Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal

Dewatering: Thickening, Filtering, CCD, Water Treatment & Tailings Disposal 2017-04-04T06:57:46+00:00
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Treatment for sulphate (79 replies)

Bill Fraser
2 years ago
Bill Fraser 2 years ago

Government regulators are beginning to ask proposed or operating mines to treat for sulphate. As I become involved in these projects, I see that this is a daunting challenge and I would like to hear from people who have experience in this area.

As a base case, imagine a mine that discharges at 500 m3/hr and needs to remove 1g/L SO4. A treatment system would need to remove 12,000 kg/d sulphate. This boggles my mind! In practice, how do you deal with the massive amounts of reagent required for treatment or sludge generated during treatment? If sulphate is converted to elemental sulphur, how do you safely manage the 4,000 kg/d of sulphur generated? Is this causing more problems than it solves?

I would appreciate very much hearing from people who have faced this problem and developed workable solutions for it.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

It won't be applicable in most places, but the flow back and production brine from fracked gas wells in the Marcellus and elsewhere is very high in alkaline earths, so mixing it with AMD can get rid of both sulfate and Ba,Ra, Sr, Ca from the brine.

Obergruppenfuhrer
2 years ago
Obergruppenfuhrer 2 years ago

Studies were done for sulfate removal related to the Idaho Cobalt Project EIS. I am not sure who did the actual technical analysis study but will see if I can find out. I do know that R-O was compared to biological and the preferred alternative was some sort of biological, which would make me nervous as an operator unless the effluent limit is pretty high.

Hydrometrics was the contractor to the USFS. This is a relatively small facility so it will not have the impacts that a scale you are describing will.

Unterstarm
2 years ago
Unterstarm 2 years ago

I have experience in insitu anaerobic treatment of SO4 in aquifers downstream mine tailings. Also I can give good recommendations for industrial onsite anaerobic treatment (in bioreactor).

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

Some years ago INAP commissioned a study of sulfate treatment in mining effluents - I believe it was Lorax from Vancouver who prepared the white paper. It covered most of the generic approaches still available and presented advantages and disadvantages. I recall it as touching on costs, though that would probably need updating.

Fundamentally one has three choices:

  • Ultrafiltration, of which RO is one technology, but not necessarily the obvious choice depending on the rest of the chemistry (especially pH and the concentration of Ca as well as SO4, because of precipitation of gypsum that fouls the membranes during concentration). Ultrafiltration will always produce brine that requires specialized disposal.
  • Precipitation. In addition to cost for something like Ba addition, you will run into a solubility limit, which may or may not be adequate to meet discharge criteria, and this will always have sludge-management cost associated with it.
  • Biological sulfate reduction. An attractive alternative, it nonetheless requires careful evaluation, in terms of reagent costs, long-term stability, practicability at large scales, and potential for adverse byproducts (especially H2S).

In some jurisdictions, there exist sulfate standards, and they may be astonishingly low (as in Minnesota, where discharge to certain surface-water systems may be limited to either 10 or 15 mg/L (I can't recall which), based on evidence of toxicity to a protected species (wild rice during germination).

Bill Fraser
2 years ago
Bill Fraser 2 years ago

I know well the review by Lorax. It was a contract job done by a geochemist (or similar) with little to no experience in water treatment. Consequently, the literature review was very comprehensive, but uncritical.

I am familiar with all the technologies you mentioned (membrane filtration, chemical precipitation and biological reduction), but they do not feel well suited to treat the large loadings of SO4 typically encountered in drainage from sulphide ore deposits.

As I understand, South Africans have made great strides in the area of chemical precipitation, but it isn't clear to me that any of the barium-based processes they have developed are ready for prime time. The economics of precipitating with barium, followed by carbon thermo reductive regeneration of the barium reagent, seem more feasible and attractive than the other options on the table. I would love to hear the experience of people who have used this process or technology in treating mine drainage.

It seems that we are now asked to select and implement technologies to meet new, stringent criteria for sulphate, with little experience to guide us.

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

Kennecott Utah Copper treats 3,000 USgpm of mine-affected water using RO to supply potable water to the equivalent of 4,300 residences, under administrative order on consent. The treated waters originate in the peripheral zones (at circum-neutral pH and modest [SO4]) of an acidic plume. In addition, the operation treats up to 5,000 gpm of acidic water with very high (ca 20,000 mg/L) SO4 by reacting the acidic water with the operational tailings stream, which has sufficient available acid-neutralization capacity to neutralize the pH (from 3.5 to > 6.7 su, and typically > 7.2), precipitate metals, and precipitate a portion of the SO4 as gypsum - all reporting to the permitted tailings impoundment. The net effluent at discharge maintains a designated excess of ANC so that there is little or no risk of acidification of the tailings from this source. The tailings line acts as a plug-flow pipe reactor; the pipeline is about 25 km long, so there is plenty of retention time (about 4 hours). Because of the massive loading of solids from the tailings (nominal operations are 150,000tpd tailings solids), the incremental loading of metals and S from this 5,000 gpm source is only a few percent. This has operated for more than 10 years at full scale (plus another two years of test-phase work during Remedial Design), and discharges from the impoundment have met discharge limits 100% of the time.

