Impact Assessment of Biotreated Wastewater Effluent on Receiving Surface Water Quality

Rapid urbanization in tropical regions increases pressure on freshwater ecosystems through wastewater discharges. In Bujumbura (Burundi), treated effluent from the Buterere wastewater treatment plant (BWWTP) is discharged into the Kinyankonge River, which ultimately flows into Lake Tanganyika. This study evaluated spatial variations in turbidity, total organic carbon (TOC), ammonium, nitrate, and phosphate in the treated effluent, the Kinyankonge River, mixing zones, and the river-lake confluence. Results revealed marked variations among sampling sites. Turbidity and phosphate concentrations were the highest at the wastewater outlet, whereas high ammonium and TOC concentrations were observed downstream. Nitrate concentrations remained high throughout the study area, indicating persistent nitrogen inputs. These findings suggest that treated wastewater and other environmental sources contribute to water quality changes within the Kinyankonge River system before its discharge into Lake Tanganyika. Continuous monitoring and integrated watershed management are essential to minimize nutrient enrichment and protect the ecological integrity of receiving aquatic ecosystems. Furthermore, nutrient recovery strategies should be considered and implemented for their use in agriculture as green fertilizers.