The mining of coal most often leads to the development of Acid Rock Drainage (ARD) because during peat accumulation anoxic and reducing conditions establish and an availability of sulphate and reducible iron, even at low concentration, leads to the formation of iron sulphides (mostly pyrite). Once exposed oxidation and acid generation occurs, which may mobilize trace metals from the coals. The combination of acid and metals can seep into water ways where it can effectively sterilize many km of stream, and deposit substantial quantities of iron oxy-hydroxides. Frequently waste rock and coal washery tailings are stored where they provide suitable habitat for bacteria that accelerate the oxidation of pyrite and the production of acid. Aberdare East colliery is a former underground mine located in Cessnock, New South Wales, Australia. Coal washery tailings from the mine are impounded in a series of overlapping stacked cells in a small catchment. Relatively clean water enters the south eastern extent of the tailings and moves to the northwest down the hydrological gradient, and exit the north western batter slope into the a small creek. During flow through the tailings salinity, metal content, redox potential, and temperature all increase; solution pH decreases. Investigations indicate that the impoundment contains 109,445 m 3 of water, 337,793 m 3 saturated fines, 720,113 m 3 of unsaturated fines, and 184,568 m 3 of clay capping. Treatment rates indicate that the water requires 5.123kg/m 3 of Bauxsol™ Acid B Extra™ C5T5 blend (561 t) and that a further 24,000 t of Bauxsol™ ViroMine™ is required to prevent further acidity at the site being generated. This compares favourably with lime of 0.951 kg/m 3 for the water (104 t) and 32,750 t to prevent further acid production from the tailings. Additional benefits from the Bauxsol™ based treatments are lowered sludge volumes during water treatment, increased chemical stability of the residues and therefore greatly reduced disposal costs, a decreased susceptibility to dissolution of the ANC from the soil/tailings profile that reduces the possibility of having to reapply after 5 or 10 years and, consequently, a reduced safety margin for the Bauxsol™ application is required.
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