Acid Mine Drainage

Author: Amit Kumar (Norman B. Keevil Institute of Mining Engineering - University of British Columbia)

Revised: April 2013

In This Review

Introduction
Chemistry
Problems Associated with Acid Mine Drainage
Prediction of Acid Mine Drainage
Methods for Treatment
Modeling
Software
Organizations
Books and Articles
Research
Consultants
Suppliers
References and Additional Resources

Summary

This review looks at the basic concept of Acid Mine Drainage, its chemistry, concerns along with prediction methodology and treatment options. Information about books, consultants, suppliers and research institutes related to acid mine drainage is also provided.

INTRODUCTION

Acid Mine Drainage (AMD) is the acidic metal rich water formed by the reaction between the water and rock containing sulfur-bearing minerals. It especially occurs in metal mines and coal mines. When the rocks containing sulfur are excavated from a surface mine or an underground mine, they react with water and oxygen to form sulfuric acid. This acid is carried off the mine site by rainwater or surface drainage and gets to the nearby streams, rivers or lakes, creating environmental risks.

CHEMISTRY

Wikipedia have significant description regarding the chemistry of the acid formation in case of pyrite, which is the most common sulfide mineral and plays a major role in creating Acid mine drainage problems in coal, metal (gold) mines. The overall reaction is shown below:

4FeS2 + 14 H2O + 15 O2 --> 4Fe(OH)3 + 8 SO42- + 16 H+

The net outcome is the formation of H+ and SO42- ions that are responsible for ARD.

The major factors regarding the aftermath of the AMD are:

pH of the environment
Concentration and type of the sulfur in rock
Type and concentration of Carbonate mineral present
Mineral Surface area available for reaction
Particle size of waste
Extent of mineral liberation in the rock
Available water and oxygen
Biological environment etc.

PROBLEMS ASSOCIATED WITH ACID MINE DRAINAGE

Some of the problems associated with AMD are:

Water Contamination: Due to the acidic water along with the metal ions such as Fe, Cu, As etc. increases the toxicity of the water and thus effect the aquatic life and get to the food chain. For broad information, click here.
It may disturb the reproduction system of aquatic life such as fish and thus may decrease their population.
It also affects the infrastructure by corrosion.

PREDICTION OF ACID MINE DRAINAGE

The objectives of predictive testing are to: (1) determine if a discrete volume of mining waste will generate acid and (2) predict the quality of the drainage based on the rate of acid formation measured (California Mining Association, 1991).

Different Authors have outlined different strategies adopted for the prediction of Acid Mine Drainage.

Ziemkiewicz, Renton and Rymer have talked about three-component procedure listed as:

Identify AMD producing Rocks
Apply the SSPE/PSM Model
Identify required amounts of phosphate

For complete information regarding this method, check Prediction and control of Acid Mine Drainage, effects of rock type and Amendment.

Rose, Williams and Parizek have identified some procedure for predicting Acid Mine Drainage from Coal Mines in their paper Prediction of Acid Mine Drainage potential from coal mines where he have described four methods for this purpose.

US Environmental Protection Agency have suggested the steps for prediction of Acid Mine Drainage as sampling, static tests and Kinetic tests. For more information on this method, click here.

METHODS FOR TREATMENT

Wikipedia has a list of some methods such as Lime neutralization, Calcium Silicate neutralization, Carbonate neutralization, Ion exchange, Constructed wetlands, precipitation of metal sulfides.

Fripp, Ziemkiewicz and Charkavorki, in their paper Acid Mine Drainage Treatment, have suggested some other treatment options as Grout Injection, Sealing of Mine Portals, Mine Capping, Limestone dumping, Limestone dosing, Anoxic limestone drain (ALD), Anaerobic Wetlands, Aerobic Wetlands, Successive Alkalinity Producing systems (SAPS), Open Limestone Channel (OLC), Modified Open Limestone Channel (MOLC), Leach Bed and Oxic Limestone drain.

Christine Costello, in her paper on Acid Mine Drainage: Innovative Treatment Technologies, have discussed some new treatment methods such as Bioreactors, Successive Alkalinity Producing Systems, Permeable Reactive Barriers, Bio-solids and Phytoremediation.