You are dead right that the total flux-based capacity must be very large, and the reliability (including availability) of the treatment system must be very high. And for many/most/all mine-waste systems the drainage will need management as far into the future as one cares to look, so finding a cost-effective approach that can be used reliably is a very great burden. (After tailings operations cease, eventually, KUC will have to establish a direct water-treatment system with sludge management, and that will have to manage through some viable financial-assurance financing arrangement.)

You cannot use RO on low pH waters - the membrane is not designed to operate at low pH. That's why their 3,000 gpm RO plant deals only with the peripheral waters. Given that we had neutral waters with modest SO4, RO was selected as the best available proven practicable technology for producing a clear-water stream that reliably meets drinking-water standards, which was the process requirement.

The sample you have of tailing is not very typical; perhaps it is some skarn ore. Most samples, especially in the last number of decades have much lower pyrite. As the tailing emerges from the concentrator, it has negative NAPP (positive NNP in the North American nomenclature and testing format). The NNP values (using modified Sobek NP) are not great - usually + 15-25 kg CaCO3 eq/tonne, but because of the very high flux of tailing (and the slurry water that also has titratable alkalinity), the total capacity to neutralize acidic water introduced into the line through the line is very large.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Sulphate can be removed using a weak base anion resin. The resin can be regenerated using lime - producing gypsum. Alternatively ammonia can be used producing ammonium sulphate - with can have an application as a fertilizer.

OberstGruppen
2 years ago
OberstGruppen 2 years ago

This has been a hot topic in Minnesota recently, due to a surface water standard of 10 mg/L for sulfate. The leading approach, similar to described above in UT, is RO (perhaps with a green sand or alternative pre-filter). However, depending on flow rates and discharge limits, other options may be viable as well.

 

Oberstorm
2 years ago
Oberstorm 2 years ago

It’s a fact that AMD is a big issue among the environmental agencies and within the mining companies but a lot has been made in the last years regarding this type of expertise.

One good example is the Emalahleni AMD plant in one of the Anglo American mines (South Africa); they have installed a ZLD plant amazing! They treat the AMD with several physical & chemical processes (softening, filtration, RO), the brine is used to produce gypsum...about 100 ton/day.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

That is an important issue.

No matter what technology we use, there will be a by product/waste produced. In the case of gypsum from gold mining areas this will contain Uranium, Radium and a number of heavy metal contaminants.

Gruppen
2 years ago
Gruppen 2 years ago

As a company we have been looking at a new practical solution to the treatment of Sulphate rich waters. Currently we are conducting a pilot plant trial of our preferred solution in conjunction with a UK University.

We would (subject to your approval) be delighted to provide our assistance, review any data for a real water which you may be considering to treat with a view to further developing our ideas and assisting you with any feasibility assessments which you might be undertaking.

As a company Siltbuster has a wealth and respected track record in the provision of mine water treatment systems (www.siltbuster.com).

Hauptsturm
2 years ago
Hauptsturm 2 years ago

The best technology to remove 1 g/L SO4 depends on the starting concentration that you do not mention. Also important to know are the reduced iron and manganese concentrations.

Bill Rico
2 years ago
Bill Rico 2 years ago

The International Network for Acid Prevention (INAP) with the assistance of the Acid Drainage Technology Initiative (ADTI) the US Global Alliance member will sponsor a workshop on this subject after the SME Annual Meeting. Come, discuss and we can forge a path forward.

 

Sturmbann
2 years ago
Sturmbann 2 years ago

Treatment of sulphates using our proprietary technology is core to our business. We will soon build a very large plant in S.E Asia to treat sulphates using our DeSALx process.

Helena Russell
2 years ago
Helena Russell 2 years ago

In response to dated posts, here are a few items that might be of interest:

INAP and the Environmental Division of SME are hosting a sulphate treatment workshop immediately following the SME Annual Meeting.

There is a membrane-based sulphate removal technology that operates at low pH (e.g. 2.8 S.U.) during pre-treatment for solids removal, then neutral pH for membrane rejection of salts. Information can be obtained from this website:http://www.veoliawaterst.com/amdro/en/

I can fill you in on the treatment selection process for Idaho Cobalt, as I was the water treatment technical lead for the EIS.

Welcome advances have been made in the Ettringite/Gibbsite sulfate precipitation process. SO4 effluent at 50-100 mg/l, plus recovery and re-use of Al has been proven in pilot trials. This process is being developed by Veolia Water and has been reported on at the SME ED technical sessions the last two years. A third progress report is included in the upcoming SME Water in Mineral Processing Symposium in Salt Lake City to be held in conjunction with the SME Annual Meeting.

