CHARACTERISTICS OF GRANULAR METHANOGENIC SLUDGE GROWN ON GLUCOSE IN A UASB REACTOR

The formation of granules grown on glucose in an upflow anaerobic sludge blanket (UASB) reactor was investigated. Total granular sludge concentration retained in the UASB reactor was 34.5 g MLSS/l (30.0 g MLVSS/l) during 240 d operation on glucose minimum medium with the supplementation of 1.07 g NaHCO3 per 1 g glucose. This realized a high-rate methanogenic fermentation of glucose of 17.6 g COD/l-reactor.d at 3.4 d-1 of space velocity. The granules formed were relatively small, ranging mainly from 0.4 to 0.5 mm, had a relatively low cell density of 0.0542-0.0560 g MLVSS/ml, and had low specific gravity (0.97-1.19) due to very low ash content (11-13%). Electron microscopic analysis showed that Methanothrix spp. appeared dominant over the granules. The specific metabolic activities of bacterial trophic groups were the highest for H-2 followed by glucose, acetate, and propionate.