Textile dye-house wastewater

Fresh water is an increasingly scarce resource as the demands of an ever-growing world population and the agricultural activity needed to support it consume a steadily rising proportion of global fresh water resources. Consequently, industry generally needs to find ]ways to reduce its water consumption. As a major user and potential polluter of water, the textile wet processing industry is under particular pressure to reduce water consumption on both environmental and economic grounds. Main coloured compound in dye- house waste waters are azo dyestuffs. Azo dyestuffs are the most important dyestuffs applied today. Azo dyes are used for dyeing natural and synthetic fibres. Azo dye molecules include one or more azo groups and may be acid, direct, disperse, basic or reactive dyes. Since an only 85–90% of the value of the dye is fixed on the fabric in dyeing, the waste streams represent the largest point source discharges from the textile industry. Dyes containing an azo bond (-N=N-) during wastewater purifying undergo rapid reductive cleavage under anaerobic conditions. Some azo dyes can be carcinogenic even without being cleaved into aromatic amines. Many azo dyes and their reductively cleaved products as well as chemically related aromatic amines are reported to affect human health, causing allergies and other human maladies. Due to the above, it is important to take into account the choice of method of wastewater treatment of the dye-house, which will not affect the chemical structure of the dye. In addition, law prohibits dyes that can adversely affect human health and the environment.