Continuous mineralization of concentrated phenol dissolved in an electrolyte-containing tap water by integrating biological-photocatalytic treatment with TiO_2 separation: utilization of sunlight and reuse of TiO_2

摘要

The continuous mineralization of concentrated phenol (200 mg l~(-1)) in an electrolyte-containing tap water was investigated using a biological-photocatalytic treatment integrated with TiO_2 separation. Black light and sunlight were used as the light source, and the reuse of TiO_2 was also studied. The mineralization of phenol in tap water and the reuse of TiO_2 were conducted in a flow system in which a bioreactor is combined with a narrow tube photoreactor operated under single pass and circulative flows, and the sedimented TiO_2 is recycled. A high circulative flow rate prevented the TiO_2 particles from coagulating due to the electrolytes in the tap water. A flow-circulation-flow operation mode using the integrated biological-photocatalytic-TiO_2 separation system was the optimum for treating the concentrated phenol in the electrolyte-containing tap water without interrupting the inflow of the wastewater and the discharge of the treated water. The optimum mineralization (phenol: 0.6 mg l~(-1) and total organic carbon: 6.5 mg l~(-1)) was attained by recycling the biologically treated phenol solution (20.1 mg l~(-1)) at the flow rate of 600 ml min~(-1) under sunlight irradiation, while maintaining the inflow and the discharge rates at 15 ml min~(-1). The TiO_2 particles were spontaneously sedimented by coagulation in a separation tank during the operation and the TiO_2 can be reused without reducing the efficiency of five repeated treatments.