WET COFFEE PROCESSING EFFLUENT QUALITY AND ITS ENVIRONMENTAL INFLUENCE ON RIVER WATER: THE CASE OF KACHA BIRA AREA, SNNPR, ETHIOPIA

Abstract

This study was conducted at Kacha Bira district, SNNPR to assess the levels of physical water quality parameters of rivers water before and after receiving coffee wastewater, and coffee effluent discharged from wet coffee processing plants. Water samples for analysis were collected from three different rivers and coffee processing plants located along the banks of these rivers. The physical water quality parameters such as temperature, pH, electrical conductivity, turbidity, total dissolved solids and total suspended solids were examined by standard methods. Besides, same physical water quality parameters were analyzed from sand filtered wastewater. The mean results obtained from wet coffee processing plants were TSS (5386.2±6.57 mg/L), TDS (5693.2±33.8 mg/L), and turbidity (492.2±3.03 NTU). The minimum pH values at discharge points of effluent and at downstream were 3.99±0.15 and 4.12±0.25, respectively. One way analysis of variance (ANOVA) showed significant difference (p<0.05) for all examined physical water quality parameters at all sample sites. In all sample sites there were significant differences at p<0.05 level for the pair comparisons of group means with the exception of pH values at Ketalla site effluent discharged from the processing plant versus downstream. In sand filtered samples, turbidity was reduced by 39.97% and total suspended solids were also reduced by 36.91%, revealing its significance. After the effluent is released, the downstream water quality does not satisfy WHO standards set for drinking water quality. This could mainly be due to low pH values 4.12±0.25 to 5.43±0.40 and elevated turbidity 107.2±4.38 to 216.6±10.31 NTU in all sites. The high TSS values obtained for downstream ranging between 2428±4.24 and 3614.6±10.67 mg/L were above the permissible limit set by WHO for welfare of aquaculture due to possible adverse effect. The low pH values also restrict the same water from being used for irrigation purpose as the criterion set by FAO. However, sand filtration, which was implemented with a relative low cost, has altered the water quality bringing substantial improvement.