Field efficacy evaluation and post-treatment contamination risk assessment of an ultraviolet disinfection and safe storage system

Abstract

Inconsistent use of household water treatment and safe storage (HWTS) systems reduces their potential health benefits. Ultraviolet (UV) disinfection is more convenient than some existing HWTS systems, but it does not provide post-treatment residual disinfectant, which could leave drinking water vulnerable to recontamination. In this paper, using as-treated analyses, we report on the field efficacy of a UV disinfection system at improving household drinking water quality in rural Mexico. We further assess the risk of post-treatment contamination from the UV system, and develop a process-based model to better understand household risk factors for recontamination. This study was part of a larger cluster-randomized stepped wedge trial, and the results complement previously published population-level results of the intervention on diarrheal prevalence and water quality. Based on the presence of Escherichia coli (proportion of households with ≥ 1 E. coli/100 mL), we estimated a risk difference of -28.0% (95% confidence interval (CI): -33.9%, -22.1%) when comparing intervention to control households; -38.6% (CI: -48.9%, -28.2%) when comparing post- and pre-intervention results; and -37.1% (CI: -45.2%, -28.9%) when comparing UV disinfected water to alternatives within the household. We found substantial increases in post-treatment E. coli contamination when comparing samples from the UV system effluent (5.0%) to samples taken from the storage container (21.1%) and drinking glasses (26.0%). We found that improved household infrastructure, additional extractions from the storage container, additional time from when the storage container was filled, and increased experience of the UV system operator were associated with reductions in post-treatment contamination. Our results suggest that the UV system is efficacious at improving household water quality when used as intended. Promoting safe storage habits is essential for an effective UV system dissemination. The drinking glass appears to represent a small but significant source of recontamination that is likely to impact all HWTS systems.

Optimizing household survey methods to monitor the Sustainable Development Goals targets 6.1 and 6.2 on drinking water, sanitation and hygiene: A mixed-methods field-test in Belize

“…The study found that drinking water consumed in the household was somewhat more likely to be contaminated than water collected at the source, similar to other studies of contamination of drinking water after collection from the main source [ 28 , 29 ]. It also highlights that the proportion of population using sources which meet the new SDG criteria for ‘safely managed’ drinking water is likely to be substantially lower than estimates based on the old MDG indicators [ 30 ].…”

Safe Drinking Water for Low-Income Regions

“…An RCT of a SODIS intervention in Cambodia found the mean incidence rate ratio for nondysentery diarrhea to be 0.38 (63). A cluster randomized trial of an in-home UV tube system in rural Mexico showed significant declines in E. coli in treatment compared to control households (43); however, a companion study found no effect on diarrhea from the same intervention, possibly because the baseline incidence rates were already low (64).…”

“…Household models using UV tubes are viable only for middle-income regions; the full cost in 2008 was $50 (50) for a locally manufactured device in Mexico. Finally, there is limited evidence that stand-alone safe storage is a cost-effective intervention (e.g., 36,43).…”

Field evaluation of a novel UV water disinfection system for use in underserved rural communities

“…In recent years, a number of studies have been performed to investigate various aspects related to the use of UV disinfection in underserved communities (Anon., ; Brownell et al., ; Lui et al., ; Reygadas, Gruber, Ray, & Nelson, ; Sun, Liu, Cui, & Liu, ). Vidal et al.…”