Sodium Hypochlorite Generation for Household Water Disinfection: a Case Study in Nepal

Low concentration (0.5-0.8%) sodium hypochlorite is a viable solution for point-of-use drinking water chlorination programs in Nepal, and it can be produced on a small-scale at a low cost using relatively cheap, safe, and robust generators, appropriate for developing country conditions. This thesis describes the set-up and the testing of a sodium hypochlorite generator in Kathmandu, at the laboratory of the Environmental and Public Health Organization, a Nepalese water research institute. The major technical and organizational factors for successful commissioning of a sodium hypochlorite generation program are identified. The 0.56% sodium hypochlorite solution produced by this generator showed an average decay rate of 230 mg/L (0.023%) per month over the first three and half months, if proper production and storage conditions are met. A higher decay rate (0.10% per month) resulted from accidental contamination with iron, by use of an iron spigot, subsequently replaced by a plastic spigot. Protection from iron contamination is essential to ensure sufficient shelf life to the solution. In addition, alkalinization of the solution is recommended to achieve a greater stability. Chlorine demand of tap water in Kathmandu was found to be about 0.5 mg/L and thus a sodium hypochlorite dose of three drops per liter (about 1.5 mIJL) proved adequate to provide a free residual chlorine level above 0.2 mg/L. However, further investigation of the actual chlorine demand in different seasons and in different areas of the country is suggested. Based on the outcome of such a survey, daily household sodium hypochlorite consumption may be estimated and appropriate re-design of the chlorine dispensing bottle and the dosing cap can be undertaken. A Business Plan for the marketing of a sodium hypochlorite water disinfectant complements the above technical assessment. The logical framework for establishing a micro-enterprise is presented, and marketing, distribution, and promotion strategies for approaching the three main market segments urban households, rural households and bulk hypochlorite solution customers are suggested. Production costs and alternative micro-enterprise structures are evaluated, with specific attention to the issue of the financial viability of the business. Finally, an integrated evaluation of the sustainability of sodium hypochlorite generation in Nepal is presented. Thesis Supervisor: Susan Murcott Title: Lecturer, Department of Civil and Environmental Engineering