Abstract
An anaerobic reactor was used to treat cattle manure diluted with tap water to achieve a volatile solids content of 4.5%, and process performance and microbial population dynamics were followed as the operation temperature was raised from 55 to 65 degree C. Increasing the temperature to 65 degree C caused an instant drop in volumetric gas production and a change in the quality of biogas, and the levels of total volatile fatty acids increased. The concentrations of acetate, butyrate, and iso-butyrate increased steeply, while propionate concentrations increased slowly. The overall activity of methanogens was reduced at the higher temperature, and new microbial populations were established. The increase in temperature resulted in a significant decrease in the level of bacteria, followed by a significant increase in the level of archaea.