Organic pollutants such as phenol are one of the refractory organic pollutants that can be found widely in various industrial wastewaters. The improper treatment of phenol will lead to the discharge of phenolic compounds into the receiving waters which contribute to various adverse effects towards the environment. The new treatment systems were developed by integrating photocatalytic process and sequencing batch reactor (SBR) into a single system in order to overcome the limitation of physicochemical and biological treatment. The microorganisms were available during the photocatalytic process to assist the rapid degradation of the biodegradable intermediates as soon as they produced. Simultaneously, the bio-recalcitrant compounds were degraded by hydroxyl radicals from photocatalytic process. In order to integrate the photocatalytic process with SBR system, a hybrid growth SBR (HGSBR) was initially establish in order to make it compatible for the integration. The performance of HGSBR was evaluated for the mineralization of the phenol including under various toxicity conditions. Then, the photocatalytic hybrid sequencing batch reactor (PHSBR) was develop and the performance of the simultaneous photo-biodegradation process was studied. Complete COD removal was achieved by HGSBR for phenol concentration up to 50 mg/L. The co-existence of bio-sludge and biofilm increased the efficiencies of HGSBR due to high concentration of biomass. The biofilm develop on the fixed bed materials was homogeneous and the thickness varied from each materials. Thicker biofilm indicated that larger number of bacteria accumulated in the surface. This would promote the removal of substances in HGSBR. Bio-kinetics models First order, Stover-Kincannon and Grau Second Order kinetic model were applied for HGSBR in degrading phenol. The performance of the HGSBR was different for the three conditions of toxicity studied (toxic, acute and chronic). The mineralization of 100 mg/L phenol in single photodegradation and biodegradation process recorded only 64% and 53% respectively. While, for the simultaneous process in PHSBR, the mineralization increased significantly to 92%. Besides the mineralization of phenol, the removal of ammonium (NH4+) in PHSBR was also investigated. The toxic characteristic of phenol that was subjected to inhibit the nitrification process was able to be reduced through PHSBR treatment system. In PHSBR the removal efficiency of NH4 + increased compared to the single reaction of photocatalytic and nitrification. The NH4 + removal during 50 mg/L of phenol was 94.4%, while for 100 mg/L of phenol, the average removal efficiency was slightly lower which is 92.9%. The threshold limit of phenol for NH4 + removal during the simultaneous reaction was increased to 300 mg/L. The results demonstrate the simultaneous reaction allowed for the higher mineralization rates of phenol. PHSBR allowed both reaction occurred simultaneously and consequently overcome the disadvantages of one process with another. This contributed to higher percentage mineralization of phenol. PHSBR highly potential in totally removed phenol from wastewater and ensure zero discharge into the water bodies
