From import dependence to on-site chlorination: techno-economic analysis of water disinfection options in Zambia
Zambia's water utilities import chlorine gas and high-test hypochlorite (HTH) for disinfection. The imports pose service reliability and governance risks, because utilities must maintain residual chlorination despite foreign-exchange shocks, long transport corridors, and periodic stockouts. This study evaluates whether on-site electrolytic chlorination (OSEC), producing sodium hypochlorite from salt and electricity, can provide a cost-effective substitution pathway and whether local salt resources support scale-up. Choma was selected because it combines two interconnected treatment plants (Munzuma and ZESCO), an 18 km trunk main to Kalundu Station, HTH use, and a network representative of small-to-medium utility systems in Zambia. The analysis combines 16 months of plant records, engineering sizing, a 15-year discounted cash-flow analysis (8% discount rate), sensitivity testing, and an assessment of chlorine gas, HTH, and OSEC-grade salt. Results show that OSEC is most viable when deployed at critical network nodes rather than widespread rollout: Kalundu-plus-ZESCO reduces annual disinfection cost by 49% compared with HTH use. Demand uncertainty and system sizing are the main risks. Substituting HTH at suitable plants creates demand for an OSEC-grade salt value chain, but use depends on impurity removal and quality assurance. The study contributes a transferable utility-industry framework for improving disinfectant reliability in import-exposed water sectors.