The least costly and most effective method of controlling Acid Mine
Drainage is to prevent its initial formation. On occasion, despite the
application of sound mining and reclamation principles, Acid Mine Drainage
will be formed and must be treated to meet existing Federal and State
standards before it is released from the minesite. Prior to opening
the mine the operator should evaluate the potential for creating Acid
Mine Drainage that would require treatment and should become familiar
with the extent of the costs that such treatment might impose. Consideration
should also be given to the possibility that treatment might have to
be continued well into the future, specifically until such time that
the discharge meets effluent standards without treatment.
Treatment, as normally applied to Acid Mine Drainage, involves chemical
neutralization of the acidity followed by precipitation of iron and
other suspended solids. Treatment systems include
1. equipment for feeding the neutralizing agent to the Acid Mine Drainage
2. means for mixing the two streams (Acid Mine Drainage and neutralizing
agent)
3. procedures for ensuring iron oxidation
4. settling ponds for removing iron, manganese, and other co-precipitates
A number of factors dictate the level of sophistication of the treatment
system that is necessary to ensure that effluent standards will be met.
These factors include: the chemical characteristics of the Acid Mine
Drainage, the quantity to be treated, climate, terrain, sludge characteristics,
and projected life of the plant. The chemicals usually used for Acid
Mine Drainage treatment include limestone, hydrated lime, soda ash,
caustic soda, and ammonia. The following discussion highlights some
of the characteristics of each of these neutralizing agents.
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