Removal of imidacloprid from wastewaters by ozonation and photo-ozonation

Sönmez, Büşra
The widespread occurrence of micropollutants in the receiving water bodies apparently shows that conventional wastewater treatment plants (WWTP) are not capable to remove these compounds. Imidacloprid (IMI), which is a specific pollutant and an insecticide, exceeded Environmental Quality Standards (EQS) value (0.14 µg/L, annual average) in several receiving water bodies of WWTPs in Yeşilırmak basin. With the aim of examining advanced treatment methods to meet EQS value and to achieve good surface water quality in Yeşilırmak basin, the removal of IMI from water and wastewaters by ozonation and O3/UV was comparatively studied for the first time. To this end, kinetic study under different pH, ozone doses, ozone gas flowrates, initial IMI concentration and wastewater matrices was sought. The higher pH was effective for IMI ozonation. The water matrix effect on IMI removal was more pronounced during ozonation, than during O3/UV. For all wastewater matrices, O3/UV led to the best results in terms of both IMI and degradation by-products’ elimination since production rate of OH• enhanced under UV irradiation. Within 10 min treatment, IMI removal efficiencies in Milli-Q water were 55% and 99.5% during ozonation and O3/UV, respectively. IMI degradation mechanism proved that it is an ozone-resistant pollutant and is mainly degraded by OH• via indirect mechanism. The second-order rate constants of IMI reacting with OH• calculated as 2.23×1011 and 9.08×1011 M-1s-1 during ozonation and O3/UV, respectively. The IMI degradation pathway showed that IMI lost NO2 and HNO2. In addition, similar by-products were determined after IMI treatment by ozonation and O3/UV.
Citation Formats
B. Sönmez, “Removal of imidacloprid from wastewaters by ozonation and photo-ozonation,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Environmental Engineering., Middle East Technical University, 2019.