Fate and removal of pesticides in solid and liquid phases of metropolitan, urban and rural-scale wastewater treatment plants

In this study, the change of occurrence, distribution, seasonal variation and removal of pesticides, atrazine (ATZ), chlorpyriphos (CPR) and chlorfenvinphos (CFV), were investigated both in liquid and solid phases of three different types of wastewater treatment plants (WWTPs). Treatment configurations of the studied WWTPs consist of a metropolitan advanced biological treatment system (4-stage Bardenpho), urban-scale waste stabilization pond (WSP) and rural-scale horizontal subsurface flow constructed wetland (HSSCW). ATZ removal efficiencies (59.8 %-92.4 %) were higher than CPR and CFV removal efficiencies at all WWTPs. CPR and CFV are removed at 78.5 % and 53.1 % efficiency, respectively, from the influent of advanced biological treatment system. CPR and CFV removals were 21.6 and 22.7 % at WSP, respectively. One of the important findings is that ATZ and CFV were removed at higher percentages in primary treatment than in biological treatment in advanced biological WWTP. Sorption onto sludge has been evaluated as an effective removal mechanism for pesticide elimination, at least as much as biodegradation/biotransformation. All investigated pesticides were detected in higher concentrations in primary sludge (168.8-399.5 mu g/kg) compared to secondary sludge (21.9-146.3 mu g/kg) in advanced biological WWTP and in facultative sludge (447.8-1044.7 mu g/kg) compared to anaerobic sludge (250.0-613.0 mu g/kg) in WSP. It was determined that ATZ was the most treated compound in the liquid phase under anaerobic conditions among the studied pesticides. In line with these results, approximately 45 % removal efficiency was determined for CPR and CFV in the anaerobic digestion process present in advanced biological WWTP.

Automated summary

This study investigates the occurrence, distribution, seasonal variation, and removal of pesticides in three different types of wastewater treatment plants. The results show that the removal efficiency of atrazine (ATZ) is higher compared to chlorpyriphos (CPR) and chlorfenvinphos (CFV). ATZ is mainly removed in the primary treatment stage, while CPR and CFV are primarily removed in the biological treatment stage. Sorption onto sludge is found to be an effective removal mechanism for pesticides. The highest removal efficiency is observed for ATZ in the liquid phase under anaerobic conditions.