Reuse of the treated textile wastewater and membrane brine in the wet textile processes: distorting effects on the cotton fabric

In this work, a pilot plant consisting of granular activated carbon (GAC), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) processes was tested for the reuse of biologically treated textile wastewater (BTWW). The treated wastewaters were reused in the dyeing and bleaching of cotton fabric. To achieve zero discharge, NF brine was treated by lime soda then reused in the dyeing process as salt liquor. The main polluting parameters monitored in the posttreatments were: particle size distribution, divalent hardness ions, conductivity, soluble chemical oxygen demand (SCOD), and color. To determine the effects of reuse on the wet textile processes, color difference (dE), Berger whiteness degree, scanned electron microscopy images, and elemental analysis were followed on the treated cotton fabric. Application of UF, following GAC treatment, reduced SCOD concentration from 195 to 86 mg L−1. Over 99% Pt–Co and color540 were removed by NF/RO membrane treatments. Both NF and RO permeates were found to be suitable for reuse. After treatment of NF brine by lime-soda softening process, 89.5 and 93.5% reductions in total hardness and SCOD were achieved, respectively. The reuse of softened NF brine was found to be acceptable, since dE values in dyeing process were less than 1.0.