Federal Water Pollution Control Act, commonly referred to as the Clean Water Act (CWA), publicly owned wastewater treatment plants must meet a technology-based standard referred to as “secondary treatment.” Under EPA’s secondary treatment regulations (at 40 C.F.R. Part 133), discharges from a wastewater treatment plant must meet specified 7-day and 30-day average effluent concentration limitations for total suspended solids (TSS) and biochemical oxygen demand (BOD), reduce TSS and BOD by 85% (on a 30-day average), and maintain a neutral pH. In addition, the CWA requires more stringent limitations where secondary treatment levels are insufficient to meet water quality standards.

EPA’s regulations do not specify the type of treatment processes to be used to meet secondary treatment and water quality standards. Many wastewater treatment plants use a combination of clarification, biological processes, and chemical disinfection to achieve secondary treatment and meet water quality standards. The details of how a wastewater treatment plant is designed to achieve secondary treatment and meet water quality standards are specified in the CWA permit issued to the plant, and the treatment plant may not discharge any wastewater except in compliance with its permit.

Wastewater treatment plant design varies, in part, because the volume and quality of wastewater received by plants varies both geographically and over time. For example, during periods of excessive rain or snow melt, the volume of wastewater flows to a treatment plant can increase substantially. In communities that have a combined stormwater and sewage collection system, the increase in flow is generally due to stormwater runoff. In communities that have separate sanitary sewers, increased flow during wet weather is often the result of infiltration and inflow of water into concrete pipes from rainfall, snowmelt, and resulting high groundwater levels. Under EPA’s secondary treatment regulations, excessive infiltration and inflow is prohibited. Most wastewater treatment plants experience some amount of infiltration and inflow during periods of unusually wet weather.

Sending a large volume of wastewater through a biological treatment unit of a facility’s treatment process can reduce treatment efficiency, exceed the hydraulic or operational capacity of the treatment process, and make the treatment unit inoperable, including by washing out the biological organisms that treat the wastewaters. Different communities have employed various strategies to address these large wet weather flows, while protecting their biological treatment units. Some plants were originally designed with sewer overflow outfalls, which can send raw sewage to a river or other receiving waters, to avoid exceeding the capacity of a treatment facility or allowing sewage to back up into people’s homes. Sewer overflow outfalls result in discharges that do not meet secondary treatment or water quality standards. Such discharges are illegal unless the utility has a long term control plan that is incorporated into its permit or an administrative or judicial order, which will bring the plant into compliance with the Clean Water Act. Many of the discharges currently subject to enforceable long term control plans are associated with combined sewer overflows.

Other plants are designed with excess capacity to address periodic wet weather flows. In general, it is not possible to design a biological treatment component of a plant with large amounts of excess capacity, because a relatively steady flow of wastewater is necessary to maintain a stable population of biological organisms. However, some plants can be designed with excess storage capacity.

Another way to address excess wet weather flows is to design a plant in a way that allows an operator to first treat all the wastewater with the primary clarifier, then route a portion of the peak wastewater flow that exceeds the capacity of the plant’s biological treatment unit around the biological treatment unit, and then recombine that flow with the rest of the wastewater flow that went through the biological treatment unit to receive chemical disinfection treatment. This practice is commonly referred to as “wastewater blending.” In many plant designs, the re-routed wastewater flow also receives supplemental physical or physical/chemical solids and pathogen removal treatment before it is recombined with the main flow prior to final disinfection. This resulting “blended” wastewater stream in a well designed and operated treatment facility meets secondary treatment standards and all applicable water quality standards. In states that have adopted water quality criteria for pathogens and pathogen indicator organisms, this includes applicable standards for pathogens. In 2000, Congress amended the CWA to require EPA to conduct studies to improve the scientific basis for and issue new and revised water quality criteria for pathogens and pathogen indicator organisms, and to require States to incorporate new pathogen and pathogen indicator criteria into the State water quality standards for coastal recreation waters (which is defined to include the Great Lakes, as well as marine coastal waters).

Is Blending Legal?

Some EPA regional offices and representatives of some environmental advocacy groups have taken the position that existing regulations prohibit wastewater blending. Other EPA regional offices and numerous states still allow utilities to design treatment facilities to use blending as a tool for managing unusual peak wet weather flows in appropriate circumstances.

