Quantitative microbial risk assessment of Salmonella and Enterococcus in Marina Reservoir and catchments

This study assesses the infection risks associated with non-swimming recreational activities in Marina Reservoir, Singapore. Apart from serving as a reservoir for potable water use, Marina Reservoir is also a place where various water recreations are carried out. Quantitative microbial risk assessment (QMRA) was applied to Marina Reservoir and its four main feeders. QMRA was performed based on the occurrence data of the potential pathogen, Salmonella spp. and bacteria indicator, Enterococcus spp. through Monte Carlo simulation techniques. The results suggest that microbial risks from Salmonella and Enterococcus at the reservoir were below the United States Environmental Protection Agency (USEPA) acceptable freshwater recreational illness rate of 0.8%. All upstream catchments showed acceptable microbial risks from Salmonella. However, the probability of gastrointestinal illness risks calculated for Enterococcus exceeded the USEPA guideline values in one of the upstream catchments, but far enough upstream from recreational areas that are used frequently.