Coupling microfiltration and nanofiltration processes for the treatment at source of dyeing-containing effluent

Dye baths of low volume compared to the volume of water used in other processing operations generate significant pollution and contaminate other wastewaters that are generally less loaded with pollutants. The aim of the present work is to treat different combination of selected dyeing cycle baths of using the combination of Microfiltration (MF) with Nanofiltration (NF) in order to reuse the treated water in the dyeing process. The characterization of the effluents coming from the different dyeing steps shows that the cotton preparation and dyeing baths are the most polluted due to the presence of dye and to high salinity content. The performances of the combination MF/NF to treat two types of effluents (Effluent 1 which is a mixture of the more polluted baths and effluent 2 which is a mixture of all baths used during the dyeing cycle) were studied. The pretreatment by MF leads to a 50% of pollutant retention except for salts which do not exceed 13%. The addition of NF leads to a high quality of treated effluent with retention of salt, color, suspended matter and COD respectively of 47–52%, 100%, 99.9% and 73–85% depending of the effluent load. The use of MF as a pretreatment prior to NF improves the treatment effectiveness by increasing the operating time and the permeate flux. NF permeate quality was satisfactory enough to be reused in reactive dyeing baths.

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► Different combination of a selected bath of dyeing cycle was treated at source using membrane processes.
► MF used as a pretreatment prior to the NF improves the effectiveness of the treatment.
► Permeation flux was enhanced by MF/NF treatment.
► Retention of all parameters was up to 70% expected for salinity which did not exceed 37%.
► The dying tests prove the possibility to reuse NF permeate as process water.