Bill Rico
2 years ago
Bill Rico 2 years ago

The Acid Drainage Technology Initiative (ADTI) is also co-sponsoring the Salt lake City Workshop on Sulphate.

Rahil Khan
2 years ago
Rahil Khan 2 years ago

Thanks for the heads up about Salt Lake City.

Oberfuhrer
2 years ago
Oberfuhrer 2 years ago

Following the SME Annual Meeting, The International Network for Acid Prevention and the Acid Drainage Technology Initiative will sponsor the Sulphate Treatment Workshop at the Hilton Doubletree at the Salt Lake City Airport. Over 20 presenters and panel members will discuss issues relating to sulphate standards, environmental risks and toxicological factors driving the need for the mining industry response.

Participants include representatives from mining companies, regulators, consultants, service providers and the International Finance Corporation.
Case studies will include sites in USA, Canada, South America, Europe and Africa. Commercial and pilot operations as well as innovative technologies will be discussed.

Obersturmbann
2 years ago
Obersturmbann 2 years ago

I just came across this - and old thread by now but I thought I would add my two cents.

The bottom line is that large-scale sulphate treatment and subsequent disposal of residuals is relatively difficult/complex and costly regardless of the method chosen. I recommend that you look at the trade-off study completed for the eMalahleni Water Reclamation Plant in the Witbank District in South Africa. This is the largest operating sulphate treatment plant I am aware of.

We have completed many sulphate treatment assessments for proposed mines and legacy sites over the years. The conclusion is always the same: focus on mitigating potential effects of sulphate in the receiving environment. We have seen many examples of fish and aquatic life thriving in water with sulphate concentrations that are well above guidelines and near gypsum saturation in some cases. Drinking water guidelines are more difficult to argue of course...

Although most operating mines and other operations can pay for sulphate treatment when they are generating revenue many of the projects we have worked on simply wouldn't be feasible if they had to bond for long-term (in perpetuity) treatment of sulphate.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Removal of sulphate is possible with a Weak Base Anion resin. It can be regenerated with ammonia to make ammonium sulphate fertilizer.

Bill Rico
2 years ago
Bill Rico 2 years ago

I am wondering how selective the weak base resin is for sulphate and what is needed to manage the stripping solution.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

BioteQ markets Sulf-IX, an ion-exchange process for calcium and sulphate removal. Calcium and sulphate are removed on separate cationic and anionic resins. These are stripped off with sulphuric acid and lime, and I gather that the resulting concentrated brines are reacted to precipitate gypsum, the by-product they produce. I don't know if they recycle back the stripped brines into the feed or deal with them in some other fashion. It would be helpful to know what conditions favour this process and what conditions are unfavourable.

Standartenfurer
2 years ago
Standartenfurer 2 years ago

I worked with the Sulf-IX process at BioteQ for a couple of years. I cannot provide you with any proprietary information but as you can imagine the devil is in the details. BioteQ will likely provide you with a fair bit of information about the process if you inquire. I don't think there are any operating commercial Sulf-IX plants out there yet but ask BioteQ.

About using IX to remove sulphate and produce ammonium sulphate. While this certainly is possible, some ammonia solution stays within the resin after it has been regenerated and reports to rinse water or to the treated effluent. The problem is that the regeneration solution must contain very high ammonia concentrations (several percent) and that ammonia can cause environmental effects at concentrations in the 1 mg/L range. Therefore, ammonia treatment would likely be required as well.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

I appreciate that IX can look good on paper, but be difficult to implement. I recall reading about the eMalahleni project, how it took 3 years to work out the process on a commercial scale, and expect it will be the same for every other technology applied to this problem.

Makes you wonder why we are asked to put so much effort in developing treatment processes for sulphate, for the marginal benefit it seems to provide. 

Obergruppenfuhrer
2 years ago
Obergruppenfuhrer 2 years ago

Without a process that has potential for substantially cheaper treatment costs than RO, I too wonder if it is worth the effort. The problem being from my experience is that if you have sulphate needing treatment there is probably a lot of other "stuff" needing removed too. Totalling up all of the marginal costs of multiple piggy-backed treatment processes make for a Rube Goldberg style treatment operation as well as costs that likely approach RO. That is not to say that I am an advocate for RO and wouldn't welcome something if it can be done at say 25% or less the cost of RO.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

Your comment is generally valid for precious and base metal mines, but not for coal mines, such as those we have in BC. They can produce effluents with marginally elevated sulphate, with little else, and be on the hook for treatment plants.

Incidentally, this is one of the reasons why I was interested in the barium precipitation/regeneration process, because barium regeneration relies on thermal carbon reduction. All you need is coal and a kiln, and coal is (obviously) abundant at coal mines.

