Long term operation of a continuous submerged photocatalytic membrane reactor utilizing membrane distillation: Membrane performance and treatment efficiency

Abstract

Long term (200 h) continuous operation of a submerged photocatalytic membrane reactor utilizing direct contact membrane distillation (SPMR-DCMD) is presented. Various types of feed contaminated with ketoprofen were treated: brackish water (BW), seawater (SeaW), and secondary wastewater effluent (SE). Ketoprofen decomposition after 24 h exceeded 99.5 %, regardless of feed type. The distillate showed no toxicity to Aliivibrio fischeri. A significant decrease in flux after 100–124 h of BW and SeaW treatment occurred due to scaling, while for SE the flux remained almost constant for 200 h. This indicates that a shorter study would not allow a proper analysis of the process. A scaling layer was formed regardless of feed type, and the formation of CaSO₄⋅2H₂O, CaCO₃ or (Ca,Mg)CO₃ was proved. The porous structure of the deposit during SE treatment prevented significant flux deterioration. The formed TiO₂ layer protected the membrane from damage by the growing salt crystals.