Acid neutralization within limestone sand reactors receiving coal mine drainage.
Pulsed bed treatment of acid mine drainage (AMD) uses CO2 to accelerate limestone dissolution and intermittent fluidization to abrade and carry away metal hydrolysis products. Tests conducted with a prototype of 60 L/min capacity showed effective removal of H+ acidity over the range 196-584 mg/L (CaCO3) while concurrently generating surplus acid neutralization capacity. Effluent alkalinity (mg/L CaCO3) rose with increases in CO2 (DC, mg/L) according to the model Alkalinity=31.22+2.97(DC)0.5, where DC was varied from 11-726 mg/L. Altering fluidization and contraction periods from 30s/30s to 10s/50s did not influence alkalinity but did increase energy dissipation and bed expansion ratios. Field trials with three AMD sources demonstrated the process is capable of raising AMD pH above that required for hydrolysis and precipitation of Fe3+ and Al3+ but not Fe2+ and Mn2+. Numerical modeling showed CO2 requirements are reduced as AMD acidity increases and when DC is recycled from system effluent.
Watten
Barnaby J
BJ
United States Geological Survey, Leetown Science Center, 11649 Leetown Road, Kearneysville, WV 25430, USA. barnaby_watten@usgs.gov
Sibrell
Philip L
PL
Schwartz
Michael F
MF
D002119:Calcium Carbonate; D002245:Carbon Dioxide; D003032:Coal Mining; D003247:Conservation of Natural Resources; D006256:Hazardous Waste; D006863:Hydrogen-Ion Concentration; D014865:Waste Disposal, Fluid / Q000379:methods*; D014877:Water Pollution, Chemical; D018508:Water Purification / Q000379:methods*
D006256:Hazardous Waste; D002245:Carbon Dioxide; D002119:Calcium Carbonate