Evaluation of the Treatability of Pharmaceuticals, PAHs, and Pesticides during Wet Weather Flows in a Wastewater Treatment Plant

Pharmaceuticals and personal care products (PPCPs) are of particular interest to scientists, because of the lack of information on their effects on ecosystems and lack of regulations affecting their discharges. These pollutants are produced in very large quantities and discharged in sewage where partial treatment occurs before their discharge. They have been detected in surface waters throughout the country. Some of the pharmaceuticals excreted from the body are unmetabolized into the domestic wastewater stream and are more toxic and untreatable than their parent compound. Wastewater treatment systems receive PPCPs, along with other poorly understood contaminants including PAHs and pesticides. Wastewater treatment systems were not designed to treat these chemicals. Factors that can influence their treatability by wastewater treatment systems include the physical and chemical characteristics of the pollutants, the retention time in the unit treatment processes, and flow rates that can be influenced by rainfall. During this EPA-funded study, we are looking for the relationship in wastewater treatment efficiency and weather conditions, specifically examining treatment during wet weather flow. The operation of a local wastewater treatment facility was examined at several locations during seven wet weather events and seven dry weather events for these compounds. During wet weather, there was an increase in mass discharges to the treatment plant for both PAHs and some of the pharmaceuticals. Gemfibrozil had a higher mass during dry weather. Although, the mass entering the treatment plants increased for the analytes, there were still significant reductions in the secondary treatment phase of the facility. Based on these data, treatability appeared to remain similar during both wet and dry weather. Hydraulic retention times and hourly flow variations are being examined during the final portion of this project.