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 ofachieving the required quality. Therefore, it is necessary to apply processes that in an efficient andeconomically justified way reach the necessary limits in order to discharge wastewater into therecipient. The process of photolysis represents the degradation of the starting pollutant practically towater and carbon dioxide. The whole process takes place under the action of a UV lamp that imitatedsolar irradiation. The process is environmentally justified since, unlike some other advancedoxidation processes - AOPs, there is no use of additional, hazardous, chemicals which possibly resultsin the precipitates formation that are leading to further treatment. In this paper, photolytic degradationof pesticide thiophanate methyl was performed in doubled wall quartz reactor equipped with athermoregulation 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 anaim to determine the concentration of xenobiotic. Complete degradation of present xenobiotics wasobtained after 240 min. With an aim to enhance the degradation process, hydrogen peroxide wasadded as a boosting agent which cause a shortening in demanded time (150 min) for completedegradation. Verification of the success of decomposition was confirmed by the obtained values ofchemical oxygen demand (COD), which reveal that the established system has a basis for realapplication in industrial or municipal wastewater.