Coliphages Bring A New Standard For Detecting Contamination

As more wastewater reclamation systems are brought online and testing methods become more advanced, industry thought leaders have questioned a commonly accepted standard for detecting fecal contamination in our water.

New research has challenged the status quo, which dictates fecal indicator bacteria (FIB) as the best gauge for water contamination. In April, the U.S. EPA released its “Review of Coliphages as Possible Indicators of Fecal Contamination for Ambient Water Quality,” summarizing the scientific information it will use to determine coliphage-based water quality criteria.

The initiative was spurred by shortcomings in the traditional FIB testing.

“Unfortunately, because bacteria respond to water treatment processes and environmental degradation processes differently than viruses, traditional FIB may not be the best indicators of viral pathogens associated with fecal contamination,” the review reads.

The Case For Coliphages

As the title indicates, the review proposes measuring coliphages to determine the potential presence of fecal contamination. “This is based on their greater similarity to human enteric viruses in their physical structure, composition and morphology, survivability in the environment, and persistence in treatment processes compared to FIB,” it says.

“There has been interest in the use of coliphages as virus indicators of fecal contamination, potential enteric virus pathogen contamination, and effectiveness of wastewater and water treatment processes for several decades,” added Mark D. Sobsey, the Kenan Distinguished Professor of Environmental Sciences & Engineering at the University of North Carolina and a member of the review’s external peer workgroup. “Furthermore, growing evidence from epidemiological studies of recreational waters has suggested that coliphages may be predictive of human health risks such as gastrointestinal illness from recreational use of water.”

The study compared the merits of gauging coliphages to the commonly used FIBs E. coli and enterococci.

Ultimately, the review concludes that “While some of the same limitations exist, coliphages are likely a better indicator of viruses in fecal contamination than the current FIB.”

Implementing A New Standard

The review lists several methods for detecting coliphages in wastewater, from the lengthier “culture-based” methods to “rapid” methods, which take a day or less. A table in the report lists the advantages and disadvantages of each recommended method, along with an expected duration for results.

“I recommend that water reclamation facilities test for infectious coliphages by modifications of EPA Methods 1601 or 1602,” said Sobsey. “These are relatively simple, culture-based methods that can be done by practically any utility lab or commercial lab.”

The EPA considered a study by the Water Environment Research Foundation (WERF) which evaluated the reduction of pathogens, FIBs, coliphages and other indicators of fecal contamination at six wastewater treatment plants. Samples of tertiary recycled water were collected five times over the course of a year and evaluated under the microscope.

“Although no correlation of the density of coliphages and enteroviruses was found, the authors [of the WERF study] suggest that it is possible to predict the absence of entroviruses based on coliphage levels,” writes the EPA.

Specifically, the study claims that levels of less than 10 coliphage plaque-forming unit (PFU) per 100 mL indicate effluents with no detectable viruses associated with fecal contamination.

The Future

Following this major step in creating a new normal, it’s time to implement coliphage testing on the utility level. This will mean additional research to determine the most practical methods for doing so.

“At this time, we are gathering questions from representatives in our industry to enable identification and pursuit of research needs,” said Carrie Capuco, WERF’s director of communications. WERF hopes to initiate research in 2015 to determine the future of coliphage testing methods.

As far as establishing coliphages as the standard monitors for fecal contamination, it’s simply a matter of time.

“I predict that coliphage detection will become more widely implemented and used in future guidance or regulations,” said Sobsey.

For more information on contamination monitoring, visit Water Online’s Wastewater Treatment Solution Center.