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METHODS FOR DETERMINING RECREATIONAL WATER QUALITY
Citation:
Brenner, K P. METHODS FOR DETERMINING RECREATIONAL WATER QUALITY. Presented at USGS Workshop "Building Capabilities for Monitoring & Assessment in Public Health Microbiology", Columbus, OH, March 14-16, 2000.
Impact/Purpose:
Develop new bathing beach monitoring protocols and new approaches for communicating risks associated with swimming and other recreational water activities.
Description:
The goal of the clean water act of 1972 was to restore and maintain physical, chemical & biological quality of waters in the U.S. Although great progress has been made in cleaning up lakes, rivers and coastal waters many still do not meet water quality standards. Most beaches have been closed for at least one day because of high bacterial concentrations or other sources of contamination. In 1986 EPA recommended the use of two new membrane filter methods, mE agar and mTEC agar for monitoring recreational water for enterococci and e.coli, because the previous indicator orgaanisms, total and fecal coliforms, were not specific for fecal contamination. The recommendation was based on epidemiological studies that showed illness rates were directly related to enterococci and e.coli concentrations in the water, but not fecal coliform concentrations. Enterococci levels were correlated with illness rates in both fresh and marine recreational water while e.coli concentrations were correlated in fresh water only. Since then, two improved methods have been developed: mEI agar method for enterococci and modified mTEC agar method for e.coli. These methods allow faster and easier enumeration of target microorganisms. The mEI method is able to recover the same number of enterococci in 24 hours that mE method recovered in 48 hours, and modified mTEC method eliminated the filter transfer step to a second medium. However, results from both of these methods are not available until 24 hours after samples are collected, and other enterococci methods cited in the literature may take up to 72 hours. This means detection of unsafe levels of indicator organisms in recreational water occurs after exposure to the swimmers, bathers and other users. Therefore, rapid methods with results obtained the same day the sample is taken, preferably within hours, are needed to quickly assess the condition of recreational water so the public can be warned of risk of possible exposure to pathogens.