Removal effect and mechanism of typical pharmaceuticals and personal care products by AAO-MBR and UV/Chlorine in black water

Pharmaceuticals and personal care products (PPCPs) are emerging pollutants that have gradually attracted the attention of researchers. PPCPs in urban sewage treatment plants mainly originate from human excreta, while water that is mainly composed of human excreta and flushing water is referred to as black water. Based on a traditional anaerobic-anoxic-oxic-membrane bioreactor (AAO-MBR) design, we optimized the strategy of prolonging the anaerobic-anoxic section length and tested its effect on the bioreactor's efficiency in removing conventional pollutants and PPCPs from blackwater. We assessed the PPCP removal mechanism and efficiency of the AAO-MBR system and a combined advanced ultraviolet (UV)/chlorine treatment system. Under the condition with a hydraulic retention time of 40 h, reflux ratio of the mixed liquid of 400%, and carbon source addition to the blackwater (chemical oxygen demand = 780 mg/L), the removal of ibuprofen, carbamazepine, and bezafibrate by the improved AAO-MBR process exceeded 90%. The PPCP removal mechanisms in the AAO-MBR system were mainly biodegradation, sludge adsorption, and effluent residue. More than 95% of ibuprofen and bezafibrate were biodegraded, and the remaining portions were adsorbed on sludge or remained in the effluent, whereas only approximately 50% of carbamazepine was biodegraded, and the rest was adsorbed on sludge or remained in the effluent. When the UV intensity was 8.0 W/m2, the pH was 6, and the free chlorine concentration was 18 mg/L in the NaClO system, the target PPCPs were completely removed after 23 min. The effective removal of PPCPs from blackwater is essential for alleviating potential environmental risks. Our research provides technical support for the discharge of conventional pollutants and the coordinated removal of PPCPs using a UV/chlorine treatment process.