Treatment of Acid Mine Drainage Water Using Fly Ash and Water Softening Sludge
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TREATMENT OF ACID MINE DRAINAGE WATER USING FLY ASH AND WATER SOFTENING SLUDGE ASMARE ATALAY*,
SRINIVAS CHALUVADI*,
JOAKIM G. LAGUROS*,
AND JERRY J.
BLACK"
*The University of Oklahoma, 202 West Boyd, Norman, Oklahoma 73019, U.S.A. Black and Associates, 1908 West Boyd, Norman, Oklahoma 73069,
"**Consultant, U.S.A.
ABSTRACT Acid mine drainage (AMD) is being recognized as a major pollution source to surface water. Heavy trace metals emanating from abandoned mines are continuously being released and contaminating surrounding lakes and streams. The potential for utilizing fly ash and water softening sludge (WSS) as buffering and adsorption media for AMD water was assessed. The results indicated that AMD water treated with fly ash either met or exceeded the U.S. Environmental Protection Agency water quality criteria for effluent standards for total iron, manganese, suspended solids, and pH. The optimum dosage of fly ash and sludge needed for treating the acid mine water from Picher field, an abandoned lead and zinc mine in Oklahoma, has been determined. It was observed that each had better than 90 percent efficiency for removal of heavy metals from the AMD water. The combined use of fly ash and WSS was also investigated, but there was no significant improvement compared to using fly ash alone. In general fly ash had a greater buffering capacity to treat acid mine water than did WSS. Consequently, fly ash can be used to treat AMD water and minimize its environmental impact.
INTRODUCTION Acid mine drainage causes environmental concern because it impacts both aquatic and terrestrial life. The impact of acidity on fish and other aquatic fauna is well documented [1]. The greatest effect of acidity on fish population seems to be targeted to impairing reproduction. The source of AMD water in coal mine operations is the oxidation of pyrite (FeS 2 ). This mineral can be oxidized either upon exposure to atmospheric oxygen or by selected bacterial species (2]. Nordstrom [3] has isolated T. ferroxidans, T. thiooxidans, and T. acidophilus from acid mine wastes. These organisms are known to oxidize pyrite, iron, and/or sulfur. Fly ash is produced in large quantities throughout the world, with over 100 million tones annually in the United States alone [4]. The annual production of WSS in the U.S. is in excess of two million tons [5]. Both of these solid wastes are currently being disposed off either in landfills or in open pits. Some of the fly ash, approximately 20 percent, is being used for various purposes in the construction and ceramic industries [6]. Water softening sludge has been used as a soil conditioner in agricultural fields, but due to the growing environmental concern its use has been curtailed. However, both of these waste materials are highly alkaline and can be used to neutralize acid mine drainage water. The significance for utilizing fly ash and WSS is based on their ability to raise the pH of AMD water. Both alkalinity and surface area of these waste materials play important roles in the neutralization of ac
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