An integrated sewerage optimization model for performance assessment of urban sewerage networks: a capacity, reliability and sustainability framework validated on Mwanza, Tanzania

ABSTRACT Sewerage networks in rapidly urbanizing cities are deteriorating under hydraulic overloading, structural failure, and escalating operational costs. The Integrated Sewerage Optimization Model (ISOM) was developed and applied to the Mwanza City sewerage network (62.86 km; January 2022–December 2025 operational monitoring period) using monthly operational data (across 48 monthly observations). About 26 variables were initially collected; 21 variables were retained after screening for significance and structural collinearity and were analyzed using descriptive statistics, Pearson correlation, principal component regression (PCR), and temporal split-sample validation. Peak wet weather flow exceeded design capacity by 33.8–45.8%. Three principal components explained 100% of predictor variance: PC1 (hydraulic-structural deterioration, 76.4%), PC2 (financial stress, 19.6%), and PC3 (rainfall and I/I, 4.0%). Temporal holdout validation on 2025 data confirmed satisfactory predictive accuracy (holdout R2 = 0.714; Nash–Sutcliffe efficiency = 0.714; percentage bias = 3.11%). Network performance index declined from 100.0% (2022) to 5.0% (2025). Priority interventions, within a proactive asset management framework, include hydraulic capacity expansion, mechanized sediment removal, and targeted pipe rehabilitation. The ISOM framework provides a validated, evidence-based rehabilitation-planning tool for data-constrained sewerage utilities in rapidly urbanizing sub-Saharan African cities, directly supporting SDG 6 monitoring and investment prioritization.