Skousen, Hilton, Faulkner have provided a list of chemicals generally used in Acid Mine Drainage Treatment in his paper Overview of Acid Mine Drainage treatment with chemicals.

Chemical Compounds used in AMD treatment

MODELING

The InfoMine site on the 7th International Conference on Acid Rock Drainage (ICARD) provided the following information regarding Acid Mine Drainage Modelling.

Modeling of the gold slimes dams in the South African Witwatersrand using PYROX, PHREEQC, and spreadsheets establish that buffering will continue for thousands of years and that it may take between 1,000 and 10,000 years for the piles to generate acid drainage.

HYDROGEOCHEM was used to model uranium mine waste rock dumps at Pocos de Caldas, Brazil. Modeling showed that acid drainage would continue for at least 600 years.

At the Svartliden Gold Mine in Sweden, the fourteen percent of potentially acid generating waste rock will be encapsulated into benign rock. Modeling with SULFIDOX showed that encapsulation would limit acid seepage.

POSSUM is an object-oriented program that models the evolution of mine water quality, accounting for contaminant sources and sinks, water level change (due to seasonal fluctuations), reaction kinetics, variable flow regimes, infiltration through porous media, and inflow from secondary roadways.

HYDRUS and POLYMIN were used to model hypothetical waste rock dumps and their moisture conditions and acid generation.

Geochemical modeling of the Antamina waste dumps included collection and collation of field and laboratory data, and water quality modeling to simulate short and long-term trends.

SOFTWARE

AMDTreat, a member of OSM's Technical Innovation and Professional Services (TIPS) suite of software, is a computer application for estimating abatement costs for pollutional mine drainage, commonly referred to as Acid Mine Drainage.

ORGANIZATIONS

International Network for Acid Prevention (INAP): An industry-wide organization of mining companies wishes to collaboratively address acid drainage. Objective: Promote significant improvements in the management of sulfidic mine materials and the reduction of liability associated with acid drainage through sharing knowledge and research and development of technology.
Global ARD Alliance: A group sponsored by INAP and that includes those organizations listed below. Objective: Share information and work collaboratively with like organizations across the world.
Mine Environment Neutral Drainage Program (MEND): A Canadian federal government funded group. Objectives: Develop scientifically based technologies to reduce the effects of acid drainage.
Acid Drainage Technology Initiative (ADTI): A United States group that includes representatives from industry, state and federal governments, and universities. Originally formed by representatives of federal agencies, the National Mining Association (NMA) and the Interstate Mining Compact Commission (IMCC). Objective: To build consensus among industry and federal and state regulatory agencies on acid drainage technology development technology transfer issues.
Partnership for Acid Drainage Remediation (PADRE) in Europe: A permanent commission of the International Mine Water Association (IMWA). Objective: Foster best practice based on the latest research, in the remediation of acidic drainage in active and abandoned mines throughout Europe.

BOOKS AND ARTICLES

The best book available for the basic study for Acid Mine Drainage is Acid Mine Drainage by Miller, Vandome and McBrewster. Some others books for detailed information are:

Acid Mine Drainage: Cases, Assessment, Prevention and Remediation by Jacobs, Lehr and Testa.
Acid Mine Treatment: Control and Treatment by National Mine Land Reclamation Center, West Virginia University.
Principles of Environmental Chemistry by Girard.
Chemical and Physical Properties of Acid Mine Drainage Floc by Catherine M Bohan.
Acid Mine Drainage: proceedings of the eleventh annual British Columbia Mine Reclamation Symposium, convened at the Discovery Inn, Campbell River, British Columbia - April 8, 9, and 10, 1987
Acid Mine Drainage: a bibliography with abstracts: search period covered, 1964 - September 1976
Environmental Regulation of Coal Mining: Smcra's Second Decade by James M. Mcelfish Jr.

Very good videos regarding acid mine drainage are given at:

There are two courses on InfoMine's EduMine section that are related to AMD:

RESEARCH

AMD has been the subject of intensive research since the 1960's. Research efforts have proceeded recently through the Acid Drainage Technology Initiative by West Virginia Water Research Institute. The major areas of research on AMD are Prediction of AMD and Prevention/Mitigation.