Journal of Environmental Management 265 (2020) 110502 Available online 8 April 2020 0301-4797/© 2020 Elsevier Ltd. All rights reserved. Research article Catalytic ozonation of textile wastewater as a polishing step after industrial scale electrocoagulation Lucyna Bili � nska a, * , Kazimierz Blus a , Magdalena Foszpa� nczyk b , Marta Gmurek c , Stanisław Ledakowicz d a Textile Company Bilinski, Mickiewicza 29, 95-050, Konstantynow Lodzki, Poland b Lukasiewicz Research Network – Textile Research Institute, Brzezinska 5/15, 92-103, Lodz, Poland c Department of Molecular Engineering, Lodz University of Technology, Wolczanska 213, 90-924, Lodz, Poland d Department of Bioprocess Engineering, Lodz University of Technology, Wolczanska 213, 90-924, Lodz, Poland A R T I C L E INFO Keywords: Industrial textile wastewater Catalytic ozonation Toxicity assessment By-products removal ABSTRACT The main objective of this study was to develop the treatment system to change wastewater into a reliable source of recyclable water within the textile plant. Therefore, a highly polluted industrial wastewater originated in the dyeing of cotton was subjected to a multi-step treatment. The raw wastewater was characterized by the con- centration of Reactive Black 5, the azo dye, as high as 842 mg/L, extreme alkalinity (pH 11.26) and salinity (NaCl concentration 52,290 mg/L). Correspondingly, the chemical oxygen demand (COD) was equal to 3440 mg/L and the total organic carbon (TOC) was 1790 mg/L in this wastewater. This salty, hardly degradable wastewater underwent the electrocoagulation (EC) on an industrial scale in the frst step of the treatment. Although the industrial EC resulted in 84% of color removal in a very short time of 8 min, the wastewater was still charac- terized by an extremally high absorbance which corresponded to 100 mg/L of RB5. Moreover, EC resulted in the occurrence of burdensome by-products, of which one was identifed in this study as an aniline derivative. The by- products contributed to high residual COD and TOC after EC (2120 mg/L and 1052 mg/L, respectively). Consequently, the catalytic ozonation was used by us as a second, the polishing, step of the treatment. The catalytic ozonation was found effcient in the removal of the residual color and colorless by-products. The wastewater after catalytic ozonation was colorless and the fnal COD and TOC decreased to 1283 and 695 mg/L, respectively. The average oxidation state (AOS), spectra analysis, and the toxicity assay showed catalytic ozonation effcient in the by-products oxidation. Consequently, the catalytic action of activated carbon (AC) was proved for the ozonation of textile wastewater. Ultimately, the recycling of purifed wastewater into dyeing resulted in a very good color quality of textile samples (DE CMC values below limiting value equal to 1.0). 1. Introduction A recent report of the Organization for Economic Co-operation and Development (OECD) on the textile industry can be a vivid image of how the global community see the problem of the environmental manage- ment within this branch. The report points out generation huge amounts of textile wastewater which is a severe threat to the environment (OECD, 2017). Correspondingly, according to the data revealed by Ghaly and co-workers, the use of water within textiles processing can reach as high as 933 L/kg of textile product and the average amount is 100 L/kg of textiles (Ghaly et al., 2013). While the textile wastewater was recog- nized as a serious source of the pollution, the OECD within their report encourage the manufactures of textiles to undertake the corrective ac- tions. The purifcation and reuse of textile wastewater were suggested by OECD as the most benefcial approach. This idea implemented in the textile industry can be a component of building a sustainable economy. As far as textile wastewater is concerned, dyeing is the main opera- tion within the chemical processing of textiles which results in intense color of these effuents. However, besides the residual color (after usage of reactive dyes) this kind of wastewater is characterized by extreme alkalinity and salinity. These features make the textile wastewater from dyeing operation almost completely non-biodegradable and their treatment appears as a complex issue. During our research, the electrocoagulation was found by us as an * Corresponding author. Textile Company Bilinski, Mickiewicza 29, PL 95-050, Konstantynow Lodzki, Poland. E-mail address: l.bilinska@farbiarniabilinski.pl (L. Bili� nska). Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: http://www.elsevier.com/locate/jenvman https://doi.org/10.1016/j.jenvman.2020.110502 Received 15 October 2019; Received in revised form 10 March 2020; Accepted 25 March 2020