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

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 (<i>Aliivibrio fischeri</i>) was reduced, and the degradation products were identified. Overall, TiO₂ layers are a high-potential method for removing pharmaceuticals from MBR-treated greywater.