Comparison of the effectiveness of photon-based oxidation processes in a pilot falling film photoreactor

Progress on the exploitation of photon-based oxidation processes for the tr eatment and purification of water and wastewater could be achieved by combi ning the most effective oxidation processes with optimal reactor designs. I n this work, the effectiveness of six different photon-based processes on t he oxidation of a model organic pollutant-salicylic acid-was studied in a p ilot plans Falling film photoreactor designed for optimal light absorption. The photon-based processes studied were UVA-photocatalysis, UVA-photocatal ysis-peroxidation, UVC-photolysis, UVC-photolysis-peroxidation, UVC-photoca talysis-photolysis, and UVC-photocatalysis-photolysis-peroxidation. The eff ects of major process variables on each of these processes were examined. T he highest oxidation rates were obtained with concomitant photocatalysis, p hotolysis, and UV-peroxidation, The oxidation rates of salicylic acid obtai ned by this combined process were 1 order of magnitude higher than with UVA -photocatalysis alone, 2-fold higher than UVA-photocatalysis-peroxidation, and 3-fold higher than UVC-photolysis-peroxidation. In addition, a high deg ree of mineralization of salicylic acid was obtained. An economic analysis shows the cost of treatment by this combined process to he much lower than that of other processes, making this process a suitable photon-based oxidat ion technology for further development and commercialization.