Predicting diffuse-source transfers of surfactants to surface waters using SWAT.

Area of Science:

• Environmental chemistry
• Hydrology
• Environmental modeling

Background:

• Chemicals in wastewater can transfer to soil via biosolids application.
• These chemicals may then enter surface waters through runoff.
• Estimating this transfer is crucial for environmental risk assessment.

Purpose of the Study:

• To evaluate the utility of the SWAT 2000 model for predicting "down-the-drain" chemical exposure in surface waters.
• To model the behavior of linear alkylbenzene sulphonate (LAS) in a UK catchment.
• To assess the sensitivity of chemical transport to biosolids application rates and land coverage.

Main Methods:

• Application of the SWAT 2000 model to a small catchment in Bedfordshire, UK.
• Hypothetical simulation of LAS transfer under realistic and worst-case scenarios.
• Sensitivity analysis of model output based on sludge application proportions.

Main Results:

• Soil wetness and the total quantity of biosolids applied were identified as key factors controlling chemical transport.
• The model successfully estimated LAS transfers under different application scenarios.
• The model demonstrated sensitivity to the proportion of the catchment receiving sludge.

Conclusions:

• The SWAT 2000 model is a valuable tool for estimating diffuse-source surface water exposure to down-the-drain chemicals.
• Findings highlight the importance of soil moisture and biosolids loading in chemical runoff.
• The model shows potential as a higher-tier assessment tool in environmental risk evaluations.