Environmental impacts of Sheba tannery (Ethiopia) effluents on the surrounding water bodies

Abstract

The levels of hexavalent chromium from direct and treated Sheba tannery effluents, downstream river and spring water samples and upstream river water samples were determined spectrophotometrically by the s-diphenylcarbazide method at 540 nm. Temporal and representative samples were collected from the untreated tannery effluent (S1), sedimentation pond (S2), chromium oxidation pond (S3), downstream river (S4), downstream spring (S5) and 5 kms upstream river (S6). The mean levels of hexavalent chromium in S1, S2, S3, S4, S5 and S6
were 10.54, 9.15, 7.82, 0.58, 0.54 and 0.015 mg/L, respectively. The levels of hexavalent chromium in the downstream river and spring water samples exceed the World Health Organization (WHO) permissible limit of
total chromium in drinking waters (0.05 mg/L) as opposed to the levels in the upstream waters. The increased concentrations of Cr(VI) in the water samples indicate the possible environmental pollution of the downstream
water bodies by the Sheba tannery effluents. In view of the toxicity and related environmental hazards, the levels of hexavalent chromium from the Sheba tannery effluents must be reduced to a permissible limit before
discharging into the down stream waters being used for domestic purposes by the nearby communities.