Tuesday, December 18, 2012

Can Acid Mine Waste Save the Bay?

LEETOWN, W.Va. – A byproduct resulting from the treatment of acid mine drainage may have a second life in helping clean waters coming from agricultural and wastewater discharges, according to a recent study by scientists from the U.S. Geological Survey Leetown Science Center.

The report, published in the Journal Water, Air, and Soil Pollution, shows that dried acid mine drainage sludge, or residuals, that result from treating acid mine drainage discharges can be used as a low-cost adsorbent elsewhere to efficiently remove phosphorus from agricultural and municipal wastewaters. The phosphorus that has been adsorbed by the mine drainage residuals can later be stripped from the residuals and recycled into fertilizer. The mine drainage residuals can be regenerated and reused for a number of additional treatment cycles. Application of this novel, patented technology has the potential to simultaneously help to decrease acid mine drainage treatment costs, prevent degradation of aquatic ecosystems, and recycle valuable nutrients...
Acid mine drainage residuals in Elk County, Pennsylvania.

When acid mine drainage is remediated, it is neutralized with a base, such as limestone or lime, and an iron-rich sludge is formed that must be disposed of, sometimes at considerable cost. The new process of using the sludge to filter wastewaters has the potential to reduce the need to dispose of the sludge, while providing an added and previously unknown benefit of using the residuals to effectively reduce phosphorus from wastewater discharges wherever needed.

Excess phosphorus releases to the environment from agricultural and municipal wastewaters have resulted in significant impairment of aquatic ecosystems such as the Chesapeake Bay and other bodies of water worldwide. At the same time, as depletion of high-grade phosphorus-bearing deposits continues, the possibility of future shortages of fertilizer phosphorus has been suggested.
A couple years ago, I visited Laurel Run, an acid mine waste source in Western Maryland.  A huge abandoned network of tunnels from coal mining was pouring thousands of gallons of acidic, iron rich water into a wetland.  Maryland DNR has a lime doser installed to add lime to neutralize the waste, and precipitate out the iron.  A few yards from the doser, the iron started precipitating out as a red mass, but the whole valley was stained red for a mile or more.   It would be cool if the iron being formed could somehow be captured and used to remove phosphorus from municipal sewage or agricultural water.

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