A study was conducted to characterize Modjo tannery effluent (wastewater)
and determine its impact on the Modjo River using some physicochemical
parameters. Accordingly, three tannery wastewater samples along wastewater
channel at different distances have been taken and three river water samples
(one upstream and two downstream) were collected along the river to determine
its impact on the river. The samples have been analyzed for temperature, pH,
electrical conductivity (EC), total dissolved solids (TDS), total suspended
solid (TSS), chloride(Cl﹣), biological oxygen demand (BOD5),
chemical oxygen demand (COD), total ammonia (as
N), total nitrogen, total phosphorus and sulphide. The result of tannery wastewater showed that the values of temperature,
pH, EC, TDS, TSS, Cl﹣, BOD5, COD, total ammonia, total nitrogen, total phosphorus and sulphide along the
wastewater channel ranged from 26.97℃ to 24.93℃,
9.33 to 8.33, 15,670.00 to 14,496.67 mg·L﹣1, 9370.00 to 8723.33 mg·L﹣1, 4979.33 to 2647.67 mg·L﹣1, 6111.67 to 5555.78 mg·L﹣1 , 960.34 to 842.00 mg·L﹣1,
2011.00 to 1950.75 mg·L﹣1, 520.44 to 401.23 mg·L﹣1,
720.46 to 665.43 mg·L﹣1, 30.12 to 19.55 mg·L﹣1, 35.56 to
21.05 mg·L﹣1 respectively. And most of the effluent characteristics except pH and temperature were
beyond the provisional discharge limit of tannery effluent to water body set by
the Ethiopian Environmental Protection Authority (EEPA) and Federal Environmental
Protection Agency (FEPA). Analysis of variance (ANOVA) also showed that
variation among sampling points was statistically significant (p < 0.5). Similarly the levels of all
these physicochemical parameters in the downstream site of the river were
higher as compared to the values obtained from the upstream site (control). This
indicated that the downstream site of the river was polluted as the result of
the direct discharge of the tannery effluent to it.