Treatability of emerging contaminants in wastewater under wet weather conditions

Emerging contaminants, which include pharmaceuticals, personal care products and pesticides, amongst other pollutants that have not received much prior attention, are produced in large quantities and many are discharged to wastewaters and processed through wastewater systems in mass quantities. A large number of pharmaceuticals and personal care products have been found in surface water across the country. Most of the pharmaceuticals excreted from the body are unmetabolized when they enter the domestic wastewater stream. Some of the metabolites that are excreted from the body are more toxic or untreatable than their parent compound. Some of these chemicals are endocrine disruptor chemicals and have been shown to adversely affect the reproductive organs offish species. Wet weather flows, including stormwater, combined sewer overflows, and separate sewer overflows, can also contribute emerging contaminants to receiving waters. During wet weather, stormwaters can enter the wastewater stream and affect wastewater treatment facilities. This EPA-funded research is focusing on the wet weather flow contributions of emerging contaminants, including wastewater treatment plants during wet weather operations. Factors that can influence the treatability of wastewater treatment systems are the physical and chemical characteristics of pollutants, the retention time in the system, and rainfall (flow rates). The dilution effect during wet weather could significantly reduce a wastewater system's effectiveness in treating emerging contaminants. In our study, we are comparing wastewater samples collected during wet weather conditions to wastewater samples collected during dry weather conditions to determine if wet weather significantly affects the treatment plant's treatability of emerging contaminants. We are examining a treatment plant receiving combined sewage and a plant having increased flows due to typical inflow and infiltration of stormwater during wet weather. Composite samples are being collected during five rain events and five dry weather events from the inlet of the plant, the primary clarifier, the secondary clarifier and the area of disinfection by UV. Duplicates were conducted for some rain events. The EC samples were extracted by SPE extraction and the PAHs were extracted by separation funnels with KD concentrations. The analyses were conducted using HPLC for the ECs, GC-ECD for the pesticides, and GC-MS for the PAHs. The targeted pharmaceuticals include sulfamethoxazole, fluoxetine, carbamazepine, and trimethoprim, compounds that have been commonly observed at treatment plant effluents. Targeted PAHs include naphthalene, acenaphthylene, acenaphthene, phenanthrene, fluorine, anthracene, flouranthene, pyrene, benzo(a)pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, and benzo(ghi)perylene. Standard pesticide analyses are also being conducted. Significant variability was observed amongst the initially monitored events, but most indicated contaminants in the discharges being below the detection limits, with negligible concentrations remaining after biological treatment. Some of the primary concentrations were higher than the influent concentrations, possibly caused by conjugation or deconjugation of metabolites in the primary clarifier. The preliminary results show that the effectiveness of the treatment plant for the removal of these organic compounds remains high during wet weather events.