Sequencing batch reactor technology coupled with nanofiltration for textile wastewater reclamation

Textile wastewaters are characterized by high organic matter concentration and colour presence. Conventional treatments do not remove completely the colour since the aerobic bacteria cannot degrade the azo-bond of the reactive dyes. However, their elimination is a requirement for wastewater reuse. In this study, it is proposed the reuse of textile wastewater as process water by a hybrid process combining a sequencing batch reactor (SBR) process with nanofiltration (NF) membranes. The aim is to evaluate the colour removal yield in the SBR and to study the influence of the addition of NF retentate on the SBR feed. The laboratory SBR was operated in cycles of 20 h and was fed with a solution containing a mixture of three reactive dyes: Remazol Yellow RR, Remazol Blue RR and Remazol Red RR. Every day colour and COD removal efficiencies were determined. The NF retentate was stored in order to mix it with the synthetic wastewater for the SBR feed. Colour removal yield ranged from 85 to 90% for the red and blue dyes and from 70 to 75% for the yellow one when the SBR feed was only the textile synthetic wastewater. However, when the SBR feed was the mixture of 50% synthetic wastewater and 50% of NF rejection the colour removal efficiency was reduced between 10 and 15%.