Anaerobic Detoxification of a Chemi-Thermomechanical Pulp Effluent by Two Acclimating Sludges

Abstract

Detoxification of a chemi-thermomechanical pulp effluent (CTMP) was examined by monitoring toxicity and resin acid concentration during treatment in batch reactors. Two treatments were carried out — one performed with an industrial granular sludge and the other with a municipal anaerobic digester sludge. The two sludges were acclimated to the CTMP effluent by successive 6-day suspended growth cycles on fresh effluent. In both cases, several growth cycles showed resin acid and toxicity increases, probably caused by resin acid desorption from bacterial cell walls to the aqueous phase. Detoxification of the effluent was achieved with both sludges during the last growth cycle. Since measurements were performed on filtered samples, the observed decreases of toxicity and resin acid concentration may be the result of bacterial degradation or of adsorption of toxic substances on particulate matter. Major increases of resin acid were associated with major toxicity increases within one given growth cycle.