Characterization and treatment of condensates generated from softwoods that have been radio-frequency/vacuum kiln dried

Three softwoods (Douglas-fir, western hemlock, and western redcedar) were subjected to radio-frequency/vacuum (RFN) drying and the condensates were characterized. These condensates were acidic, acutely toxic to Daphnia magna and Photobacterium phosphoreum (Microtox), and could contribute significantly to biological oxygen demand (BOD5). Therefore, the condensates could have a detrimental effect on receiving waters if discharged without prior treatment. Several abiotic treatment strategies were evaluated for their ability to reduce BOD5 and detoxify the three condensates. Treatments included pH adjustment, filtration, adsorption, and H202 oxidation. Sequential H202/anion exchange was the most effective means of treatment, removing 70 to 90 percent of the condensate BOD5 and chemical oxygen demand (COD), and detoxifying all three condensates. Detoxification was complete as assayed by Microtox. However, treated condensates were still slightly toxic toward Daphnia magna. The results of this study demonstrate RFN condensates can be physico-chemically treated to produce an effluent that has reduced BOD5 and acidity. Preliminary results also show that detoxification is possible by such treatments. However, further toxicity studies on fish are required to confirm this observation.

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