高温UASBリアクターにおける生物間相互作用とグラニュレーションにおよぼす温度の影響

抄録

Two identical scale of UASB reactors set at two different temperatures, i. e., at 55°C (Run 1) and at 65°C (Run 2), were used to investigate the effect of temperature on granulation and interaction of thermophilic anaerobes. When acetate was used a feed substrate to the reactors no granulation occurred in both experimental runs. Microscopic observation revealed that the predominant methanogen was Methanothrix in Run 1 while Methanobacterium existed to significant extent in Run 2. The acetate-utilizing methanogenic activities of these sludges increased with increasing temperature in the range from 55°C to 65°C. Because of the high hydrogenutilizing methanogenic activities of these acetate-grown sludges, it could be considered that the syntrophic association of acetate-oxidizing bacteria with hydrogenotrophic methanogens plays an important role for acetate-cleavage in thermophilic anaerobic sludge. Subsequently, the feed substrate was changed to the mixture of acetate and sucrose for the second experiment. Granules coated with filamentous bacteria and cocci-type bacteria were obtained in Run 1 and Run 2, respectively. Since the acetate-utilizing methanogenic activities of these granules were 4 to 5 times higher than those of the sludges cultivated on acetate only, these “coating bacteria” appeared to hold acetate consumers within the granules.