An efficient wastewater treatment approach for a real woolen textile industry using a chemical assisted NF membrane process

•NF process at optimum conditions and after chemical pretreatment has an effective efficiency for real woolen textile wastewater treatment.•The results showed that the best conditions for the pretreatment process were pH of 8, FeSO4 of 600 mg/L.•For the NF process, by increasing pH and pressure, removal efficiency of turbidity and COD increased up to 98%.•For the NF process, by enhancing the color concentrations, the COD removal efficiency reduced to about 90%.

Woolen textile industries produces a significant high contaminated wastewater streams which have raised environmental concerns as their turbidity (>40 NTU) and COD (>1500 mg/L) are very high. To address their issue, usually a high level of chemical treatment is utilized; however, the addition of such level of chemicals itself creates another issue such as high concentrated sludge. In this study, chemical pretreatment (FeSO4 as coagulant, 400-800 mg/L, pH 6-10,) experiments was employed to reduce COD and turbidity to maximum 200 mg/L and 25 NTU respectively. The chemically assisted nanofiltration (NF) process (operating conditions: 4-8 bar, COD of 50-200 mg/L and pH of 6-10) by using a commercial spiral wound polyamide nano filter (TFC) was used to treat a real woolen textile effluent. Response surface methodology (RSM) was employed to determine the effects of operating parameters. The results showed that the best conditions for the pretreatment process were pH of 8, FeSO4 of 600 mg/L. For the NF process, by increasing pH and pressure, removal efficiency of turbidity and COD increased up to 98%. However, by enhancing the color concentrations, the COD removal efficiency reduced to about 90%. The results demonstrated that NF process at optimum conditions and after chemical pretreatment has an effective efficiency for real textile wastewater treatment.