Wat. Res. Vol. 31. No. 4, pp. 825-831, 1997 © 1997Elsevier ScienceLtd Pergamon All rights reserved. Printedin Great Britain PII: S0043-1354(96)00307-7 0043-1354/97$17.00+ 0.0o TOXICITY REDUCTION AND REMOVAL OF DEHYDROABIETIC AND ABIETIC ACIDS IN A CONTINUOUS ANAEROBIC REACTOR A. PATOINE*, M. F. MANUEL, J. A. HAWARI and S. R. GUIOTt @ 'Biotechnology Research Institute, National Research Council, 6100 Royalmount Avenue, Montrral, Qurbec, Canada, H4P 2R2 (First received December 1995; accepted in revised form September 1996) Abstract--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 saspended 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). © 1997 Elsevier Science Ltd. All rights reserved Key words--anaerobic treatment, inhibition, resin acid, dehydroabietic acid, abietic acid, toxicity, Microtox INTRODUCTION pulp and paper effluents under continuous flow conditions do not report any inhibition of the sludge Resin acids are diterpenic substances found in pulp (Maat and Habets, 1987; Wilson et al., 1987; Frenette and paper mill efflttents in concentrations ranging et al., 1989; Winslow, 1989; Schnell et al., 1990; from 2 to 17 mg/L (Lavallre, 1991). They can, Kennedy et al., 1991; Kudo et al., 1991; Mermillod however, reach up to, 550 mg/L in more concentrated et al., 1992; Rintala and Lepisto, 1992). In addition, waters of chemi-thermomechanical pulping (CTMP) these studies indicate that the anaerobic treatment of processes (Habets and de Vegt, 1991). These acids are pulp and paper effluents under continuous flow responsible for most of the fish toxicity exhibited by results in the elimination of chemical oxygen demand pulp mill effluents (Rogers, 1973; Leach and Thakore, (COD) or the elimination of resin acids, although to 1976; Kovacs and Voss, 1992; Rowbottom et al., a lesser extent than in the aerobic treatment. 1992). Aerobic treatment of pulp and paper Nonetheless, two studies report indications of wastewaters has been successful in the elimination of anaerobic sludge inhibition under continuous flow resin acids or the detoxification of these effluents conditions. The first one (Sierra-Alvarez et al., 1990b) (Servizi and Gordon, 1986; Kantardjieffet al., 1990; reported a decrease in COD removal from a soda Habets and de Vegt, 1991; Gibbons et al., 1992; Liu pulping liquor. The authors attributed the sludge et al., 1993a). Batch studies show that methanogens, inhibition to resin acids, although the resin acid the bacteria that mineralize a few intermediate concentration was not specified. The second case of products such as formic and acetic acids along with sludge inhibition was reported by Habets and de Vegt hydrogen and carbon dioxide during the anaerobic (1991) and concerned an upflow anaerobic sludge bed treatment of organic matter, are easily inhibited by (UASB) reactor treating a pulp and paper effluent at resin acids (Field et al., 1988; Sierra-Alvarez and an average organic loading rate of 12 g COD/L/d. Lettinga, 1990; Sierra-Alvarez et al., 1990a). How- These authors suggested that local overloading of ever, many case studies of the anaerobic treatment of resin acids may have been the cause of the sludge inhibition. In contrast, Rintala and Lepisto (1992) *Present address: Uniw;rsit6de Montrral, Drpartement des observed no inhibition when treating a thermomech- sciences biologique% Montrral, Qurbec, Canada, H3C anical pulp whitewater at organic loading rates as 3J7. tAuthor to whom all correspondence should be addressed high as 81 g COD/L/d in a UASB reactor. However, [Fax: +1 5144966265]. NRC Paper #34540. these authors did not mention the resin acid 825