Obergruppenfuhrer
2 years ago
Obergruppenfuhrer 2 years ago

Thank you for pointing that out. I agree my perspective is fairly limited. Perhaps I should have pointed that out as well. This is interesting for me to learn from as with most people working in a given sector of the mining industry, there is always the possibility that our horizons will be broadened at any given moment!

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

The removal of ammonia from the product water is trivial using a Strong Acid cation resin. This is regenerated with nitric acid, making ammonium nitrate.

The processes of using ammonia and nitric acid for regeneration have been well tested by Arionex. They have several large reference plants.

Bob Mathias
2 years ago
Bob Mathias 2 years ago

Maybe you already know this paper, it’s called the Lorax report it already has some years but still up to date.

http://www.inap.com.au/public_downloads/Research_Projects/Treatment_of_Sulphate_in_Mine_Effluents_-_Lorax_Report.pdf

you can find useful information regarding these last posts about RO and IX and its applications in AMD treatment.

Have you been able to determine the feasibility of barium regeneration?

Bill Fraser
2 years ago
Bill Fraser 2 years ago

I am familiar with the Lorax review and commented on it earlier in this discussion.

The barium precipitation process (in various forms) has been championed most extensively in South Africa. I understand that pilot studies have been conducted, but I have never been able to obtain information on them, despite repeated inquiries. It would be great if we could learn more about these studies at the upcoming SME workshop mentioned above.

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

The barium precipitation has been developed by Prof Maree of the University of Tshwane. He has written a number of papers on this, and holds a patent on the process.

Of course the regeneration of the barium is the main challenge, and I believe that they are researching a thermal technique.

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

Looking at the growing and very interesting messages, it seems pretty clear to me that sulphate management is a horses-for-courses matter. There are approaches that are attractive when the sulphate concentration is relatively low, pH is circum-neutral, and the matrix is low ionic strength, but these may not be well suited to, for example, an porphyry-copper effluent with pH 3, SO4 in the range of 20,000 mg/L, high ionic strength (with lots of Mg to complex the SO4, etc.

Whatever we have to deal with, the First and Second Laws assure us that we will have to manage waste products (and energy): mass and energy must be conserved in the total system. So a single "silver bullet" approach seems very unlikely, from basic principles, to be possible for the mining industry (or anyone else) at large. Maybe the ADTI conference will disabuse me of this, but ...

There is something that strikes me as fundamental: there needs to be clarity as to whether sulphate abatement is to be managed on the basis of risks or on the basis of rules. Of course, there is an expectation that the rules are set in light of some risks, but as its pointed out, toward the lower end (say under 2,000 mg/L SO4), there are certainly natural ecologies that have adapted themselves to the sulfate (and total TDS) load: the very extensive outcropping of the Yeso (Spanish for gypsum) Formation in New Mexico provides many examples, and I am sure, given sea-water composition, the same is true in selected terrains in many other places. However, I am sure we pretty much all would agree that citing sulphate concentrations in the low thousands of mg/L in natural waters in New Mexico is not a very interesting or useful matter if the water we are looking to protect is the surface water of the Canadian Arctic at a TDS of say 20 mg/L. I am sure all of us understand that the ultimate authority for setting water-quality policy is not given to geochemists, much less to geochemists who are working for project proponents. We can whinge about that all we want to do, but until or unless there is regulatory relief, we also have to live in the real world. 

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

I agree that SO4 removal is very site/project specific. In my opinion, aside from the influent water quality, the biggest factor is what to do with by product - unless one's SO4 treatment system involves fission, one way or the other there will be sulphur by product. The by product may be gypsum cake, concentrated RO brine, crystallized salt, elemental sulphur, H2S gas - the off take/disposal/long term management for each of these things differs wildly. In the context of long term AMD liability, no matter what you make you are going to be making a lot of it for a long time.

David Kano
2 years ago
David Kano 2 years ago

Yes, sulphate removal is a very site specific problem. Although, AMD does not necessarily need to be a long term problem. We use an active biological method of removing sulphate from water that is usually very efficient. The system uses sulphate reducing bacteria combined with a specific, balanced carbon electron donor. It works by converting the sulphates into carbonates. The carbonates may be utilised to reduce long term acidity and sulphates from the waste rock on the site. High purity elemental sulphur is also produced which is recycled by industry. No stored wastes are produced on site and, other than the electron donor; no imported chemicals are normally required.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

Your proposition sounds interesting, but raises a number of questions.

Using the example I provided to begin this discussion, I estimate that 7,500 kg/d of organic carbon would be required to remove 12,000 kg/d SO4. Assuming USD $2/kg for the organic carbon, this represents an annual reagent cost of USD $5.5 million. Even at half this cost, many operators will look for less expensive technologies before they start considering biological options.

Do you have information that provides a better economic argument?

Bill Rico
2 years ago
Bill Rico 2 years ago

I was wondering, also, how to manage any excess carbon, sulphide and TDS?

