The increasing number of tailings dam failures is causing significant global reactions that will have a lasting impact on how the mining industry manages its mineral processing wastes. Last year's tailings dam breach at the Córrego do Feijão iron ore mine in Brumadinho, near Belo Horizonte in Minas Gerais state in Brazil, was not only an appalling human tragedy but also a major setback to the international mining industry's bid to improve its image and to promote responsible and sustainable mining.
A couple of weeks ago the Cornish Institute of Engineers held a Women in Mining (WIM, UK) Panel Discussion on the topic ‘Making Tailings Safe’. Audience members heard the panel’s thoughts, and were invited to give their opinions on several questions relating to making tailings safe. I am not sure what those thoughts and opinions were in detail, but panel member Prof. Karen Hudson-Edwards, of Camborne School of Mines, tells me that there was agreement that significant advances are being made in safer tailings management using phytoremediation, dry stacking and underground storage.
However, the historical legacy of often abandoned tailings dams, especially those within short distances of habitations, is of significant concern and needs more research and funding for remediation.
So I put the questions to you, blog readers, for your comments. I am sure that many of you have been involved with tailings disposal at some time in your careers. Let us have your thoughts on:
- Some of your experiences, both good and bad, with tailings management?
- What are the biggest challenges for mining companies and governments in making tailings safe?
- What are the best future management strategies for preventing tailings dam failures?
- Who is responsible for making tailings safe – including historic ones? Governments, companies or communities?
Hoping for some interesting and useful response.
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O começo do fim das Barragens
ReplyDeletePaulo Ferreira, Brazil
Certainly the beginning of the end of upstream dams I hope Paulo
DeleteI am not an expert, but based on my present experience and observations; I will recommend tails disposal to Tailing Dams, only through a Paste Thickener. Owing to increased yield stress and homogeneity the flow ability reduces and drying becomes faster. These two can help in reducing the hydraulic load and stress on dam wall. Also lesser water in paste serves the purpose well.
DeleteNot an expert on the subject but I know it is a complex hydrological science with many variables to fully define wall strength. An option is dewatering slurry to a "dry" paste or at least a Cyclone to classify coarser particles onto the wall. Many operations utilize paste deposition with a hardener - costly but compared to structural failure, which is usually disastrous. A nightmare to any accountable team, person and owner. Remove the risk - even if it is costly!
ReplyDeleteKobus (JP) Prinsloo, Welkom, South Africa
The mining company must be considered dewatering before disposal or storage of tailing slurry. It must be linked to the mining licence and consent to opeate certification process for the dry storage of tailing. At present, most of the mining companies are trying to maintain the slurry dam due to cost-economics involved in the dewatering process.
ReplyDeleteSunil, Universite de Lorraine, France
Merriespruit disaster - saw the results first-hand, very ugly and many casualties. The negative is, more often than not, it is neglected, until it fails catastrophically! Blocked Penstocks, one of the reasons - maybe stretching profits?
DeleteKobus (JP) Prinsloo, South Africa
Certainly the best way to make Tailings safer is to stop producing slurry to contain in the first place. Drier, compacted, engineered residuals can be built into landforms, and possibly used for construction (if chemically inert or stabilized). There is much work happening on the global scale on improving tailings management practices, dam design, and finally - looking towards the elimination of tailings. Reflecting on a video I just watched - it is not worth trying to keep doing something better if it is, in reality, the wrong thing. Much better to do the right thing and change for the better overall. Tailings can no longer be left as an afterthought for others to deal with - we are all responsible to design better outcomes - without the risk.
ReplyDeleteKaren Chovan, Saskatchewan, Canada
We made some trials in our sieving lab on high frequency screener type WAFL in order to reduce the water to the max. to find an answer to this environmental drama.
ReplyDeleteTo summarise we could separate the water and the solids. The solids became nearly like a paste, the volume has been reduced and the water could be re-used. The best separation were realized below 100 microns. How it works? Here: https://youtu.be/QzrGs-QvWvQ
Sigurd Schuetz, Managing Director at RHEWUM GmbH, Germany
Sigurd, a paste is exactly what you needed and achieved - a Tanzanian Gold Mine pumps it in this state to tailings - it becomes a landscape c/w with vegetation. They do it with vacuum filters, repulping followed by Schwing hydraulic high-pressure pumping to the tailings "dams" hills.
DeleteKobus (JP) Prinsloo, South Africa
The need to ensure proper sequester of mine tailings needs to be considered in the very beginning when one is financing a project. Proper preparation of the mining project with secure tailings facilities is crucial. The best consultants need to be brought in before the construction phase to produce a foolproof plan for dealing with tailings. The resulting plan needs to be followed and adhered to throughout the development and operation of the entire mining facility.
ReplyDeleteDayton Conway, Director, Americas at Program for National Development, USA
Just now saw this Blog--very timely and relevant.
ReplyDeleteI know nothing and so take my remarks as coming from novice.
With so much expertise available on rock mechanics(rock structure included) is it really a rocket science to build a safe tailing dam? If we know what we have to store and its characteristics, I am sure solution will be there. But if we bring moisture, space, economics etc, we get confused and go to filtration and thickening leaving the main point. World built Dams but if one cuts corners in execution, the disaster will follow. More than the above, we are forgetting the contamination of ground water due to storage in tailing dams--we have to keep this in mind as an important factor because ground water is precious for society.
