Destruction of toxic organics in water by an injection-type downflow UV/O3 oxidation reactor

An injection-type downflow UV/O-3 oxidation reactor (IDUOR) was developed mainly with the combination of a configuration of two concentric cylinders with the UV lamp in the bottom axial position and a downflow mixing gas-liquid injector. This configuration leads to atomizing of the solution resulting in higher levels of dissolved ozone which is then illuminated by UV light to generate hydroxyl radicals. Four different toxic wastewaters including 4-chlorophenol, carbofuran, dye-auxiliaries and pesticide wastewater with a COD range of 164 to 1602 mg/L and a microtoxicity (EC50) range of 3.008% to 19.062% were used to investigate the performance of the device. It was found that the ozone utilization efficiency attained was more than 75% with very satisfying COD and TOC reduction for wastewater treated with IDUOR. The IDUOR when compared to a conventional stirred bubble UV/O-3 reactor exhibited increased efficiency for ozone utilization and GOD, TOC, microtoxicity reduction. Also, the pseudo-first rate constants on the basis of COD and TOC reduction indicated much higher oxidation rate of organics in IDUOR, providing additional evidence of the considerable treatment potency of IDUOR for destruction of toxic organics in water.