Photocatalytic Oxidation in Drinking Water Treatment Using Hypochlorite and Titanium Dioxide

The main focus of this thesis is to study the advanced oxidation processes (AOPs) of water pollutants via UV/hypochlorite (homogeneous AOPs), and UV solar light/TiO2 (heterogeneous AOPs) in which the highly oxidative hydroxyl radicals (\u95OH) are produced. These radicals are capable of destructing the emerging organic pollutants in water. The combined action of both \u95OH and Cl\u95 that are produced during the NaOCl/UV processes increased the chlorination potential of humic acids (HA). In addition, at a high free-radical dose, such as in swimming pool water recirculation systems, the equal levels of adsorbable organic halogens (AOX) and CHCl3 are formed with both low pressure (LP) and medium pressure (MP), respectively. CHCl3, once formed, is not degraded with either LP or MP. Moreover, the photo-degradation of HA in LPUV/NaOCl process is higher than that for the MPUV/NaOCl process, which results in a higher initial rate of AOX and CHCl3 formation. This raised the attention to the risk of using the LPUV/NaOCl process especially at the short reaction times that are relevant for water treatment. Based on the obtained results, a fixed-bed photocatalytic reactor can be applied for a small scale drinking water purification plants. This is mainly due to that TiO2 coated by the electrophoretic deposition technique on stainless steel woven meshes fitted in layers has major advantages over the commonly used flat-plate reactor and the dispersed-phase reactor. This presents a novel reactor in the oxidation of water contaminants such as humic acids and atrazine. Up-scaling of such reactors is feasible. It is worth to highlight that the results obtained has led to an improved understanding and applications of AOPs for water treatment. The findings can be used to improve the performance of both small and large scale water purification plants.Water ManagementCivil Engineering and Geoscience