Water requirements of selected industries

Abstract

The copper industry in 1955 used about 330 million gallons of water per day in the mining and manufacturing of primary copper. This amount is about 0.3 percent of the total estimated withdrawals of industrial water in the United States in 1955. These facts were determined by a survey, in 1956, of the amount and chemical quality of the water used by the copper industry. A large part of this water was used in Arizona, Nevada, New Mexico, and Utah, where about five-sixths of the domestic copper is mined. Much of the remaining water use was near New York City where most of the electrolytic refineries are located, and the rest of the water was used in widely scattered places. A little more than 100,000 gallons of water per ton of copper was used in the production of copper from domestic ores. Of this amount about 70,000 gallons per ton was used in mining and concentrating the ore, and about 30,000 gallons per ton was used to reduce the concentrate to refined copper. In areas where water was scarce or expensive, the unit water use was a little more than half the average. About 60 mgd (million gallons per day) or 18 percent of the water was used consumptively, and nearly all of the consumptive use occurred in the watershort areas of the West. Of the water used in mining and manufacturing primary copper 75 percent was surface water and 25 percent was ground water, 89 percent of this water was self-supplied by the copper companies and 11 percent came from public supplies. Much of the water used in producing primary copper was of comparatively poor quality; about 46 percent was saline containing 1,000 ppm (parts per million) or more of dissolved solids and 54 percent was fresh. Water that is used for concentration of copper ores by flotation or even any water that comes in contact with the ore at any time before it reaches the flotation plant must be free of petroleum products because they interfere with the flotation process. The water used in mining and ore concentration was higher in dissolved solids and was harder than the water used in smelting and refining. Water used in mining and ore concentration had a median dissolved solids content of about 400 ppm and a median hardness (as CaCOg) of about 200 ppm. The median values for water used in smelting and refining were only half these amounts. INTRODUCTION More water is used to produce a ton of copper, on the average, than to produce a ton of any other major metal. This conclusion is obtained from a survey of the quality and quantity of water required by the copper industry. The purpose of this survey and 181 182 WATER REQUIREMENTS OF SELECTED INDUSTRIES similar surveys of other industries is to supply knowledge of water use so that new industrial plants will be able to select sites that are near adequate supplies of water of suitable quality without infringing on the requirements of established industries and other activities with which they will share the available water. This report is limited to a study of the water use of that part of the copper industry concerned with mining copper ores and reducing domestic and imported ores and intermediates to refined copper; it does not include any subsequent processing or fabrication. This study also includes domestic and municipal water for housing and company towns where such facilities were established by the copper companies. The water used in the conversion of new and old scrap metal to unalloyed refined copper is also included because it is usually processed with primary copper and forms an integral part of the refinery output. The investigation began with a review of the literature directed toward finding how much and what kind of water was used by the industry. Previously unpublished results of a 1951 survey of water use by the copper industry are also included in this report. Some quantitative and qualitative water-use information was found in the literature; details are shown at appropriate places in the text. The review of the literature was followed by a field survey in the spring and summer of 1956. The field survey consisted of investigations at mines and leaching and flotation plants that produce the concentrates for about 98 percent of our primary domestic copper. Also the survey included visits to all the copper smelters and refineries in the United States. At each mine or plant, information was obtained on the source of water, adequacy of the supply, temperature of the water, treatment given the water, and any unusual practice in water use and the reasons for such practice. The acquistion of these types of information involved the determination of how much and what kind of water was used at each mine or plant, how the water was used, how much water was used consumptively, how much water was reused, the nature and quantity of the raw materials, and the finished product at each mine or plant. In addition, water from each source was classified as process or wash water, cooling water, boiler feed, sanitary and service, and miscellaneous. Process or wash water is defined as water that comes in contact with an end product or with materials incorporated in an end product. Cooling water is water that is used only for cooling. Under these definitions water used to cool a product by being brought into contact with it is classified not as cooling water but as process water. Boiler-feed water is that introduced into boilers for conversion into steam. Sanitary and service water includes water for drinking,