Marshal Meru
2 years ago
Marshal Meru 2 years ago

I can send some information on how we deal with Sulphates.

David Kano
2 years ago
David Kano 2 years ago

You are right. One of the barriers to using bacteria used to be the cost of organic carbon. That's why we have developed our own organic carbon. For a 12,000 kg/day of SO4, the ANNUAL organic carbon cost is USD$190,000. Other than a small energy cost to run some small low pressure pumps, there is no other operating cost as the system does not normally require imported chemicals. Our organic carbon is fully utilised by the bacteria so there is no excess carbon. The only sulphide that is produced is hydrosulphide which is oxidised into high purity elemental sulphur which we have no problem in recycling by industry. Regarding TDS, this system will remove the sulphates from the water. Most AMD applications have very little chlorides compared to the sulphates. But if that is not the case this system does not treat chlorides. Usually we find the treated water is of such high quality it is recycled around the mine site or used by stakeholders. If the chlorides are too high you can use desalination or we have a unique evaporator that does not consume energy. The good quality chloride solid can then be recycled by industry.

Maya Rothman
2 years ago
Maya Rothman 2 years ago

I did some work using a novel technology called Eutectic Freeze Crystallization for the treatment of highly concentrated mining wastewaters (high sulphate concentrations). Actually, the research was conducted on an effluent obtained from the eMalahleni Water Reclamation Plant mentioned earlier in this thread. See this research paper for more information if you are interested:

http://www.sciencedirect.com/science/article/pii/S0011916410006284

Tony Verdeschi
2 years ago
Tony Verdeschi 2 years ago

Do you know why Emalahleni haven't implemented this?

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Not sure. I am no longer involved with that specific project. However, there are some mining houses that are pursuing this technique in-house and there are other engineering companies within South Africa who are also pursuing the technology.

David Kano
2 years ago
David Kano 2 years ago

As RO treatment plant manufacturers, we played with freeze diesel a few years ago when we were researching AMD treatment. We made it work to site pilot plant level, but it wasn't feasible because:

Conventional compressors to freeze the water are not suitable. We tried hydraulic compressors but still not practical.

Separation of the water from the ice was not practical at a large scale.

It uses less power, but it's still too much.

Most importantly, the root problem with RO is that it produces a mixed sulphate waste product that is not recyclable. EPA's are requiring it to be removed from the site, as it can produce acid mine drainage. Freezing doesn't deal with this problem, it concentrates it, which is useful for transporting it off site, but no one will take it.

That was why we went with biological treatment. We designed the bacterial process so we convert the sulphates in the brine into carbonates which can be recycled, mostly for neutralising of acid producing rock on the site. The process eventually expanded in potential until now it makes RO redundant for sulphate treatment in water. It also removes the metals and converts them into oxides that are recycled. It does nothing for chlorides though. So we use a solar evaporator that is about 15 times for efficient than the sun to crystallise the chlorides. As these are not acid mine drainage producing and are in much smaller volumes than the sulphates they are manageable on the site. 

Obergruppenfuhrer
2 years ago
Obergruppenfuhrer 2 years ago

DETAILS, we need DETAILS, please my friend. 🙂

While I am not an expert by any stroke of the word, I am unaware of how a specific carbon source can be utilized so much more efficiently than say ethanol. Isn't there a specific carbon requirement for molar equivalence such as what was mentioned above that cannot change regardless its source? It would have to be a very dense and cheap source that is also easily digestible by the microbes.

Maybe I am showcasing my ignorance today, but I am unaware of any plant-scale biological treatment systems that effectively and completely digest sulphate. Partially, and sufficient for metals removal yes, but not for sulphate.

Do you have any sort of a presentation/paper on this process? Is it something that can be widely implemented in diverse locations with a reasonably obtainable carbon source?

Apologies to everyone if my questions/thoughts are tedious for you.

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

What is/are the reaction(s) by which sulphate mineral in RO sludge are thought to be acid generating? Is there any evidence in reviewable documentation showing this to happen in actual cases?

Bill Fraser
2 years ago
Bill Fraser 2 years ago

There is enormous interest in economical treatment for sulphate. Your information is intriguing and potentially a positive development. However, we have seen too many unsubstantiated claims and false starts to accept this proposition without more substantive back up.

What supportive evidence/documentation can you make available for us?

David Kano
2 years ago
David Kano 2 years ago

OK, some details....Your calculation for organic carbon volume was correct. We have developed a very cheap source of carbon and designed the carbon to be fully utilised by the bacteria. Sorry, we can't describe it further than that at this stage. We should be able to shortly, then we will tell everyone about it.

Briefly, our patent pending process first removes the metals from the acid mine drainage water (AMD) by oxidation. These oxides are recycled by industry. With the metals gone, we have found a precise balance of carbon and sulphates will cause sulphate reducing bacteria to convert the sulphides into carbonates. As the metals have been previously removed these are mostly Na,K,Ca and Mg as carbonates. There remains hydrosulphide (due to the alkaline pH) which is converted into high purity elemental sulphur by chemical and bacterial partial oxidation. The carbonates are used to neutralise acid producing rock on the mine site and we recycle the sulphur through industry.

