Economic Valuation for Cost–Benefit Analysis of Health Risk Reduction in Drinking Water Systems

Microbial risk mitigation measures in drinking water systems aiming at preventing gastrointestinal disease can provide substantial societal health benefits if implemented properly. However, the procedure of including and monetising the health benefits in cost–benefit analysis (CBA) has been somewhat scattered and inconsistent in the literature, and there is a need for a comparison of available methods. First, through a literature review, we identified the methods to include health benefits in decision support and to monetise these benefits in CBA. Second, we applied the identified health valuation methods in a case study. In the case study, we investigated if changing the health valuation method could change the rank order of the decision alternatives’ net present values. In the case study a risk-based decision model that combined quantitative microbial risk assessment and CBA was used. Seven health valuation methods were identified, each of them including different aspects of health benefits. The results of the case study showed that the choice of the health valuation method can change the rank order of decision alternatives with respect to their net present values. These results highlight the importance of choosing an appropriate health valuation method for the specific application. Although this study focused on the drinking water context, the identified health valuation methods can be applied in any decision support context, provided that input in terms of the health risk reduction is available

Mechanistic, mechanistic-based empirical, and continuum-based concepts and models for the transport of polyelectrolyte-modified nanoscale zerovalent iron (NZVI) in saturated porous media

Controlled emplacement of polyelectrolyte-modified NZVI at a high particle concentration (1–10 g/L) is needed for effective in situ subsurface remediation. For this reason, a modeling tool capable of predicting polyelectrolyte-modified NZVI transport is imperative. However, the deep bed filtration theory is invalid for this purpose because several phenomena governing the transport of polyelectrolyte-modified NZVI in saturated porous media, including detachment, particle agglomeration, straining, and porous media ripening, violate the fundamental assumption of such a classical theory. Thus, this chapter critically reviews the literature of each phenomenon with various kinds of nanoparticles with a special focus on polyelectrolyte-modified NZVI. Then, each phenomenon is elaborated using three kinds of mathematical models, including mechanistic (such as extended DLVO theory), mechanistic-based empirical (correlations to predict NZVI agglomeration and deposition), and continuum-based (Eulerian continuum-based models). These proposed modeling tools can be applied at various scales from column experiments (1-D) to field-scaled operations (3-D) for designing NZVI injection and emplacement in the subsurface