Coliphage Testing Enhances Water Quality Assessment

The Orange County Water District (OCWD; the District) has a commitment to providing exceptional water quality and has comprehensive knowledge of groundwater quality. OCWD tests for many more contaminants than are required by regulations, allowing it to anticipate and react early to water quality risks. The result is that customers enjoy water that complies with all drinking water regulations 24 hours a day 7 days a week.

As water quality steward, OCWD continues to implement a robust and proactive water quality monitoring program to ensure the quality of water resources in Orange County.  Coliphage monitoring is one type of water quality test that OCWD has performed for many years at many different locations. 

Coliphages are a group of bacteriophages (or bacterial viruses) that are found in coliform bacteria, such as E. coli.  Bacteriophages are found throughout the environment, wherever bacteria exist. Coliphages can be used to indicate the possible presence of fecal material and pathogens in a water source.

There is no regulation or requirement for coliphage monitoring by state or federal water quality agencies, yet OCWD has performed monitoring at various sites throughout the groundwater basin for over a decade.

Accurately measuring viruses in water can be challenging; the measurement of coliphage has proven to be one of the more reliable and cost-effective techniques, with the added advantage of U.S. Environmental Protection Agency (EPA)-certified methods. OCWD began implementing coliphage monitoring programs and projects as far back as 2005 when very few water agencies performed this type of water quality testing.  OCWD has collected samples from many different locations throughout Orange County such as groundwater monitoring wells, surface water sites (lakes, rivers, and creeks), and at multiple points within the Groundwater Replenishment System (GWRS) treatment facility.  The GWRS is the world’s largest advanced water purification project for potable reuse. It is located at OCWD headquarters in Fountain Valley.

OCWD has a regular monitoring program to measure coliphage removal by the GWRS reverse osmosis process to demonstrate virus removal. OCWD also continues to perform testing on research and pilot water treatment systems to provide information on the effectiveness of water treatment for the removal of bacteria and viruses; coliphage samples were recently collected from microfiltration and ultrafiltration units being evaluated for the GWRS Final Expansion, as well as from older operating GWRS microfiltration units immediately prior to scheduled replacement.

All coliphage samples are collected by trained OCWD personnel and sent to an outside laboratory that is contracted by OCWD to perform the coliphage tests using EPA-approved methods.  In addition to the coliphage monitoring at many sites, OCWD performs extensive monitoring for various indicator microorganisms in order to provide additional information to protect the quality of Orange County’s water resources.