AWWA WQTC65880

In an attempt to reduce health risk from bathing waters, microbiological standards for E. coli and intestinal enterococci were implemented in European legislation. Furthermore, water quality management is required with respect to sources and spreading of fecal pollution. One of the tools in this process is predictive modeling which requires quantitative data on the decay rate of both indicator bacteria. The decay rate index (DRI) at different water temperatures for E. coli and enterococci in freshwater was determined based on batch experiments with environmental and pre-cultured indicators. Results showed that enterococci were similar or less persistent than E. coli in freshwater. In salt water, however, enterococci are more persistent. Decay increased with temperature, and for E. coli and enterococci the Arrhenius constant was estimated at 1.05 and 1.06, respectively. The high variability of the calculated DRI-values implicates high uncertainty of the concentrations derived from predictive modeling. More research is needed to elucidate the microbial and environmental factors influencing the decay rate of both indicators which enables the use of more precise and specific DRI-values for local situations. Includes 2 references, table, figures.