Removal of xenobiotics from wastewaters using photolysis under sun-light irradiation: experimental approach and process design

Abstract

Conventional wastewater treatment processes are increasingly difficult to fulfill strict standards of achieving the required quality. Therefore, it is necessary to apply processes that in an efficient and economically justified way reach the necessary limits in order to discharge wastewater into the recipient. The process of photolysis represents the degradation of the starting pollutant practically to water and carbon dioxide. The whole process takes place under the action of a UV lamp that imitated solar irradiation. The process is environmentally justified since, unlike some other advanced oxidation processes - AOPs, there is no use of additional, hazardous, chemicals which possibly results in the precipitates formation that are leading to further treatment. In this paper, photolytic degradation of pesticide thiophanate methyl was performed in doubled wall quartz reactor equipped with a thermoregulation system. Reaction was forced under Osram ULTRA VITALUX UV lamp (300W). Kinetics of photodecomposition process was followed by pseudo-first order. In certain time periods, specimens were sampled, filtered and monitored by UV spectrophotometer Shimadzu 1800 with an aim to determine the concentration of xenobiotic. Complete degradation of present xenobiotics was obtained after 240 min. With an aim to enhance the degradation process, hydrogen peroxide was added as a boosting agent which cause a shortening in demanded time (150 min) for complete degradation. Verification of the success of decomposition was confirmed by the obtained values of chemical oxygen demand (COD), which reveal that the established system has a basis for real application in industrial or municipal wastewater.