Optimization of alum recovery from water treatment sludge in Manafwa water treatment plant in Busoba sub county, Mbale district.
No Thumbnail Available
Date
2026-06-19
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Busitema University
Abstract
The generation of alum sludge from water treatment plants poses significant economic and environmental challenges, particularly in developing countries where disposal is largely unregulated and resource recovery is rarely practiced. This study aimed to optimize the recovery of alum from water treatment sludge at Manafwa Water Treatment Plant in eastern Uganda using acid leaching with sulphuric acid, evaluate the coagulant performance of the recovered alum against commercial alum, and assess the financial viability of implementing alum recovery at the plant. Alum sludge was characterized for physical and chemical properties, and recovery optimization was performed using Response Surface Methodology (RSM) with a Central Composite Design, varying acid concentration (0.5–2.5 M H₂SO₄) and pH (2–6), while temperature and contact time were held constant at 90°C and 60 minutes, respectively. Aluminium concentration was determined via Atomic Absorption Spectroscopy (AAS), and coagulation performance was evaluated through jar tests. The sludge exhibited high moisture content (95.8–97.6%), total suspended solids (71,300–106,470 mg/L), near-neutral pH (6.5–6.7), and total aluminium content of 6.8–8.5% by dry mass. RSM optimization identified optimal conditions of 2.17 M H₂SO₄ and pH 3.01, yielding a predicted recovery efficiency of 94.1% with a desirability score of 0.955. The recovered alum was off-white, had a pH of 3.2, and contained 9.4% aluminium by mass. Jar tests using dosages of 30–80 mg/L showed that recovered alum achieved turbidity removal efficiencies of 55–94%, compared to 63 99.6% for commercial alum at equivalent dosages, representing a performance gap of approximately 5%. Financial analysis revealed a Net Present Value of UGX 292,038,935 over 10 years at a 12% discount rate, a Profitability Index of 4.65, and a payback period of approximately 1 year and 3 months, confirming strong economic viability. In conclusion alum recovery from water treatment sludge is both technically feasible and financially attractive, with acid concentration and pH as the dominant control parameters. Further purification and pilot-scale validation are recommended.
Description
Dissertation
Keywords
Citation
Kwagala, J. (2026) Optimization of alum recovery from water treatment sludge in Manafwa water treatment plant in Busoba sub county, Mbale district. Busitema University. Unpublished Dissertation.