Methanosaeta dominate acetoclastic methanogenesis during high-rate methane production in anaerobic reactors treating distillery wastewaters

BACKGROUND: Anaerobic treatment of vinasses wastewater can result in high methane production rates, which depends on the ability to maintain a high specific methanogenic activity in the reactor. Here, it was investigated whether methane production could be increased by optimizing (1) temperature and (2) organic loading rate. It was expected that by maintaining high residual acetate concentrations, due to systematic overloading, anaerobic sludge with higher methanogenic activity would develop. RESULTS: A pilot-scale experiment of 180 days showed that Methanosarcina were unable to dominate acetoclastic methanogenesis in an upflow anaerobic sludge bed (UASB) reactor, despite the favorable conditions. This could be attributed to their reduced tendency to incorporate into sludge granules. Conversion rates of 40 to 50 kg COD m(-3) d(-1) were obtained for vinasses in mesophilic UASB reactors. CONCLUSION: These high methane production rates open the possibility to achieve electricity production of more than 2 kW m(-3) reactor, with concomitant economic perspectives. (C) 2013 Society of Chemical Industry