Wastewater, dyestuffs

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). 

T. M. Keinath, Technology Evaluation for Priority Pollutant Removalfrom Dyestuff Manufacture Wastewaters, USEPA report 600/S2-84-055, Washington, D.C., Apr. 1984. 

High salt concentrations up to 15-20% can be found in wastewater from dyestuff industries. Moreover, textile manufacturers located on coastal areas can cause pollution of seawater. The biological treatability of wastewater with a high saline concentration is limited because most of the microorganisms that are able to degrade azo dyes are not active in these conditions, in which the selection of halophilic or halotolerant bacteria capable to degrade azo dyes is necessary [79]. 

As shown in Table 1 the wastewater limit for chromium is 0.5-1 mg/L and Cr is 0.1 mg/L. While conventional 1 2 and 1 1 dyes permit chromium concentrations in the dyebath at the end of the dyeing process of 3.0-13.0 mg/L Cr, the application of modem dyestuffs and optimized processes permits final concentrations to approximately 1 ppm. By general optimization of the process (e.g., dosage of acid), use of dyes with a high degree of exhaustion, and minimal concentration of free chromium [15], final bath concentrations below 4 ppm can be reached, even for black shades. By application of such procedures the exhaustion of the chromium should reach values of better than 95% of the initial value. 

Particularly in the case of dyes with a limited degree of fixation the dyestuff content in the wasted water leads to intensively colored wastewater. As the reactive group of the unfixed dyestuff is hydrolyzed into an inactive form, a reuse is not possible. On the basis of an exhaust dyeing with 5% color depth, a liquor ratio of 1 10, and a degree of dyestuff fixation of 70-80% corresponding to 3.5-4 g/L of dye are fixed on the goods and 1.5-1 g/L of hydrolyzed dyes are released with the dyebath. 

For a dyestuff fixation of 70-80% and a color depth of 5% a concentration of 1.5-1 g/L hydrolyzed dye is expected in the wastewater, when 10 L of washing water is applied per 1 kg of goods. The emission of colored wastewater here can be divided into two different sources, the wastewater from the washing of the dyed material and the residual filling of the padder. 

Besides an optimization of the dyestuff and the dyeing processes with regard to improved dyebath, exhaustion, the problem of colored wastewater released from dyehouses, has led to numerous technical developments proposed to overcome it. 

The wastewater from dyeing processes contains a lot of components in various concentrations, for example, dyestuff, alkali, acid, salt, and auxiliaries [85]. In a first basic step, a separation of the wastewater stream according to the degree of chemical load should be performed. 

In pigment printing the dyestuff pigments are bound to the textile by means of a polymer binder system and no additional washing is performed however, wastewater is released from the cleaning of the equipment and machinery. 

L losses, part of dyestuff released into the wastewater stream (dimensionless)... 

Schonberger H, Baumann A, Keller W, Pogopetris P (1997) Study of microbial degradation of polyvinyl alcohol (PVA) in wastewater treatment plants. American Dyestuff Reporter August 1997 9-18. Available at http //www.p2pays.org/ref/02/01722.pdf. Last accessed 16 Aug 2011... 

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. 

Large amounts of toxic dyestuffs can be found in wastewaters from the textile industry because dye fixation is sometimes as low as 60%. Most dyes... 

Ozonation has so far found application mostly in the treatment of surface-water, but there is also some experience in using it for wastewaters including those coming from textile mills. Thus, for example, it has been reported [1,2] that ozonation can decolour textile wastewaters, particularly those containing reactive and acid dyestuffs, whereas with the waters that contain direct, disperse or sulphur dyestuffs, the effect of ozone is markedly less persuasive. 

Many contaminants in wastewater today, such as dissolved dyestuffs, lignins, detergents, proteins, fatty acids, tannins, and so on, possess surface-active properties that decrease surface tension and oxygen transfer rate, but increase the demand for dissolved oxygen. Particularly, the sharp reduction in surface tension of water by these pollutants seems to be a basic cause of increasing the susceptibility of aquatic life to the surfactant poison. 

Bran Cereal Dyestuff wastewater Metal Cutting Fluids Rocket Propellants... 

Green J.M. and Sokol C., Using color to decolorize dyeing plant wastewater . American Dyestuff Reporter, 74, No.4 50-51, 67. (1985)... 

Nitrites occur as the simple NO anion. It is formed particularly by biochemical oxidation of ammonia nitrogen or biochemical reduction of nitrates. Some industrial wastewaters are very rich in nitrites, for example those from the production of some dyestuffs or from engineering works employing cutting liquids for cooling of machine tools such liquids contain nitrites as corrosion inhibitors. Nitrites in waters occur with nitrates and ammonia nitrogen only at low concentrations since they are biochemically and chemically labile. In clean ground- and surface waters only trace... 

Pollution of wastewaters by phenols of artificial origin is caused particularly by those from the thermal processing of coal, oil refineries, from sulphite woodworking, dyestuff industry, and from the mamufacture of pesticides. These wastewaters contain monovalent and multivalent phenols at concentrations of units of g 1 . In the process of biological treatment of phenolic wastewaters different polyphenols are formed which have a similar cha-... 

Another fairly toxic group of phenolic compounds present in wastewaters is that of the nitrophenols. They are toxic when applied perorally, as well as when inhaled or absorbed through the skin. The most toxic is 2,4-dinitrophenol employed in the dyestuff industry (sulphur black). In biochemical reactions, its inhibiting effect on the vital functions of the cell is known. The solubility of some nitrophenols is presented in Table 3.17. 

The increasing environmental concerns also relate to the presence of industrial dyestuffs and emerging pollutants, ca. pharmaceutical compounds, in surface and ground waters and wastewaters. Manganese oxides are common minerals in the environment and are among the most important... 

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