Conventional wastewater treatment systems are designed to treat organic wastes that enter from municipal sewers. Many synthetic pollutants, such as pharmaceuticals and personal care products, also are in the wastewater stream. Some of these pollutants are produced in very large quantities and are discharged in sewage where partial treatment occurs before their discharge. 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.
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. In our EPA funded research, we are examining the effect of stormwater infiltration on the treatability of targeted pharmaceuticals, PAHs and pesticides. Seven dry weather and seven wet weather samples sets taken from several locations at the treatment plant are compared to determine if there is a significant change in removal and if there is a reduction in treatability. From the preliminary data, treatability appears 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.