Integration of microfiltration and nanofiltration to promote textile effluent reuse

This study investigates the application of a hybrid microfiltration–nanofiltration (MF–NF) process for textile wastewater reclamation. Indigo blue dye was efficiently retained by an MF membrane, allowing its recovery from the concentrated stream. NF technology was successfully applied to polish textile effluent. The NF membrane was evaluated under different transmembrane pressure (8–15 bars), crossflow velocities (0.21–0.84 cm s^?1), pH (7–11), and feed temperature (20–40 °C). The best NF performance was provided at a pressure of 12 bar and a crossflow rate of 0.63 cm s^?1. The NF performance (in terms of COD, conductivity, colour, and nitrogen removal) was not influenced by pH; however, higher feed pH values resulted in increased membrane fouling. The principal cause of flux decline was due to concentration polarization. Membrane chemical cleaning was sufficient to regain the initial permeability. The NF permeate met the quality requirements for all water demands within the textile industry, while the NF concentrate could be used to wash equipment, print work screens, print paste containers, and floors. The total capital cost (CapEx) of the MF–NF system was estimated at 58,362.50 US dollars and the total operational cost (OpEx) at 0.31 US dollars per cubic metre of effluent.