A Review of Sulfate Removal Options for Mine Waters

Sulfide oxidation is a common phenomenon associated with many mined ore bodies and extracted or processed waste. Where the products of these chemical reactions can enter a water body the result is often a reduction in water quality through the increase of acidity, metals and dissolved salts. Due to an attributed lower environmental impact the release of sulfate has received little attention in many regulatory jurisdictions when compared to control of dissolved metals or acidity. Consequently the literature on sulfate removal from mine waters is comparatively small when compared to metal control despite the use and development of several technologies to reduce sulfate and total salt loadings. Sulfate control levels are based primarily on the secondary drinking water recommendations of approximately 500 mg/L, based on the laxative effect of high magnesium sulfate concentration. Sulfate control in mine waters primarily follows one of two methodologies; (1) Removal through membrane separation of salts from water; (2) Removal of sulfate by salt precipitation through ion exchange, permeable reactive barrier, biological reduction or formation of insoluble mineral precipitate. These approaches are reviewed within this paper and an economic and technical comparison made between the available technologies. Based on demonstrated technology and economic benefits the most promising technologies to date are biological sulfate reduction, SAVMIN, and GYPCIX. At sulfate concentrations less than 2000 mg/L the limestone/lime process is an effective low-cost or pre-treatment removal option for sulfate. As with any mine water treatment option site-specific conditions will control the most suitable option for a particular mining operation. Bowell, R. J. (2004): A review of sulphate removal options for mine waters. – In: Jarvis, A. P., Dudgeon, B. A. & Younger, P. L. (eds): mine water 2004 – Proceedings International Mine Water Association Symposium 2. – p. 75-91, 6 fig., 7 tab.; Newcastle upon Tyne (University of Newcastle).