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Alkaline injection: an overview of recent work.
Ladwig KJ; Erickson PM; Kleinmann RLP
Control of acid mine drainage: proceedings of a technology transfer seminar. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, IC 9027, 1985 Jan; :35-40
Injection of alkaline fluid into surface mine spoil to control acid mine drainage (AMD) is a procedure generating considerable interest in Pennsylvania. At least six different mine companies or contractors have attempted some form of injection in the last 2 yr, and many more are considering its use. This paper gives a brief overview of the current status of alkaline injection and of the Bureau of Mines injection research. Introduction of alkalinity is the standard method of mitigating acid discharges. Surface alkaline loading prior to flow through the spoil has been used to slow down the acid-production process. More commonly, alkalinity is added-to the discharge to neutralize existing acidity with conventional water treatment. The premise of alkaline injection is the in-place neutralization of acid water stored in the spoil. In this respect, alkaline injection is not much different than conventional water treatment. Alkaline materials that have been used for injection are sodium hydroxide, hydrated lime, and sodium carbonate, all of which are commonly used in AMD water treatment. Some of the potential advantages of injection over conventional water treatment follow: 1 . Raising the pH of the spoil water may result in the precipitation and filtering of some metals prior to discharge, decreasing sludge storage and removal requirements. 2. The metal precipitates may coat pyrite surfaces, "armoring" them from further chemical weathering. 3. The alkaline environment within the spoil would be less favorable to continued pyrite oxidation. 4. The high-pH environment would limit metal leaching within spoil. 5. Spoil water that "leaks" through the mine floor discharges to the ground water system untreated. Alkalinity introduced into the spoil water reservoir may offer at least partial treatment of the leakage and decrease overall ground water degradation. 6. Treatment by could be done on an lowering labor costs. alkaline injection intermittent basis, While the premise of alkaline injection is straightforward, implementation is not. The extent to which any of the above listed advantages are realized is not known. Of the six attempts with which we are familiar, none have yet substantially improved spoil seep water quality. Unfortunately, documentation of these injections was generally incomplete. For this reason, the Bureau initiated a study to evaluate the technical merit of the injection approach. Described in the following section are two injection programs for which a reasonable amount of documentation was available. At the Fayette site, the Bureau monitored the results of an injection performed by Kaiser Refractories. Much of the data were generously supplied by Bernard Leber of Kaiser Aluminum and Chemical Corp. and Mike Popchak of the Kaiser Refractories division. Descriptions and data for the Clearfield site were kindly provided by Jim McNeil of Al Hamilton Contracting Co. Bureau research on alkaline injection is described in the final section.
Acid mine drainage; Mining; Mining industry; Waste treatment; Waste abatement
IH; Conference/Symposia Proceedings
Control of acid mine drainage: proceedings of a technology transfer seminar
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division