Sand Trap

Researchers investigate sources and transport routes of fecal bacteria in beach sand

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A researcher from the University of  Hawaii Manoa takes samples of beach sand which will be tested for fecal indicators.

A peer review team of WERF volunteer experts traveled to the island of Ohahu, Hawaii, in January, to meet Dr. Tao Yan, and to review the progress of his WERF project Concentration Dynamics of Fecal Indicators in Hawaiian Coastal and Inland Sand, Soil, and Water During Rainfall Events (PATH6R09).  Dr. Yan and his team from the University of Hawaii in Manoa are investigating how fecal indicators of pathogens are transported to beach sand and seawater during rainfall events and their rates of survival. They are also looking at the abundance levels of these indicators in stream water and bank soil to address the role of inland waters in transporting fecal contamination to coastal recreational waters. The results will provide insight into the transport routes of fecal indicators and associated health risks, and provide valuable information to inform the U.S. Environmental Protection Agency’s upcoming revisions to the national recreational water quality criteria.

Understanding possible transmission routes of waterborne pathogens into recreational waters is essential to maintain the health of our communities, and much research, including several WERF projects, has focused on pathogens and indicators in the water itself. Recent studies have demonstrated the importance of beach sand in the biological quality of water. In fact, it is now widely reported that beach sand can often harbor fecal indicators at concentration levels much higher than the surrounding water. To quantitatively assess the health risks associated with beach sand, and ultimately how to manage contamination, it is important to understand the source of the bacteria and how they survive in the beach sand environment. Dr. Yan’s project addresses this issue.

The team had an opportunity to visit the sites where sampling of water, sand, and sediment takes place. The schedule for the project includes three rounds of sampling at Waialae beach and at Monoa stream. Research team members take samples prior to, during, and after rainfall events. The target indicators include the two common fecal indicators E. coli and enterococci, as well as C. perfringens, which has been adopted as an unique fecal indicator for the state of Hawaii.

The first beach sampling had been completed prior to the team’s visit and the initial analysis of fecal indicator concentrations found enterococci to be very high in sand and low in water, while E. coli concentrations are very low in both sand and water. The team was able to discuss the results and Dr. Yan’s plans for future sampling and analysis. The next set of beach sampling will take place in late March and the stream site sampling will begin in June. The project is expected to be complete by year's end.

View more information on WERF’s Waterborne Pathogens and Human Health Program online at www.werf.org/pathogens.

March 17, 2010