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.

Abstract: During the 1990s, passive treatment technology was introduced to the United Kingdom (UK). Early hesitancy on the part of regulators and practitioners was rapidly overcome, at least for net-alkaline mine waters, so that passive treatment is now the technology of choice for the long-term remediation of such discharges, wherever land availability is not unduly limiting. Six types of passive systems are now being used in the UK for mine water treatment: ¨ aerobic, surface flow wetlands (reed-beds); ¨ anaerobic, compost wetlands with significant surface flow; ¨ mixed compost / limestone systems, with predominantly subsurface flow (so-called Reducing and Alkalinity Producing Systems (RAPS)); ¨ subsurface reactive barriers to treat acidic, metalliferous ground waters; ¨ closed-system limestone dissolution systems for zinc removal from alkaline waters; ¨ roughing filters for treating ferruginous mine waters where land availability is limited. Each of these technologies is appropriate for a different kind of mine water, or for specific hydraulic circumstances. The degree to which each type of system can be considered “proven technology” corresponds to the order in which they are listed above. Many of these passive systems have become foci for detailed scientific research, as part of a $1.5M European Commission project running from 2000 to 2003.

Abstract: For the treatment of contaminated mine waters reliable treatment methods with low investment and operational costs are essential. Therefore, passive treatment systems recently have been installed in Great Britain and in Germany (e.g. anoxic limestone drains, constructed wetlands, reactive barriers, roughing filters) and during the last eight years such systems successfully treated mine waters, using up to 6 ha of space. In some cases with highly contaminated mine water, a combination of active and passive systems should be applied, as in any case the water quality has to reach the limits. Because not all the processes of passive treatment systems are understood in detail, current research projects (e.g. EU-project PIRAMID) were established to clarify open questions.