HIGH BOD WASTE TREATMENT BY ANAEROBIC FILTER

Abstract

Industries use large volumes of water in producing finished products which inevitably results in waste streams being generated. Traditionally the industry has adhered to minimum cost production philosophy overlooking social responsibility to environment. The industry naturally questions investment in effluenttreatment and considers it as a non-productive activity„ The problem of treatment of high BOD wastes from distilleries, food processing have so far not found a suitable strategy. The conventional method o! treatment for high BOB waste is achieved by combining anaerobic processes (digestion and or lagooning) and aerobic processes(aerated lagoons, Activated sludge processes, oxidation ditches). Each of their has its own limitations. Digesters are promising units with methane recovery possible but skilled maintenance and prohibitive costs forbid their use. Lagoons are economical and easy operable units but have been found to pollute ground waters through percolation. In the present study the advantages of digesters and lagoons have been combined in an anaerobic filter. The anaerobic digestion of organic substances consists of three phases; (i) Hydrolysis of organic matter ii (ii) Acid producing phase (iii) Methane producing phase. Anaerobic digestion in a filter filled with a granular or plastic module material has been under study for about ten years by MacCarthy in U.S.A. Generally the suggested system uses immersed up-flow filters, that is, effluent flows from bottom to top, the use of very fine granules leads to rapid filter clogging. The active micro-organisms grow attached to the support material or as free floc in the interestices. Mean cell residence time (MCRT) of the order of 100 days could be obtained with short hydraulic retention time. This study presents the effect of hydraulic loadings on the decomposition of waste, the production of biogas and quality of biogas, The experiments were carried out at three hydraulic loadings, The degradation of waste for loading 3.717 kg/m3/d was better in comparison to other loadings. The quality -of gas was also good for this loading (the percentage of methane in biogas was good).