Despite the well-known potential and performance of combined biological and ozonation processes for wastewater treatment, only few full-scale applications are published. Beside the synergistic effects of such process combination, which lead to oxidation of recalcitrant and inhibitory compounds or intermediates by enhancement of their biodegradability, the key for raising applicability is the improvement of the ozonation efficiency. An overview about the history and progress of full-scale applications, which deals with combined ozonation and biological treatment is given. Recently more than 40 applications exist, but many of them are not published. Therefore, a couple of selected not yet published applications have been mentioned in this paper. Landfill leachate and industrial wastewater treatment were mostly applicated, while treatment of municial wastewater treatment plant (WWTP) effluents are of increasing interest due to several advantages such as disinfection, decolourisation and removal of persistent dissolved organic carbon (DOC) for water re-use and groundwater recharge.

This paper summarizes the potential options applying ozone for the improvement of effluents from wastewater treatment plants. A specific focus will be on the technical aspects of how to integrate ozone technique in existing or new conventional treatment plants. Additionally some large scale projects will be illustrated, where this technique is now in operation. The following aspects are of interest and are discussed: necessary ozone dose range (depends on application, water matrix and contaminants); required components of ozone systems (ozone generator, gas supply, reaction system, off-gas handling); process control, online measurement; potential parameters to be used for process control; design guidelines for the integration of ozone systems; and cost calculations.

Natural organic matter in drinking water is causing concern especially due to the formation of disinfection by-products (DBPs) by chlorine, as these are proven to have adverse health effects on consumers. In this research, humic acid was used as a source of dissolved organic carbon (DOC) in drinking water (up to 3mgL). The efficiency of DOC removal was studied by applying O, HO/O, HO/UV and O/UV advanced oxidation processes (AOPs) alone and combined with hybrid hydrodynamic cavitation (HC), generated by an orifice plate, as this technology recently shows promising potential for the treatment of water, containing recalcitrant organic substances. It was observed that the combined treatment by HC could significantly affect the performance of the applied AOPs, with as little as 3-9 passes through the cavitation generators. For O and HO dosages up to 2 and 4mgL, respectively, and UV dosage up to 300mJcm, HC enhanced DOC removal by 5-15% in all combinations, except for O/UV AOPs. Overall, the potential benefits of HC for DOC removal were emphasized for low ratio between applied oxidants to DOC and high UV absorbance of the sample. Investigated DBPs formation potentials require special attention for HO/UV AOPs and combinations with HC.

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