Improving the Solar Sludge Pasteurization Technology

This thesis presents the development and field evaluation of a low-cost, solar-powered sludge pasteurization system for decentralized sanitation in Sub-Saharan Africa. Building on a gravity-fed sludge transfer and heat-exchanger design, the study iterated through three solar water heater versions, tested at Rurri Primary School in Nakuru, Kenya, under peak summer solar irradiance. Continuous temperature and irradiance monitoring enabled time-temperature analysis against literature-based pathogen inactivation thresholds. The final configuration reliably achieved Escherichia coli inactivation across all treated samples while sustaining a treatment flow rate of approximately 3 L/h, at a potential cost as low as 405 USD. Residual heat loss at the cold sludge inlet and overnight temperature decline were identified as remaining limitations, with further work needed on thermal retention, climatic robustness, and automated flow control.