Attenuation profiles and human health risks of pharmaceuticals and agrochemicals across conventional and advanced drinking water treatment plants along the Yangtze and Han Rivers

With the exacerbation of industrial and agricultural pollution, drinking water safety is facing severe challenges posed by pharmaceuticals and agrochemicals. This study systematically investigated their occurrence, attenuation profiles, and risks across various treatment units in both conventional and advanced drinking water treatment plants (DWTPs) within the Yangtze and Han River basins. Both treatment infrastructures proved inadequate, evidenced by limited total reductions in dissolved-phase concentrations (31–44%) and erratic particulate-phase attenuation dynamics (−115–39%). Critically, sand filtration units acted as secondary contamination sources due to contaminant desorption. Notably, advanced DWTP D achieved an overall reduction of 48–61% for fungicides and neonicotinoid insecticides, far surpassing plants A–C (−24–37%), largely attributed to the superior performance of the ozone-activated carbon process configuration, alongside seasonal variations and influent concentrations. The observed reductions at DWTP D were highly compound-specific, ranging from 35–99% for acetamiprid-type compounds to 7–42% for atrazine-type compounds. These disparities are driven by the distinct molecular structures of the target pollutants, their thermodynamic propensities for reactions with key radicals during ozonation, and their bio-susceptibility within the activated carbon filtration. Under the specific toxicological endpoints and model assumptions of this study, the total hazard quotients of target compounds did not exceed the critical threshold of one, yet potential health risks from unmonitored contaminants during network distribution remain a concern. These findings provide key mechanistic insights into the fate and transformation of emerging contaminants during water treatment, establishing a scientific foundation for process optimization and enhanced drinking water security.