Development and Performance Evaluation of Modular Rainwater Harvesting and Treatment Systems for Non-Potable Water Applications in Polytechnics in South-West Nigeria

Abstract

Polytechnics in South-West Nigeria struggle to meet non-potable water needs from unreliable mains or costly boreholes, although seasonal rainfall runs off rooftops unused. This study developed and evaluated a modular rainwater harvesting and treatment system for non-potable applications in polytechnics. A design-and-development approach combined a demand-and-resource assessment with construction and performance testing at a polytechnic site in Osun State. The system comprised rooftop capture, first-flush diversion, a treatment train (screening, sand filtration, activated carbon filtration and UV disinfection), storage and pumped distribution. Over eight weeks, mean water yield was 42.6 m³/week, equal to 64.2% of demand. Treated water met WHO and Nigerian standards for non-potable use, with turbidity reduced by 98.2% and total coliforms by 99.5%. The reliability index was 0.82 and system uptime 96.8%. Capital cost was ₦1,605,000, with a payback period of 3.2 years. Expert validation rated the system highly for functionality (3.60), water quality (3.80) and replicability (3.60). Modular rainwater harvesting and treatment systems are technically feasible, economically viable and practically valuable for institutional non-potable water supply in South-West Nigeria.