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.
