Performance evaluation of a brewery wastewater treatment plant in Ethiopia: Implications for wetland ecosystem management

Abstract

Brewery industries are a major surface water pollution source since they release their waste waters into receiving aquatic systems. The Brasserieset Group Industry (BGI) located at the town of Kombolcha (Ethiopia) discharges large quantities of organically laden waste water into the Borkena River, a tributary to the Cheffa Wetland, one of Ethiopia's largest wetlands. As the efficiency of the brewery's wastewater treatment plant has not been assessed, there is no existing evidence regarding the compliance of its effluent discharges with standard discharge limits. The aim of the present study, therefore, was to evaluate the efficiency of the brewery wastewater treatment plant, as well as to assess the status of the effluent discharge compliance for the stated guidelines. Time-composite wastewater samples were collected from the treatment plant inlet and final outlet during February to March 2020. Pollutant removal efficiency was evaluated by determining the differences in the pollutant concentrations in the influent and effluent. The mean value of the treated brewery wastewater Biochemical Oxygen Demand was 23.3 ± 12.3 mg/L, Chemical Oxygen Demand was 111.9 ± 33.8 mg/L, total nitrogen (TN) was 92.4 ± 21 mg/L, total phosphorus (TP) was 12.8 ± 5.1 mg/L and nitrate nitrogen (NO₃-N) was 22.5 ± 5.2 mg/L. Although the brewery treatment plant removed large percentages of organic constituents such as BOD₅ (98.6%) and COD (96.7%), only small quantities of TP (49.8%), TN (19.9%) and NO₃-N (9.3%) were removed. As the treatment plant discharges did not meet the Ethiopian permissible limit standards for the critical parameters, deterioration of the downstream wetland and its resources is of serious concern. To better manage and conserve the Cheffa Wetland and its important ecosystem services, it is recommended that the industry improves its wastewater treatment efficiency.