Solar powered membrane bioreactor (MBR) treating wastewater for reuse at a hospital in Kampala, Uganda – Results of pilot-scale trials

Abstract

A robust and cost-effective pilot solar-powered membrane bioreactor (MBR) with downstream granular activated carbon (GAC) filter hospital wastewater treatment was developed for the Lubaga hospital in Kampala, Uganda. The MBR-GAC pilot included a 25 m² ultrafiltration (UF) module, a 100 kg GAC filter, 20 photovoltaic panels totaling 7 kW_p and a 3.55 kWh supercapacitor energy storage unit to produce non-potable and reusable water for toilet flushing, cleaning and irrigation. The pilot operated with 43% clean energy autonomy with grid and diesel generator backup for power outages of more than 1 hour. The MBR pilot produced an average flux of 10–15 L m^–2 h^–1 with 50% total organic carbon (TOC) removal. The nitrification, denitrification and filtration tanks were separated to achieve a nitrification of 80% and denitrification of 20%. The removal of typical hospital pharmaceutical residues that could not be reduced by the MBR increased to approximately 90% after the downstream GAC filter was upgraded. The removal efficiency of the GAC decreased to approximately 25% at 4,290 bed volume (BV). The significant increase of 75% in the removal efficiency of diclofenac in the MBR was attributed to the acclimation of the activated sludge. The quality of the treated wastewater from the pilot plant was sufficient for reuse by irrigation of the hospital garden, toilet flushing and cleaning. Finally, the study discussed ways to optimize the design and operation of the plant. The pilot is scalable to be replicated elsewhere and adapted in an efficient and cost-effective manner in sub-Saharan countries in Africa.