TREATMENT OF PAPER AND PULP MILL EFFLUENT BY COAGULATION

Abstract

This dissertation work deals with the removal of chemical oxygen demand (COD) and colour of paper mill effluent due to the chemical precipitation of dissolved solids using different coagulants (such as, aluminium chloride and poly aluminium chloride and copper sulphate). Stephenson et. al. (1994) found that alum based coagulant were effective in treating paper and mill effluent. Ganjidousta et. al. (1997) shown in his paper that polyelectrolyte were also effective. After treating with poly aluminium chloride, results were found as 82.85% COD removal and 91.81% colour removal corresponding to optimum pH of 5 and coagulant dose of 8 g/I. Aluminium chloride was examined for compairing it to PAC. At an optimum pH=4 and dose 7 g/I, it removed 75.5% COD and 83.18% colour. Thus PAC was found more suitable for Colour and COD removal in comparison to aluminium chloride. Garg et. al. (2005) has shown Copper sulfate as new coagulant in his paper. The results found, by using copper sulphate as coagulant, were very impressive. At an optimum pH of 6 and mass loading of 5 WI, 75% COD reduction and 75.96% colour reduction were obtained. It is very important in industrial operations to have such coagulated slurries which settle down quickly and the supernatant is therefore separated. So, the settling behavior of effluent treated with above coagulants was also studied. It was found that the aluminium chloride treated effluent settled faster in comparison to other two studied coagulants.