Textile wastewater treatment by AOPs for brine reuse

The most contaminated textile wastewater stream, dyeing discharge with a high residual salt content, was selected to undergo dedicated treatment by advanced oxidation processes (AOPs). A simulated mixture, based on an industrial recipe and containing Reactive Yellow 145 (RY145), Reactive Red 195 (RR195), and Reactive Blue 221 (RB221), was investigated. These dyes are used together in the trichromatic technique in industrial dyeing, and they occur together in wastewater. In this study, for the first time, several ozone-based AOPs (O-3, O-3/H2O2, O-3/UV and O-3/UV/H2O2) were tested under comparable conditions and assessed. Moreover, the roles of hydrogen peroxide and UV during the AOPs were determined. The influence of textile auxiliaries on the AOPs was also investigated. Due to the usage of multiple dyes in the same mixture, colour was evaluated based on whole UV-vis spectra by recalculating them as integrals. Extremely fast decolourization of the textile wastewater was observed during ozonation. Only 10% colour remained after 10 min of treatment, and satisfactory mineralization was also achieved. During the AOP experiments, it was found that ozonation is the best treatment method for implementation in the industry. Textile wastewater treated by AOPs could be reused as a source of 'ready to use' brine for the next textile dyeing operation. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.