Efficient Degradation of Recalcitrant Pharmaceuticals in Greywater Using Treatment of MBR and Immobilized TiO2 Porous Layers

Abstract

Traditional wastewater treatment often fails to remove pharmaceuticals, necessitating advanced solutions, such as TiO2 photocatalysis, for post-treatment. However, conventionally applied powder TiO2 can be cumbersome to separate from treated water. To solve this issue, this study immobilized three TiO2 photocatalysts (Anatase 16, Anatase 5, and P25) into porous layers and evaluated their efficacy for the degradation of three pharmaceuticals (naproxen, NPX; sulfamethoxazole, SMX; metformin, MTF) in standard solutions and greywater pretreated in a membrane bioreactor (MBR). In standard solutions, photocatalysis tests revealed a high degradation efficacy (NPX 100%, SMX 76-95%, MTF 57-75%) and challenged the belief that OH• is the predominant reactive oxygen species (ROS). The primary ROS were 1O2 for NPX and OH• for SMX and MTF. The raw greywater (NPX, SMX, MTF - 0.5 mg·L-1) treatment in MBR removed only 17-22% of the pharmaceuticals, highlighting the need for post-treatment. Using this pretreated greywater, P25 layers excelled for NPX (78 ± 5%) and SMX (73 ± 4%) but were less effective for MTF (40 ± 16%) compared to Anatase 16 (60 ± 10%). Moreover, the effluent toxicity (Aliivibrio fischeri) was reduced, and the degradation products were identified. Overall, TiO2 layers are a high-potential method for removing pharmaceuticals from MBR-treated greywater.