An integrated process composed of of 5 mu m cartridge filter, ultrafiltration and nanofiltration membranes has been used for the pre-treatment of cotton dyeing textile wastewater. Treatability of membrane concentrate has been further investigated by means of the anaerobic treatment with and without pre-ozonation. Two identical fermentors have been simultaneously operated to compare the effect of pre-ozonation on removals of organic carbon, total Kjeldalh nitrogen, total phosphorus and sulfate from the concentrate. During the study, average removal efficiencies of COD and SO42- have been determined as 54% and 59% for non-ozonated and 45% and 52% for ozonated concentrate, respectively. Results demonstrate that ozonation has a slight positive effect on the biodegradability of membrane concentrate and the removal of possible hazardous pollutants. Low methane content of the produced biogas is attributed to high sulfate concentration in the textile wastewater. Findings of this study indicates that the combination of ozonation and anaerobic treatment can be a suitable alternative for the post-treatment of the concentrate from the membrane treatment of the textile wastewater.