Using Economic Optimization to Derive Site-Specific Treatment Objectives

A procedure to estimate the economically efficient site- or system-specific treatment objective for enteric viruses in drinking water is presented. The health benefits of treatment are estimated using an existing quantitative microbiological risk assessment model for Rotavirus, which yields a reduction in burden of disease, measured in DALYs. The community’s willingness to pay for this reduced disease burden is then inferred using an estimate of the value of an avoided DALY from the literature. Economically efficient treatment occurs where the marginal cost of additional treatment equals the marginal benefit in terms of willingness to pay for avoided illness. In a case study on a small water system, capital and operating costs are estimated for four alternative treatment levels using commercially available UV disinfection systems. The case study results compare the economically efficient virus disinfection level, risk of infection, and burden of disease to international guidelines. A sensitivity analysis suggests that source water quality, population served, and the dose–response model are key inputs. Site-specific treatment objectives offer a viable alternative to prescribed national standards while respecting water safety and local autonomy.