Characteristics of Granular Methanogenic Sludge Grown on Different Substrates in an Upflow Anaerobic Sludge Blanket (UASB) Reactor

Abstract

Application of the UASB process has been expanding for anaerobic treatment of wastewaters. In UASB reactor, the self-granulated sludge is being naturally accumulated in a high concentration(e.g., 50 g/1). Generally, the granules consist not only of microorganisms but also of inorganic matters, and vary widely in physical, chemical, and microbiological characteristics, depending on liquid velocity/ seed sludge, chemical composition of wastewaters, and so on[l]. To elucidate such complex mechanisms of granule formation, it would be necessary to analyze firstly the granulation process in simple mixed-cultures in an anaerobic digestion system. The anaerobic digestion requires three functionally different trophic groups of bacteria: hydrolytic fermentative (acidogenic), syntrophic acetogenic, and methanogenic bacteria.