Abstract
The effect of temperature on the characteristics of substrate degradation and bacterial population in a single and two phase anaerobic digestion was investigated using anaerobic chemostat-type reactor fed with soluble starch as a substrate. Three series of reactors were used for investigation. One of the reactors was a single phase anaerobic reactor and two other series were two phase reactors. Temperature was decreased from 30°C to 20°C over 8 hours and thereafter maintained at 20°C in a single phase reactor and two phase anaerobic reactors. In the other methanogenic phase reactor, temperature was maintained at 30°C as a control. The degradation efficiency of the substrate decreased by about 4% after 5 days in a single phase anaerobic digester, about 20% after 7 days in the acidogenic reactor of two phase anaerobic digestion, but no significant impact was observed in methanogenesis. Steady state condition in a single phase anaerobic digestion was established after about 60 days, and in two phase anaerobic digestion, after about 30 and 60 days in acidogenesis and methanogenesis, respectively. The n-butyrate was accumulated most highly in the temperature stressed digester. The methanogenesis was not significantly affected by rapid temperature change in the acidogenesis of two phase anaerobic digestion in spite of significant effect observed in the acidogenesis. The rapid change in temperature did not have a significant impact on the acidogenic bacteria, home-acetogenic bacteria, acetate-consuming methanogenic bacteria and H2-consuming methanogenic bacteria in a single phase anaerobic digestion. In two phase anaerobic digestion, however, the number of acetate-consuming methanogenic bacteria significantly decreased, but no impact was observed in other bacteria enumerated.
