Enhanced emerging pharmaceuticals removal in wastewater after biotreatment by a low-pressure UVA/FeIII-EDDS/H2O2 process under neutral pH conditions

Abstract

The widespread occurrence of pharmaceutically active compounds (PhACs) in aquatic environment has become a worldwide concern. This work investigated the removal of four representative emerging PhACs, including carbamazepine (CBZ), crotamiton (CTMT), N,N-diethyl-meta-toluamide (DEET) and ibuprofen (IBP) in two internal circulation biological aerated filters (IcBAFs). Results showed that DEET (>95%) and IBP (>80%) were removed efficiently in the IcBAFs, whereas CTMT (<30%) and CBZ (<5%) were poorly removed due to their recalcitrant characteristics. The mechanism for DEET and IBP removal in the IcBAFs was biodegradation and autotrophic microbes were responsible for their degradation. The major biotransformation products of IBP included hydroxy-IBP and 1-(4-isobutylphenyl)ethanol, while one major biodegradation product of DEET was identified as N,N-diethylbenzamide. In addition, the removal of residual PhACs in IcBAF effluents by various advanced oxidation processes (AOPs) were evaluated in either batch or continuous-flow mode. The results showed that the low-pressure UVA/FeIII-EDDS/H2O2 process was very effective for the treatment of residual PhACs in IcBAF effluents under neutral pH conditions, e.g., resulting in more than 90% degradation of the PhACs in continuous-flow mode. The impacts of photo-Fenton reagents doses (i.e., FeIII-EDDS dose, H2O2 dose and the EDDS:FeIII molar ratio), as well as the UV light sources (UVA/UVC) and intensities on the residual PhACs removal were evaluated in detail. The LC-QTOF-MS analysis revealed that not only the target PhACs but also their biodegradation byproducts were efficiently degraded by the low-pressure UVA/FeIII-EDDS/H2O2 process, suggesting that this process had great potential for the treatment of residual PhACs in wastewater after biotreatment.