An evaluation of a bucket chlorination campaign during a cholera outbreak in rural Cameroon

Bucket chlorination (where workers stationed at water sources manually add chlorine solution to recipients' water containers during collection) is a common emergency response intervention with little evidence to support its effectiveness in preventing waterborne disease. We evaluated a bucket chlorination intervention implemented during a cholera outbreak by visiting 234 recipients' homes across five intervention villages to conduct an unannounced survey and test stored household drinking water for free chlorine residual (FCR). Overall, 89 per cent of survey respondents reported receiving bucket chlorination, and 80 per cent reported receiving the intervention in the previous 24 hours. However, only 8 per cent of stored household water samples that were reportedly treated only with bucket chlorination in the previous 24 hours had FCR ≥0.2 mg/l. Current international guidelines for bucket chlorination recommend an empirically derived dosage determined 30 minutes after chlorine addition, and do not account for water storage in the home. In controlled investigations we conducted, an initial FCR of 1.5 mg/l resulted in FCR ≥0.5 mg/l for 24 hours in representative household plastic and clay storage containers. To ensure reduction of the risk of waterborne disease, we recommend revising bucket chlorination protocols to recommend a chlorine dosage sufficient to maintain FCR ≥0.2 mg/l for 24 hours in recipients' household stored drinking water.