The distribution and fate of pesticides in full-scale drinking water treatment plants

Abstract

This study utilized HPLC-MS/MS combined with improved solid-phase extraction techniques to investigate the distribution and fate of 31 pesticides in three drinking water treatment plants (DWTPs), which source their water from the Yangtze River, the Yellow River, and Taihu Lake. The total concentration of pesticides in the raw water of the three water treatment plants ranged from 145.4 to 257.1 ng/L, while in the treated water it ranged from 22.8 to 59.0 ng/L, with an average removal efficiency of 78.3 %. Atrazine emerges as the predominant pesticide substance in the raw water of all three plants, indicating its continued widespread use. In the conventional treatment process, sand filtration and disinfection can remove a small amount of pesticides, while coagulation and sedimentation are ineffective. However, adding a pre-ozonation step before coagulation and sedimentation can enhance the removal efficiency of pesticides. Ozone and BAC are the most effective removal processes, with pesticide removal rates ranging from 31.8 % to 64.6 % for ozone and from 20.9 % to 47.7 % for BAC. The combination of ozone and H2O2 (64.6 %) has a higher pesticide removal efficiency compared to the ozone process alone (31.8 % and 50.7 %), especially for substances that are resistant to degradation by ozone. However, BAC's effectiveness in pesticide removal decreases significantly with increasing years of usage. After 2 years of use, the removal rate of BAC is 83.3 %, whereas after 4 years, it decreases to only 26.6 %. This study contributes to the understanding of the fate of pesticides in the drinking water treatment process.