ABSTRACT
High-rate anaerobic processes for wastewater treatment offer several advantages over conventional aerobic process. In anaerobic treatment, most of the energy in the waste can be recovered as methane. The microbial community involved in the anaerobic processing of complex organic matter such as sewage sludge has been divided into three groups. The fermentative bacteria breakdown complex substrates into short-chain fatty acids, H2 and CO2. Fatty acids longer than acetic acid, such as butyric and propionic acids, are oxidized to acetate by a second group of bacteria known as acetogenic bacteria. Hydrogen and CO2 are also formed by the group of bacteria. Finally, waste stabilization takes place when the methane-forming bacteria convert acetate and H2/CO2 into CH4 and CO2. Butyrate is a major intermediate compound in anaerobic processes. Its conversion to CH4 is carried out by acetogenisis followed by methanogenesis. The butyrate fed fluidized bed reactor consistently removed greater than 90% of the applied Chemical Oxygen Demand (COD) at specific loading rates.
