Chemical precipitation of aluminum-bearing acid rock discharge

The purpose of this book is to explain the interactions of suspended and soluble aluminum with sulfate and silicates during the active treatment of acid mine drainage (AMD) or acid rock drainage (ARD). Active treatment consists of a multi-basin system with NaOH neutralization followed by settling of formed precipitates before discharge to surface waters. Measured supernatant compositions were compared with calculated values from MINEQL+ computerized equilibrium model.Particle size analysis revealed that sulfate and/or silicates reduced the mean suspended particle size from that which would have existed from the sole formation of amorphous Al(OH)3. Suspended aluminum levels will lead to an increase in the total Al that would be in a settling tank discharge.