Behavior assessment of sulfonamides and N4-acetyl sulfonamides from wastewater effluent in subsurface constructed wetlands: Removal, distribution, and biotransformation

Wastewater treatment plant (WWTP) is the point source of antibiotic contamination, yet the removal of antibiotics from WWTP effluent has not been given necessary attention. In this study, subsurface constructed wetlands (SCWs) were used to investigate the removal, distribution, and biotransformation of sulfonamides (SAs) and their N-4-acetyl sulfonamides (Ac-SAs) from wastewater effluent. The results showed that SCWs was demonstrated as capable for removing SAs with their Ac-SAs efficiently from WWTP effluent. The removal of SAs was significantly impacted by the occurrence of biotransformation behavior of SAs, not only SAs degraded into Ac-SAs, but also some Ac-SAs converted into SAs. Microbial aerobic degradation is the major removal pathway of SAs and Ac-SAs in the SCWs. SCW configuration such as vertical flow is conductive to the oxygen transport inside system and therefore promote the aerobic process of contaminants. Plants also play an important role on affecting the temporal and spatial variation of SAs through rhizosphere effect, i.e. accumulating SAs in the vegetation biomass by plant uptake and transpiration, concentrating SAs in the root zone by rhizosphere sorption and interception, and enhancing microbial influence on their aerobic decomposition by root oxygen release. The knowledge obtained in this study will be helpful for advanced purification of WWTP discharge and bioremediation of antibiotic contamination.