The resulting treated water is high in sodium carbonate (precipitating Ca, K and Mg carbonates removed) which neutralises the acidic effects of acid producing soil on ore processing plant or trucks and prevents scaling in the water. The carbonates are typically mixed with neutral acid producing (NAP) clays from the site excavated waste and a blanket formed over the acid producing waste rock heaps. I can suggest some papers that deal with that if you are interested. We usually do not need to import chemicals (except for the organic carbon) and produce no stored wastes on site.

We have operated pilot plants on actual mine site AMD water and are preparing to install two 6 ML/day treatment plants for two global mining companies in the coming months. An Australian state government is also talking to us about using our system to manage an AMD legacy closed mine. We are receiving requests from around the world to assist with the management of AMD based on our results so far.

Yes, our process is certainly producing a lot of interest, and our mining customers always have stories about how much money they have wasted on false starts. So we took a steady approach with the development of this system, scientifically validating each step at we went. We do suggest however, as every AMD water is different this probably is not the silver bullet for AMD water treatment that everyone is hoping for. We prefer to test each water in our lab before suggesting how we can assist someone manages their AMD.

Ace Levy
2 years ago
Ace Levy 2 years ago

The concerns you mentions for conventional freeze desalination are indeed valid. However, Eutectic Freeze Crystallization is novel in the sense that it concentrates the brine AND produces salts by operating at the eutectic temperature. In fact, EFC works best with a concentrated stream.

As for the compressors, there are novel methods which we are investigating to provide the freezing capacity that is needed. We have partnered up with a refrigeration company who are currently optimising this aspect of the process. There is substantial literature on interesting methods to achieve freezing on a large scale and at low costs.

As for separation of water and ice, this is definitely feasible on a large scale and TNO in the Netherlands have developed patented Hydraulic Wash Columns which utilises the principles of melt crystallization.

As for power, the power consumption is high BUT if you use clever heat integration and the cooling capacity of the ice that is formed, this can be reduced substantially.

As for the freezing not dealing with the problem, I agree with this but as mentioned before EFC does because it produces ice and salt. The other added benefit of EFC is that it can produce many pure salts by operating at different eutectic temperature. Going a step further, the chemistry of the stream can be changed to force the system to produce a more valuable salt product from the AMD thus obtaining value from a waste stream.

Hope this clarifies some concerns.

Victor Bergman
2 years ago
Victor Bergman 2 years ago

There is nothing new about treatment for sulphate using anaerobic bioreactors. They constructed a commercial scale plant at Budel as described here.http://www.environmental-expert.com/Files/587/articles/5499/paques22.pdf

At the Budel plant they used hydrogen gas as the electron donor but a range of carbon sources can be used instead. Acetic acid was used at the Bioteq plant in Bisbee AZ. This plant reduced elemental sulphur to H2S but reduction of sulphate is essentially the same process (but relies on different microorganisms). Although biological sulphate reduction surely works there is nothing cheap or easy about the process. Of course a source of quality and very, very low cost carbon things may look better. However, at the carbon cost I’d set myself up with a biodiesel plant and forget all about sulphate treatment.

David Kano
2 years ago
David Kano 2 years ago

You are correct, bacterial treatment of sulphate is indeed well established. That is why we used it as the basis for our process. Each of the processes we use is well established. The reason bacterial processes have not been on anyone's radar is because there were some very real concerns regarding the capital and operating cost, reduction of the imported chemicals and reliability.

We could probably get into biodiesel, one challenge at a time. Right now we are trying to help out with the acid mine drainage headache around the world. Solving the world energy crisis is probably a challenge for later days.

Sachin Prakash
2 years ago
Sachin Prakash 2 years ago

News solutions for sulphates removal are available, reducing Capex and Opex of the Lorax alternatives...but the main point is still available: how managing sub-products generated?

Circular economy seems the solution...
Available for any details on new solutions and for reflex ion for sludge management

David Kano
2 years ago
David Kano 2 years ago

I found it difficult to follow your post. Are you a miner, consulting engineer or treatment plant supplier?

Sachin Prakash
2 years ago
Sachin Prakash 2 years ago

I'm just an engineer, curious, not so good in chemistry, working for Degrémont a french water treatment company (justifying my poor English)

I have been working in South America for more than 15 years and I came back recently to Europe to dedicate my time to Africa.
I have also dedicated last 3 years studying AMD treatment

If you discovered a cheap carbon source for the Bioteq, you have the solution because as its been mentioned at the beginning : volume of contaminated sludge is the main issue.
Biological solutions (Paques or Bioteq) optimize by-products generation.

Are you piloting the solution?

