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TEMPORAL VARIABILITY OF MICROBIAL INDICATORS OF FECAL CONTAMINATION OF MARINE AND FRESHWATER BEACHES
Citation:
WYMER, L. J., A. P. DUFOUR, AND C. MCGEE. TEMPORAL VARIABILITY OF MICROBIAL INDICATORS OF FECAL CONTAMINATION OF MARINE AND FRESHWATER BEACHES. Presented at American Society for Microbiology General 107th Meeting, Toronto, BC, CANADA, May 21 - 25, 2007.
Impact/Purpose:
The objectives of this research are: (1) to evaluate rapid state-of-the-art measuement methods of pathogens that may indicate the presence of fecal pollution in recreational waters (beaches); (2) to obtain, jointly with a sister laboratory (NHEERL), a new set of water quality data and related health effects data at a variety of beaches across the U.S., in both marine and non-marine waters; (3) to analyze the research data set to evaluate the utility of the tested measurement methods, the new EMPACT monitoring protocol, and the health effects data / questionnaire, in order to establish a relationship between measured pathogens and observed health effects; and (4) to communicate the results to the Office of Water in support of their efforts to develop new state and/or federal guidelines and limits for water quality indicators of fecal contamination, so that beach managers and public health officials can alert the public about the potential health hazards before exposure to unsafe water can occur.
Description:
Monitoring methods for microbial indicators of fecal contamination are an integral component for protecting the health of swimmers exposed to potentially contaminated bathing beach waters. The design of monitoring systems which will accurately characterize the quality of water is dependent on knowledge of the variability associated with water sampling. This study was conducted to determine the
temporal variability encountered at bathing beaches. High frequency sampling was conducted at marine and freshwater beaches over a sixty day period. Multiple samples were taken at minute, 10 minute, hourly and daily time intervals. Water samples were assayed for E. coli or enterococci using membrane filter methods. In general, as the time interval between samples increased so did their variability. Based on the average freshwater and marine results, samples taken within seconds of each other had a coefficient of variation (CV) of 0.7. Samples taken at 10 minute intervals had a CV of 1.1. Samples taken at hourly intervals had a CV 1.7, and samples taken daily had a CV of 2.2. The results of this study show that single samples do not adequately characterize the quality of beach waters and that temporal variability must be given serious consideration when developing sampling plans for beach waters.