August 18, 2016
EPA Investigating Switch from Bacterial to Viral Indicator for Recreational Water Quality
POSTED BYWilliam Shane, P.E.
The EPA is developing recreational water quality criteria (RWQC) for coliphage, a viral indicator, to ensure public health protection when recreating in water bodies that may be affected by human fecal contamination. The new criteria are expected to be released in 2018. The use of a viral indicator represents a significant change from current practice. For over a century, fecal indicator bacteria (i.e., total coliforms, fecal coliforms, E. coli, fecal streptococci, and enterococci) have been used to detect sewage contamination associated with fecal material. Currently, the bacteria E. coli and enterococci are used by EPA as recreational water quality indicators. In Kentucky, standards for primary and secondary contact recreation are based on the fecal coliform and E. coli content in the water. (Note that the fecal coliform criteria will no longer apply beginning November 1, 2019).
So, what is a coliphage? A coliphage is a type of bacteriophage (commonly referred to as phages), which are viruses that infect bacteria. They exist for all known bacterial species, and a wide variety have been isolated. The significance of coliphage is that it infects E. coli, which is why EPA is investigating it as both an indicator of fecal contamination and viruses in treated wastewater. It has been suggested that viral pathogens cause the majority of recreational waterborne illnesses. Unfortunately, traditional fecal indicator bacteria are not the best indicators of viral pathogens, and the Agency does not currently have a recommended indicator of viruses in surface waters. The EPA feels that coliphages can fill this void because they exhibit numerous desirable indicator characteristics. For example, they:
- are of fecal origin and present in high numbers in sewage;
- are physically similar to viruses causing illnesses associated with primary contact recreation;
- do not re-grow in surface waters, thus their presence specifically indicates fecal contamination;
- are non-pathogenic;
- can be counted cheaply, easily, and quickly;
- show correlations to gastrointestinal illness; and
- are similarly resistant to sewage treatment and environmental insults as enteric viruses of concern.
EPA’s research into the use of colipages as possible indicators of fecal contamination in ambient water is ongoing. On April 17, 2015, the EPA published a literature review of scientific information regarding coliphages (EPA 820-R-15-098) and, in March 2016, conducted a Coliphage Experts Workshop. A summary of findings from the workshop was published in July 2016 (EPA 823-F-16-001).
William Shane is an Environmental Engineer at Smith Management Group. William can be reached at firstname.lastname@example.org.