Membrane separation for wastewater reuse in the textile industry

A technical and economical analysis of the application of a membrane separa tion technique for the purification of wastewaters aimed at their reuse is described. The investigation has been carried out by treating wastewaters o f a pilot plant, reproducing on a smaller scale a separation system based o n ultrafiltration and reverse osmosis. Significant indications for the expl oitation of this approach on the fulling industrial scale were gained durin g 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, fo llowed by a separation in an ultrafiltration membrane module. The last sepa ration step, reverse osmosis at 8 bar pressure, produced a permeate (60% of the inlet flow) that, relying on the analytical screening performed, was o f much better quality with respect to process water presently in use. There fore the permeate produced can be re-used in all production steps, includin g the most demanding ones concerning water quality such as dyeing with ligh t 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.