Laboratory, Pilot And Full Scale Investigations Of Catalytic Ozonation For Upgrading Drinking Water Quality

With the increasing concern on drinking water contamination problems and the advent of more stringent drinking water standards, it is essential to improve further the existing water treatment process. In order to enhance the ozonation process, this study investigated the combined process of catalytic ozonation and biological activated carbon (catalytic ozonation—BAC) through pilot and full scale studies.In the experiment, a novel catalyst was introduced into the ozonation contact tank to enhance the ozonation process. The pilot-scale (60t·d-1) and full-scale studies (30000t·d-1) were conducted with the typical surface waters with micropollution in Northern China and Eastern China and the major efforts focused on the effect of catalytic ozonation on improving the efficiency of ozonation performance, increasing the drinking water quality and safety. Special attention was paid to the effect of preoxidation on the performance of the following biological activated carbon process.The efficiency of catalytic ozonation was evaluated by measuring the ozone mass transfer and ozone utilization,·OH production, and the stability and life time of catalyst based on a long-term pilot-scale experiments. In lab-scale experiments, it was found that the observed·OH formation in the catalytic ozonation process was about 5 times more than the case of ozonation alone. It was shown that the presence of catalyst promoted the ozone mass transfer and increased ozone utilization efficiency through pilot-scale studies. The catalysts employed in this study had thermal stability, acid-base stability and mechanical stability, which could be observed through long-term operations.Most of the previous studies focused on improving the biodegradability of organics by ozonation to enhance the effectiveness of following water purification process but few efforts have been made to improve the ozonation process. A series of pilot-scale experiments had been performed to examine the efficiency of catalytic ozonation in removing various organic pollutants (especially environmental priority pollutants), reducing chlorinated disinfection by-products (DBPs) precursors and controlling ozonation by-products (Bromate and AOC) formation. Furthermore, umu test was adopted to evaluate the variation of effluent quality of ozonation process due to the introduction of catalyst. Considering the influence of the quality of influent, technical parameters of catalytic ozonation process were optimized to control organic pollutants, chlorinated disinfection by-products and bromate.In pilot-scale and full-scale studies, we explored the mechanism of pollutants removal by heterogeneous catalytic ozonation—BAC. It indicated that catalytic ozonation had positive influence on reducing the pollution load and improving the microorganism activity and the biodegradability of organics for the following BAC treatment. The introduction of catalysts increased the contaminants removal capacity of ozonation-BAC process by 110%~140%, it was also found that the life time of BAC was extended obviously.Pilot-scale and full-scale studies were also carried out to examine the performance of catalytic ozonation-BAC process in treating drinking water suffering from sudden pollution problem. The results suggested that catalytic ozonation can control not only the sudden organic pollution load but also the micro-particles and unexpected algae pollution that have penetrated the conventional treatment process. Moreover, catalytic ozonation could improve the drinking water safety when the performance of BAC was deteriorated.The effects of catalytic ozonation technology on the cost of drinking water treatment were evaluated with regard to the cost of catalysts and the efficiency of catalytic ozonation to establish a systematic method about economical and technical evaluation of catalytic ozoantion.