Peroxymonosulfate activation by suspended biogenic manganese oxides for polishing micropollutants in wastewater effluent

Abstract

The activation of peroxymonosulfate (PMS) to generate radical oxygen species (ROS) for in situ chemical oxidation has been shown to be an efficient technology for polishing micropollutants in wastewater effluent. Thus, it is also of great importance to develop environmental-friendly catalysts for PMS activation. The present study employed suspended biogenic manganese oxides (BioMnOx) to activate PMS for the efficient micropollutant removal. In a feasibility test, relatively high removal efficiencies (>80 %) of 14 selected micropollutants were obtained over short reaction times (20 min), in particular for refractory micropollutants such as carbamazepine (98 %), diclofenac (100 %) and metoprolol (81 %). The inhibition effect of coexisting anions to PMS activation was also investigated, which showed that the addition of HCO3– inhibited this process, while the addition of Cl– showed negligible effect. Based on radical quenching experiments, sulfate radical, hydrogen radical and singlet oxygen were all involved in the PMS activation process, while the responsible ROS for micropollutants removal were compound-specific. Furthermore, a novel BioMnOx/PMS system was established by utilising BioMnOx-coated carriers as catalyst, which were obtained from a previously engineered moving bed biofilm reactor (MBBR). This special BioMnOx/PMS system was then applied as an effluent polishing step. Results showed that most micropollutants were efficiently removed through the BioMnOx/PMS system, such as diclofenac (91 %) and sulfamethoxazole (98 %). Lastly, the toxicity of the MBBR effluent was determined by Vibrio fisheri, which showed minimum toxic effect after the polishing treatment.