Passive treatment overview
This information was largely taken from EPA Region 3 publication A Citizen's Guide to Address Contaminated Coal Mine Drainage, EPA-903-K-97-003.
Passive systems remove or neutralize contaminants in mine drainage by exposing them to air, limestone, vegetation in ponds, neutralization ditches, buried channels, and wetlands. Exposing AMD to air helps to precipitate metals through oxidation processes; limestone contact neutralizes acid by adding alkalinity; vegetation such as cattails filter contaminants and aid in oxidation and metals removal; and organic wetlands remove metals and provide habitat for bacteria that break down sulfates.
Since passive systems are designed to make use of gravity flow through ponds, buried channels, ditches and wetlands, they can treat AMD without the continual addition of chemicals or neutralizing agents. In general, ponds are used to collect mine drainage, settle out larger particles of sediment, oxidize metals, and can reduce acidity when underlain with organic material and limestone. Ditches convey drainage to ponds or wetland cells, and often contain crushed limestone rock for acid reduction. Wetlands serve a variety of treatment functions, including filtration of smaller sediment particles, uptake of water and some contaminants, oxidation/adsorption of metals, and removal of sulfates through bacterial action.
Acid Mine Drainage In Pennsylvania Streams: "Ironing Out" The Problem
Paper that describes and evaluates techniques to remove pollutants from the landscape as part of a restoration/reclamation project.
AMD Treatment Bucknell University
Handbook of Constructed
Wetland Volume 1 (PDF Format, 789KB)- This Handbook has been prepared as a general
guide to the design, construction, operation, and maintenance of constructed
wetlands for the treatment of domestic wastewater, agricultural wastewater, coal
mine drainage, and stormwater runoff in the Mid-Atlantic Region.
Handbook of Constructed Wetland Volume 4:Coal Mine Drainage (PDF Format 2329KB) has information particular to treating AMD. This is a very good reference.
Overview of Passive Systems for Treating Abandoned Mine Drainage Passive Treatment Discussion from WVU
SOME PASSIVE AND SEMI-PASSIVE TREATMENT METHODS FOR ACID MINE DRAINAGE Buchnell University
Acid Mine Drainage Treatment by Jon Fripp, Dr. Paul F. Ziemkiewicz and Hari Charkavorki May 2000 (PDF Format)
Coal Mine Drainage Prediction and Pollution Prevention in Pennsylvania... book produced by PA DEP
Passive Treatment Alternatives for Remediating Abandoned-Mine Drainage George H. Berghorn & George R. Hunzeker