Toxicity reduction and removal of dehydroabietic and abietic acids in a continuous anaerobic reactor

The inhibition of microorganisms in an upflow anaerobic sludge bed and filter reactor was evidenced by a sudden decrease in methane production, a decrease in the chemical oxygen demand elimination, and an increase in the acetate concentration of the treated effluent. The inhibition occurred after a cumulative loading of 3486 mg of resin acids (66% dehydroabietic acid and 34% abietic acid) on 10 g volatile suspended solids of an anaerobic granular sludge. The acetoclastic methanogens were the most inhibited group of bacteria following the reactor failure, while the activity of the hydrogenotrophic methanogens was not affected. During the phase of 9.5 mg/L/d of resin acid feeding, no resin acids were detected in the effluent; sorption of resin acids on the sludge amounted to 6.6 mg/g volatile suspended solids. During the feeding phase of 59 mg resin acids/L/d, the effluent showed an average resin acid concentration of 19 mg/L; the toxicity was half that of the influent (Microtox toxicity tests).