Discoloration and mineralization of a textile azo dye using a hybrid UV/O3/SBR process

Abstract Most synthetic dyes are toxic and hardly biodegradable compounds that enter the environment mainly through the discharged of non-treated textile industry effluents. The present study investigated the removal of the textile monoazo dye Reactive Red 198 (RR-198) from aqueous solutions using the ultraviolet light and ozonation alone and in combination (i.e., UV/O3) followed by a Sequencing Batch Reactor (SBR). The pH (5 ≤ pH ≤ 9) and dye initial concentration (50–300 mg/L) parameters were optimized in the ozonation process at reaction time of 0–60 min. Then, TOC removal and dye discoloration percentage was compared with the O3, UV and O3/UV processes. In order to compare the performance of the SBR in dye discoloration of RR-198 and TOC removal, four types of effluent, including Raw dye, O3-pretreated dye, UV-treated dye and UV/O3-pretreated dye were separately treated in the SBR system. In the ozonation process, by increasing the pH and reducing the initial dye concentration increased the discoloration percentage. The highest dye discoloration percentage and TOC removal obtained in the hybrid UV/O3/SBR process. Combining biological systems and Advanced Oxidation Processes is an appropriate option for the decomposition of resistant pollutants and increasing the biodegradability of these compounds and is applicable in the water and wastewater industry.