The Tannery Industry

Chromium is an important heavy metal used in leather, electroplating, and metallurgical industries. More than 170,000 tons of Cr wastes are discharged into the environment worldwide each year. In India in 1999 700,000 tons of wet salted hides and skins were processed in about 3000 taimeries, which discharged a total of 30 billion liters of waste water with a concentration of suspended solids between 3000-5000mg/L and chromium as Ci between 100-200mg/L (Rajamani). 

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Benzene (BS) and naphthalene sulfonates (NPS) are commonly used in the textile industry as dye bath auxiliaries and in the tannery industry as dispersants and wetting agents. After application, these compounds are discharged into surface waters and their presence in industrial effluents was not reported due to the lack of an appropriate analytical technique. Recently, ion-pair chromatography-ESI-MS and LC-ESI-MS was developed to determine BS and NPS with the final goal of determining polar, ionic, and water-soluble pollutants in wastewater [7],... 

Guruprasada Rao, M., Nandakumar, N.V., 1982. The tannery industrial effluent effect on succinate dehydrogenase activity pattern in a freshwater snail Pita globosa. Proc. Ind. Acad. Sci. 91, 427 31. 

Europe is still the main market for leather products and leather produced in the developing countries, e.g. Southeast Asia, may therefore end up on the European market and to European consumers. Chemicals that are added during the production, and which stay on/in the product, will hence be transported by the product to the final markets, and there will be a chemical flow around the world through the transport of leather and leather products containing chemicals. Since the tanning industry is a chemically intensive industry, an efficient chemical management in tanneries is necessary in order to minimise the overall use of chemicals and in particular also to reduce the amount of hazardous chemicals used in order to minimise eventual health effects on the consumer. 

The relevant legislation for tanneries regarding the use of chemicals can be found both in legislation regarding environmental permits for the industrial installations which in some cases addresses substitution of chemicals. One example of this is the EU Industrial Emissions Directive [4] which regulates emissions from industrial installation within the EU. One key aspect in this directive is how problematic chemicals should be substituted to more environmentally friendly alternatives by tanneries. 

The leather industry is a traditional industrial sector using a high number of chemicals as it is not uncommon that tanneries use 30CM-00 different chemicals in their production. 

Globally, it can be estimated that the tanning industry use around 3 million tons of chemicals for the production of leather. The chemicals will end up in the product or waste or will be directly discharged to the water, air or soil. Although a major part of the chemicals are standard organic chemicals and standard inorganic chemicals, it is important for tanneries to have a careful control of the chemicals both for environmental and health reasons. 

Rautenbach and MeUis [75] describe a process in which a UF-membrane fermentor and a subsequent NF-treatment of the UF-permeate are integrated. The retentate of the NF-step is recycled to the feed of the UF-membrane reactor (Fig. 13.8). This process has been commercialised by Wehrle-Werk AG as the Biomembrat -plus system [76] and is well suited for the treatment of effluents with recalcitrant components. The process also allows for an additional treatment process, like adsorption or chemical oxidation of the NF-retentate, before returning the NF-retentate to the feed of the UF-membrane fermentor. Usually, the efficiency of these treatment processes is increased as the NF-retentate contains higher concentrations of these components. Pilot tests with landfiU leachates [75] and wastewater from cotton textile and tannery industry have been reported [77]. An overview of chemical oxygen demand (COD) reduction and COD concentrations in the permeate are shown in... 

According to the 1990-93 CAREX database for 15 countries of the European Union (Kauppinen et al., 1998) and the 1981-83 National Occupational Exposure Survey (NOES) in the United States (NOES, 1997), approximately 45 000 workers in Europe and as many as 27 000 workers in the United States were potentially exposed to pentachlorophenol (see General Remarks). Recent figures give rough estimates of 500 pentachlorophenol-exposed workers in wood treatment facilities in the United States (Norman, 1998). No current data on numbers of workers exposed to other chlorophenols were available. Occupational exposures to chlorophenols have occurred in their production, in the production and use of some phenoxy acid herbicides, in sawmills and other wood-related industries, the textile industry and tanneries. Occupational exposures to penta-... 

Exposures to chlorophenols and their salts have occurred in their production, in the production of some phenoxy acid herbicides, in the wood industry, the textile industry and tanneries. They have been detected at low levels in ambient air and water. 

The ELM pertraction technology has good potential for more applications at industrial scale in the near future. The industries in question might include metal mining and refinery operations (precious metals and platinum group metals are good examples), tannery industry (recovery of hexavalent chromium), and processing of nuclear wastes (recovery of uranium, strontium, and other metals). 

Pentachlorophenol is a common organochlorine compound that is found in environmental samples. It is used as a preservative for wood and glue as well as an insecticide, herbicide and as a defoliant. It has been found in effluent from the paper industry, tanneries and textile plants. 

An EPA survey has shown that leather tanneries typically ( rate 10 to 12 d [15] and are specialized in dyeing either grain or suede sides. The most common dyeing method applied is so-called drum-dyeing in which the dye preparation is mechanically pumped into rotation wheels. Environmental releases occur during the opening of the wheel batch and dumping the wet and rinsed dyed sides. Major dye-classes applied in the leather industry are acid dyes (which account for about 90% of the leather market), metal complex dyes and, to a lesser extent, cationic dyes. 

The annual production of chromium (Cr) ores amounts to 10 million tons. Cr is used in the production of special steels in the metal-processing industry, for chromium coating in the galvanic industry, as a pigment and catalyst in the chemical industry, as a dye in the textile industry, for leather production in tanneries, and for the impregnation of products in the timber industry. The use of Cr-rich products has led to Cr accumulation in the environment. Local Cr exposure of soil and the environment can occur via sludge, water and air (Anke et al. 

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