Improved treatment of tannery wastewater treatment plant effluent using polymeric coagulants

This study examined the physico-chemical treatment of industrial tannery effluent from a wastewater treatment plant (WWTP) by coagulation with metal salts and polymers. Optimum dosage of coagulants like lime, alum, anionic polyelectrolyte (APE) and cationic polyelectrolyte (CPE) were studied in individual, combined dosage in lab and plant scale. Studies on dosage of seven different combinations were conducted with the primary settling tank influent. The optimum dosage of coagulants were found to be (alum – 650 ppm, lime – 800 ppm and CPE – 5 ppm). The percentage removal of turbidity, total suspended solids (TSS) and chemical oxygen demand (COD) were found to be in the range of 80–97%, 50–60%, 50–60%. The feasibility of using anionic and cationic polymers as coagulant aid with lime and alum were evaluated. Sludge production rate, cost of treatment and disposal, efficiency of different combination of metal salts and polyelectrolyte were studied. Treatment cost comparison studies were done for metal salts with polymers as coagulant aid and only for polymers as coagulants. The cost of sludge disposal remarkably reduced in the use of polymer alone as coagulant.