Risk-based cost-benefit analysis for evaluating microbial risk mitigation in a drinking water system.

Area of Science:

• Environmental Science
• Public Health
• Risk Management

Background:

• Waterborne gastrointestinal diseases incur significant societal costs.
• Holistic and transparent risk management is crucial for effective mitigation.
• Microbial risks in drinking water require robust assessment and management strategies.

Purpose of the Study:

• To investigate microbial risk mitigation measures in drinking water systems.
• To develop and apply a novel decision model integrating probabilistic risk assessment and cost-benefit analysis.
• To compare the effectiveness and economic viability of different risk mitigation alternatives.

Main Methods:

• Probabilistic risk assessment to estimate health effects in Quality-Adjusted Life Years (QALYs).
• Cost-benefit analysis to calculate the net present value of mitigation alternatives.
• Application of a risk-based decision model using Lake Vomb, Sweden as a case study.

Main Results:

• Only UV disinfection (Alternative A4) reduced infection risk below WHO guidelines (10^-4 per person per year) at the 95th percentile.
• All evaluated alternatives (A1-A4) yielded a negative net present value when only monetised benefits were considered.
• Including non-monetised benefits (e.g., environmental, property value) could result in a positive net present value under specific conditions (50th percentile, 1% discount rate).

Conclusions:

• The developed risk-based decision model offers a robust and transparent tool for microbial risk mitigation in drinking water systems.
• The model is flexible and adaptable to various local settings.
• Further refinement of health effect valuation, monetization, and uncertainty propagation is recommended to enhance the decision model.