Buffering municipal wastewater pollution using urban wetlands in sub-Saharan Africa: a case of Masaka municipality, Uganda

Abstract

In many sub-Saharan Africa municipalities and cities, wastewater is discharged with limited or no treatment at all, thus creating public and environmental health risks. This study assessed the performance of a conventional municipal wastewater treatment plant (WWTP), based on effluent pollution flux, in Masaka Municipality, Uganda. Also, the downstream pollution attenuation through a natural wetland was analysed to ascertain its role in buffering the WWTP performance deficits. Generally, there was deficiency in WWTP performance, with 100% failure over a five-year assessment period, for example, the mean effluent biochemical oxygen demand (BOD)₅ and chemical oxygen demand (COD) concentrations (mg l⁻¹) were found to be 316 ± 15 and 582 ± 28 compared with 50 and 100 maximum permissible environment discharge limits, respectively. Despite these deficits in WWTP performance, the wetland buffer effectively reduced pollutant loads for suspended solids (73%), organic matter (BOD₅, 88% and COD, 75%), nutrients (total nitrogen, 74% and total phosphorus, 83%) and pathogens (faecal coliforms, 99%). These findings underpin the challenge of managing municipal wastewater using centralized mechanical WWTPs in the region. However, the wetland buffer system demonstrated a critical role these ecosystems play in abating both pulse and intermittent pollution loads from urban environments of sub-Saharan Africa whose sanitation systems are defective and inadequate. Therefore, it was concluded that integrating wetland ecosystems in urban planning as natural landscape features to enhance municipal wastewater management and pollution control is paramount.

Keywords:

• municipal wastewater
• wastewater treatment plant
• pollution
• wetland buffer
• mass removal efficiency

Acknowledgements

National Water and Sewerage Corporation (NWSC), Uganda is sincerely appreciated for the technical support during the study. Special thanks to MSc students Mr Bunyanga Jackson and MS Nakijoba Marion (Makerere University) who participated in data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Austrian Development Corporation (ADC) under the OeAD–GmbH, Centre for International Cooperation & Mobility (ICM) grant (individual grant) awarded through the Austrian Agency for International Cooperation in Education and Research.