Micropollutant emissions from combined sewer overflows

Area of Science:

• Environmental Chemistry
• Water Quality Monitoring
• Environmental Science

Background:

• Combined sewer overflows (CSOs) are recognized as potential pathways for micropollutant release into aquatic environments.
• Existing data on the spectrum and concentration of micropollutants discharged via CSOs, particularly at a regional level, require further consolidation.

Purpose of the Study:

• To quantify event mean concentrations of diverse micropollutants (heavy metals, PAHs, pesticides, pharmaceuticals, etc.) at multiple CSO facilities in Bavaria, Germany.
• To assess the significance of CSOs as a source of micropollutant emissions compared to wastewater treatment plants.

Main Methods:

• An extensive monitoring program involving over 110 overflow events at 10 CSO facilities in Bavaria.
• Utilized large volume samplers for a harmonized approach to collect volume-proportional event composite samples.
• Analyzed concentrations of 12 heavy metals, 16 PAHs, 9 pesticides/biocides, 3 pharmaceuticals, 3 benzotriazoles, acesulfame, and DEHP.

Main Results:

• All analyzed substances were detected in CSO samples, with most quantified in over 80% of samples.
• Significant variability in substance concentrations was observed between events and sites, indicating distinct substance-specific patterns.
• CSOs were identified as crucial pollution sources, especially for ubiquitous, stormwater-transported pollutants like mercury (Hg) and PAHs, impacting surface water quality.

Conclusions:

• CSOs are confirmed as important contributors to micropollutant emissions and must be considered in environmental assessments.
• Understanding regional micropollutant concentrations from CSOs is essential for effective water resource management.
• Substance-specific source, pathway, and transport behavior differentiation is necessary for targeted pollution control strategies.