Acid Mine Drainage

There are two main approaches to controlling Acid Mine Drainage (AMD): eliminate the source and treat the AMD.

Eliminate the Source

The first approach is to reduce or eliminate the source of the AMD.  There are two methods for this:

Prevent Oxidation

The first method attempts to prevent oxidation by replacing the air in the mine with groundwater.  The mine openings are sealed with an impermeable grouting material.  Then groundwater is pumped into the mine, displacing the air, and preventing oxidation.

Fill the Mine

Another method attempts to fill the mine with a solid such as a clay slurry in order to eliminate the oxidation.

Treat the AMD

The second approach to control AMD involves treating the AMD itself.  There are three methods for this:

Chemical Treatment

Chemical treatments attempt to neutralize the acid by adding an alkali such as soda ash or lime, and using a sedimentation basin downstream to retain metal precipitates that result from the pH adjustment.

Biological Treatment

Biological treatments use wetlands, for example, to filter the AMD and add biological nutrients to accelerate natural restoration to a normal pH.  Generally, wetlands receive water after it has been nearly-neutralized by a chemical treatment.

Physical Treatment

Physical treatment attempts to eliminate AMD by re-routing streams to avoid problem areas.

Information from Ohio University and Wikipedia.

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