LAUSR

Abstract The complexity of textile effluents demands innovative treatment capable to promote the water reuse and by-products recovery. Taking this into account, an advanced oxidation process (AOP, photo-Fenton) was combined with microfiltration (MF) and nanofiltration (NF) in two distinctive processes: (1) MF-NF-AOP(c) and (2) MF-AOP-NF; aiming for the NF concentrate treatment in the first, and as a NF pre-treatment in the second. The MF was able to reject > 99.1% of the indigo blue, which can be reused in the dyeing process. The AOP applied to MF permeate had a higher COD degradation (78%, compared to 69% when applied to NF concentrate treatment), but the residual iron content resulted in a pronounced concentration polarization effect in the NF. Due to that fact, the NF in the second treatment systems had a higher fouling rate and lower permeate flux (average value: 19 L/m2h) compared to the first (average value: 38 L/m2h). In both cases, the residual iron concentration in the NF concentrate and in the AOP effluent prevented their reuse. However, the NF permeate from both treatment processes can be considered for yarn washing-off and equipment washing down. Furthermore, for the combination MF-NF-AOP(c), the NF permeate met the requirements to be recycled back to the process. The better performance of the first system (MF-NF-AOP(c)) in textile wastewater treatment was reassured by its lower operating expenditure (0.421 US$/m3) compared to MF-AOP-NF (0.736 US$/m3). Overall, the treatment combining MF-NF-AOP(c) was considered the most cost-effective alternative for textile wastewater treatment reuse.