Assessment of the effect of effluent discharge from coffee refineries on the quality of river water in Southwestern Ethiopia

Abstract

The ecohydrological quality of water resource of Ethiopia is declining at an alarming rate, resulting in severe environmental degradation. This study finds out the effects of effluent discharge from intensive coffee refineries on river water quality based on physicochemical parameters and benthos assemblages as biological indicators. The experiment was done using complete randomized design (CRD) with three composite replicates in each refinery and on 24 river water sampling sites selected from four rivers in Limu Kosa District. A total of 72 water samples were collected from six sites: (upstream site (UPS), influent (INF), effluent (EFF), entry point (ENP), downstream one (DS₁) and downstream two (DS₂) in four rivers. Data analysis was performed by analysis of variance (ANOVA) using statistical analysis software (SAS). Spearman’s median rank correlation among physicochemical and benthos assemblages as biological indicators of ecohydrological river water quality was characterized. Results reveal that there is a highly negatively significant difference in effect between the four rivers and 24 sites at p<0.05 and 0.01. The benthos assemblage communities of DS2 and UPS of the ecohydrological rivers were more influenced by the effluents. Quality of DS₂ was more adversely affected compared to UPS. The alteration in river water quality parameters was more pronounced during the peak of coffee refineries. The impact of private refineries on receiving water was more significant than that of government refineries. Therefore, urgent attention should be given to the coffee refinery for effluent management options to avoid further damage to the ecohydrological river water quality using well-designed treatment technologies.

Keywords: Biological indicators, benthos, ecohydrolological integrity, upstream downstream