UVC irradiation-based water treatment

Advanced oxidation processes (AOPs) have widely been used in water and wastewater treatment. The AOPs are constantly improved with the aim of producing more energy-efficient and environmentally friendly technology for the growing need of the water treatment. In photochemical and photocatalytic AOPs, the sources of external radiation and novel photocatalytic materials are constantly developed. In addition, new applications and combinations of treatment processes emerge frequently.Within this thesis, novel UV light-emitting diodes (LEDs; 255, 269, and 276nm) and atomic layer deposited (ALD) TiO₂ were tested in aqueous phenol and salicylic acid treatment. UV LEDs were also used in studying the inactivation of Escherichia coli (E. coli). In addition, novel applications, i.e., water matrices, for selected AOP was examined. Limited number of studies exist using AOPs in treatment of the precoagulated surface waters, creosote-contaminated groundwater, and 1,2-dichloroethane (1,2-DCE) containing water (washing water from the plant manufacturing ion exchange resins). Therefore, conventional UV/H₂O₂ system was employed in the treatment of the kind of water matrices.UV LEDs (with H₂O₂) were found to be feasible but need further development due to the rather low radiation power. The applicability in E. coli deactivation was, however, considered to be competitive in comparison to other UV radiation sources. The TiO₂ films prepared by ALD were discovered to be useful in photocatalytic water treatment. Crystallinity affected to the photocatalytic properties of the TiO₂ films, i.e., the mixture of anatase and rutile was the most efficient in salicylic acid destruction. The UV/H₂O₂ treatment of different water matrices was successful in terms of total organic carbon (TOC) removal when precoagulated waters and groundwater was used. TOC removal from washing water was inefficient, but the target pollutant 1,2-DCE was more readily decomposed. Altogether, the novel materials and UV light sources tested were considered to be feasible alternatives for the conventional ones and the applications studied were mostly suitable for the selected AOP.