Acid Mine Drainage (AMD), or the outflow of acidic water sites, is a worldwide issue. Generally, the acid comes from the oxidation of iron sulfide, also called pyrite or “fool’s gold.” The problem, found primarily in hardrock mines, when metal ore is bound up with sulfur. It’s causing ecological devastation of our watersheds and contamination of our water sources. The heavy metals found in AMD include arsenic, copper, and lead, just to name a few. When acid-generating rock is crushed and exposed to oxygen, containing the acid generation is nearly impossible. In fact, Roman-Era mines are still producing acid mine drainage today, because it can continue for thousands of years until the sulfide minerals are exhausted.
Why is acid mine drainage such a major problem? The process of turning inert ore into hazardous waste is irreversible, the extremely long life of the matter, and the inability to contain it.
Iron sulfide exists naturally in large quantities undergrounds. Due to its depth, it is isolated from surface waters and has little no surface area. Thus, it cannot react to water or oxygen and acid formation occurs at a harmless rate. However, when people start crushing the ore to extract valuable metals, like copper, gold, lead, silver, or zinc, they become exposed to acid-forming reactions. The iron sulfide is now exposed to air, or dissolved oxygen in water, and it oxidizes into sulfate and turns into sulfuric acid. Sulfuric acid is used in car batters, for instance, and is toxic t most living organisms.
What are some of the negative effects on our environment? Waterways become entirely inhospitable to aquatic life. Streams no longer buffer against chemical changes. Precipitates, such as “yellow boy,” smother life in streams. This water turns a distinctive orange/red color and it becomes coated by the chemical precipitate. Drinking water is contaminated.
Three basic forms of prevention are to prevent sulfuric acid from forming altogether, neutralize the acid after if forms, or collect the runoff in order to contain the acid. These strategies often fail. Water treatment with the use of neutralization causes an increase in the total dissolved solids (TDS) in the water, which also has negative impacts on aquatic life and human health.
While some strategies have proved worthwhile, such as artificial wetlands, it is impractical due to the immense areas of land that would be needed. Bioreactors have also proved positive, but the technology is very expensive for use in large-scale mines and would also require too much land.
Total Remediation Solutions TS1 system is a portable system for used onsite. It is designed specifically to treat contaminated mine water. The contaminated water passes through the unit and is combined with TS1 to turn heavy metals, such as copper, lead, and zinc, into safe, non-toxic waste for easy disposal.
Ground Truth Trekking. Acid Mine Drainage. October 29, 2014, http://www.groundtruthtrekking.org/Issues/MetalsMining/AcidMineDrainage.html.