[Handmade devices for continuous delivery of hypochlorite for well disinfection during the cholera outbreak in Douala, Cameroon (2004)].

Well disinfection is generally recommended as an emergency response measure during cholera outbreaks. However few studies have been carried out to document chlorination techniques, prove the efficacy of chlorination, or determine how often disinfection should be performed. The purpose of this study was to test a handmade device for continuous chlorination, to measure the initial concentration of free residual chlorine, and monitor chlorine concentration to determine when renewal is necessary. Eighteen wells in 2 neighbors of Douala, Cameroon, i.e., 9 wells/neighborhood, were tested. Testing included daily measurement of water volume, pH, and residual chlorine for a period of two weeks after installing the handmade device composed of river sand and hypochlorite in a pre-perforated plastic bag that was renewed after disappearance of free residual chlorine. The maximum concentration of residual chlorine was reached after 1 day in 31 out of 36 chlorinations or 2 days in 5 out of 36. On day 4 the chlorine level was less than 0.2 mg/l in half of the wells. The chlorine concentration was higher in family than community wells. Notwithstanding feasibility and acceptability issues, the device allowed chlorination at effective nontoxic levels for 3 days. These findings open the possibility of developing devices allowing longer diffusion at lower cost for use within the framework of integrated cholera epidemic control programs.