IDENTIFICATION OF WOOD AND BARK EXTRACTIVES AND THEIR TOXICOLOGICAL EFFECTS ON THE TMP EFFLUENTS

INTRODUCTIONThermomechanical pulp (TMP) mill effluents contain toxicants that may cause acute death of fish in a short term and/or affect long-term growth and reproduction of fish in receiving water. The toxicants in the effluents considerably vary with pulping processes and pulpwood species. The former effect is referred as acute toxicity, and the latter chronic or sublethal toxicity (Spinger, 2000). Unlike chemical pulping, TMP is produced through physically shredding wood chip…

IDENTIFICATION OF WOOD AND BARK EXTRACTIVES AND THEIR TOXICOLOGICAL EFFECTS ON THE TMP EFFLUENTS

Wood extractives in model TMP effluents and bio-treated TMP mill effluent were extracted, isolated with liquid-liquid extraction, and analyzed with GC/MS following sylilation. Acute and chronic toxicity of the effluent samples were tested with Ceriodaphnia dubia. Wood and bark extractives are responsible for the toxicity of the TMP effluent to aquatic life. Resin and fatty acids have a dominating contribution to acute toxicity. Removal of them from the effluent cannot deplete all toxicants, some neutral extractives such as phytosterols, are still chronically toxic to Ceriodaphnia dubia. Wood bark has a dramatic impact on acute toxicity of the TMP effluent. Only 5% of spruce bark addition can increase acute toxicity by 38.4%. However, it has a reverse trend for chronic toxicity, which indicates that some neutral wood extractives may play important role in chronic toxicity of the TMP effluent as well. Successful control of the debarking process and debark effluents is essential for achieving high-quality effluent treatment.