REMOVAL OF COLOUR AND COD FROM DISTILLERY SPENT WASH BY ELECTRO-COAGULATION

Abstract

In 21 centaury the energy security is a major issue due to rapid depletion of fossil fuels. Amongst various efforts to meet the energy demand the application of ethanol as blending material with gasoline is very important. Although ethanol can be produced either from beet sugar or cane sugar, in India it is produced from cane sugar in distillery. This process produces around 10-15 L of wastewater per liter of alcohol production, which is acidic (3.9-4.3) in nature and contains high amount of COD (80000-1040000 mg 1 1 ), BOD (46 100-96000 mg Y') and appears dark reddish colour. An estimate shows that around 320 distilleries in India supposed to produce around 3.25 billion liters of alcohol and 40.4 billion liters of effluent per annum. Distillery wastewater contains high BOD and organic content, which is conventionally converted to methane by anaerobic treatment in a bio digester and approximately 60-65 % of total COD, is reduced. However, bio digester effluent still contains high amount of COD (40530-50000 mg 1 5, BOD (16200-20000 mg 1), colour etc., which needs further treatment before its discharge [1- 4]. Various treatment technologies are available for distillery wastewater treatment such as biomethanation followed by solar evaporation, bio-methanation followed by aerobic treatment followed by irrigation, bio-methanation followed by two stage aerobic treatment followed by tertiary treatment to surface water discharge and bio-methanation followed by evaporation, incineration followed by potassium recovery [5]. All the above processes are time consuming. Further, the BOD/COD ratio of bio digester effluent is very less in comparison to distillery wastewater and hence, biological treatment is not so effective. Thus, alternate option for the -* treatment of bio digester effluent is required and electro coagulation can be an alternative of those steps. Electro-coagulation is the treatment technologies in which the dissolve organic and inorganic compound is removed as floes with flow of electric current without use of any coagulant.