Modeling and Evaluating Wastewater-Derived Pesticides in Surface Water

Pesticide use has reached alarming levels globally, causing potential risks to human health and the environment. With its high population densities and rapid development, California emerges as one of the country's leading users of pesticides in the country. Recognized point and non-point pathways for pesticides entering surface water include mixed indoor and outdoor applications and treated municipal wastewater effluent, indicating that conventional wastewater treatment plants (WWTPs) treatment processes are inefficient at removing pesticides from effluents. Recent studies have assessed the fate of pesticides in surface water with a limited understanding of watershed characteristics. This project aimed to quantify WWTP discharges, a lesser-known source of pesticide loads, and investigate the potential environmental benefits of their removal. To evaluate WWTP pesticide concentrations, we developed a geospatial model with municipal WWTP discharges, streamflow characteristics, and pesticide loading data to estimate pesticide concentrations within wastewater receiving streams. Next, we set a multimetric Pesticide Vulnerability Index (PVI) to identify the most vulnerable California watersheds to wastewater-derived pesticide loading. Finally, we investigated the environmental benefits of incorporating advanced WWTP processes for pesticide residue removal from treated effluent before surface water discharge using estimated WWTP life-cycle costs. This work presents an integrated assessment of pesticides in surface water to support source control and mitigation efforts. It highlighted the significance and effects of municipal WWTP pesticide loading in California’s urban waterways. In addition, completing this project provided insight into the environmental and economic costs associated with municipal wastewater-derived pesticide mitigation.