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Treatment of Tannery Wastewater Using Natural Coagulants

Tasneembano Kazi, Arjun Virupakshi

Tanning industry is one of the oldest industry which is highly complex and is characterized by high BOD, COD, suspended solids, settleable solids, sulphide, chloride and chromium. Untreated tannery effluents when discharged directly into the water bodies or into the open lands cause irreversible damage to the environment. Coagulation–flocculation is one of the most important physicochemical treatment steps employed in industrial wastewater treatment to reduce the suspended and colloidal materials responsible for turbidity of the wastewater. During the last decade, more interest has been given on the use of natural coagulants in treating industrial wastewater. Natural coagulants are, in general, used as point-of-use technology in less-developed communities, since they are relatively cost-effective compared to chemical coagulants. Also they can be easily processed in usable form and biodegradable Cicer arietinum, Moringa oleifera, and Cactus were used as locally available natural coagulants in this study to reduce turbidity and COD of tannery wastewater. The tests were carried out, using tannery wastewater with conventional jar test apparatus. Optimum dosage and optimum pH were determined. The optimum dosage of Cicer arietinum, Moringa oleifera, and Cactus were found as 0.1,0.3 and 0.2gm/500ml respectively. The optimum pH value with Cicer arietinum, Moringa oleifera, and Cactus was found to be 5.5, 4.5 and 5.5, respectively. In case of Cicer arietinum, Moringa oleifera, and Cactus maximum reduction in turbidity were found to be 81.20%, 82.02% and 78.54%, and maximum reduction in COD were found to be 90%, 83.33% and 75%, respectively. Among the natural coagulants used in this study maximum turbidity reduction of 82.02% and COD reduction of 90% was found with Moringa oleifera and Cicer aretinum, respectively.