Opponents of blending argue that blending results in an illegal discharge in violation of the secondary treatment regulations. EPA’s existing bypass rule prohibits intentional diversion of waste streams from any portion of a treatment facility except where necessary for essential maintenance, or when unavoidable to prevent loss of life, personal injury, or severe property damage, and there were no feasible alternatives to the bypass. (40 C.F.R. § 122.41(m).) As interpreted by EPA, if excess capacity could have been provided when the treatment plant was designed and built, the utility cannot meet the “no feasible alternatives” test. This interpretation of the bypass rule would prohibit approval of a treatment plant design with peak flow treatment facilities that are used only occasionally.

Proponents of blending argue that the secondary treatment standards were never intended to prohibit blending. Proponents base this argument on the fact that the CWA does not dictate the design of wastewater treatment plants, leaving the choice of technology and plant design up to the utility, as long as a plant’s permit limits are met. Proponents also maintain that wastewater blending is not an illegal bypass, and argue that the bypass rule only requires that permittees operate the treatment plant as designed, consistent with technology-based requirements. In fact, under the old CWA Title II construction grants program, EPA funded treatment plants that included blending in their plant designs. EPA also disapproved some plant designs with excess capacity, on the ground that such excess capacity exceeded the needs to be served by those plants.

In an attempt to clarify the regulatory uncertainty about when wastewater blending under peak wet weather flow conditions may be allowed, in November 2003, EPA published a proposed policy regarding wastewater blending and NPDES permit requirements for treatment plants under peak wet weather flow conditions. (See 68 Fed. Reg. 63,042 (Nov. 7, 2003).) The proposed policy was aimed at ensuring that treatment plants and collection systems are managed consistently nationally and in a manner that protects human health and the environment.

According to the proposed policy, peak wet weather discharges from wastewater treatment plants that consist of effluent routed around biological or other treatment units blended together with the effluent from the treatment units prior to discharge are not a prohibited bypass and may be authorized in an NPDES permit, if specified requirements are met. These requirements pertain to secondary treatment standards, generally accepted good engineering practices and long-term design criteria, water quality standards, and appropriate safeguards, including monitoring, are met.

EPA has received a large number of comments on the proposed blending policy, many in favor of and many in opposition. In addition, some commenters have questioned whether this matter can be addressed by a policy, in lieu of a regulation.

Is Blending Protective of Human Health?

However the legality issue is resolved, there remains the issue of whether or not blending is protective of human health.

Some opponents of blending have called it an illegal bypass of raw sewage. Others acknowledge that blending is not the discharge of raw sewage, but argue that blended waste streams will result in the discharge of more pathogens, creating risks to human health.

Proponents of blending disagree. They point out that blending involves specific treatment plant engineering designs and operational practices for managing peak wet weather flows during more extreme events. Applicable permit limitations continue to be met. Blending is not intended to occur routinely. Many facilities designed to blend during unusual peak wet weather flows incorporate, into their designs and operational plans, the use of supplemental wet weather storage and/or supplemental physical or physical/chemical solids removal treatment (for example, enhanced high rate clarification, flocculation, filtration) for the re-routed wastewater, resulting in enhanced removal of solids (and therefore enhanced removal of pathogens) equivalent to secondary treatment.

Proponents also point out that the environmental engineering community considers blending a long-standing and accepted means to cost-effectively design treatment facilities to maximize the ability to treat occasional peak incoming flows and protect biological and other treatment systems from process disruptions that could be caused by peak flow conditions. Blending prevents raw sewage discharges that may otherwise occur and helps protect the environment and human health.

Should Blending Be Available as a Wastewater Management Tool?

Even if wastewater blending is demonstrated to be protective of human health, but uncertainty remains as to its legality, this leads to the question of whether or not blending should be available as a wastewater management tool. According to EPA, prohibiting blending could require municipalities to expend an additional $80 billion to $200 billion nationwide on wastewater infrastructure. If blending can be protective, then prohibiting blending may be a waste of scarce resources at a time when municipalities are already over-burdened by the need to upgrade their wastewater infrastructure.

EPA has not finalized any blending policy so the lack of consistency among Federal and state regulators remains, and municipalities still face substantial uncertainty. In addition, there is substantial confusion regarding what blending actually entails and when it is used.

At the hearing, the Subcommittee is expected to hear representatives of viewpoints, both in favor of and in opposition to the practice of wastewater blending, discuss the basis for their positions.