the Afon Pelena in the River Afan valley above Port Talbot where highly ferruginous discharges from the Whitworth mine have been successfully treated. Precipitation of metal sulfides Most base metals in acidic solution precipitate in contact with free sulfide, e.g. from H2S or NaHS. Solid-liquid separation after reaction would produce a base metal-free effluent that can be discharged or further treated to reduce sulfate, and a metal sulfide concentrate with possible economic value. As an alternative, several researchers have investigated the precipitation of metals using biogenic sulfide. In this process, Sulfate-reducing bacteria oxidize organic matter using sulfate, instead of oxygen. Their metabolic products include bicarbonate, which can neutralize water acidity, and hydrogen sulfide, which forms highly insoluble precipitates with many toxic metals. Although promising, this process has been slow in being adopted for a variety of technical reasons. Technologies Many technologies exist for the treatment of AMD. Metagenomic study With the advance of large-scale sequencing strategies, genomes of microorganisms in the acid mine drainage community are directly sequenced from the environment. The nearly full genomic constructs allows new understanding of the community and able to reconstruct their metabolic pathways. Our knowledge of acidophiles in acid mine drainage remains rudimentary: we know of many more species associated with ARD than we can establish roles and functions. Microbes and drug discovery Scientists have recently begun to explore acid mine drainage and mine reclamation sites for unique soil bacteria capable of producing new pharmaceutical leads. Soil microbes have long been a source for effective drugs and new research, such as that conducted at the Center for Pharmaceutical Research and Innovation, suggests these extreme environments to be an untapped source for new discovery. List of selected acid mine drainage sites worldwide This list includes both mines producing acid mine drainage and river systems significantly affected by such drainage. It is by no means complete, as worldwide, several thousands of such sites exist. Africa West Rand Goldfield, Witwatersrand, South Africa Europe Avoca, County Wicklow, Ireland Aznalcollar mine on the Guadiamar, Spain Wheal Jane, Cornwall, England Tinto River, Spain Odiel River, Spain Libiola's mine, Italy Spree River, Germany The Lusatian Lake District and the Central German Lake District, both the product of open pit lignite mining, have to deal with acid mine drainage North America Argo Tunnel, Idaho Springs, Colorado, US Berkeley Pit superfund site, covering the Clark Fork River and 50,000 acres (200 km2) in