Pyrethroid pesticide residues in a municipal wastewater treatment plant: Occurrence, removal efficiency, and risk assessment using a modified index

Abstract The presence of pesticides in municipal wastewater and aquatic environments is showing an increasing trend and leading to adverse environmental and health effects. The present study investigated the occurrence of pyrethroids in the municipal wastewater of Tabriz, a city in northwestern Iran. The performance of a wastewater treatment plant for the removal of pyrethroids was also investigated. For this purpose, lambda-cyhalothrin, cypermethrin, permethrin, and deltamethrin in both the influent and effluent of wastewater treatment plant in summer and fall seasons were measured. The toxicity of target pesticides on rainbow trout and Daphnia Magna was also investigated by a new modified index of environmental relevance of pesticides from wastewater treatment plants. The results show that permethrin was the dominant pesticide in the samples in both seasons with the highest detected concentration in the influent wastewater of 1838 ng/L. Furthermore, cypermethrin was among the highly-detected pesticides with concentration as high as 1742 ng/L. It was also found that 77% and 85% of permethrin, as the dominant pesticide, was removed in summer and fall seasons, respectively. Investigation of the risk of pesticides presence in the effluent presents a very high risk to the aquatic environment which was obtained by calculating the proposed index. Although there is a high removal efficiency of pesticides in wastewater treatment plant, higher toxicity and detection frequency of permethrin in the collected samples is the main reason of high risk to the aquatic environment.