Removal of Chromium From Effluents of Tanning Industries and its Reuse
Air and water are the basic needs of human being and other living entities on the earth. Tanning industry uses water and some chemicals and so creates environmental problems, depending basically on two principal sources, hide and water. The processes of tanning are based on chromium sulphate and vegetable treatment of hide. According to the national environment quality standards (NEQS) the effluent or disposed water should contain phenol less than 0.5 ppm, Cr<0.05 ppm, BOD 140-150, COD 800 and pH 8-8.5. Tanning produced effluents are of high organic, Cr, sulphates, chloride and other salts content. About 30-40 litres of water are used to process one Kg of raw hide into finished goods. Total installed capacity of hides and skins chrome tanning is 53.5 million square meter, earning a large amount of foreign exchange for our country. In the present work, seven tanning industries effluents from the suburbs of Multan City have been collected and analysed. The pH of the liquors have been found to vary from 2.72 to 4.4. and the constituent Cr have been found to be from zero to 8000 ppm from vegetable to chrome tanning industrial effluents studied. The stages Involved in tanning and treatment of the effluent water waste including chemical treatment of Cr has been described with a special reference to supported liquid membranes process for removal of chromium ions.