Impacts of Rainfall Events on Wastewater Treamtent Processes

Current research is revealing that stormwater can carry pathogens and that this stormwater is entering wastewater treatment facilities. During periods of intense rainfall, not only can stormwater carry higher amounts of pathogens, but it also increases the flow rate to the wastewater treatment facility. In many instances, the flow rate exceeds the facilities\u27 treatment capacity and can impact treatment performance. The purpose of this study was to identify whether wastewater treatment is impaired during periods of increased rainfall, and to compare current policies that address this issue. The study was conducted using a case study approach to analyze historical precipitation and wastewater treatment data from facilities located in Clearwater and St. Petersburg, Florida. The effluent from the biological nutrient removal system operated at the facilities located in Clearwater was compared to the effluent from the activated sludge treatment system operated by the facility located in St. Petersburg. Statistical analyses were conducted to identify significant differences in either the loading or performance of wastewater treatment facilities under wet and dry flow conditions. In this case, the Clearwater facilities operating below their treatment capacity were better equipped to handle peak wet weather flows and efficiently treat wastewater than the St. Petersburg facility which has a less advanced treatment system and was operating at and above its treatment capacity