Effect of organic loading rate on the performance of two-stage anaerobic digestion of the organic fraction of municipal solid waste (OFMSW)

Two-stage anaerobic digestion of the organic fraction of municipal solid waste (OFMSW) was carried out: hydrolysis and acidogenesis in a continuous anaerobic hydrolytic leach bed (AHLB) reactor loaded at different rates (B-v = 3.8-7 gVSS L-1 d(-1)) and methanogenesis of leachates, diluted with municipal wastewater in an upflow anaerobic sludge blanket (UASB) reactor at organic loading rates of 6.6-13 gCOD L-r(-1) d(-1). In the AHLB reactor, 51-76% and 58-71% volatile solids and chemical oxygen demand (COD) removal efficiencies were obtained. During the hydrolysis and acidogenesis phases, the effluents were at pH 4.93, the leachate had a volatile fatty acids concentration of 35 g/L and the biogas was composed only of CO2. The average methane production in the UASB in the load of 4.4 gVS L-1 d(-1) in the AHLB was 3.32 L-CH4 L-r(-1) d(-1) (y(CH4) = 80%), with COD removal efficiency of 95% and methane yield 279 LCH4 KgVS(OFMSW)(-1) (degraded).