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 7×105 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 the most important aspect and is a major concern to meet environmental regulations. This chapter presents a review of literature on the significance of bioremediation technologies over other physicochemical methods for efficient removal of textile dyes from industrial waste effluents to improve the fragile ecosystems in different regions of the world.
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Indigo, the first known organic blue dye was used as a colorant and also found in mummies wrap 4000 years ago Commercially, there are 100,000 dyes available. Mainly they find application in textile industry, Silveira et al. (2009) followed by food, cosmetics and paper printing industry. To make the fabric more attractive and to provide the customer with variant shades, it becomes imperative to use variety of chemicals in dyes like direct dye, processing dye, reactive dye etc. But this variance and increasing use of chemicals marks a serious concern as its manufacturing and application are associated with several environmental issues, effecting textile industry.
In early 1856 it was Perkin who pioneered the synthetic organic dye, mauve. Later on in 1871, Wolfe prepared picric acid dye by nitration of indigo blue dye. Since then, many of other synthetic dyes have been introduced in the non-ending list of dyes (Mathur et. al (2006).
‘Natural dye’ includes all dyes that are derived from natural sources like plants, animal and minerals. Natural dyes are applied to the fiber by using mordent, which should attach with both, color and the fiber, and are mostly non-substantive. Synthetic dyes also find application in industries like paper, rubber, chemical, but has been majorly used in textile industry (Keharia & Madamwar (2003). It has been reported that textile industries are using more than 10,000 commercial dyes, which accounts for 10-15% of waste being discharged into the environment (Reisch, 1996).
To reduce its toxicity it is necessary to depolarize the effluent before it gets discharged into the water stream. Major problem associated with the treatment of these dyes from effluents includes its water solubility and presence of harmful chemicals, making it difficult to depolarize and poses a great challenge for environmental managers (Ho & Chiang, 2001). Sometimes it is obvious to use combinational methods to remove different kind of contaminant present in the dye (Hamza and Hamoda, 1980; Shaul, 1982; Shelley, 1976). Adsorption method may also be employed to remove color from the waste water of dying and textile industries (Mckay, 1980; Yeh, 1993; Mckay, et. al.1990). Different adsorbate used are (sludge) Zahangir Alam (1993), magnetically modified brewer’s yeast, cassava peel activated carbon (Safarikova, 2005) tapioca peel activated carbon (Rajeshwari, 2001), soil (Chidambaram and Selvaraju, 2007, fly ash (Singh 2006), jack fruit peel activated carbon (Mall and Upadhyay, 1998), groundnut shell activated carbon activated with Zinc chloride solution (Inbaraj & Sulochana, 2006), neem leaf powder Inbaraj & Sulochana (2002), kaolinite, montmorillonite, hazelnut activated carbon (Malik et. al. 2006), bagasse pith, natural clay, maize cob, rice bran based activated carbon (Aydın & r Yavuz, 2004), guava seeds activated with Zinc chloride solution followed by pyrolysis (Nassar and Geundi, 2004) etc.