Evaluation of water treatment sludge for ameliorating acid mine waste.
This study investigated the liming effect of water treatment sludge on acid mine spoils. The study was conducted with sludge from a water purification plant along the Vaal River catchments in South Africa. The optimum application rate for liming acid spoils and the speed and depth with which the sludge reacted with the mine waste were investigated. Chemical analysis indicated that the sludge is suitable as a liming agent because of its alkaline pH (8.08), high bicarbonate concentration (183.03 mg L(-1)), and low salinity (electrical conductivity = 76 mS m(-1)). The high cation exchange capacity of 15.47 cmol(c) kg(-1) and elevated nitrate concentration (73.16 mg L(-1)) also increase its value as an ameliorative material. The soluble concentrations for manganese, aluminum, lead, and selenium were high at a pH of 5 although only selenium (0.83 mg L(-1)) warranted some concern. According to experimental results, the application of 10 Mg ha(-1) of sludge to acid gold tailings increased the leach water pH from 4.5 to more than 7.5 and also increased the medium pH from 2.4 to 7.5. The addition of sludge further reduced the solubility of iron, manganese, copper, and zinc in the ameliorated gold tailings, but increased the electrical conductivity. The liming tempo was highest in the coal discard profile that had a coarse particle size distribution and took the longest to move through the gold tailings that had a fine particle size distribution. Results from this study indicate that the water treatment sludge investigated is suitable as a liming agent for rehabilitation of acid mine waste.
Van Rensburg
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School of Environmental Sciences and Development, Potchefstroom University for Christian Higher Education, Potchefstroom 2520, South Africa. plblvr@puknet.puk.ac.za
Morgenthal
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TL
D017610:Calcium Compounds / Q000737:chemistry; D003247:Conservation of Natural Resources; D006046:Gold; D006863:Hydrogen-Ion Concentration; D008670:Metals / Q000737:chemistry; D008906:Mining; D010087:Oxides / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D012995:Solubility; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
D017610:Calcium Compounds; D008670:Metals; D010087:Oxides; D012722:Sewage; D006046:Gold; C016538:lime