Field trial of an automated batch chlorinator system at two shared shallow tubewells among camps for forcibly displaced Myanmar nationals (FDMN) in Cox's Bazar, Bangladesh

Abstract Background: There are considerable benefits of point-of-use water chlorination programmes in emergencies but remaining challenges include lack of standard dosing recommendations for water treatment, inappropriate chlorination technologies, and limited published evaluations. We conducted a small-scale before-and-after field trial to assess the accuracy and consistency of an automated chlorinator named Zimba in camps housing forcibly displaced Myanmar nationals (FDMN), Cox's Bazar. Methods: From August-September 2018, we selected two shallow tubewells [one with high (6.5 mg/L) and one with low (1.5 mg/L) iron concentration), and enrolled 20 households (10 having access to each tubewell) to participate in household surveys and water sampling. At baseline, field-team tested tubewell, and household stored water for iron, turbidity, free and total chlorine from using digital field-test kits. At baseline, the team collected water samples from selected tubewells (N=2), from Zimba chlorinators immediately after chlorination. (N=8) and household stored drinking water (N=20). Over four weeks, they collected post-treated water stored in household vessels (N=84), and post-treated household stored water in a project provided safe storage container (N=15). Water samples were tested for E. coli. Results: At baseline, 12 (60%) samples of water stored in household vessels were contaminated with E. coli (mean log10 E. coli=0.62 MPN/100mL). After installing the Zimba, all water samples (100%) collected immediately after chlorination and project provided safe storage containers were free from E. coli, but 41% of post-treated water stored in household were contaminated with at least one E. coli/100mL. Log10 mean E. coli concentrations storage containers water stored in household vessels at baseline were similar to the post-treated water stored in the household vessels. E. coli concentrations were significantly lower in the project-provided safe storage containers [(log10 mean difference=0.92 MPN, 95% CI 0.59-1.14)] compared to baseline and to post-treated water stored in household vessels [(log10 mean difference=0.57 MPN, 95% CI 0.32-0.83)]. Conclusions: The Zimba is a potential water treatment technology for groundwater extracted through tubewells with different iron concentrations in humanitarian settings. Future research should address the low chlorine residual in household stored water and its impact on water contamination.