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Aspects of the chemistry of some persistent organic contaminants and their removal from river and wastewater

Liquid/liquid extraction, glass fibre and 3-0.05 µm filtration and SIM-GC/MS procedures were used to determine the levels of free and particle bound resin acids in Tarawera River water samples collected at the State Highway 30 bridge, downstream of the discharge point of the Tasman and Carter-Holt-Harvey Tissue pulp mills. Typically, 78-80% of the recoverable resin acids and resin neutrals were found to be associated with particulate matter. Addition of 0.1% sodium azide at the time of collection was found to inhibit the biodegradation of resin acids in Tarawera River water samples for periods of up to 90 days. In the absence of sodium azide the biodegradation of resin acids in Tawawera River water samples stored in glass winchesters at 4°C proceeded with a half-life of ca. 19 days. Analyses of the upper and lower zones of sodium azide stabilised Tarawera River water samples which were allowed to stand undistributed for 30 days water showed that partial settling of resin acid carrying particulate matter occurred on standing. An experiment performed using a bulk 19.6 L sample of sodium azide stabilised Tarawera River showed, that after the progressive withdrawal of analytical samples over a 30 days period, there was a 300% increase in the level of resin acids remaining in the residual 1.6 L water sample. Provided that well mixed, sodium azide stabilised Tarawera River water samples were extracted and analysed together, total resin acids levels exhibited a coefficient of variation (CV) (for 5 or 6 replicates) of less than 7%. Prior filtration through sintered glass to remove gross particulate matter further reduced the CV to 4%. These CVs are appreciably smaller than those previously determined for unstabilised Tarawera River water samples. Filtration experiments performed using Whatman No.1, glass fibre, 0.8, and 0.45 µm filter papers, followed by liquid/liquid extraction of filtrates and Soxhlet extraction of dried filter papers, showed that for Tarawera River water samples, typically 11, 36, 34, and 47% of the recoverable resin acids were associated with particles of size greater than the pore size of Whatman No.1, glass fibre, 0.8 and 0.45 µm filter papers respectively. Similar results were obtained in sequential filtration experiments performed using glass fibre, 3, 0.8, 0.45, 0.2, and 0.05 µm filter papers and sodium azide stabilised Tarawera River water that had been stored for up to 90 days. Sequential filtration of water samples from Tasman’s clarifier and biological treatment ponds (ponds 1-4) showed that particle bound resin acid levels increased from ca. 5% (clarifier) to 70% (pond 4 outlet) during the passage of effluent water through the treatment system. During treatment, free pimaric acid and dehydroabietic acid levels fell substantially, while the bound levels were approximately constant. The level of free abietan-18-oic acid remained approximately constant in ponds 2, 3 and 4, while the level of particle bound abietan-18-oic acid in these ponds increased as levels of particle bound abiet-13-enoic acid decreased. Incubation of clarifier water for 31 days under aerobic conditions at 25°C, showed that very little degradation of resin acids present in the clarifier occurred. This result showed the clarifier water to be largely sterile. Glass fibre filtration of pond 1 water removed little resin acid and ca. 10% of the initial of 5 day biological oxygen demand (BOD₅). Since filtration removed the component BOD₅ that degraded slowly it was concluded that particulate BOD₅ degrades more slowly than free BOD₅ dehydroabietic acid (DHAA) group resin acids (= secodehydroabeitic acids 1 and 2, dehydroabietic acid, abietic acid and abiet-13-enoic acid), pimaric acid, and abietan-18-oic acid showed similar degradation kinetics irrespective of whether they were free or particle bound. Soluble BOD₅ degraded at approximately the same rate at which resin acids were degraded. The optimal doses of polyaluminium chloride (PAC) and polyferric sulfate (PFS), followed by Whatman No. 1 filtration, required to remove turbidity, colour and resin acids from Tarawera River water were found to be 60-70 mg/L (for PAC) and 20 mg/L (for PFS) respectively. Filtration of pond 1 water through 0.85 mm pumice reduced colour and resin acids by ca. 54-46%, whereas PFS flocculation followed by pumice filtration reduced resin acid, colour and BODs levels by 89, 89 and 88% respectively. These reductions are greater than those achieved for pond 1 water in the existing biological treatment system. Flocculation alone using 20 mg/L PFS removed most of the colour, turbidity and resin acids from pond 4 water samples. The finding that resin acids could be recovered from floes prompted the hypothesis that it might be possible to design an analytical technique based on pre-concentration by flocculation of the low levels of resin acids in massively diluted receiving water samples. 95-100% of expected resin acids levels were recovered in experiments performed using 5, 10 and 50-fold diluted Tarawera River water.
Type of thesis
Kanber, S. A. (2001). Aspects of the chemistry of some persistent organic contaminants and their removal from river and wastewater (Thesis, Doctor of Philosophy (PhD)). The University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/14265
The University of Waikato
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