David Kano
2 years ago
David Kano 2 years ago

The system has been successfully piloted. We are in the process of building our first full size treatment plant.

There are zero onsite stored waste outputs from this system.

Bill Rico
2 years ago
Bill Rico 2 years ago

If we have zero waste from the treatment plant, we must be able to explain what happens to the sulphate, and other contaminants. Ammonium sulphate from IX can be used as a fertiliser, but only if it is free of toxic and radioactive contaminants. The same applies to gypsum as a building material.

Paul Morrow
2 years ago
Paul Morrow 2 years ago

Are you aware of the KNEW process? Tronox has ordered a plant for their Namakwa Sands mine. Should you be interested I can arrange for you to view the process.

David Kano
2 years ago
David Kano 2 years ago

Absolutely, one must be able to explain what happens to the sulphate. More importantly, if one is to deal with the contaminants in the water, it must be done without bringing more contaminants on site in the first place. As they only add to the products that need to be removed, this is expensive.

As it has been developed in conjunction with the Australian mining industry, our patented process uses the age old proven bacterial approach to reduction of sulphates. It does this without bringing chemicals on site and it usually has no stored wastes on site. Only our low cost, fully utilised nutrient is bought to site to feed the bacteria.

Our process is an acid mine drainage management tool, not just a treatment plant. In that respect, it converts the sulphates into carbonates. These carbonates are stored and applied to the acid and sulphate producing rock on site as a blanket. This blanket has been proven over 10 years of testing to substantially reduce long term acid and sulphate in the water. Of course one could always sell the carbonates if one wishes, but we expect most mines will prefer to use it to manage future acid mine drainage production. To be useful, a process must deal with all the contaminants. Our process converts the metals into recyclable products and the sulphide into elemental sulphur for reuse by industry.

The process uses only long term proven systems, and is installed by long term proven suppliers. Also, for over 60 years we have been servicing and maintaining our water management systems to the Australian mining industry.

Thank you for your interest in this process.

John Koenig
2 years ago
John Koenig 2 years ago

It is probably way too late to worry about exposing my ignorance, but I need some help: What is the pathway by which ozone would eliminate SO42- (aq)? I am having trouble with the thermodynamics since the S is already in valence 6. And I must admit I simply don't understand what "using ozone in a plasmic reaction" would mean.

Thanks for any guidance you can give.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

I have no reason to think that it will.There is obviously interest in this question, as seen from the lively, relevant discussion. We've heard of good prospects and I am looking forward to promise results from various demonstration projects.

If nothing else, I hope that every participant and visitor to this thread finds something useful in it.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

I have been made redundant from my role at Clean TeQ Water & Mining. I am interested to meet and discuss employment opportunities with anyone; my skill set is technical BDM preferably in water/mining sector.

Sudhirkumar
2 years ago
Sudhirkumar 2 years ago

I am doing Ph.D. in Microbial sulphate reduction in mine water (thesis submitted). I am looking for a suitable job. If anybody require Postdoc student or fresher in Industry or consulting firm.

Subhash-Kumar-Roy
2 years ago
Subhash-Kumar-Roy 2 years ago

By oxidizing that sulphate or separate the between S and O.

Marshal Dienes
2 years ago
Marshal Dienes 2 years ago

Multiple jurisdictions worldwide are focusing attention on the regulation of sulphate in mine-affected water - even, as several point out above, down to quite low concentrations to accommodate agricultural concerns for specific wild rice crops. Sulphate has been the less important consequence of sulphide oxidation-affected mine water for many years, but its ability to accumulate under evaporative stress (and the challenges associated with its removal) make it an increasingly important issue.

Beginning with an analysis of the toxicological and social factors driving stricter regulation of sulphate in mining effluent worldwide, a team of industrial and academic chemical and process engineers with global expertise in this arena will examine sulphate treatment technologies, process technologies, and waste stream management. We will use case studies to link our analysis of success and failure back to trends in regulation.

Alan Carter
2 years ago
Alan Carter 2 years ago

Reduction at source is essential as a long term cost effective solution. i.e. we need to focus on reducing sulphate release through appropriate design of mining waste facilities and mining voids. For leagacy sites, sulphur needs to be seen as a potential revenue stream, elemental sulphur is a great feed for acid plants (as is pyrite), rubber and chemical manufacture. Also production of metal sulphides can form a commodity themselves. So if we are to look at treatment, we need to look at methodologies that return a usable product. A good review of sulphate removal technologies was included in the proceedings of the IMWA conference by one of our lead geochemists. The paper can be downloaded from the following link:

http://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CCMQFjAC&url=http%3A%2F%2Fwww.imwa.info%2Fdocs%2Fimwa_2004%2FIMWA2004_43_Bowell.pdf&ei=aOzwVM3MNMXxapmagrAC&usg=AFQjCNE_1crTuUdZDs4Zr8kAdf8wPkVKLA&sig2=02YGOxqz3ruoYsk7NcydsQ&bvm=bv.87269000,d.d2s

So production of elemental sulphur is not such a bad thing, BSRT technologies may therefore be very cost effective.

http://www.imwa.info/bibliographie/17_1_008-027.pdf

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

As a geochemist I share your perspective that source control should be our first priority. At times, that is not accomplished, and cost effective treatment technology to meet rising social expectation then becomes increasingly important.

