At the first stage of this study, model and real post-dyeing wastewater was concentrated by nanofiltration (NF). In this process a filtrate characterised by an over 98% colour reduction, expressed in DFZ (spectral absorption coefficient) and a concentrate of high organic load were obtained. Further on, the NF concentrate was subjected to anoxic biodegradation. In the anoxic biodegradation of real wastewater, the degree of COD reduction was 50% on average. The filtrate coming from NF of wastewater was reused as process water in repeated dyeing processes. As a result of the end-use properties of the dyed products, it was found that the purified filtrate could be applied as process water for dyeing.