The use of glucose as a growth factor to counteract inhibition in anaerobic digestion

The effect of adding gallic acid, an inhibitory compound, and mixtures of g allic acid and glucose to well mixed batch digesters and to a two-stage dig estion system was examined. The results of the batch studies showed that gl ucose (10 and 20 mg l(-1)) increased both the degradation of the gallic aci d and the rate at which this occurred. They also showed that gallic add alt ered the amounts of ten hydrolytic enzymes in the sludge. The addition of g lucose reversed this effect. The two-phase digester was operated with a hyd raulic retention time of 3 hours in the acidogenic stage and 10.5 hours in the methanogenic reactor. The results showed that there was little removal of gallic acid in the acidogenic reactor. At concentrations of 10 and 20mg l(-1), gallic acid had little effect on the methane production. However, at a concentration of 50 mg l(-1) there was a drop of about 15% in the volume of methane produced. The addition of glucose (15 mg l(-1)) reversed this e ffect. A similar set of results was obtained for the removal of soluble GOD . An effect of adding gallic acid was to increase the concentrations of but yrate and propionate. It is not yet known how glucose operates to counterac t these inhibitory effects.