A total solution for simultaneous organic degradation and particle separation using photocatalytic oxidation and submerged microfiltration membrane hybrid process

Advanced oxidation process (AOP) with reactor capacity of 150 L, using ultraviolet (UV) radiation and titanium dioxide (TiO₂) photocatalyst, was evaluated for the destruction of toxic organic chemical, bisphenol A (BPA). TiO₂ in the form of powder, was suspended as slurry in the water, as against the commonly adopted practice of immobilizing it onto a carrier material such as glass, concrete or ceramics. Adsorption of BPA by TiO₂ was evaluated and was performed as a pretreatment to AOP. The combined effect of ozone with the AOP process was also studied. Applying ozone along with UV/TiO₂, brought about a synergistic effect on BPA degradation. Within three hours, entire 10 ppm of BPA and the intermediate organic compounds were completely removed. The highlight of this study was the simultaneous degradation of BPA and separation of TiO₂ particles from water after photocatalysis, in order to obtain reusable quality water. Separation of TiO₂ particles was carried out by a unique two stage coagulation and settling process followed by submerged hollow fiber microfiltration membrane technique. With initial turbidity of 4,000 NTU, the turbidity of the final permeate water was well below 0.1 NTU. Almost complete removal of TiO₂ 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; easy separation of TiO₂ after treatment and reuse as it is free from chemical coagulant contaminants; reusable quality water, and the potential for continuous operation with simple process modifications.