Improving the quality of acidic water in e.g. ponds left after ceasing open-cast mining by treating with alkaline wastes and also air to raise the pH

摘要

Improving the quality of acidic waters, especially raising the pH and buffering effect by addition of alkaline waste materials, is effected by introduction of Ca- and Mg-containing waste materials together with inorganic salts, CO2-containing and/or organic-loaded waste or process water and also air. Improving the quality of acidic waters, especially raising the pH and buffering effect by addition of alkaline waste materials, is effected by introduction into acidic water of pH below 6 or water with acid inflows of: (i) power station ash with total Ca + Mg content above 5%; and/or (ii) waste ash or sediment with total Ca + Mg content above 5%; and/or; (iii) water-treatment sludge with total Ca + Mg content above 2%; and/or (iv) Al production red mud or other wastes in a solids concentration of 1-20% with a total Na aluminate concentration in the introduced material of 1-300 ppm. In the case of water of pH above 4.3 and up to 8.2 there is also added an inorganic carbonate-containing salt (mixture) and/or impure lime or chalk (CaCO3) in an amount of 0.1-10 kg/m<3> seawater with a total Na aluminate concentration of 0.1-50 ppm or, additionally and pro-rata, CO2-containing and/or organic-loaded waste water and/or CO2-containing process water from combustion or gasification processes and/or air at 1-50 volume% of the total water/solids/air mixture. The air is added via a pipe or the total additions are made more than 20 cm above the water surface and/or air at a volume of 10 to above 100% of the water/solids mixture being separately introduced into the water.