Treatment of textile plant effluent by ultrafiltration and/or nanofiltration for water reuse

The textile wastewater treatment by membrane processes presents some limitations such as membrane fouling which causes a rapid flux decline. In fact, the membrane processes efficiency can be affected by membrane pore blocking or/and cake formation. In order to limit the effect of membrane fouling caused by plugging particles in textile effluent, a combination between two membrane processes was studied. The ultrafiltration (UF) was used as pretreatment for nanofiltration (NF) process. A comparison between direct NF and UF/ NF combination performances was carried out. Experimental results showed that the second treatment improved the textile permeate quality by increasing the retention values of the majority of analyzed parameters. In fact, color retention was about 95%, conductivity and total dissolved salts retentions were about 80% and the bivalent ions retention values exceeded 95%. In the case of direct NF, permeate flux remained constant until a volume reduction factor (VRF) reaching 1.35. After coupling UF with NF process, a stable permeate flux was observed until a VRF equal to 2.77. This result showed that using UF process as pretreatment for NF process improved the efficiency of textile effluent treatment by increasing the membrane run-time.

The most important limitations appeared in textile wastewater treatment by membrane processes is membrane fouling which causes a rapid flux decline. Membrane selection and operating conditions are important issues to optimize technically and economically the membrane processes. Although the textile plant effluent was treated by a biological treatment process, the quality was not sufficient to reuse it on site. NF process was successfully used to improve permeate quality, but this process required a pretreatment step.