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This study concentrated on the biological treatment and post-ozonation of mature eucalypt kraft bleachery effluents. The objectives were to optimise reduction of priority pollutants such as AOX, chlorate, high molecular weight chromophores and toxicity while maintaining high COD/BOD removals. Biological treatment was adequately modelled with Monod kinetics, using biodegradable COD. Sludge yields were of the order 0.76 g biomass/g BCOD. Treatment was most effective (70% total COD reduction and 95% BOD5 reduction) with sludge ages over 20 days and F/M ratios 0.2-0.3. Biological treatment did not reduce total AOX nor colour but reduced chlorate by 63% in preliminary trials. A fungal isolate, Aspergillus.p2 reduced colour by 54% when supplemented with glucose. Ozonation as a tertiary treatment reduced AOX by 60% and colour decrease followed first-order kinetics with respect to ozone consumption.

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Physical, chemical and rheological properties of a polysaccharide produced by an isolate of Klebsiella oxytoca were characterized. Freeze dried samples of the polysaccharide were neutral and were completely soluble in water. Samples did not form gels even in the presence of salt treatments. The major monosaccharide constituents of the polysaccharide were rhamnose (37%, w/w) and glucose (34%, w/w). Residues of cellobiose were detected, suggesting that the polysaccharide had a cellulose backbone. The gum was more comparable to broth apparent viscosities of xanthan gum than to gellan gum. The K. oxytoca polysaccharide (KOP) produced high solution viscosity at low concentrations. At a gum concentration 0.5% (w/v), an apparent viscosity of 400 cP at 24 s -1 was obtained. Rheological behavior showed that the KOP formed non newtonian fluids, indicating that it is a pseudoplastic biopolymer. Although the KOP solutions displayed pseudoplastic behavior, increases in shearing time did not result in significant changes on the apparent viscosity. This indicated that the gum is neither thixotropic nor rheopectic. The conclusion reached about the potential application of the gum was that it could be suitable for use as a stabilizing or suspending agent rather than a gelling agent.