Coagulation/Flocculation of Tannery Wastewater Using Immobilized Chemical Coagulants

Abstract

Chemical coagulants were immobilized into bead form using sodium alginate to treat tannery wastewater samples. The used chemical coagulants were ammonium aluminium sulphate (NH4Al(SO4)2), aluminium sulphate (Al2(SO4)2, calcium carbonate (CaCO3), sodium citrate (Na3C6HsO7). The effect of the chemical coagulant dose and tannery wastewater pH was studied on wastewater electrical conductance (EC), total dissolved solids (TDS), sulphates, chlorides, phenolphthalein alkalinity, total alkalinity and chemical oxygen demand (COD). The quantity of various pollutants present in waste water was reduced after treatment. The optimized dose and pH for maximum decrease in EC and TDS were 5g/L and 7, respectively. The maximum reduction in the amount of sulphates and chlorides present in tannery wastewater was observed at dosage of 0.5g/L and pH 7. A dosage of 5g/L and pH 7 was also found most favorable for maximum reduction in values of COD, phenolphtalein and total alkalinity. The chromium concentrations in tannery wastewater before and after treatment were determined by atomic absorption spectrophotometer. A reduction in chromium concentration was observed after  treatment. The promising results of the present study demonstrate that immobilization of chemical coagulants can make them more effective for wastewater treatment.