Advanced treatment of bio-treated dyeing and finishing wastewater using ozone-biological activated carbon: A study on the synergistic effects

The advanced treatment of bio-treated dyeing and finishing wastewater (BDFW) in textile industries is urgently necessitated to reduce the discharge of pollutants from industrial wastewater and enhance wastewater reclamation. In this study, it was found that ozonation and biological activated carbon (O-3-BAC) can synergistically degrade the dissolved organic carbon (43.0%), chemical oxygen demand (45.8%), color (73.0%), and specific UV absorbance (SUVA254) (29.7%) of BDFW. BAC alone could hardly degrade the fluorophore, but ozonation can transfer hydrophobic or hydrophilic protein-like fluorophore to less fluorescent transformation products that were more susceptible to biological degradation by BAC treatment. In comparison to BAC alone, O3-BAC, on one way, promoted the mineralization (27.0%-36.3%) of DOC and the degradation of chromophores (43.8%-48.0%) with low MW (< 1 kDa); on another way, inhibited the formation of high MW fraction (> 3 kDa) that was formed by BAC. Ozonation of BDFW resulted in a larger decrease of SUVA(254) than electron donating capacity (EDC), while the BAC treatment of BDFW and ozonated BDFW induced contrasting results. This was likely due to the different degradation patterns that O-3 decomposed DOM dominantly via the O-3-addtion reactions, while biological process would simultaneously reduce low MW fractions with relatively higher EDC and form high MW fractions with lower EDC and more aromaticity.