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MICROORGANISMS DIE-OFF RATES IN URBAN STORMWATER RUNOFF 2007
Citation:
SELVAKUMAR, A., M. BORST, AND S. D. STRUCK. MICROORGANISMS DIE-OFF RATES IN URBAN STORMWATER RUNOFF 2007. Presented at 2007 TMDL Conference, Bellevue, WA, June 24 - 27, 2007.
Impact/Purpose:
to present information
Description:
Stormwater best management practices (BMPs) are often considered effective tools to mitigate the effects of stormwater pollutants before they are discharged to receiving waters. However, BMP performance for microorganisms removal is not well documented. Microorganisms die-off in stormwater runoff is a complex process involving various types of environmental factors such as temperature, sunlight, dissolved oxygen, salinity, etc. This bench-scale study was designed to determine the effects of individual factors that influence the microorganisms die-off in BMPs. In this study, organism-specific die-off constants in stormwater were developed assuming temperature and sunlight as the major influential parameters. The temperature study indicated that the organisms persisted at higher levels at lower temperatures. The die-off rate constants increased with increasing temperatures. These observed temperature effects on die-off were well documented in other literatures as well. Out of all the organisms studied, total coliforms had a much slower die-off rate. Fecal coliforms, fecal streptococci, E. coli, and enterococci have similar die-off rate constants. The temperature coefficient values obtained in this study are similar to the ones reported in the literature. Except for total and fecal coliforms, the effect of sunlight on die-off constant is significant. The initial concentrations of organisms in the stormwater have an effect on the die-off rates.