Operational and Financial Studies of Hydrogen Peroxide versus Hydrated Lime and Hydrogen Peroxide versus Sodium Hydroxide at Two Pennsylvania Mine Drainage Treatment Sites

The Pennsylvania Department of Environmental Protection (PA DEP) oversees a number of mine drainage treatment trust funds. Recent financial market conditions have reduced revenue generation needed to pay for treatment. Cost-reduction evaluations were performed at two sites: the Mon-View Mathies and LTV Banning facilities. At Mon-View, 20% sodium hydroxide solution (w/w) was used for treatment and at Banning hydrated lime (Ca(OH) 2 ) was used. The evaluations consisted of characterizing chemical consumption and costs, pilot testing alternative treatment strategies and conducting a cost and treatment performance comparative analysis. The evaluation of the original Mon-View sodium hydroxide system showed hydroxylation and ferrous iron (Fe(II)) removal were the dominant alkali-consuming reactions and calcite formation was minor. The actual NaOH dose was less than half the theoretical dose required to neutralize all alkali-consuming reactions. The treatment process utilized influent alkalinity contained in the mine drainage to aid in neutralization and saves $108 per day in NaOH costs. While this treatment scheme effectively utilized influent alkalinity, avoidable hydroxylation reactions doubled alkali consumption and increased costs. The evaluation of the original LTV Banning hydrated lime system showed the daily Ca(OH) 2 cost was $569, of which $190 was spent on hydroxylation reactions, $39 on Fe(II) removal and $340 on calcite formation. Unlike Mon-View, this treatment system did not utilize influent alkalinity and dosed at the theoretical rate required to neutralize alkali-consuming reactions. A small portion of alkali added actually contributed to Fe(II) removal, which was the sole parameter targeted for treatment. The evaluations showed significant chemical costs as a result of alkali consumption due to hydroxylation and calcite-formation reactions. Year-long hydrogen peroxide (H 2 O 2 ) field trials were conducted at each site to eliminate costs due to hydroxylation and calcite formation. At Mon-View, a 35% H 2 O 2 dosing rate of 14 gallons per day achieved effluent concentrations