Chapter 16
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Bench-Scale Chemical Treatability Study of the Berkeley Pit Water Hsin-Hsiung Huang and Qi Liu Department of Metallurgical Engineering, Montana Tech of the University of Montana, Butte, MT 59701
Lime and limestone are the most commonly used and most effective chemical reagents to treat acid mine drainage. They can be used to treat the Berkeley Pit water in Butte, Montana by two-stage neutralization processes to meet E P A Water Quality Criteria for Aquatic Life (Gold Book). Over 92% of copper in the Berkeley Pit water can also be cemented by industrial scrap iron without any ill effect on the subsequent neutralization treatment. The two-stage lime neutralization process, with several polishing steps tested, was confirmed by an 80 gallon water test.
The oxidation and leaching of sulfide minerals in the mines and in mine wastes are the major causes of producing acid mine drainage. The Berkeley Pit, located at the northeast edge of Butte, Montana, is one of the world's largest ore deposits that contains copper and other metals. Mining began in the Butte area in the late nineteenth century. The Anaconda Copper Mining Company began open pit mining in 1955, and during the operation, drainage water was pumped, treated and discharged. Since the shut-down of the Berkeley Pit in 1982, the drainage pumps were turned off. Both underground mine workings and the Pit are flooding with the water. In terms of contained volume of the water and quantity of metal pollutants, the Berkeley Pit is unmatched by any acid producing mine in the United States and possibly in the world. It has been filling at a rate that ranges from 5 to 7.6 million gallons per day, and has accumulated over 20 billion gallons. The water will probably reach an alluvium bedrock contact exposed in the Pit wall approximately in the year 2011. This will create a serious threat to the ground water quality in the Butte area. About 1/3 of the water entering the Pit is surface water and 2/3 is from underground water.
0097-6156/95/0607-0196$12.00/0 © 1995 American Chemical Society Tedder;Pohland; Emerging Technologies in Hazardous Waste Management V ACS Symposium Series; American Chemical Society: Washington, DC, 1995.
16. HUANG & LIU
Chemical Treatability Study of the Berkeley Pit Water
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The hazardous constituents in the water are several orders of magnitude greater than discharge regulations and they clearly need removal and disposal. To develop or to evaluate processes for treating the water requires an understanding of the chemical properties and the sources of the water itself.
Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 11, 2018 | https://pubs.acs.org Publication Date: November 9, 1995 | doi: 10.1021/bk-1995-0607.ch016
CHEMISTRY The chemistry of the Berkeley Pit water was studied for treatment purposes. Unlike most of the waters which are anionically dominated by chloride or carbonate, the Pit water is dominated by sulfate. Sulfate waters are usually associated with metals or coal mining wastes or with current geothermal activity. The Berkeley Pit water also contains extremely high levels of dissolved heavy and transition metals, and is highly oxidized and acidified compared even to most of the acid mine drainage. The major cation is iron. The chemistry study for speciation calculation, saturation with solids, neutralization and oxidation are availablefrom(1). Composition of the Berkeley Pit Water The Berkeley Pit water has been sampled and reported on by EPA, Montana Bureau of Mines and Geology (MBMG), and Montana Tech since 1984. The composition of the water about 200 feet below the surface, the E P A Gold Book regulations and the drinking water standards are listed in Table 1.
Table 1. Composition of the Berkeley Pit Water and EPA Water Criteria (ppm) Nov. 84 62 feet fAll 142 iAsl 0.2 [Cdl 1.54 rcai 477 fCul 164 TFel 256 4.4 ΓΚ1 236 fMRl fMnl 106 [Nil / iNal 61.7 iPbl / fZnl 255 SiO, / 12.3 ci4410 Sulfate 2.78 PH 1 Eh, mv /
Jun. 85 100 feet 172 0.43 1.62 435 229 451 8.8 261 116 / 60 / 329 / 83 5550 2.48 /
Oct. 86 200 feet 192 0.04 1.74 457 204 918 243 291 144 0.91 65.8 / 460 / / / / /
Oct. 87 216 feet 193 1.2 1.76 479 202 1010 18.7 279 161 0.99 70.5 0.66 494 / 21.8 6940 3.15 463
May. 91 225 feet 288 0.83 1.57 492 191 1088 20 418 182 1.05 68 0.08 552 / 10.9 8010 2.84 650
Oct. 92 200 feet 304.5 0.43 2.00 525.1 215.1 1112 19.9 517 225.5 0.91 107.7
