Sustainable water reuse in textile processing: A hybrid nanofiltration–reverse osmosis–persulfate oxidation treatment approach

Water reuse is becoming a key strategy for improving the environmental sustainability of textile processing, particularly in water-intensive operations such as dyeing and finishing, where membrane processes such as nanofiltration (NF) and reverse osmosis (RO) are increasingly applied. However, their implementation is often constrained by the management of highly concentrated residual streams. This work proposes a hybrid membrane–oxidation strategy to enable practical minimal liquid discharge (MLD) by combining selective separation with targeted post-treatment of the concentrate. Biologically treated textile wastewater was processed by NF and RO under different operating pressures to assess permeate quality, energy demand, and retentate composition. The NF–RO configuration produced very low-salinity permeate with specific energy consumption as low as 0.38–1.2 kWh m ⁻³ , with NF at 6 bar identified as the most energy-efficient condition. At this pressure, NF selectively concentrated sulfate-rich salts and refractory organics in the retentate, reducing scaling propensity in the downstream RO stage. The NF retentate was subsequently treated by heat-activated persulfate oxidation, optimized using a Box–Behnken design. Temperature was the dominant factor, and optimal conditions (90°C, 100% persulfate stoichiometric dosage, 10 mg L ⁻¹ Fe(II)) achieved a total organic carbon removal of ~64%. Integrating selective membrane fractionation with thermally driven oxidation offers a robust, energy-efficient route for practical MLD implementation in saline textile wastewater treatment.