Accounting for Unexpected Risk Events in Drinking Water Systems

Abstract

Unexpected risk events in drinking water systems, such as heavy rain or manure spill accidents, can cause waterborne outbreaks of gastrointestinal disease. Using a scenario-based approach, these unexpected risk events were included in a risk-based decision model aimed at evaluating risk reduction alternatives. The decision model combined quantitative microbial risk assessment and cost–benefit analysis and investigated four risk reduction alternatives. Two drinking water systems were compared using the same set of risk reduction alternatives to illustrate the effect of unexpected risk events. The first drinking water system had a high pathogen base load and a high pathogen log10 reduction in the treatment plant, whereas the second drinking water system had a low pathogen base load and a low pathogen Log10 reduction in the treatment plant. Four risk reduction alternatives were evaluated on their social profitability: (A1) installation of pumps and back-up power supply, to remove combined sewer overflows; (A2) installation of UV treatment in the drinking water treatment plant; (A3) connection of 25% of the OWTSs in the catchment area to the WWTP; and (A4) a combination of A1–A3. Including the unexpected risk events changed the probability of a positive net present value for the analysed alternatives in the decision model and the alternative that is likely to have the highest net present value. The magnitude of the effect of unexpected risk events is dependent on the local preconditions in the drinking water system. For the first drinking water system, the unexpected risk events increase risk to a lesser extent compared to the second drinking water system. The main conclusion was that it is important to include unexpected risk events in decision models for evaluating microbial risk reduction, especially in a drinking water system with a low base load and a low pathogen log10 reduction in the drinking water treatment plant.

Multi-criteria decision analysis framework for engaging stakeholders in river pollution risk management

“…The choice of solid waste management as the stakeholders’ primary decision alternative aligns with its immediate practical importance, while the emphasis on education (stakeholders’ secondary choice to improve the uMsunduzi water quality) acknowledges the need for a sustainable, long-term solution. These results should guide the development of comprehensive BMPs that combine practical infrastructure improvements with educational initiatives 57 . Additionally, broadening the stakeholder base and refining the methodology through using workshops for stakeholder engagement could further enhance decision-making in this context.…”

Risk-Based Evaluation of Improvements in Drinking Water Treatment Using Cost-Benefit Analysis

“…The QMRA was set up in a similar way to that of Bergion, Lindhe, Sokolova, and Rosén [19,31] by assessing the health-related impact of the improved treatment at Kvarnagården DWTP, in a number of gained QALYs, using the incidence data for three reference pathogens Campylobacter, Norovirus, and Cryptosporidium (each pathogen represented their respective pathogen group in the corresponding order: bacteria, virus, and protozoa). The selection was based on the pathogens' low infection doses, their prevalence in Swedish waters, and their connection to previous waterborne disease outbreaks in Sweden [32,33].…”

An Optimal Maintenance and Replacement Strategy for Deteriorating Water Mains

“…As a matter of fact, unexpected water main breaks are very common in reality. A main reason is that water mains are buried underground, and thus, it is very difficult to inspect and monitor their service conditions nondestructively, non-disruptively, timely, and easily [2,3].…”