Adsorption and transformation of organic micropollutants in wastewater : New insights from 14C-labeling

Abstract: This thesis focuses on the removal of organic micropollutants and transformation products using ozone and activated carbon treatment processes. A combination of 14C-labeled and non-radiolabeled organic micropollutants was used to study aspects of micropollutant removal from novel perspectives. 14C-labeled ozone transformation products (OTPs) were generated by ozonation of 14C-labeled micropollutants and used to study the combined removal of OTPs via adsorption onto powdered activated carbon. A successive decrease in OTP adsorption was observed with increasing ozone doses, compared with adsorption of the parent compounds, suggesting that adsorption onto activated carbon alone is not viable for removing OTPs.14C-labeled micropollutants were also used to separate biological degradation (biodegradation) from adsorption in granular activated carbon (GAC) filters via the formation of 14CO2 from 14C-labeled moieties. It was shown that previously adsorbed diclofenac could be subsequently degraded, and the GAC biofilm demonstrated diclofenac biodegradation rates high enough for substantial diclofenac removal by GAC filters under typical operating conditions. The retention of micropollutants in GAC filters, by decoupling biological degradation time from hydraulic retention time, was then hypothesized to improve the conditions for biological degradation of certain micropollutants.Lastly, 14C-labeled micropollutants were used to examine the mineralization (14CO2 formation) of 14C-labeled moieties in organic micropollutants during ozonation. Based on 14CO2 formation, several transformation pathways were confirmed during ozonation, including the cleavage of aromatic rings in sulfamethoxazole, sulfadiazine, and bisphenol A and the decarboxylation of carboxylic groups in diclofenac and ibuprofen.