Acid Mine Drainage Treatment

USP’s Acid Mine Drainage Program is a Successful, Cost Effective Solution

Turn-key program reduced chemical expenses, solids , and energy costs.

A Northeast Acid Mine Drainage (AMD) treatment facility was using calcium hydroxide (lime) to precipitate iron from the mine pool water. The iron in the water stream is in soluble form known as ferrous iron (Fe2). Lime was used to raise the pH of the water from 6.2 s.u. to over 8.0 s.u. to precipitate out ferrous hydroxide (Fe(OH)2).

USP Technologies was selected as the Hydrogen Peroxide program provider for this Northeast AMD treatment facility for our full service, turn-key approach.

Technology

Hydrogen peroxide (H2O2) has been widely used to accomplish the same task by oxidizing soluble ferrous iron (Fe2) to ferric iron (Fe3), creating ferric
hydroxide (Fe(OH)3) which precipitates out of solution. The reaction is nearly instantaneous as follows:

2 Fe2 + H2O2 + 4 OH- → 2 Fe(OH)3 (precip.)

A near neutral to alkaline pH is typically required for high levels of iron removal. Therefore, some pH adjustment may be necessary prior to hydrogen peroxide addition.

Solution

The facility treats an average flow of 4,000 gallons per minute (gpm) or roughly 5.67 million gallons per day (MGD) with an iron concentration of 30 mg/l. Before hydrogen peroxide was used, lime was added at a rate of 6.94 lbs per pound of iron. The theoretical dose rate of hydrogen peroxide required to oxidize iron is 0.3 lbs of hydrogen peroxide (100% weight basis) per pound of iron. Hydrogen peroxide’s selectivity to react with iron is instantaneous. A complete reaction is accomplished in seconds and therefore, the actual dose rate was 0.37 lbs of hydrogen peroxide (100% weight basis) per lb of iron.

USP’s turn-key program reduced chemical expenses by greater than 60%, solids were reduced more than 80%, and energy costs decreased by nearly 25%.

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