Spatial Differences among Micropollutants in Sewer Overflows: A Multisite Analysis Using Passive Samplers.

Area of Science:

• Environmental Science
• Water Quality Assessment
• Environmental Chemistry

Background:

• Sewer overflows are a significant source of micropollutant contamination in receiving waters.
• Limited data exists on the occurrence and spatial distribution of micropollutants from sewer overflows.
• Understanding these contaminants is crucial for effective water resource management.

Purpose of the Study:

• To quantify polar organic micropollutant concentrations from combined sewer overflows (CSOs).
• To identify indicator micropollutants and assess their ecotoxicological relevance.
• To evaluate spatial variability and inform monitoring strategies for CSO catchments.

Main Methods:

• Passive samplers deployed at 20 CSO sites, collecting data over 95 events.
• Analysis of 13 representative polar organic micropollutants.
• Comparison of measured concentrations with environmental quality standards (EQS).

Main Results:

• Concentration ranges for 13 micropollutants were established, with municipal wastewater and stormwater identified as sources.
• Benzotriazole, carbamazepine, diclofenac, and others were identified as key indicator micropollutants.
• 13 out of 20 CSO sites exceeded acute EQS for at least one micropollutant, highlighting the need for dilution.

Conclusions:

• Micropollutant discharges from CSOs are ecologically relevant and exhibit high spatial variability.
• Intersite variability in micropollutant concentrations is greater than within-site variability.
• Site-specific management strategies are needed, and future monitoring should focus on broader spatial coverage.