Environmental Flows Risk Assessment of Effluent Outfalls from Conventional Wet Washed Coffee Refineries in Limu Kosa District of Southwestern Ethiopia

Abstract

The objective of this study was to assess the effects of recurrent effluent outfall from conventional wet washed coffee refineries (CWCR) on environmental flows (Eflows) based on the physicochemical parameters & benthos assemblages as biological indicators. The experiment was done using complete randomized design (CRD) with 3 composite replicates at each 24 sampling sites of 4 river water basins. Six sampling sites were selected for physico-chemical & 2 sampling sites were selected for benthos assemblages samples along each 4 river basin. Data analyses were performed by different statistical analyses such as analysis of variance (ANOVA) using SAS 9.2 and Minitab 16.0 software. Results of physicochemical parameters with biological revealed that there is highly significant effect between 4 Eflows & among 24 sites at (p<0.05). Characteristics of effluent outfall from CWCR has a BOD of up to 2993 mg/L and a COD of up to 2867 mg/L as well as the acidity of pH below 3. These results can lead to depletion of DO and a decrease in pH (due to fermentation of organic matter) may hamper the sustainability of water bodies, which can kill off virtually all aquatic life. Except pH and DO, the other physico-chemical parameters exhibited that they were negative correlation with benthos assemblages. The results suggest that Eflows status of DS2 were depredation by effluent outfall from the conventional wet coffee refineries as compared to UPS. Therefore, face urgent intervention in the area of coffee refinery for effluent management and well designed treatment technologies (lagoons) for coffee waste treatment is highly recommended.