Kinetics of Catalytic Thermal Pretreatment (Catalytic Thermolysis) of Distillery Wastewater and Bio-Digester Effluent of Alcohol Production Plant at Atmospheric Pressure

Abstract

This paper presents the kinetics of catalytic thermolysis of the sugarcane molasses based alcohol distillery wastewater coming out from distillation unit (distillery wastewater or DWW) and the biodigester (biodigester effluent or BDE) having high biochemical and chemical oxygen demand (BOD and COD). The effluents were thermally pretreated at 80-100°C and atmospheric pressure in the presence of various catalysts. The homogeneous copper sulphate and the heterogeneous metal oxide catalysts, such as CuO, MnO2-CeO2 and ZnO were used for the catalytic thermolysis. The CuO catalyst was found to be best amongst all the catalysts, giving 47% COD reduction, 68% colour reduction for DWW and 61% COD reduction, 78% colour reduction for BDE at 100°C using 4 kg m-3 catalyst loading in 12h. The experimental data on the catalytic thermolysis exhibit two clearly distinct COD reduction phases: the first phase being fast followed by the second phase which is a slower. Both the phases of the catalytic thermolysis are found to follow first order COD reduction kinetics. Catalytic thermolysis with 3 kg m-3 CuO at 100°C and atmospheric pressure shows about 1.6 and 1.5 times higher COD reductions in comparison to that without using a catalyst for the DWW and BDE, respectively.