Determination of pesticide residues in the influent and effluent of Tabriz wastewater treatment plant

Abstract

The presence of pesticides in municipal wastewater and aquatic environments is showing an increasing trend and leading to adverse environmental and health effects. Since the conventional wastewater systems are not capable of completely removing pesticides, so the presence of pesticides in effluent of wastewater treatment plant (WWTP), causing contamination of surface water, soil and aquatic life.The present study investigated the occurrence of pyrethroids in influent and effluent of wastewater treatment plant of Tabriz city, their seasonal variations, the removal efficiencies in a WWTP, and the environmental relevance to the aquatic environment. For this purpose, lambda-cyhalothrin, cypermethrin, permethrin, and deltamethrin in both the influent and effluent of a WWTP in summer and fall seasons were measured. The air-assisted liquid-liquid microextraction (AALLME) method was used for the extraction of target pesticides in this study. Then they were determined by LC–MS/MS. 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 (MERPWI). Data normality was evaluated using the Shapiro-Wilk test. According to the results of the normality test and because of the strong correlation existing between input and output values, the paired t-test for normally distributed variables and the Wilcoxon Signed Ranks Test for non-normal variables were used to compare input and output amounts. IBM SPSS version 25 was used for data analysis. The results showed that the highest detected pesticide concentration in the influent wastewater was 1838 ng/L, and permethrin was the most highly relevant pesticide in wastewater samples with detection frequencies of 80% and 100% for summer and fall seasons, respectively. It was also found that the WWTP was able to remove almost 77% and 85% of permethrin in summer and fall seasons, respectively. Finally, calculating the MERPWI showed that permethrin presents a very high risk to the aquatic environment, mainly due to its higher toxicity and detection frequency in the studied WWTP.