Membrane separation for wastewater reuse in the textile industry

A technical and economical analysis of the application of a membrane separation technique for the purification of wastewaters aimed at their reuse is described. The investigation has been carried out by treating wastewaters of a pilot plant, reproducing on a smaller scale a separation system based on ultrafiltration and reverse osmosis. Significant indications for the exploitation of this approach on the fulling industrial scale were gained during the work. The effluent from dyeing and finishing plants, after activated sludge oxidation, was treated at an 800 1/h by means of sand filtration, followed by a separation in an ultrafiltration membrane module. The last separation step, reverse osmosis at 8 bar pressure, produced a permeate (60% of the inlet flow) that, relying on the analytical screening performed, was of much better quality with respect to process water presently in use. Therefore the permeate produced can be re-used in all production steps, including the most demanding ones concerning water quality such as dyeing with light coloration. A preliminary analysis of investment and operating costs also gave encouraging indications of the economic feasibility of the approach. (C) 2001 Elsevier Science B.V. All rights reserved.