Anaerobic digestion of kitchen wastes in a single-phased anaerobic sequencing batch reactor（ASBR） with gas-phased absorb of CO2

The performance of the single-stage anaerobic digestion of kitchen wastes was investigated in an anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO2. The ASBR was operated at four chemical oxygen demand(COD) loading rates, 2.8,5.1, 6.2 and 8.4 g/( L· d) respectively. The COD loading rate was increased with the TS concentration and HRT changing. At maximum COD loading rate of 8.4 g/( L· d), the COD, total solid (TS) removal rate and methane gas yield were 69 %, 68 % and 2.5 L/( L. d) respectively, The operation of the reactor with gas-phased absorb of CO2 was stable in spite of the low pH(2,6--3,9) and high concentration of TS( 142 g/L) of input mixture. The output volatile fatty acid (VFA) concentration was between 2.7--4.7 g/L and had no inhibition on the methanogenic microorganism. The reactor without gas-phased absorb of CO2 became acidified when the total COD loading rate was increased to 5.1 g/( L· d). Stoichiometry of the methanogenesis for kitchen wastes showed a considerable amount of alkaline will be required to keep pH in the appropriate range for the methanogenic microorganism based on theoretical calculation. Gasphased absorb of CO2 effectively reduced the alkaline consumption, hence avoided excessive cation into the reactor.