In the refining of ores large amounts of fine-grained mineral particles (tailings) are generally transported together with water (slurry) in pipelines, sometimes as far as several kilometers to the disposal area.

Great savings of energy and water can be obtained at concentrators if the tailings slurry is thickened more effectively and water is reused directly instead of being transported the long way around the disposal area. With direct circulation in sub-arctic regions, large amounts of heating energy can be recovered using a heat pump arrangement. The potential savings at a Swedish concentrator were estimated to be about 10-20 GWh per year, the majority of which would be savings in oil. Furthermore, handling of mine tailings products at low water content offers environmental benefits, and more effective deposition techniques can be used.

In cold areas, temperature and hydrological conditions greatly influence spreading and dissipation mechanisms of pollutants released in the process. Monthly variations of the discharge to the recipient of a substance emitted in the process were simulated in an example. The degree of direct circulation in flotation of complex sulphide ores may be limited by water quality problems in the process. A mathematical model was developed and used to simulate the accumulation of a substance in the process for different degrees of direct circulation.

Finally, a schematic layout of a simple aeration plant for recycled process water was outlined and some regional water-related problems were discussed.