INFLUENCE OF TREATED EFFLUENT FROM THE QUILOMOSSO WWTP (UIGE, ANGOLA) ON THE QUALITY OF THE BOLONGONZO RIVER BASED ON COD AND BOD INDICATORS

This study examined wastewater management in the city of Uige, focusing on the Quilomosso area, with the aim of assessing the effectiveness of the existing treatment system and the environmental impacts of effluent discharge into the Bolongonzo River. Analyses of parameters such as Biochemical Oxygen Demand (BOD?) and Chemical Oxygen Demand (COD) showed that at the inlet, average values were 470 mg/L for BOD? and 1558 mg/L for COD, which is expected due to the high pollutant loads in the raw water. After the decantation stage, at the decanter outlet, the parameters dropped to 5 mg/L for BOD? and 48 mg/L for COD, indicating significant efficiency in solid separation. Finally, at the point of discharge into the river, the measured values were 3 mg/L for BOD? and 41 mg/L for COD, both within the limits set by Angolas Presidential Decree 261/11. It was recognised that the final effluent disposal has a regulated impact but could be optimised to align with environmental sustainability principles. Based on these results, suggestions included improving maintenance of the treatment infrastructure and enhancing effluent quality monitoring.