Removal of Emerging Contaminants in Wastewater Treatment Plants

Wastewater treatment plants (WWTPs) have been identified as a key collection point for emerging contaminants in the water cycle and potentially an ideal location at which to treat to remove them. Few studies have been performed to monitor or understand the capability of conventional or innovative wastewater treatment processes to remove or reduce the concentrations of a wide variety of ECs at wastewater facilities.  This study was designed to provide baseline information on this topic.  Wastewaters appear to contain a wide range of ECs.  Over 55 of the 63 target contaminants were detected in the five different wastewaters examined during the course of this study, 44 of them frequently. The median cumulative concentrations of EC in the wastewaters ranged from between 120 µg/L to just over 500 µg/L.  The raw wastewater characteristics were not as variable as anticipated.   Conventional wastewater treatment processes were effective in removing significant amounts of the ECs.  Results indicated that the type of technology operated and the mode of operation both had an impact on the removal capability of the plants.   Over half of the frequently detected ECs were reduced by 95 percent or more in samples collected at Plants which operated an activated sludge process. Less than 10 percent of the ECs were reduced by 95 percent or more at Plant D, which uses a trickling filter treatment process Furthermore, focused pilot studies indicated that increased removals of ECs were closely associated with increased SRTs in the activated sludge process.  The most significant impact of SRT appeared to occur as the sludge age increased above 5 days.   While removals continued to improve as the SRT increased above 10 days the benefits were less marked.