The worldwide appearance of toxic cyanobacterial blooms in drinking water supplies has raised concerns about systemic effects on human health. Conventional water treatment methods are poor at removing low concentrations of cyanotoxins, and specialized treatment is usually necessary for treatment of contaminated water. In this study, the applicability of heterogeneous photocatalytic degradation of low concentrations of the cyantoxin microcystin-LR in a natural organic-aqueous matrix is examined using titanium dioxide as the photocatalyst. The initial rate of toxin degradation is strongly pH dependent in a manner mirrored by the pH dependence of toxin adsorption to TiO 2 . Rapid degradation of toxin occurs in the acidic pH range in the presence of light and TiO 2 with a maximum initial rate of degradation occurring at pH 3.5, while at higher pH, a distinct lag is observed prior to commencement of toxin degradation. It is proposed that in the pH range where microcystin-LR adsorbs to TiO 2 , it is degraded principally by long-lived organic radicals generated through oxidation of adsorbed cyanobacterial exudate. At higher pH, where microcystin-LR adsorption to TiO 2 is insignificant, it is proposed that these organic radicals diffuse into solution and (after a lag) initiate oxidation of the toxin in dissolved phase.

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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.