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NACWA has learned that the U.S. Environmental Protection Agency (EPA) is working to develop water quality criteria using bacteriophage as an indicator for the presence of viruses. For decades, Clean Water Act (CWA) compliance and wastewater treatment plant design has been based on the use of bacterial indicators (e.g., fecal coliform, enterococcus, E. coli). EPA has, however, continued to point to viruses as one of the major causes of waterborne illness and environmental activist groups have been pressuring EPA to move in the direction of a virus-based criterion.  NACWA believes that the new criterion would have widespread and substantial impacts on all aspects of CWA implementation.

This Advocacy Alert provides an overview of the issue and NACWA’s activity to date.  NACWA is recommending that if any public agency members are currently evaluating changes to their disinfection practices, they should follow the development of this new criterion very carefully.

Background and Overview 

The Association learned earlier this year that EPA is working to develop a water quality criterion for bacteriophage, a viral indicator with properties similar to many of the viruses the Agency is concerned about. NACWA met with key staff from EPA's Office of Science & Technology (OST) in June. During the meeting, OST officials briefed NACWA on the Agency’s efforts to develop a bacteriophage criterion based on existing data in the peer-reviewed literature, and to develop and validate a test method for bacteriophage for use in CWA programs. EPA's current timetable would have a proposed criterion ready for public comment in late 2015.

For decades, CWA programs have relied on fecal indicators such as fecal coliform or E. coli and enterococcus to evaluate public health risk associated with effluent, combined sewer overflow control, and other programs. In discussing the issue with EPA, NACWA stressed that development of a criterion for viruses could have widespread and major impacts on all aspects of the CWA and encouraged the Agency to move forward cautiously. The Association also urged OST staff to work closely with their counterparts in the Office of Wastewater Management to evaluate the impact on the CWA permitting program.

During its June meeting with OST, NACWA also recommended that EPA work with the Water Environment Research Foundation (WERF) to conduct studies on how bacteriophage behaves in wastewater treatment plants, how it is affected differently by current disinfection practices, and how levels of bacteriophage compare to current indicators that are tracked by clean water agencies. NACWA, the Water Environment Federation (WEF) and WERF are coordinating on this issue and WEF organized an initial stakeholder meeting during WEFTEC. Betsy Southerland, Director of OST, briefed meeting attendees on the Agency’s ongoing work on bacteriophage, while WEF and NACWA members outlined a number of concerns and issues that need additional research.

WEF will be forming a special task force to address this issue and NACWA will continue to work through its Water Quality Committee and engage EPA to encourage a more open process that involves the wastewater community earlier on in the criterion development process. 

Potential Impacts on Disinfection Processes

NACWA has heard from several member agencies currently evaluating or planning upgrades or major changes to their disinfection processes that the establishment of a water quality criterion based on viruses could alter the designs for their projects. While there is still a significant lack of understanding of the efficacy of wastewater treatment plant disinfection processes on inactivating bacteriophage, it is generally understood that bacteria are easier to disinfect than viruses. With little data comparing the performance of disinfection processes at killing bacteria versus bacteriophage/viruses, it is hard to predict the extent of the changes that might be required to existing disinfection practices to meet the new criterion.

NACWA is recommending that clean water agencies currently evaluating changes to their disinfection practice closely follow the development of this new criterion. If the criterion is finalized in 2016 or 2017, it is possible that some states might begin incorporating the new numbers into their standards and permits as early as 2018.

Additional Data and Information Needed

As NACWA, WEF and WERF work together to identify information and research gaps, the organizations are interested in receiving any data or studies comparing bacteriophage/virus inactivation to existing bacterial indicators.  Any information, whether in peer reviewed literature, treatment plant studies, etc. would be valuable.  Please send any relevant information you have to Chris Hornback at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Next Steps

NACWA is actively tracking EPA’s efforts and has requested regular updates from EPA.  NACWA will also be coordinating with WEF’s new task force as well as WERF staff and researchers.  If you are interested in tracking this issue, please contact Chris Hornback at This e-mail address is being protected from spambots. You need JavaScript enabled to view it to be added to a working group that has been following EPA’s efforts to revise its recreational water quality criteria.