Reliability and Maintenance Optimization for Water Treatment Infrastructure in Enugu State

Safe and reliable water supply is a constitutional obligation of Nigerian state governments, yet water treatment infrastructure in Enugu State, South East Nigeria, suffers from frequent breakdowns that disrupt supply to hundreds of thousands of urban residents. This study applies reliability engineering and maintenance optimization methods to evaluate and improve the operational performance of the Oji River Water Treatment Plant, a major supply facility for Enugu metropolis. Equipment failure data covering 30 months for six critical process units including intake pumps, sedimentation tanks, filter beds, and chlorination systems are analysed using Weibull distribution fitting to characterize failure behaviour. Reliability, hazard rate, and mean time between failures are computed for each unit. System-level reliability under series and parallel configurations is assessed using reliability block diagram analysis. Optimal preventive maintenance intervals minimizing total expected maintenance and failure costs are derived for each component. Results indicate that two process units are operating beyond their optimal maintenance intervals, significantly elevating failure risk. Implementing the recommended maintenance schedule is estimated to reduce unplanned downtime by 43 percent annually. The study also identifies two components where parallel redundancy would provide cost-effective reliability improvements. Recommendations include establishing a computerized maintenance management system and training plant engineers in reliability analysis. This research provides an actionable reliability improvement framework for aging water infrastructure across South East Nigeria. Keywords: reliability analysis, maintenance optimization, water treatment, Enugu State, Weibull distribution