Application of slurry type photocatalytic oxidation-submerged hollow fiber microfiltration hybrid system for the degradation of bisphenol A (BPA)

A pilot scale, slurry type photocatalytic reactor, followed by submerged hollow fiber microfiltration (MF) membrane hybrid system was evaluated for simultaneous and complete destruction of toxic organic chemical bisphenol A (BPA) and separation of photocatalyst TiO2; in order to obtain a reusable quality water. With simple modification to the treatment operation, the effect of photocatalytic reaction at modest variations in temperature was examined. Adsorption pretreatment was carried out prior to photocatalysis (UV/TiO2). BPA adsorption ability on TiO2 was very less (about 15%) at 25 degrees C. However, adsorption pretreatment followed by photocatalytic oxidation (UV/TiO2,) at an elevated nearly constant temperature (about 70 degrees C) helped in increasing the BPA degradation efficiency. The effect of ozone introduction into the treatment stream was also analyzed. Applying ozone along with UV/TiO2, brought about a synergistic effect on BPA degradation. Within 3 h, entire 10 ppm of BPA and the by-product organic compounds were completely removed. TiO2 particle separation performance using hollow fiber membrane was enhanced by adopting a two-stage coagulation/sedimentation pretreatment. With initial turbidity of 4000 NTU, the turbidity of the final permeate water was well below 0.1 NTU. Almost complete removal of particles was achieved. Some of the main advantages of this hybrid treatment system include, large-scale treatment, complete and efficient BPA and its organic intermediates degradation, TiO2 easily separated after treatment and capable for reuse as it is free from chemical coagulant contaminants, reusable quality water is obtained, and the system has the potential for continuous operation with simple process modifications.