TOXICITY REDUCTION AND REMOVAL OF DEHYDROABIETIC AND ABIETIC ACIDS INA CONTINUOUS ANAEROBIC REACTOR

The inhibition of microorganisms in an upflow anaerobic sludge bed and filter reactor was evidenced by a sudden decrease in methane producti on, a decrease in the chemical oxygen demand elimination, and an incre ase in the acetate concentration of the treated effluent. The inhibiti on occurred after a cumulative loading of 3486 mg of resin acids (66% dehydroabietic acid and 34% abietic acid) on 10 g volatile suspended s olids of an anaerobic granular sludge. The acetoclastic methanogens we re the most inhibited group of bacteria following the reactor failure, while the activity of the hydrogenotrophic methanogens was not affect ed. During the phase of 9.5 mg/L/d of resin acid feeding, no resin aci ds were detected in the effluent; sorption of resin acids on the sludg e amounted to 6.6 mg/g volatile suspended solids. During the feeding p hase of 59 mg resin acids/L/d, the effluent showed an average resin ac id concentration of 19 mg/L; the toxicity was half that of the influen t (Microtox toxicity tests). (C) 1997 Elsevier Science Ltd.