When rock surfaces containing sulfide minerals are exposed to air and water, chemical reactions can occur resulting in soluble oxidation by-productsThese oxidation by-products, when they are dissolved in water, can acidify the water. This acidification can be catalyzed by the presence of bacteria (primarily members of the Acidithiobacillus genus). The resulting effluent is known as acid drainage (also acid rock drainage (ARD) or acid mine drainage (AMD)).
As the water becomes more acidic, its capacity to leach other elements from the rock, such as metals, increases and is known as metal leaching (ML). In some cases, the rock contains sufficient neutralizing capacity such that acidification does not occur. In these cases oxidation by-products may still dissolve into contact waters and can cause environmental impact.
Although these weathering processes are natural mining activities can accelerate weathering by exposing sulfide rock to water and oxygen. Fortunately, by recognizing the potential of sulfide rock to oxidize, mine planners can isolate these rock types and prevent or minimize the environmental impact of these weathering processes. To assist mine planners, INAP developed and maintains a best practice guide for the prevention and mitigation of ARD (See GARD Guide).
Don’t miss the following upcoming meetings that relate to acid drainage.
- Australian AMD Workshop 2017
November 19-23, 2017, Burnie, Tasmania
- 24th Annual BC/MEND Workhop
November 29-30, 2017. Vancouver, BC, Canada
- 11th ICARD/IMWA 2018
September 10-14, 2018. Johannesburg (Midrand), South Africa
Please let us know of other events not listed that INAP and GA members would be interested in participating. If you have ARD related events you would like to have posted on our web-site, please forward the details to firstname.lastname@example.org
Interested in acid drainage? Have a look at the following list of organizations and information sources on acid drainage.
If you would like to add a link, please contact the INAP Technical Manager
Indonesian Network for Acid Drainage (INAD)
South American Network for Acid Prevention (SANAP)
The Institute of Materials, Minerals, and Mining (formerly Institution of Mining and Metallurgy)
Sulfate Treatment Workshop
February 27-28, 2014, Salt Lake City, UT, USA
INAP (International Network for Acid Prevention) and ADTI (Acid Drainage Technology Initiative) hosted the Sulfate Treatment Workshop on 27-28 February in Salt Lake City, UT. Over 120 delegates from five countries attended the workshop. The participants were eagerly engaged in over 20 excellent presentations. Attendees examined sulfate standards, environmental risk and toxicology and other regulatory factors that have been driving an ever broadening industry response to sulfate discharge management. Topics discussed focused on both proven and innovative technologies to treat mine and process-impacted waters containing sulfate.
The objectives of the workshop were to 1) identify key technical issues; 2) promote and coordinate partnering between industries, regulatory and stakeholders personnel; and 3) discuss site-specific strategies for operations and closure management through a mix of industry, regulatory and other stakeholders’ views. This exchange occurred though a panel discussion which included representatives of industry, regulatory agencies, academia, service providers and financial organizations. Multiple break-out sessions also created a more individual exchange between attendees. Following the workshop, a tour of the Rio Tinto Reverse Osmosis Plant gave participants a close up view of a current process being used to treat groundwater containing sulfate.
INAP and ADTI organizing backers of the workshop want to thank the and recognize the organizing committee (Scott Benowitz, Chris Howell, Lisa Kirk, Linda Figueroa, Jim Fricke, Carol Russell, and Charles Bucknam), whose tireless efforts brought this excellent symposium to fruition. We also want to thank the Sulfate Workshop sponsors: Veolia Water, Golder and Associates, and Arcadis for their support; and thanks to Brian Vinton and Ian Schofield of Rio Tinto for organizing a great field trip.
Path Forward Symposium
May 21 & 25, 2012, Ottawa, ON, Canada
On May 21, 2012, the day before the International Conference on Acid Rock Drainage (ICARD) in Ottawa, Canada Division, 70 international experts met to identify new directions to meet the challenges of mine-impacted waters. The purpose of this symposium was to discuss ARD issues with many of the world’s leading practitioners and then use these suggestions to help guide INAP’s future strategic planning .
