Reduction of Wastewater Organic Micro-pollutants and Genotoxicity in a Hybrid Process Involving Anaerobic-anoxic-oxic and Ozonation Treatments

Abstract

In recent years, researchers have drawn greater attention to the occurrence, fate, and risk of organic micro-pollutants (OMPs) in the environment. Effluent from municipal wastewater treatment plants (WWTPs) are an important source for the release of OMPs into aquatic environment and should be monitored and controlled. The migration and transformation of 14 selected OMPs and their reduction of genotoxicity after treatment by a hybrid process of anaerobic-anoxic-oxic (AAO) and ozonation were investigated. Results showed that the activated sludge process was poor in removing most OMPs, with removal rates of less than 50%. However, ozonation improved OMPs removal, and the hybrid process could reduce most of the OMPs by more than 90%-with OMPs containing phenolic, aniline, and anisole groups in their aromatic structures showing particular vulnerability to attack by ozone. The results of genotoxicity analyses showed that the wastewater influent and secondary effluent exhibited genotoxicity to an extent, and ozonation reduced the genotoxicity of secondary effluent by 98%, thus largely reducing the environmental risk posed by OMPs in WWTP effluent.