Chlorine taste can increase simulated exposure to both fecal contamination and disinfection byproducts in water supplies.

Expanding drinking water chlorination could substantially reduce the burden of disease in low- and middle-income countries, but the taste of chlorinated water often impedes adoption. We developed a Monte Carlo simulation to estimate the effect of people's choice to accept or reject drinking water based on chlorine taste and their subsequent exposure to E. coli and trihalomethanes, a class of disinfection byproduct (DBP). The simulation used empirical data from Dhaka, Bangladesh, a megacity with endemic waterborne disease. We drew on published taste acceptability thresholds from Dhaka residents, measured residual chlorine and thermotolerant E. coli inactivation following the addition of six chlorine doses (0.25-3.0 mg/L as Cl2) to untreated piped water samples from 100 locations, and analyzed trihalomethane formation in 54 samples. A dose of 0.5 mg/L, 75% lower than the 2 mg/L dose typically recommended for household chlorination of low-turbidity waters, minimized overall exposure to E. coli. Doses of 1-2 mg/L maximized overall exposure to trihalomethanes. Accounting for chlorine taste aversion indicates that microbiological exposure increases and DBP exposure decreases above certain doses as a higher proportion of people reject chlorinated water in favor of untreated water. Taken together with findings from other modeling analyses, empirical studies, and field trials, our results suggest that taste acceptability should be a critical consideration in establishing chlorination dosing guidelines. Particularly when chlorination is first implemented in water supplies with low chlorine demand, lower doses than those generally recommended for household water treatment can help avoid taste-related objections while still meaningfully reducing contaminant exposure.

Effective Demand for In-Line Chlorination Bundled with Rental Housing in Dhaka, Bangladesh.

Delivering safe water in cities of lower- and middle-income countries remains elusive even where there is a piped supply. Passive, in-line chlorination upstream of the point of water collection reduces child diarrhea without the behavior change required for point-of-use water treatment products or manual chlorine dispensers. We conducted a price experiment to measure effective demand (willingness and ability to pay) for an in-line chlorination service using tablet chlorinators among 196 landlords of rental housing properties in Dhaka, Bangladesh. We offered a 12-month subscription using Becker-DeGroot-Marschak auctions with real money payments. The service consistently delivered chlorinated water and satisfied tenants. Landlords' effective demand for in-line chlorination was similar to or greater than that for point-of-use treatment products and manual chlorine dispensers previously documented among Dhaka households. Over the service period, landlords renting to low-income households had lower effective demand than those renting to middle-income households despite similar initial rates of payment across both groups. Making in-line chlorination financially viable for the lowest-income consumers would likely require service cost reductions, subsidies, or both. Our findings suggest that even revealed preference experiments may overestimate the effective demand needed to sustain water supply improvements, especially in low-income populations, if they only measure demand once.