Abstract: Decades of atmospheric acid deposition have resulted in widespread lake and river acidification in the northeastern U.S. Biological effects of acidification include increased mortality of sensitive aquatic species Such as the endangered Atlantic salmon (Salmo salar). The purpose of this paper is to describe the development of a limestone-based fluidized bed system for the treatment of acid-impacted waters. The treatment system was tested at the Craig Brook National Fish Hatchery in East Orland, Maine over a period of 3 years. The product water from the treatment system was diluted with hatchery water to prepare water supplies with three different levels of alkalinity for testing of fish health and Survival. Based on positive results from a prototype system used in the first year of the study, a larger demonstration system was used in the second and third years with the objective of decreasing operating costs. Carbon dioxide was used to accelerate limestone dissolution, and was the major factor in system performance, as evidenced by the model result: Alk = 72.84 X P(CO2)(1/2); R-2 = 0.975. No significant acidic incursions were noted for the control water over the course of the Study. Had these incursions occurred, survivability in the untreated water would likely have been much more severely impacted. Treated water consistently provided elevated alkalinity and pH above that of the hatchery source water. (C) 2005 Elsevier B.V. All rights reserved.

Abstract: Acid mine drainage (AMD) is one of the most significant environmental challenges facing the mining industry worldwide. Water infiltrating through the metal sulphide minerals, effluents of mineral processing plants and seepage from tailing dams becomes acidic and this acidic nature of the solution allows the metals to be transported in their most soluble form. The conventional treatment technologies used in the treatment of acid mine drainage are expensive both in terms of operating and capital costs. One of the methods of achieving compliance using passive treatment systems at low cost, producing treated water pollution free, and fostering a community responsibility for acid mine water treatment involves the use of wetland treatment system. These wetlands absorb and bind heavy metals and make them slowly concentrated in the sedimentary deposits to become part of the geological cycle. In this paper a critical review of the heavy metal removal mechanism involving various physical, chemical and biological processes, which govern wetland performance, have been made. This information is important for the siting and use of wetlands for remediation of heavy metals.

Abstract: The uncontrolled release of acid mine drainage (AMD) from abandoned mines and tailing piles threatens water resources in many sites worldwide. AMD introduces elevated concentrations of sulfate ions and dissolved heavy metals as well as high acidity levels to groundwater and receiving surface water. Anaerobic biological processes relying on the activity of sulfate reducing bacteria are being considered for the treatment of AMD and other heavy metal containing effluents. Biogenic sulfides form insoluble complexes with heavy metals resulting in their precipitation. The objective of this study was to investigate the remediation of AMD in sulfate reducing bioreactors inoculated with anaerobic granular sludge and fed V with an influent containing ethanol. Biological treatment of an acidic (pH 4.0) synthetic AMD containing high concentrations of heavy metals (100 Mg Cu2+vertical bar(-1); 10 mg Ni2+vertical bar(-1), 10 mg Zn2+vertical bar(-1)) increased the effluent pH level to 7.0-7.2 and resulted in metal removal efficiencies exceeding 99.2%. The highest metal precipitation Cn rates attained for Cu, Ni and Zn averaged 92.5, 14.6 and 15.8 mg metal l(-1) of reactor d(-1). The results of this work demonstrate that an ethanol-fed sulfidogenic reactor was highly effective to remove heavy metal contamination and neutralized the acidity of the synthetic wastewater.