Methane fermentation of coastal mud sediment by a two-stage upflow anaerobic sludge blanket (UASB) reactor system

The removal of organic matter from a coastal mud sediment was carried out b y a methane fermentation process under anaerobic conditions. In a batch aci dogenic fermentation, the addition of vitamins containing thiamine, nicotin ic acid and biotin dramatically enhanced acetate production from the mud se diment (200 g wet wt l(-1) artificial sea water), yielding 77 mM acetate af ter 6 days, which corresponded to 77% of the organic matter in the mud sedi ment, measured on the basis of chemical oxygen demand. Thereafter, the two- fold diluted, post-acidogenic fermentation liquor (PAF liquor) was continuo usly treated at 2.4x original dilution rate day(-1) for 30 days, using an u pflow anaerobic sludge blanket methanogenic reactor containing the acclimat ed methanogenic sludge from the mud sediment. Acetate, 42 mM in the PAF liq uor, was converted to methane at a maximum methane production rate of 96 mm ol l(-1) day(-1); and 87.5% of the acetate and 88.7% of the total organic c arbon in the PAF liquor were removed. Moreover, an efficient treatment of t he mud sediment was carried out by a semi-continuous, two-stage reactor sys tem, where the culture broth was circulated between acidogenic and methanog enic reactors. This two-stage reactor system gave a stable operation at 4-d ay intervals for one treatment period, yielding 112 mmol methane from the w et mud in the PAF liquor (278 g l(-1)).