Coal Mine Drainage Pollution and Its Remediation

Abstract

Contaminated mine water is a ubiquitous persistent and detrimental ­environmental problem. Coal mine water is often acidic and if acid consuming minerals are present it is having neutral pH. The terms acid mine drainage or acid rock drainage (AMD/ARD) are not universally applicable to all mine drainages, however these terms are used even for non acidic mine water. Several chemical and biological factors are responsible for coal mine drainage generation. The environmental issues related to coal mine water pollutants are attributable to the exposure of reduced iron, sulphides and coal materials to oxygen and water. In the generation of mine drainage pollution microorganisms play both beneficial and destructive roles. Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans accelerate the chemical rate of pyrite oxidation about 500,000–1,000,000 fold, which is responsible for high concentration of sulphate, acid and turbidity of surface and underground waters. Control of sulphide oxidation may reduce or even eliminate the possibility of AMD/ARD generation, which is the main cause of most of the mine water pollution problems. On the other hand biochemical processes involving sulphate reducing bacteria and wetland or controlled reactor systems are used for removal of sulphate, metals and neutralisation of acid mine drainage. Other established treatment procedure for prevention of sulphide oxidation and AMD generation includes isolation, selective handling, co-disposal, blending and surface treatment of waste materials produced at mine site. Microbial activity may be controlled by addition of organic waste and use of bactericides.