Rapid-rate thermophilic, single-stage and two-phase methane fermentation of synfuel-industry wastewaters

Thermophilic (55 degreesC) anaerobic digestion of wastewaters from wet carb onization of Minnesota peat was conducted in a simple, upflow digester at a n HRT of one day to provide a methane yield of 0.20 SCM/kg VS added and a B OD5 reduction of 85%. Carbonization of Maine peat conducted for a much long er duration of thermal treatment produced recalcitrant and potentially toxi c end products that reduced the biodegradability of wastewaters. Methane fe rmentation of the Maine-peat wet-carbonization waste was inhibited at an HR T of one day in the single-stage digester. However, two-phase digestion wit h separate acid-phase fermentation to promote hydrolytic degradation of tox ic end products followed by separate methane fermentation at an HRT of 2 da ys exhibited a methane yield of 0.21 SCM/kg VS added and a BOD5 reduction o f 76 %. Volatile fatty acids profiles along the depths digesting cultures i ndicated that single-stage and two-phase digestion could be accomplished at one-half the reactor residence times tone day for single-stage and three d ays far two-phase) used in this research.