Reuse of textile wastewater after homogenization–decantation treatment coupled to PVDF ultrafiltration membranes

• Textile effluents were treated with homogenization–decantation and UF membranes.
• The treatments provided almost 66% and 30% of COD and colour removal, respectively.
• The study performed in lab pilot plants was scaled up to a semi-industrial system.
• The membrane showed low fouling during the lab and semi-industrial study.
• The permeate was reused in a new dyeing process with acceptable results.

The textile industry is one of the largest consumers of water in the world and its wastewater is a serious problem when it is discharged without the proper treatment. In this work, wastewater generated by textile industry was treated coupling a homogenization–decantation treatment with polyvinylidene difluoride (PVDF) ultrafiltration membranes.Initially, the wastewater was aerated in a homogenization–decantation tank where 17% colour and 10% chemical oxygen demand (COD) were removed. The aerated effluent was treated with an ultrafiltration membrane in order to reuse the permeate in new dyeing processes. Firstly, the ultrafiltration treatment was performed in a laboratory plant. The permeate analysis showed 20% colour removal and 60% COD decrease. On the basis of these results, a semi-industrial system was built. With this plant, the permeate characterization showed similar results. The system was found to be scalable and suitable for the treatment of this kind of effluents.Finally, new dyeings were performed with both permeates. Monochromatic dyeings were carried out with 100% permeate whereas 50% permeate was reused for dyeings with a mixture of three dyes. The colour differences were found to be lower than 1.5, which was the acceptance value established.