From lab-scale to pilot-scale treatment of real wastewater from the production of rayon fiber

The subject of our study involved the treatment of real process wastewater from the production of rayon fiber. During the annual monitoring of the production facility, we performed a mass balance of three problematic sources of process wastewater and analyzed them repeatedly. All three sources showed high values of COD = 0.4-30 g/L, TOC = 0.09-7.1 g/L and the concentration of Zn2+ 0.09-0.5 g/L. At a total volume of 1.84 million m3, this represents a significant pollution source for the Elbe River. At lab-scale, we tested a combination of filtration, microfiltration, and oxidation using the Fenton, electro-assisted Fenton, and the electrochemical oxidation methods, both on the plate and newly developed macroporous BDD electrodes on a ceramic substrate, along with the final adsorption of Zn2+ emissions on the strongly acidic cation exchange resin Lewatit Mono plus S108. It was tested in Na+ and H+ cycles. Using an optimized technological sequence, we have achieved a COD reduction of up to 98%, and a TOC reduction of 85%. During the H+ cycle cation regeneration by sulfuric acid, Zn2+ emissions were converted to zinc sulfate that can be recycled in the spinning bath of the production process. The method was verified at a pilot scale.