Synthetic Dyes find use in a wide range of industries but are of primary importance to textile manufacturing. Wastewater from the textile industry can contain a variety of polluting substances including dyes. The environmental and subsequent health effects of dyes released in textile industry wastewater are becoming subject to scientific scrutiny. Environmental legislations are being imposed to control the release of dyes, in particular azo-based compounds, into the environment. Wastewater from the textile industry is a complex mixture of many polluting substances ranging from organochlorine-based pesticides to heavy metals associated with dyes and the dyeing process. During textile processing, inefficiencies in dyeing result in large amounts of the dyestuff being directly lost to the wastewater; which ultimately finds its way into the environment.
Colorants that enter the wastewater streams normally pass through a wastewater treatment plant where they are eliminated to a large degree by adsorption on sludge. The extent to which residual amounts reach the surface waters depends on the efficiency of treatment processes. Low concentrations of dyes in waste water do not normally pose any significant environmental hazard. Environmental problems arise mainly from inefficient removal of dyes or disposing the untreated dye effluent to water receiving bodies. This is normally the case in most developing countries.
This article was originally published in the Textile Review magazine, May, 2013 issue, published by Saket Project Limited, Ahmedabad.
About the Author:
Prof. R. B. Chavan is associated with the Institute of Tech. for Textile, Garment and Fashion Design at the University of Bahir Dar, Bahir Dar, Ethiopia.