I may be off the beam ; if so ignore my comments.
Tailings disposal can safe as long as TUV aren't involved. All the disasters resulted from penny pinching management.
ReplyDeleteIt seems the lessons from Aberfan have not been translated across disciplines nor languages. The technology is available, unfortunately the will isn't there. Vale still has potential danger spots but is doing very little. It's just the Dutch boy who left his finger in the dyke all night. The story is that old.
John Gateley, ConveyO'Wright, Indonesia
Mining companies must consider and practice dry disposal and utilization of tailings for back fill as well as making it greenery. Some of underground mining utilizing its tailings in to under ground back filling due to this water can be recovered as well dry tailings life time will increase. In open pit they can use it for making bricks, tiles and road construction with that they can dump in open pit and compact it for green fields and plantation work. i'm part of it and constructed multiple dry tailing disposal, hydrofoil and paste fill projects successfully.
ReplyDeleteHemanth Kumar, India
Dewatering prior to discharge in tailings pond is a must. There are several technologies available today to take care of tailings.. effective flocculation, thickening, filtration can be adopted..this will enable to recover water as well as lesser requirement of dumping area
ReplyDeleteAbhay Shankar, Tata Steel, India
I am surprised that, apart from the safety concerns around tailings dams, with water scarcity becoming a major issue in many parts of the world, there is not a stronger move to dry stacking of tailings. We have some very successful projects in South America where we are dewatering tailings with centrifuges.
ReplyDeleteSome only dewater to a thick paste as the client wants a material that will flow like lava into a designated natural depression.
In diamond mines, on the other hand where the tailings contain quite a lot of coarse material, the fines can be removed by the centrifuge and then combined with screened hydrocyclone underflow to produce a very dry, stackable material.
These centrifuges are easy to operate and require very little operator interaction and maintenance.
Dry stacking may be logistically more complex, but the smaller footprint, lower cost of the deposition site, greater water recovery and lower risk should make dry stacking a viable option for a lot of projects.
Nils Schwarz, Schwarz Global Consulting, South Africa
Nils, you summarized it perfectly.
DeleteKobus Prinsloo, South Africa
I think every mine without a thickener should be shut down until one is installed. Else the price of a multi billion dollar lawsuit should be reflected in the share price. We are just seeing the tip of the ice berg as 1 in 100 year weather events will become 1 in 20.
ReplyDeleteRichard Jermyn, Australia
Nowadays, every processing plant has thickened but still, the slurry contains 40-65% water which is not sufficient. Unless it is been further dewatered by filtration or high-density thickener. The safety aspect of slurry density at 5% solids and 50% solids are not significantly different.
DeleteSunil Tripathy, University of Lorraine, France
Not every mate. Most of the failures are the old plants without thickeners. Do some reading and we can catch up after.
DeleteRichard Jermyn
The topic is flavor of the day/month and years. Everyone in the mining industry is talking about it from a long time and the disasters continue. However, no significant action on the ground is evident. Every business's core principles are Ethics, safety and sustainability. Going for tailings dam doesn't fall in any of these three. The safest way of tailings dischrge is the dry discharge, understanding of this doesn't need serious research, but common sense. The main reason driving against our common sense is that the tailings management facility considered as cost centre and it is not a revenue / profit centre. Most of the mining companies which have chosen to dischrge dry is due the stringt implementation of the regulation or they don't have enough sapce to build a tailings dam. Many of the big mining houses have given an interesting angle to this and are asking the engineering, equipment and technology supplying companies to initiate and develop a disruptive technology around tailings mamagement, even if someone is adventureous to come up with idea, it won't be 'One solution - fits all', as every mine, its tailings is also unique and problem is unique. The motivation for this asking could be just a time buying / delaying strategy as no investor wants to sink their money in tailings. The problem has a simple solution, which is common sense, not disruptive technology. We can try all the intermediary technologies like high density thickening or paste thickening, it does not fit into any of the areas of Ethics, safety and sustainability. Untill tailings management facilities are considered as cost centre, we can't see the tailing dams vanishing in the near future. We will keep ourselves busy discussing this topic in every forum, conference, every year.....
ReplyDeleteCompletely agree. If there is a will to do , technologies will evolve and serve the purpose. Every dewatering technique serves in or the other way depending on tailings properties.
DeleteIt is time for tougher measures by Govt's across world. Safe disposal methodology should be the key to sanction a mine plan. Unless it is included in investment it will be treated as additional cost and No Mine Owner spends on it because treating tailings does not fetch a penny. Until Human life is valued more than metals and materials, the situation remains same.
PM
These ponds should use concentrating solar power technologies (CST) to dry the water and use the steam for electricity generation. The concentrating setup will generate enough temperature to evuprate water. It should deal with fresh slurry only. It can fullfill electricity demand, can reduce fresh water intake and can reduce ground water contmination.
ReplyDeleteWell said, Veerendra--thinking out off box; I fully support your way and hope more do so.
ReplyDelete