Alan Carter
2 years ago
Alan Carter 2 years ago

100% agree with you there.

Standartenfurer
2 years ago
Standartenfurer 2 years ago

Appropriate source control for sulphide oxidation is the most sensible sustainable solution.

Jean Rasczak
2 years ago
Jean Rasczak 2 years ago

Winner Water is currently operating a process developed by the Battelle Memorial Institute to remove sulphate from mine water. The technology is based on a liquid to liquid ion exchange process, removing the sulphate from the influent water and concentrating it into a sodium sulphate solution. We are working with oil and gas industry to use the sodium sulphate solution for flow back water treatment. In the past we have demonstrated the system on abandon mine sites in the US and Norway.

Bill Fraser
2 years ago
Bill Fraser 2 years ago

The best method of presenting your technology to the mining industry is not by sending emails to interested individuals, but through presentations at well-recognized international conferences.

We desperately need new solutions for problems like excessive sulphate, but equally we need to gain confidence in proposed solutions. We need to critically evaluate candidate technologies, to ask and hear questions relevant to us and our peers, and listen to your answers. 

Raje Singh
2 years ago
Raje Singh 2 years ago

Thanks for posting the notice about the upcoming sulphate treatment short course in Santiago. This sulphate treatment short course is an out-growth of the INAP Sulphate Treatment Workshop held last February in Salt Lake City, Utah. Many of the INAP members requested a more focused "short course" format to be held in conjunction with the joint INAP-IMWA technical conference in Santiago. This short course will provide a focused curriculum on sulphate treatment and residuals management prefaced with the regulatory and toxicological framework that is driving the need for sulphate treatment of mine influenced water.

The short course is appropriate for individuals who have no experience with sulphate water treatment through those seasoned professionals & educators who desire to learn more about specific case studies from around the world. There will also be descriptions of some forward looking yet unproven treatment processes that the industry is evaluating.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

We extract the sulphuric and return it as a saleable sulphate salt or sulphuric acid concentrate up to 80% concentration, we recover the heavy metals and either delist them in a concrete that is non-leachable or recover those with value like the copper at Berkeley pit – return 96% of the AMD water to river water standards and turn the cations into pot nitrate to cover the cost of all these operations – in some cases it returns more than the cost leaving enough profit to make the capex required a good investment. (The 4% water loss occurs due to forced evaporation in recovering the Pot Nitrate).

We do all this without producing any polluted gypsum that has to be stored somewhere very ever.

Unterstarm
2 years ago
Unterstarm 2 years ago

An alternative is to use Barium Chloride, in Peru I developed a small treatment plant, Q = 36m3 / h to reduce the concentration of 1040ppm sulfate to 180 ppm. The effluent comes from a tailings pond.

David Kano
2 years ago
David Kano 2 years ago

What you speak of is already happening. We are building and operating plants that convert most of the contaminants in the high sulphate water into recyclable products. Sulphates into high purity elemental sulphur. The treated water is potable standard. This is particularly useful when the sulphates result in acidic water, resulting in dissolved metals. We then sell the products and share the revenue with the miner. There are no imported chemicals, energy consumed or stored wastes. http://WWW.globalaquatica.com.au

Carl Jenkins
2 years ago
Carl Jenkins 2 years ago

Controversial subject the sulphate removal issue for sure. Especially in Southern Africa. When I hear statements like "recover all metals" or "convert all to saleable products" I can't help to giggle about it.

With the large volumes in our region simple mass balances will show certain products are produced at 100% or more of yearly global consumption. Certainly not a sustainable situation.
Sulphuric acid production: what if you have an excess in your market already? Not sustainable either.
My view is that it will have to be "horses for courses"! This means clients must choose carefully from various solutions to suit their specific requirements.

Hauptsturm
2 years ago
Hauptsturm 2 years ago

An option that could be plausible is conversion to h2s with srb then to sulphur via vanadium oxide oxidation.

David Kano
2 years ago
David Kano 2 years ago

Perhaps, further explanation is required. The markets for the recycled products from the Global Aquatica process are international. The demand for all the products outstrips supply internationally, hence the reason the products are of value to the consumers. This would be particularly useful in South Africa as it would generate much needed exports from the acid mine drainage liability.

More importantly, the sale of the products create a revenue for the miner, which in turn encourages him to 'do the right thing' regarding cleaning up the acidic waste water.

The Global Aquatica process converts the sulphuric acid (Acid mine drainage) into elemental sulphur.

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