Biological methods for textile dye removal from wastewater: A review

The textile sector is 14% of total industrial production in India and contributes to about 4% of the gross domestic product and earns about 27% of India's total foreign exchange. Worldwide, up to 10,000 dyes are available and their annual production is above 7 x 105 metric tons, which are being used not only in textile sector but also applied in paper, food and pharmaceutical industries. Textile industries in India have been consuming more than 100 L of water to process 1 kg of textiles, and have contributed heavily in polluting surface and ground water resources in many regions of the country. The toxic and carcinogenic effect of untreated textile effluent is well understood. The decolorization and detoxification of industrial dye effluents is most important aspect and is major concern to meet environmental regulations. This paper presents a review of literature on the significance of bioremediation technologies over other physico-chemical methods for efficient removal of textile dyes from industrial waste effluents to improve the fragile ecosystems in different regions of the world. The present review paper (a) symbolizes the applications of existing conventional physical and chemical approaches for the decolorization/degradation of textile dyes, (b) describes their merits and demerits, (c) emphasizes on the existing literature on microbial decolorization of textile dyes precisely by using bacteria (aerobic and anaerobic conditions), fungi and algae, and (d) involvement of various enzymes from different biological sources for the decolorization of various textile dyes and their mechanism of action. Over the years, researchers have developed several bioremediation technologies to treat textile effluents, but little effort has been made to put the entire literature review of these technologies in one refereed paper, our review paper is an attempt to compile the existing information on various treatment technologies of textile effluent, so that these technologies can be shared widely for site specific situations.