Influence of operation conditions on methane production from swine wastewater treated by a self-agitation anaerobic reactor

This study aimed to evaluate both the feasibility of using ambient temperatures (15, 20 and 25 degrees C) in a self agitated anaerobic baffled reactor (SaABR) fed with swine wastewater, and the impact of decreasing the hydraulic retention time (HRT) down to 3 days. The highest specific methane yield (0.61 +/- 0.14 L/gVS(in)) and organics conversation efficiency (66% on TCOD basis) were attained by elevating temperature from 15 to 25 degrees C under an HRT of 10 days. Even though the highest volumetric methane yield (0.85 +/- 0.17 L/L/day) was registered during a 3-day HRT, the specific methane yield was lower as a result of volatile fatty acids accumulations (up to 790 +/- 39 mg/L). The dominant bacterium was Clostridium sensu stricto while Methanosaeta was the dominant archaea throughout all the conditions, indicating strong acetoclastic methanogenic activity under ambient temperatures. These results demonstrate that using ambient temperatures and short HRTs is a promising strategy to successfully treat wastewater with decreasing energetics entries. This can, thereby, increase the treatment capacity and enhance the methane yield during the anaerobic digestion process.