WPCAMR Awarded Grant to Study Low-Cost Iron Removal
by Jeffrey Gerard, AmeriCorps OSM/VISTA
The Western Pennsylvania Coalition for Abandoned Mine Reclamation has received a $182,595 demonstration grant to test an innovative method of treating abandoned mine drainage (AMD). The technology has the potential to improve performance at existing AMD treatment ponds, decrease the size of new treatment systems, and increase the amount of iron solids recovered for commercial use.
The new study will target a common class of AMD that is alkaline (non-acidic) and contains high concentrations of dissolved ferrous iron. Currently, these discharges are often treated by holding the polluted water in a large settling pond, allowing the ferrous iron to react with oxygen from the air, which then forms a finely divided rust-like solid that gradually settles to the bottom of the pond. This technique, however, is not very efficient in transferring oxygen from the air to the polluted water, necessitating rather large ponds and long detention times.
Since the chemical reaction with oxygen facilitates the removal of ferrous iron, the project’s principal investigator, Jon Dietz, Ph.D. of Iron Oxide Technologies, LLC, proposed using an aeration process already used by municipalities to treat wastewater and sewage. A network of specialized plastic tubing perforated with tiny holes will stretch across the bottom of the settling ponds. Compressed air pressurizes the tubing, forcing air bubbles into the AMD and speeding up the iron oxidation reaction process.
The study will evaluate this technology’s efficacy at treating high-flow AMD discharges and will determine the costs to install and operate such a system. Jon Dietz predicts that total treatment costs could be as low as 1.7ยข per 1,000 gallons, which is very cost effective in comparison with existing AMD treatment techniques. By accelerating iron removal, the aeration method may be used to retrofit existing settling ponds to increase performance, or it might allow new AMD treatment systems to use smaller ponds in the future.
April 26th, 2007 at 4:06 pm
Interesting concept that should speed up iron oxidation rates. While getting oxygen into the water is important for ferrous iron oxidation, removing carbon dioxide to increase pH is very important and may be the more significant process. Therefore, applying a system that is more efficient at sparging than aerating may be the way to go.