During the first session of the symposium, 17 innovative technologies and new ideas relating to 1) microbial ecology, 2) mine-waste repositories, 3) water treatment, and 4) engaging stakeholders were presented. Each presenter had 5-minutes to capture the attention of the audience and present the vision of their idea. The presentation was followed by a 5-minute question and answer period. The rapid flood of original ideas was both challenging and stimulating. Following this explosion of ideas, the attendees met in four groups to focus their discussions on one of the four themes. During these discussions, the earlier presentations were vetted and expanded. Each group reported back to the full body on their findings. The next day, a copy of the compilation was distributed to each Symposium participant for their further review and confirmation that their ideas were accurately captured.
A brief summary session was planned for the morning following the ICARD. This session discussed the group findings and tied them to the information presented during the excellent 3-day ICARD conference. Some key ideas that were discussed included:
- A companion volume to the GARD Guide on relevant case studies – successes and failures should be developed and published.
- An expert panel should be organized to advise INAP on relevant topics.
- Identify research needs in the areas of mine waste handling and storage and drainage discharge including:
- An investigation of waste repository construction should be initiated.
- A study of covers to determine correlation between water ingress and drainage discharge.
- Prevention and mitigation methods over extended periods should be investigated.
- Investigate zero-discharge requirements and their impact on source control and resource recovery from mine discharges.
- Research the effects of blasting on ARD formation – waste rock size and cracks in mine walls.
- Expand R & D Effort Applied to mining operations.
- Work with other funding sources to develop collaborative programs.
- INAP needs to engage all stakeholders and particularly academics and students.
- Develop techniques to communicate at a relevant level to all stakeholders.
- Maintain an independent, focused voice – ARD prevention/sustainable development.
- Utilize social media for stakeholder communications and measurement of results.
In response to these excellent ideas and inputs offered during this symposium , INAP will take these ideas and suggestions under consideration at the upcoming INAP Strategic Planning meeting, and we will keep the participants informed of the ultimate outcome of these suggestions.
Sudbury Mine Waste Workshop
May 17-18, 2011, Sudbury, ON, Canada
Hosted by Vale
Organized by Lisa Lanteigne, Vale
In May of 2011, INAP held a workshop in Sudbury, Canada. The meeting was structured as a short course on Dry Covers for management and operations personnel from the member companies. The programme began with a series of presentations covering many aspects of waste rock dumps and covers, including the internal structure and geo-chemistry of dumps, long-term cover performance, and groundwater considerations. The focus was then placed on recent pit-fill work at the Whistle mine that was carried out to deal with the 7 million tonnes of acid generating waste rock. A visit to the Whistle mine was followed by a series of interactive discussions on the different options for dealing with waste rock dumps once they have started to generate acid.
Several key findings were identified during the workshop:
- The importance of planning for closure was emphasized, including robust accounting of the full cost of design and construction at closure.
- Having a good understanding of background conditions is important, particularly for groundwater flows which can have a significant long-term impact on pits, and dumps.
- A better understanding of how closed sites perform in the long term – particularly backfilled pits – is key to help improve closure management and post closure remediation. A focus on case studies on post closure performance would be a useful step in this direction.
The event was considered a success by the participants and provided a rare opportunity for people from different mine sites to share experiences on acid drainage and dry covers. INAP will be aiming to repeat the exercise in other regions.
Water Treatment Workshop
October 7-9, 2009, Eastern Arizona College, Thatcher, AZ, USA
The Water Treatment Workshop held at the Eastern Arizona College in Thatcher, AZ covered a broad range of mine-impacted water treatment options. Twenty-one presentation cover a wide range of topics mainly focused on water treatment. Dave Riesman from EPA was invited to present by Freeport, and he presented on, ”Technical Support at Mine Influenced Sites: Advances in Remedial Technologies.” About 70 percent of the presentations were made by INAP member companies.
Over 70 attendees participated in the workshop, which included six of INAP’s nine member companies. International attendees included participants from Canada, Peru, and South Africa. The workshop was hosted by Freeport McMoRan, and they also sponsored an outstanding tour of their Process Technology Center in Safford, AZ.