Plant electroplating

Many coastal ecosystems have elevated levels of metals and radionuclides (14). Anthropogenic sources of stable isotopes of metals include sewage disposal plants, electroplating plants, and mining and dredging operations sources of radioactive isotopes include effluents from nuclear power plants and submarines, medical establishments, and uranium ore mining. The pollution from most of these operations results from routine or accidental discharges and are either continuous or episodic. 

Nickel concentrations are comparatively elevated in aquatic plants and animals in the vicinity of nickel smelters, nickel-cadmium battery plants, electroplating plants, sewage outfalls, coal ash disposal basins, and heavily populated areas. For example, at Sudbury, Ontario, mean nickel concentrations, in mg/kg DW, were 22.0 in larvae of aquatic insects, 25.0 in zooplankton, and 290.0 in aquatic weeds maximum concentrations reported were 921.0 mg/kg DW in gut of crayfish (Cambarus bartoni) and... 

The depressed prices of most metals in world markets in the 1980s and early 1990s have slowed the development of new metal extraction processes, although the search for improved extractants continues. There is a growing interest in the use of extraction for recovery of metals from effluent streams, for example the wastes from pickling plants and electroplating (qv) plants (276). Recovery of metals from Hquid effluent has been reviewed (277), and an AM-MAR concept for metal waste recovery has recentiy been reported (278). Possible appHcations exist in this area for Hquid membrane extraction (88) as weU as conventional extraction. Other schemes proposed for effluent treatment are a wetted fiber extraction process (279) and the use of two-phase aqueous extraction (280). 

Industrial Wastewater Treatment. Industrial wastewaters require different treatments depending on their sources. Plating waste contains toxic metals that are precipitated and insolubiHzed with lime (see Electroplating). Iron and other heavy metals are also precipitated from waste-pidde Hquor, which requires acid neutralization. Akin to pickle Hquor is the concentrated sulfuric acid waste, high in iron, that accumulates in smokeless powder ordinance and chemical plants. Lime is also useful in clarifying wastes from textile dyeworks and paper pulp mills and a wide variety of other wastes. Effluents from active and abandoned coal mines also have a high sulfuric acid and iron oxide content because of the presence of pyrite in coal. 

Although metals and alloy substrates account for much of the volume ia electroplating, there is a large and growing amount of plastic surfaces being plated, both for decorative trim and for electronic shielding appHcations. On a smaller scale, other materials that ate plated iaclude wood (qv), plaster, fibers (qv) and cloth materials, and plant and animal tissue, such as leaves, leather (qv), paper (qv), and seasheUs. 

Electroplating is done both in job shops, where a customer s work is plated, and in captive (in-house) shops. There were reported to be about 7500 plating plants in the United States (4) in 1992. This is a decrease from the ca 12,000 reported by the same source in 1980. The reduction, particularly in the number of smaller job shops, is related to the problems in meeting the waste regulations imposed on plating shop effluents. 

In addition, a number of small factories, including tanneries, paint and electroplating facilities, have been settled all around the inland territory. The number of residents in the hinterlands and of tourists in all the Venice area has grown constantly. The historical center of Venice (110,000 residents) still has no adequate sewage system and the connections to treatment plants have been completed only recently in the inland territory (>350,000 inhabitants). The central lagoon, where Venice is located, and the most important fresh water channels from the interior, still receive a heavy load of eutrophicating substances. 

Water reuse is practiced at several plants in this industry. Water that may be reused for such purposes as rinse water, makeup water, and cleanup water includes air conditioning water, acid treatment rinsewater, and noncontact cooling water. Reuse of acid rinsewater in alkaline rinses has been demonstrated at many electroplating plants. 

Rhine River, Germany Brazil, electroplating plant, distance from discharge site (meters) Max. 1240 3... 

Reservoir water Vicinity Brazilian electroplating plant 25,000-100,000 12... 

Chromium levels are elevated in soil, air, water, and biota in the vicinity of electroplating and metal-finishing industries, publicly owned municipal treatment plants, tanneries, oil drilling operations, and cooling towers... 

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