Membrane technology has wide range of applications in the textile industry. Various types of dyes and chemicals can be recovered from the textile effluent using this technology and a large proportion of wastewater can be reused. The problem of membrane fouling is also discussed. The suitability of the technology has been assessed. The approach of employing primary treatment methods followed by Coagulation and Reverse Osmosis through Membranes is being recommended. The effectiveness of various types of membranes available in the world needs to be demonstrated for a specific plant.
The textile industry is characterized by using a large quantity of chemicals and huge quantities of water. Detergents and caustic are used to remove dirt, grit, oils and waxes. Bleach is used to improve whiteness and brightness. Dyes, fixing agents and many inorganics are used to provide the brilliant array of colors the market demands. Sizing agents are added to improve weaving. Oils are added to improve spinning and knitting. Latex and glues are used as binders. A wide variety of specialty chemicals are used such as softeners, stain release agents and wetting agents. In some ways, the need of the textile industry was the engine which drove the development of the chemical industry.
Many of these chemicals become part of the product. Many of the chemicals perform a necessary function, but are removed from the fabric. State authorities and local municipalities have begun to target the textile industry to clean up the wastewater that is being discharged from the textile mills. Regulators are looking closely at toxicity due to high salt, the ever present BOD, non-destructible COD, heavy metals, and color of the effluent As the mill comes up for a new discharge permit, many are finding that the effluent being discharged threatens permit renewal.
Membrane separations are evolving as a solution to the many problems a mill may be experiencing. Membranes can provide a solution in such areas as: color removal, BOD reduction, salt reduction and reuse, PVA recovery, and latex recovery. Membrane technology is unique in that it can provide a return on investment as a solution to pollution abatement. Membrane solutions are generally in keeping with the Clinton/Gore philosophy of pollution prevention is better than pollution treatment. Capital investment is competitive with conventional end of pipe treatment because membranes have become more of a commodity, and because a point source strategy can be employed. In many cases, valuable products can be reclaimed and reused, adding to an overall cost reduction.
The author is Assistant Professor in the Department of Textile Technology, PSG College of Technology, Coimbatore