Comparative Study on Ozone-Based Advanced Oxidation Processes for Printing and Dyeing Wastewater Treatment

Widespread application of dyes has led to severe threats to water environments, and advanced oxidation processes (AOPs) have been confirmed as an effective solution to dye degradation. Among them, ozonation was one of the most prevalent AOPs. In this study, the effects of using AOPs—mainly based on ozone (O3)—to treat printing and dyeing wastewater (PDW) were compared. Firstly, ozone carrier active carbon fiber (ACF) was investigated for adsorption performance evaluation on pretreatment. The results showed that ACF treated by ultrasound performed best compared with ACF treated with other four pretreatment methods. Secondly, comparative studies based on individual O3, ultraviolet (UV), and combined O3/UV processes on PDW under different pH conditions were conducted. The decolorization rate of reactive brilliant blue X-BR dye under acidic conditions was higher than in alkaline and neutral dyes. In addition, with the utilization of single ozone and O3/UV under pH = 4 conditions, the decolorization rate could be above 99%. However, individual UV caused few variations in wastewater chromaticity. Thirdly, the effects of pH, UV light intensity, hydraulic retention time (HRT), and ACF filling rate on the performance of the O3/UV/ACF system were preliminarily screened using a saturated L9 orthogonal design. In terms of the results, the performance of the constructed O3/UV/ACF AOP system was superior than the conventional oxidation method, in which HRT had the largest apparent main effect on decolorization, followed by pH, ACF filling rate, and UV light intensity. Among the factor levels examined, the best-performing combination was pH 4, a UV power of 48 W, an HRT of 3 h, and an ACF filling rate of 80%. In a subsequent single kinetic experiment conducted using this combination, the final decolorization efficiency was 92.14%, the COD removal was 60%, and the biodegradability increased by 63.08%. This study offered novel insights into an O3-based AOP system for improving PDW treatment.