Abstract: Contact of oxygen contained in air and water with mining materials can increase the solubility of metals. In heaps leached by cyanide, metals can also be made soluble through complexation with cyanide. During closure, water in heaps, and water collected in mine workings and pit lakes may require treatment to remove these metals. In situ microbiological treatment to create reductive conditions and to precipitate metals as sulfides or elemental metal has been applied at several sites with good success. Treatment by adding organic carbon to stimulate in situ microbial reduction has been successful in removing arsenic, cadmium, chromium, copper, iron, lead, manganese, mercury, nickel, selenium, silver, tin, uranium, and zinc to a solid phase. Closure practices can affect the success of in situ treatment at mining sites, and affect the stability of treated materials. This paper defines factors that determine the cost and permanence of in situ treatment.

Abstract: In Alberta, oil sands bitumen is utilized for synthetic crude oil (SCO) production by surface mining, bitumen extraction followed by primary (coking) and secondary (catalytic hydro-treating) upgrading processes. SCO is further refined in specially designed or slightly modified conventional refineries into transportation fuels. Oil sands tailings, composed of water, sands, silt, clay and residual bitumen, is produced as a byproduct of the bitumen extraction process. The tailings have poor consolidation and Water release characteristics. For twenty years, significant research has been performed to improve the consolidation and water release characteristics of the tailings. Several processes were developed for the management of oil sands tailings, resulting in different recovered water characteristics, consolidation rates and consolidated solid characteristics. These processes may affect the performance of the overall plant operations. Apex Engineering Inc. (AEI) has been developing a process for, thesame purpose. In this process oil sands tailings are treated with Ca(OH)(2) lime and CO2 and thickened using a suitable thickener. The combination of chemical treatment and the use of a thickener results in the release of process water in short retention times without accumulation of any ions in the recovered water. This makes it possible to recycle the recovered water, probably after a chemical treatment, as warm as possible, which improves the thermal efficiency of the extraction process. The AEI Process can be applied in many different fashions for the management of different fractions of the tailings effluent, depending on the overall plant operating priorities.

Abstract: Pollution by mine drainage is a major problem in many parts of the world. The most frequent contaminants are Fe, Mn, Al and SO (sub 4) with locally important contributions by other metals/metalloids including (in order of decreasing frequency) Zn, Cu, As, Ni, Cd and Pb. Remedial options for such polluted drainage include monitored natural attenuation, physical intervention to minimise pollutant release, and active and passive water treatment technologies. Based on the assessment of the key hydrological and geochemical attributes of mine water discharges, a rational decision-making framework has now been developed for deciding which (or which combinations) of these options to implement in a specific case. Five case studies illustrate the application of this decision-making process in practice: Wheal Jane and South Crofty (Cornwall), Quaking Houses (Co Durham), Hlobane Colliery (South Africa) and Milluni Tin Mine (Bolivia). In many cases, particularly where the socio-environmental stakes are particularly high, the economic, political and ecological issues will prove even more challenging than the technical difficulties involved in implementing remedial interventions which will be robust in the long term. Hence truly “holistic” mine water remediation is a multi-dimensional business, involving teamwork by a range of geoscientific, hydroecological and socio-economic specialists.