January 23, 2005 - ASM Comments to the EPA on the Draft Policy for National Pollutant Discharge Elimination System (NPDES)

U.S. EPA Office of Water
1200 Pennsylvania Avenue, NW
Washington, DC 20460

National Pollutant Discharge Elimination Systems Permit Requirements for Peak Wetweather Discharges from Publicly Owned Treatment Works Treatment Plants Serving Separate Sanitary Sewer Collection Systems (Docket ID No. EPA-HQ-OW-2005-0523)

The American Society for Microbiology (ASM) is submitting comments in response to the Environmental Protection Agency (EPA) notice on the draft policy for National Pollutant Discharge Elimination System (NPDES) permit requirements for peak wet weather discharges from publicly owned treatment works treatment plants serving separate sanitary sewer collection systems, in the Federal Register, Vol. 70, No. 245 on December 22, 2005, Docket ID No. EPA-HQ-OW-2005-0523. The following comments were developed by the ASM Public and Scientific Affairs Board Committee on Environmental Microbiology Subcommittee on Water.

The ASM is the largest single life science society with more than 42,000 members, including scientists in academic, industrial, clinical, and government institutions, working in areas related to basic and applied research, the prevention and treatment of infectious diseases, laboratory and diagnostic medicine, the environment, and water and food safety.

The ASM commends the Environmental Protection Agency (EPA) for developing a policy that interprets provisions of 40 CFR 122.41(m)(4) relevant for peak wet weather flow diversions in a manner designed to promote the “highest possible treatment to the greatest possible peak wet weather flow”. The ASM recognizes that the proposed policy is intended to promote public health by minimizing and ultimately eliminating wherever possible peak wet weather flow diversions, and to minimize the impacts of any diversions that do occur.

The ASM appreciates that EPA will require a minimum of primary treatment for diverted wet weather peak flow influent, and that all discharges must meet current effluent water quality standards. The ASM further appreciates that EPA will require a minimum of daily monitoring of diverted or recombined effluent to insure that water quality standards are met.

Unfortunately, the ASM is concerned that the proposed policy may provide inadequate control of microorganisms that pose significant threats to human health through contamination of receiving waters.


  1. Microbial contaminants have been neglected within the Clean Water Act, despite the fact that sewage is a large contributor to waterborne microbial diseases as well as the cause of beach closures, limitations on shellfish harvesting, and advisories for use of recreational waters. 
  2. Historically, within the 301 waiver for achieving secondary sewage treatment under the Clean Water Act, monitoring requirements to ensure chemical, biological, and physical integrity of receiving systems were instituted as part of the waiver. However, there has been little monitoring for viruses, Giardia, or Cryptosporidium, or suitable microbial indicators for them, as part of any program that allows untreated or partially treated sewage discharges to the Nation’s waterways, despite the fact that methods are available and have been used for monitoring sewage. 
  3. The proposed policy requires a minimum of daily monitoring for water quality variables. It is not clear how this minimum has been established, or if it reflects a science-based recommendation. Unusual flow conditions that necessitate blending may require greater monitoring. 
  4. Currently required protocols for monitoring microbial contaminants, whether in treated effluents or blended effluents, do not necessarily provide the greatest protection for human health, or incorporate the predictive capabilities of rapid and economical alternative protocols. 
  5. Wastewater treatment is a public health issue, and the wastewater industry should be recognized for its role and efforts in protecting the public; in particular, communities should be made aware of these efforts to a greater extent, and encouraged to participate in decision-making processes.

Solutions and Recommendations:

  1. Enhanced monitoring should be required for viruses as well as Giardia and Cryptosporidium, and these results should be communicated to the public in a timely manner that provides for public input. 
  2. Monitoring data should be used to address the human health risks within a Quantitative Microbial Risk Assessment Framework (QMRA). 
  3. Enhanced monitoring also should include the use of appropriate indicators for viruses and protozoan parasites, specifically somatic and male-specific coliphages and spores of C. perfringens, respectively. If measured before and after wet weather treatment and blending using EPA-approved methods that are easy and affordable to perform, these indicators will give better information than enteric bacterial monitoring with respect to treatment efficacy and blending effects, and possible pathogen risks. Indicator reduction data also can be inputs for QMRA equations or models to estimate virus pathogen and protozoan parasite risks. 
  4. An adaptive management strategy can and should be implemented to address when and where blending is appropriate and the types of notices to the public regarding risk can then be developed when blending occurs.

Serious human health risks can arise from exposure to microbial contamination in surface waters receiving blended effluents. Therefore, the ASM encourages the EPA to promote efforts to eliminate peak wet weather influent diversions and to institute adequate monitoring of microbial pathogens, including viruses.

The ASM is pleased to have the opportunity to provide comments in response to the draft policy for NPDES permit requirements for peak wet weather discharges from publicly owned treatment works treatment plants serving separate sanitary sewer collection systems, and hopes that these comments and recommendations are of assistance to the EPA.


Ruth Berkelman, M.D., Chair, Public and Scientific Affairs Board
Gary King, Ph.D., Chair, Committee on Environmental Microbiology
Charles Gerba, Ph.D., Member, Committee on Environmental Microbiology
Charles Haas, Ph.D., Member, Committee on Environmental Microbiology
Joan Rose, Ph.D.,Member, Committee on Environmental Microbiology
Mark Sobsey, Ph.D., Member, Committee on Environmental Microbiology