Science, Technology and Engineering

Environmental Geoscience

Postgraduate Projects

Improved neutralisation procedures for Acid Rock Drainages

Orsolya Parkanyi

Supervisors: Dr John Webb and Dr Ian Potter

The aim of this project is to provide improved neutralisation procedures for Acid Rock Drainage (ARD). ARD is generated at metal and coal mines worldwide, and is one of the most costly and long-lived environmental issues facing these mine-sites, costing billions of dollars a year (Lottermoser 2003; Taylor and Waters 2003). Oxidation of sulphide minerals (usually pyrite) by exposure to air and water produces ARD, which is very acidic (pH often <3) and contains large amounts of dissolved iron, along with aluminium, copper, zinc and other heavy metals, depending on the specific mineral or coal deposit. ARD is often extremely toxic to the environment, and if released from the mine site will pollute adjacent waterways and groundwater. Much work has gone into preventing ARD and developing procedures to neutralise the acidity and remove the dissolved heavy metals so the water can be reused or safely discharged from a site.

Improved neutralisation procedures for ARD are required, that will produce treatment sludges that resist leaching under low pH conditions. The physical properties of the sludges have been substantially improved by the HDS process, which forms a denser, lower volume sludge that is easier to handle (solids content of 15-70 wt% compared to <5 wt% for standard lime neutralisation sludges; Tremblay and Hogan 2000; Brown et al. 2002). A new neutralisation procedure is needed to similarly improve the chemical stability (leachability) of the sludges, preferably by a modification of standard acid drainage treatment plants, and the aim of the present project is to provide this.