Acid mine drainage treatment with a combined wetland/anoxic limestone drain: Greenhouse and field systems

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20026850

Skousen, J; Sexstone, A; Cliff, J; Sterner, P; Calabrese, J; Ziemkiewicz, P

The most common methods for treating acid mine drainage (AMD) involve applying a strong base to neutralize the acidity and to precipitate metals. Limestone use in AMD treatment has been largely confined to anaerobic wetlands, anoxic limestone drains (ALDs) and open limestone channels. If Fe{sup 3+} and Al could be removed from AMD before introduction into limestone systems, then the use of limestone for AMD treatment could be greatly expanded. The authors developed and monitored a passive AMD system to determine if AMD containing Fe{sup 3+} as ferrous sulfides (FeS{sub x}) through sulfate reduction. Further, Fe and al may be adsorbed to organic matter in the wetland thereby eliminating the formation of metal hydroxides with subsequent plugging of limestone pores. A field scale wetland/anoxic limestone drain (WALD) system located at Douglas, WV exported net alkaline water (mean of 127 mg/L as CaCO{sub 3}) for one year. However, dissolved oxygen and Fe data suggest that poor hydraulic conductivity caused this system to act as an Fe-oxidizing system, rather than an Fe-reducing system. As such, the system's long term effectiveness for treating AMD was compromised. After five years of operation, the system still reduces the acidity of the water from about 500 mg/L as CaCO{sub 3} to about 150 mg/L. A small scale Greenhouse system performed more like an Fe-reducing system, decreasing acidity for seven months and exporting Fe{sup 2+}, although the water existing the wetland did not contain excess alkalinity. While complications arose in the authors systems due to high flows in the Douglas system and high acidity in the Greenhouse system, pre-treating AMD with organic material can improve the condition of the water for proper treatment by an ALD or underlying limestone. For low to moderate flows (<400 L/min) and low Fe concentrations (<50 mg/L), a passive system that pre-treats AMD with organic substrates and then directs the water into limestone may be effective for many years.

• Research Organization: West Virginia Univ., Morgantown, WV (US)
• OSTI ID: 20026850
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
ACID MINE DRAINAGE
ADSORPTION
ALUMINIUM
COAL MINING
GRANULAR BED FILTERS
IRON
LIMESTONE
ORGANIC MATTER
PERFORMANCE
WEST VIRGINIA
WETLANDS