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Site-specific risk-based threshold (RBT) concentrations for sewage-associated markers in estuarine swimming waters
Warish Ahmed1, Mary E Schoen2, Jeffrey Soller2
1CSIRO Environment, Ecosciences Precinct, 41 Boggo Road, Dutton Park, QLD 4102, Australia.
The Science of the Total Environment
|April 14, 2024
Summary
This study developed risk-based thresholds for sewage markers in recreational waters using quantitative microbial risk assessment. Findings help identify high-risk contamination days for public health protection.
Area of Science:
- Environmental microbiology
- Water quality assessment
- Public health risk analysis
Background:
- Recreational estuarine waters (EW) pose health risks due to potential sewage contamination.
- Accurate risk assessment requires understanding the behavior of sewage-associated markers.
Purpose of the Study:
- Establish site-specific risk-based threshold (RBT) concentrations for key sewage markers in EW.
- Utilize quantitative microbial risk assessment (QMRA) to determine RBTs for various sewage aging scenarios.
- Inform risk management strategies for recreational water safety.
Main Methods:
- Applied QMRA to estimate RBT concentrations for Bacteroides HF183, Lachnospiraceae Lachno3, CrAssphage, and pepper mild mottle virus (PMMoV).
- Considered site-specific decay rates and human norovirus (HNoV) as a reference pathogen.
- Analyzed marker concentrations against RBTs to identify potential high-risk periods.
Main Results:
- RBT concentrations varied significantly based on marker type and sewage aging.
- HF183 showed rapid decay, while Lachno3 and CrAssphage were more stable; PMMoV RBT increased with aging.
- Human norovirus concentration was the most sensitive parameter in the QMRA model.
- Exceedances of RBTs were observed, indicating potential elevated risks on certain days.
Conclusions:
- Multiple sewage markers are essential for accurate risk prediction in EW.
- Site-specific RBTs aid in identifying high-risk contamination events.
- Optimizing sample concentration and using multiple markers are crucial for enhanced risk management in recreational waters.
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