The use of trace organics in anaerobic digestion

Earlier work has demonstrated that the addition of small quantities of some organic compounds can have a significant effect on the performance of the activated sludge process. This paper examines the effect of some of these t race organics on an anaerobic digester inhibited by gallic acid and by fluo ride ions. An anaerobic contact digester was operated with a 24 hour hydrau lic retention time and a starch-based feed. After the reactor had reached s teady state, the digestion was inhibited with gallic acid (10 mgl(-1)). Whe n glucose was added as a growth factor, at a concentration of 10 mgl(-1) th e inhibitory effects were largely reversed. Increasing the glucose concentr ation to 15 mgl(-1) improved the reversal effect only very slightly. The co ncept that glucose acted, in some way, through pyruvate was then tested by adding fluoride, which is known to prevent the formation of phospho-enol-py ruvate, to a gallic acid-inhibited/glucose counter-acted digester. This cau sed a reduction in the specific gas yield (19% of the control). The subsequ ent addition of pyruvate (20 mgl(-1)) largely reversed this inhibition.