Abstract
Effluents from the tannery industry have been a major source of environmental pollution. There is a need to evaluate the performance of wastewater treatment plant against regulatory standards. If in compliance found with standard, Employing appropriate treatment technique to meet the permissible discharge is important. In this reaction, performance evaluation of Tannery Wastewater and Treatment by coagulation technique of wastewater was investigated. Chemical oxygen demand (COD), Dissolved oxygen (DO), Total dissolved solids (TDS), Total suspended solids (TSS), chromium III and VI were the parameters selected to characterize the tannery waste water. From the characterization result of the factory effluent treatment plant it was found that; the factory effluent treatment plant meets the permissible discharge value in DO, Chromium III and VI. However, COD, TDS and TSS are far from the standards. Calcium polysulfide (CaSx) and ferrous sulphate (Fe(SO)<sub>4</sub>) were the chemicals used for coagulation purpose. Treatment of 500ml original tannery waste with 400mg iron sulphate and variable calcium polysulfide concentrations (one, two and four v/v %) was conducted and characterized. From characterization result, 400mg iron sulphate and 20ml of calcium polysulfide treatment yields water that full fill the standard of discharge limit except for COD. In addition, at this treatment the best closer value of COD (1340mg/l) to the standard value (250mg/l) was found.
Highlights
The leather industry is one of the major economic sectors, which the developing countries has given due consideration for the development
The wastewater characterization was evaluated by Chemical Oxygen Demand (COD), Dissolved Oxygen (DO), Chromium ions, Total Dissolved Solids (TDS), Total Suspended Solids (TSS); because these are the common waste water pollution parameters [11, 12] and even difficult to minimize their values by preliminary treatment plants [13]
The supernatants were taken for characterization of dissolved oxygen, chemical oxygen demand, chromium (III), chromium (VI), total suspended solids and total dissolved solids in Ethiopian Leather Industries Development Institute (ELIDI), Addis Ababa
Summary
The leather industry is one of the major economic sectors, which the developing countries has given due consideration for the development. There are 30 tanneries, which are operational in this sector employing about 6000 workers. The current production capacity based on 15 tanneries is estimated at 6,000,000 to 8,000 000 kilograms of hides and 20, 000, 000 to 25,000,000 skins [2]. The hides are processed up to wet blues, crust and finished leather. The wet blues and crust hides are produced for export and the remaining low quality are finished for local market in the form of garments uppers and linings [3]. In Ethiopia, the annual volume of liquid waste discharge from the 15 tanneries based on their annual production capacities is estimated to vary between 2,000,000 and 2,500,000 cubic meters [4]. Almost every tannery industry uses significant amounts of chemicals in the process of transforming animal hides into leather [5]. Tannery waste water contains a complex mixture of both organic and inorganic pollutants, which brings serious environmental impact on water
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