Development of high rate anaerobic digestion treating organic solid waste for methane-energy recovery

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The aim of this study is to expand a technology of anaerobic digestion for treatment of organic solid waste such as activated sludge in sewage treatment system in order to enhance efficiency of methane gas recovery as energy. For making the efficiency bigger it was thought that biomass concentration in anaerobic digestion reactor should be increased. To investigate the biomass concentration effect a batch experiment, in which some materials supporting biofilm were installed, was conducted with activated sludge as substrate. The result indicated that biofilm having high biomass concentration could not promote biodegradation of solid waste. Tnen we examined amylase in an anaerobic digestion vial because hydrolysis enzyme was thought to play a crucial role. From the measurement of amylase we found a very important phenomenon that amylase was not released into bulk liquid as extra-cellar enzyme but it would be linked to cell membrane. This suggests that even though biomass concentration is high, hydrolysis of solid waste does not become proceed without concents of the solid waste and microorganisms. Therefore ozone treatment of solid waste was applied before fermented to improve the efficiency of methane recovery. The result revealed that the ozone treatment was effective for the hydrolysis of the solid waste and would be economically feasible. It is important for having a good idea of anaerobic digestion enhancement to understand satisfactory microbial community retained in the reactor. To analyze the microbial community molecular techniques were used. We also isolated several key novel anaerobic syntrophic bacteria and investigated these characteristics. From these results the structure and function of the microbial consortia were understood approximately half.