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: A considerable part of water obtained by drainage of Polish coal-mines is saline which creates substantial ecological problems. The load of salt (mainly sodium chloride) amounts to 5 min t/year. Despite the utilisation of saline coalmine waters is considered to be the most adequate method of solving ecological problems caused by this kind of water in Poland there are only two installations utilising coal-mine waters and producing 100,000 t salt per year. In the case of the most concentrated waters, the so-called coal-mine brines, the method of concentrating by evaporation in twelve-stage expansion installation or vapour compression is applied, after which sodium chloride is manufactured. In the case of low salinity waters they are preconcentrated first by RO method. High energy consumption in above-mentioned methods of evaporation is a considerable restriction in the utilisation of coal-mine brines. An obstacle in the application of low energy evaporation processes, e.g. multi-stage flash, is the high concentration of calcium and sulphate ions in the coal-mine waters.