Performance of UK wastewater treatment works with respect to trace contaminants

• The progress of 50 priority chemicals was determined in 16 wastewater treatment works' processes.
• Inputs and removal rates were quantified.
• Removal at different stages in the treatment process is presented.
• Effluent quality was assessed in relation to water quality criteria.
• The performance of different types of conventional treatment works is presented.

This study examined the performance of 16 wastewater treatment works to provide an overview of trace substance removal in relation to meeting the objectives of the Water Framework Directive (WFD). Collection and analysis of over 2400 samples including sewage influent, process samples at different stages in the treatment process and final effluent has provided data on the performance of current wastewater treatment processes and made it possible to evaluate the need for improved effluent quality. Results for 55 substances, including metals, industrial chemicals and pharmaceuticals are reported. Data for sanitary parameters are also provided. A wide range of removal efficiencies was observed. Removal was not clearly related to the generic process type, indicating that other operational factors tend to be important. Nonetheless, removals for many substances of current concern were high. Despite this, current proposals for stringent water quality standards mean that further improvements in effluent quality are likely to be required.