Microorganisms, biotechnology and acid rock drainage - emphasis on passive-biological control and treatment methods

Acid rock drainage (ARD) resulting from the natural oxidation of sulfide mi neral wastes has become a major concern to the mining industry, both during the operational period and after mine closure. ARD is generally characteri zed by high acidity and high concentrations of dissolved metals and sulfate s. If the generation of acid cannot be prevented or controlled, it must be treated to eliminate acidity and to reduce the concentration of heavy metal s and suspended solids before release to the Environment. Microorganisms pl ay an important catalytic role in the generation of ARD. Several prevention , control and treatment technologies that ape based on microbiological acti vities have been developed. The role of microorganisms and biotechnology, i n the generation of ARD and their role in the methods used for prevention, control and treatment are discussed in this paper Recently developed passiv e and biological treatment processes that have been implemented at mine sit es are emphasized ill this paper.. Benefits, limitations and design criteri a for passive biological processes are also presented.