Pilot-scale advanced treatment of actual high-salt textile wastewater by a UV/O3 pressurization process: Evaluation of removal kinetics and reverse osmosis desalination process

Abstract

Advanced oxidation processes (AOPs) such as ozonation and Fenton processes are widely used in the treatment of high-salt wastewater. The UV/O3 pressurization process was designed and applied at the pilot-scale for treatment of actual high-salt textile wastewater. The UV/O3 pressurization process achieved the highest decolorization (85 %) and chemical oxygen demand (CODCr, 43.2 %) removal efficiency at an O3 dosage of 200 g·t−1 and a pressure of 0.2 MPa. Compared to ordinary ozonation, the UV/O3 pressurization process improved the solubility and gas-liquid mass transfer efficiency of O3 in wastewater and generated a large number of O3 microbubbles. Hydroxyl radical (·OH), superoxide radicals (O2·−) and single oxygen (1O2) all played a significant role on the removal of pollutants in wastewater during the UV/O3 pressurization process. The reverse osmosis (RO) process was used to evaluate the effect of UV/O3 pressurization and Fenton pre-oxidation processes on the desalination process as the last process in treating high-salt organic wastewater. The pre-oxidation processes improved the initial RO water flux. Compared with the Fenton process, the UV/O3 pressurization process had less membrane fouling (thin fouling layer vs thick fouling layer), and final water flux (59.4 LMH) was higher than that of Fenton process (34.9 LHM). The total dissolved solids (TDS), Cl− and SO42− of the effluent from UV/O3 pressurization process (37.2, 7.6 and 3.0 mg·L−1) were better than that of Fenton process (65.7, 13.9 and 7.1 mg·L−1). Therefore, the UV/O3 pressurization process without secondary pollution is more suitable for the advanced treatment of high-salt organic wastewater than the Fenton process.