The industrial wastewater is difficult to treat due to the complexity of its composition by conventional treatment processes or biodegradation. As an eco-friendly technology, ozone oxidation is widely accepted for advanced treatment of industrial effluents. However, the ozonation process has limitations in treatment efficiency of industrial wastewater accounting for the low utilization of gas, together with lack of precise modulation of ozone dosage and the catalytic process parameters according to the instant water quality. In this study, microbubble ozonation was shown to enhance the gas-liquid mass transfer rate and liquid equilibrium concentration compared to macrobubble ozonation at the laboratory-scale experiments. Additionally, based on the method of chemical kinetics, the experimental results of ozonation of two probe compounds show that there is a good linear relationship between the curve of ozone exposure value and ORP curve under specific ozone dosage and specific pH conditions. The results show that ORP can reflect the oxidation degree of organic matter in the process of ozone oxidation and simultaneously identify the rapid and slow ozone reaction stages. Therefore, A two-stage ozonation technique was provided to optimize the oxidation process for the ozonation treatment of industrial wastewater. In the first stage, microbubbles were used to enhance mass transfer of ozone and offer more hydroxyl radicals, accelerating the response rate of ozone to degradable pollutants in water. In the second stage, coupled homogeneous catalytic oxidation of ozone microbubbles and hydrogen peroxide based on ORP online monitoring technology was used to optimize the dosage of ozone and catalyst according to the instant water quality. Through several typical industrial wastewater pilot experiments, this segmental ozone oxidation technology based on ORP negative feedback greatly reduces the O/C (mg ozone dosage per mg COD removal) ratio of the ozone treatment process and ensures the stability of effluent quality.

Treatment of refractory industrial wastewater by segmental ozone oxidation of MBs based on ORP monitoring technology

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