Several applications for ultrafiltration and reverse osmosis are being employed in the textile industry. These include the treatment of size and latex contaminated effluents, wool wash waters and effluents from dying operations. The membrane processes are alternatives to the classical mechanical, biological, and physical-chemical processes, such as precipitation, flocculation, flotation and adsorption. An increasing use of membranes is evident in the ultrafiltration of sizing agents used to coat yarns during weaving, where the filtration process is used for water soluble and low-viscosity size. Higher recoveries can be achieved but at higher investment cost.
Membrane processes can also be used in the treatment of bulk dyehouse effluents, wool and yarn scouring effluents, process water, and effluents containing mothproofers and other pesticides. Reverse osmosis, for example, can be used to recover up to 80% of warm dyehouse wastewater for re-use. A membrane life span of two years is typical. Ultrafiltration using polysulphone membranes may be very effective in the wool scouring process, for concentrating the more significant pollutants into a small volume. It can also produce large quantities of permeate suitable for re-use in the scouring process.