Identification and analysis of extractable organic compounds present in pulp and paper mill effluent
The extractable organic compounds present in the effluent streams of a New Zealand pulp and paper mill have been investigated. Nearly 200 compounds were detected, of which 170 were identified. Most of the compounds are released during mill operations. Some of the compounds detected in treatment system samples arise from the degradation of the released compounds. The progress of black liquor spills through the treatment system can be monitored by measuring the levels of compounds such as 4-hydroxy-3-methoxybenzaldehyde and 4-hydroxy-3-methoxyacetophen- one. Similarly, α-terpineol can be used to assess turpentine losses through the treatment system. Chlorinated pinenes and terpineols were detected in the No. 2 bleach plant along with significant quantities of chlorinated analogues of aromatic compounds such as guaiacol, 4-hydroxy-3-methoxyacetophen- one and 4-hydroxy-3-methoxybenzoic acid. The ability of the biological treatment to degrade extractable organic substances was investigated with respect to 4-day and 8-day retention times. The 8-day system was found to be more effective than the 4-day system in removing aromatic compounds and 2- cyclopentenone derivatives. It also reduced the levels of resin acids and fatty acids. BOD₅ levels were found to decrease exponentially through the extended treatment system. An anaerobic sludge lagoon which accepts solid waste from the clarifier and reject pulp was found to give rise to a series of resin acids degradation products which were resistant to further degradation in the aerated treatment system. The sediments of the aerated ponds were found to include a series of polychlorinated compounds ranging from C₂ to C₆ units. Many of these compounds, which may be degradation products of chlorinated lignin, were tentatively identified from their mass spectral fragmentations. The sediments also contained high levels of monoterpene hydrocarbons. Compounds present in the final discharge from the treatment system to the Tarawera River were detected in down-stream water and sediments. The Tarawera River was found to have little assimilation capacity; resin acids together with some chlorinated compounds and fatty acids were found in river sediment samples taken six weeks after mill closure.
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