Wastewater, textile processing wastes

In 1980, approximately 111,000 t of synthetic organic dyestuffs were produced in the United States alone. In addition, another 13,000 t were imported. The largest consumer of these dyes is the textile industry accounting for two-thirds of the market (246). Recent estimates indicate 12% of the synthetic textile dyes used yearly are lost to waste streams during dyestuff manufacturing and textile processing operations. Approximately 20% of these losses enter the environment through effluents from wastewater treatment plants (3). 

The organic chemical industry, the food processing industry, the pulp and paper industry, the textile industry, and the petroleum industry are important industries that produce organic process wastes. Unlike inorganic process wastes, they contain dissolved and insoluble matter in the main wastewater stream thus, they are more difficult to handle for disposal. They have its characteristic biological problems and spontaneous interaction with the surrounding environment, particularly, under high solar radiation. 

Recent estimates indicate 29t of the synthetic textile dyes used yearly are lost to waste streams during dyestuff manufacturing and textile processing operations. Approximately 20% of these losses enter the environment through effluents from wastewater treatment plants. 

Textile processing operations produce solid waste, wastewater, and airborne emissions. These are summarized here, and their sources are discussed in the process-by-process review that follows in later sections of this chapter. 

Production processes used in the pharmaceutical/fine chemical, cosmetic, textile, rubber, and other industries result in wastewaters containing significant levels of aliphatic solvents. It has been reported that of the 1000 tons per year of EC-defined toxic wastes generated in Ireland, organic solvents contribute 66% of the waste [27]. A survey of the constituents of pharmaceutical wastewater in Ireland has reported that aliphatic solvents contribute a significant proportion of the BOD/COD content of pharmaceutical effluents. Organic solvents are flammable, malodorous, and potentially toxic to aquatic organisms and thus require complete elimination by wastewater treatment systems. 

Benzene and naphthalene sulfonate moieties are present in the structures of many dyes that can be found in large amounts in wastewaters from textile and food industries. Even if wastes are decolored before the final discharge, not enough attention is nowadays devoted to the identification of possible uncolored degradation products, potentially toxic, that form during the decolorization process and are discharged into the aquatic systems. Besides sulfonate derivatives, aromatic amines have also been reported as possible degradation products of dyes [109],... 

Dyes are significant because of these production volumes and their potential release into the environment from manufacture, processing, and use. Spent dye solutions from textile dyeing operations ultimately are discharged to surface water after some form of waste-water treatment, and dyes not effectively removed from the wastewater may result in environmental and human exposure. 

COD testing has several advantages over BOD. Notably the COD test is more rapid, more repeatable, less susceptible to interferences and less labor intensive. On the other hand, BOD is more strongly correlated to processes that actually occur in wastewater treatment systems and receiving waters. For typical textile wastes, the COD BOD ratio is typically about 3 1. Wastewater with higher ratios (e.g. 7 1) are resistant to aerobic biological treatment. (USEPA, 1996). 

---