Treatment of wastewater during the production of reactive dyestuff using a spiral nanofiltration membrane system

In this study, a stage-2 spiral-wound nanofiltration (NF) system was used to further treat the permeate produced by a stage-1 tubular NF employed for treatment of dyestuff wastewater. Pilot-scale experiments were carried out to select the appropriate commercial NF membranes by investigating the TOC removal, color removal, the flux and VCR values, respectively. Compared with the Dow NF1 and Desal DL membranes, Desal DK NF membrane was selected for subsequent study. Using Desal DK NF membrane, the permeation flux could be kept at a relatively high value (>30 L.h−1.m−2) while the VCR reached 10.0. Meanwhile, the TOC values could be reduced to less than 400 ppm, which meets industrial requirements and would facilitate the subsequent bio-treatment unit. Based on the pilot-scale experiments, a full-scale system was set up, and the treatment system has been successfully implemented at a company in Thailand.