Abstract: In temperate areas of abundant freshwater there is seldom an urgency to recycle. The statutory protection of inland waters for beneficial uses such as drinking, food processing and game fishing is requiring industries to choose recycling. A European success in this trend is a base metal mining/milling industry which, since 1977, is implementing hydraulic, hydrological, treatment and ecological studies with wastewaters and mine tailings. A model activity, located 50 km from Dublin is considered. Zinc and lead concentrates produced and exported to smelters ultimately yield approximately 194,000 t and 54,000 t of these respective metals (32 and 21 percent of European production). Water use as originally planned would have been approximately 6m(3)/t of ore milled. While ore milling increased by 25 percent to 8,500t/d in 1993, water use declined by 33 percent to 4m(3)/t. The components making up this reduction range from milling technology efficiency to greater recycling from the 165 ha tailings pond. Environmental standards, based on framework regulations originating in EU Directives, have been instrumental in achieving wastewater savings. A conclusion is the value of integrating water quantity, quality, recycling, storage, production and other factors early in project planning. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.

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.