Grantee Research Project Results

Final Report: In Situ Treatment of Acid Mine Drainage

EPA Contract Number: 68D99036
Title: In Situ Treatment of Acid Mine Drainage
Investigators: Burnett, Mackenzie
Small Business: Burnett Engineering Inc.
EPA Contact:
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $69,968
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text |  Recipients Lists
Research Category: SBIR - Water and Wastewater , Watersheds , Small Business Innovation Research (SBIR)

Description:

Acid mine drainage with its associated dissolved metals is a major pollution problem in the United States and around the world. There are thousands of abandoned coal and metal mines that are currently polluting our streams and rivers with metal laden acid runoff. Passive treatment systems are the most promising since there is no associated recurring cost. One passive system, the limestone drain, produces alkalinity in an anoxic or open environment that neutralizes acidity, raises pH, and increases the effectiveness of other wetland systems. The advantage to constructing a limestone drain inside mine is that the acid drainage is treated while it is still contained in the mine and hasn't dispersed to a creek or through the soil where it is difficult to capture and treat. Conventional construction equipment can not build a drain longer than 20-30 feet without forcing personnel to work inside the portal, a situation not allowed due to the extreme danger.

The portal in this mine has been draining AMD for many years and data has been kept on this particular seep since the year 1994. Water flow rates historically vary from a few gallons per minute to over 300 gallons per minute over a typical year. A pneumatic stowing system was used to place 300 tons of 2-in-top size limestone into the 20-ft wide entry for a distance back from the face of 100-ft. The limestone drain was constructed without personnel entering the mine portal. Water quality and flow rate were then sampled and recorded for five months.

Water quality and flow rate were measured before and after the installation of the drain on a regular basis to determine the effectiveness of the drain.

Summary/Accomplishments (Outputs/Outcomes):

The acid load historically has been 671 mg/l at an average flow rate of 95 gpm. This is equal to 140 tons acid load per year. After the installation of the limestone drain the acid load exiting the site was 192 mg/l which equals 42 tons acid load per year, a 71% drop in acid load.

The limestone drain cost $10,000 to install and when considering the life of the limestone, the cost per ton of acid load treated is $34. Comparing this to conventional 20% caustic soda treatment which costs $441 per ton of acid load treated, a savings of $407 per ton of acid load treated over conventional methods was achieved. The estimated savings per year over conventional treatment calculates to $39,490.

Conclusions:

The research project demonstrated that the insitu limestone drain perform exceptionally well under both low and high water flow conditions. The data has shown that the drain removes approximately 70% of the acid load at a cost saving over conventional caustic soda treatment of $39,490 per year. This tremendous savings, when multiplied by the thousands of sites which are amenable to this technology, can make it possible to clean up the rivers and streams of the world affordable.

Supplemental Keywords:

pneumatic stowing, economical, insitu limestone drain, acid load, insitu., Sustainable Industry/Business, Scientific Discipline, Water, Waste, Remediation, Technology for Sustainable Environment, Engineering, Chemistry, Engineering, Chemistry, & Physics, Contaminated Sediments, cleaner production/pollution prevention, Wet Weather Flows, New/Innovative technologies, pollution prevention, acid mine drainage, mining impacted watershed, reducing degradation, in situ remediation, wastewater treatment, limestone drain, waste water treatment