Chalmers University of Technology, Department of Architecture and Civil Engineering, SE-41296 Gothenburg, Sweden.
Chalmers University of Technology, Department of Architecture and Civil Engineering, SE-41296 Gothenburg, Sweden.
Water Res. 2018 Apr 1;132:111-123. doi: 10.1016/j.watres.2017.12.054. Epub 2017 Dec 27.
Waterborne outbreaks of gastrointestinal diseases can cause large costs to society. Risk management needs to be holistic and transparent in order to reduce these risks in an effective manner. Microbial risk mitigation measures in a drinking water system were investigated using a novel approach combining probabilistic risk assessment and cost-benefit analysis. Lake Vomb in Sweden was used to exemplify and illustrate the risk-based decision model. Four mitigation alternatives were compared, where the first three alternatives, A1-A3, represented connecting 25, 50 and 75%, respectively, of on-site wastewater treatment systems in the catchment to the municipal wastewater treatment plant. The fourth alternative, A4, represented installing a UV-disinfection unit in the drinking water treatment plant. Quantitative microbial risk assessment was used to estimate the positive health effects in terms of quality adjusted life years (QALYs), resulting from the four mitigation alternatives. The health benefits were monetised using a unit cost per QALY. For each mitigation alternative, the net present value of health and environmental benefits and investment, maintenance and running costs was calculated. The results showed that only A4 can reduce the risk (probability of infection) below the World Health Organization guidelines of 10 infections per person per year (looking at the 95th percentile). Furthermore, all alternatives resulted in a negative net present value. However, the net present value would be positive (looking at the 50 percentile using a 1% discount rate) if non-monetised benefits (e.g. increased property value divided evenly over the studied time horizon and reduced microbial risks posed to animals), estimated at 800-1200 SEK (€100-150) per connected on-site wastewater treatment system per year, were included. This risk-based decision model creates a robust and transparent decision support tool. It is flexible enough to be tailored and applied to local settings of drinking water systems. The model provides a clear and holistic structure for decisions related to microbial risk mitigation. To improve the decision model, we suggest to further develop the valuation and monetisation of health effects and to refine the propagation of uncertainties and variabilities between the included methods.
水传播胃肠道疾病暴发会给社会带来巨大成本。为了有效地降低这些风险，风险管理需要具有整体性和透明性。本研究采用概率风险评估和成本效益分析相结合的新方法，调查了饮用水系统中的微生物风险缓解措施。瑞典的 Vomb 湖被用来举例说明基于风险的决策模型。比较了四种缓解方案，其中前三个方案 A1-A3 分别代表将集水区内 25%、50%和 75%的现场废水处理系统连接到城市废水处理厂，第四个方案 A4 代表在饮用水处理厂安装紫外线消毒装置。定量微生物风险评估用于估计四种缓解方案在质量调整生命年（QALY）方面的积极健康效益。使用每 QALY 的单位成本对健康效益进行货币化。对于每种缓解方案，都计算了健康和环境效益以及投资、维护和运行成本的净现值。结果表明，只有 A4 可以将风险（感染概率）降低到世界卫生组织规定的每人每年 10 次感染以下（考虑 95%分位数）。此外，所有方案的净现值均为负。然而，如果包括非货币化效益（例如，在研究时间范围内均匀分配给受研究人群的增加的财产价值以及降低对动物的微生物风险），则净现值为正（在 50%分位数使用 1%的贴现率），估计为每年每个连接的现场废水处理系统 800-1200 瑞典克朗（100-150 欧元）。这种基于风险的决策模型创建了一个稳健透明的决策支持工具。它足够灵活，可以根据饮用水系统的具体情况进行定制和应用。该模型为与微生物风险缓解相关的决策提供了一个清晰全面的结构。为了改进决策模型，我们建议进一步开发健康效益的评估和货币化，并改进包括方法之间的不确定性和可变性的传播。
