I would first, as a professional in mining environmental issues, remind that the worst in AMD is not the acidity: it is the heavy metals, metalloids and sulphate load that acid waters carry.

Using AMD run off for frocking means injecting large amounts of contaminants in groundwater, irreversibly.

Unless you are using pure pyrite drainage, with no metals/metalloids in solution, you are probably going to an extra environmental disaster for natural water resources.

AMD runoff can be reused, indeed, but in my opinion this has to be for hydrometallurgy or for tightly controlled remediation processes - for instance WEEE leaching.

But I am open to innovative options, as long as they are properly assessed by professional geochemists. 

Salinity limits the ability of companies to recycle frac-water. So using AMD, with high sulfate, in areas where groundwater is already saline (Pennsylvania, etc) might run into technical difficulties.

As an operator of an AMD plant I was asked by the DEP to consider selling (or giving away) my treated AMD to operators for Fracking. Sulfates were the biggest issue. The additional chemical costs of treating this "treated water" for use in fracking far exceeded the cost of providing other fresh water source. Especially when the operators on the western side of the state can get the water from streams for no cost or purchase from public water supplies at far less cost than the costs associated with treating AMD for use in fracking. I do have the analysis somewhere if you were interested.

Since fracking is done in shale formations thousands of feet underground (often more than 8,000 ft), I don't see a significant issue with contamination of shallow groundwater reservoirs - given, of course, that the well cement job is done properly, which is a different topic all together.

Thanks for pointing out issues with TDS/sulfates. I didn't think about that. It's interesting to hear that there is a lot of opposition to this idea from the environmentalists, when oil and gas companies have nothing to gain here and are proposing to use a contaminated water source before it enters the environment.

Sorry but I cannot see any sustainability in injecting massive quantities of arsenic or cadmium in groundwater, even at depths not yet used as valuable resources. They will become precious for mankind, sooner or later. Wasting them irreversibly for the ephemerons use of fracking does not make sense, apart maybe for the yearly balance of the beneficiaries.

I'm definitely not against the idea, just aware that there are technical limits. Possibly where water is very limited it could be an option; just a balance of costs.

http://www.gasfrac.com/in-the-news.html

Use of propane for fracking would be preferred.

This would be great and I'm all for it however, you would have to treat the water prior to using it to frac. Injecting it into the formations that are being drilled into now is not an issue. It is not contaminating any groundwater being used for drinking water.

The primary issue in addition to the sulfate and salinity already discussed are the heavy metals. After a well is fraced it goes through flow back where a lot of the water used for the frac is now produced water. So now you will have the heavy metals from the AMD (in addition to the heavy metals and other contaminants from the oil) back at the surface needing to be treated. There is also an issue of the pH itself. I believe the frac gels don't work well with low pH water.

If the cost of the treatment side can be dropped low enough or if there is a government regulation created to mandate reuse of frac and/or AMD then this could be a good option.

If I read it right, you accept heavy metals groundwater contamination by AMD water in addition to contamination from fracking operations, but you recommend treating then groundwater needed for further uses.

Not sure this is a cost effective option, unless remediation costs are borne by the sole water users - most likely further public expenditure.

The (below sea level) gas formations are extremely salty, In addition to rad’s, barium, lithium, cadmium and tons of other nastiest, these formations are too dry and too contaminated to ever be used as a groundwater supply. The water used in fracking is much better than anything that will return from the formation. The EPA uses 10,000 tds as the max for groundwater that could be treated and used as a drinking water supply. These formations are like 250,000 tds. I can’t imagine any scenario where water from these deep formations will never be used as ground water.

Agreed, the problem of water contamination is much more related to the produced water (and proper handling and disposal of it) than to the frack fluid itself. Thankfully, the days of keeping the produced water is an unlined pit are mostly gone.

As a side note, you mentioned rad's. I also think that using ARD waters would actually reduce the radioactivity of the produced waters, which is another benefit.

Propane gel as a fracking fluid sounds like a neat new technology. I have to shamefully admit I've never heard of it. It will be interesting to see if they get a permit to use it in NY, where water-based fracking is prohibited.

In talking to potential users, the big problem with this concept is the large amounts of sulfates in almost mine drainage discharges regardless of the acidity. The sulfates combine with Barium found in most deep brines and forms Barite inside the well and this acts as a strong clogging agent. Removing sulfate in mine water is very expensive, so there is not as any easy answer.

Very interesting, and great sentiment. Thank you for sharing! Despite all of the aforementioned potential qualms with utilizing this method instead of clean water, I wonder how pH levels will affect the earth after implementation. Will the acidic nature of the water cause further shale breakdown and exacerbate plate shifting?

As a resident of Colorado I have seen how fracking has affected our local rivers- and despite fracking taking place 8,000ft below the ground, we still have extensive contamination in our water supply. Seeing that fracking is not fool-proof, I have to agree with it that introducing yet another set of contaminants may not be the best option. I almost feel like containing AMD within its source and treating on site may be a better solution than spreading it around into different environments and eco-systems.

None the less- great article and really got me thinking about possibilities.

Also a great reminder that even if we bury the AMD, there is no "way" on this planet only solutions.

The simple answer is that if you are going to use AMD for another purpose, you must remove the heavy metals. This can be done with ion exchange.

Well, after reading this article. The idea of reusing AMD is smart point for solving problem of discharging treated AMD, but will catch some concerns as mentioned in discussion above.

The treated AMD may meet the water quality for discharging according to the environmental regulation. However, the treated water should be alienated to natural water as several items like ion concentrations are still too high for local aquatic environment (even water quality of the treated water is on the level). Such like hardness mostly contributed by Ca. The source of Ca is applying of lime for neutralising acidic water aiming to raising pH and removing heavy metal ions. But the leftover Ca ion could be far more than the one in local water system. In other words, the treated AMD still inputs some extra "ingredient" into the local pond. Its impact may not be seen in short term in relation of ion concentration. But it may gradually and eventually modify local eco-system if we are talking about total amount of input ions. Therefore, reusing of treated AMD in mining industry will reduce the actual discharged water and then minimises mining-related impact on environment. Also, it would also financially reduce the cost of using water for mining operation.

Then, it comes to a question mark after where to apply the treated AMD. Personally, I would apply the water to prevent dust rising during digging and loading process. Alternatively, the treated water can go for cooling down the coal dump which is easy to catch a fire at dry and hot area. Re-regatation on site also requires a large amount of water so that is a good section for reusable treated AMD water to be. Some other ways are mentioned in this article.

However, I am quite concerned by using the AMD for drilling industry. This may encourage the contact between AMD (treated or not) with natural water. If there is no 100% recovery rate in water (AMD water) during drilling process, it might mean contamination to natural way system is still possible. Cleaning underground water will be a tough job. I will think twice before moving my thought for using AMD to drilling.

Another way to look at this potential technology is:

Can produced water from fracking be used to treat ARD, since it is highly alkaline, before reuse of treated ARD in fracking?

Such a technology should include neutralization, clarification and sludge management.

Frac metals such as barium and cadmium will precipice out with the sulfates in the ARD, the alkalinity will help, thus the process works well together, (We've treated both together) but again the problem with reuse will be the same sulfates that will plate out with the barium and calcium information on the well skins . To treat this water for fracing use is 5 times as expensive as buying fresh water from a public water supply in our area.

Another problem with commingling AMD and O & G fluids is the EPA/DEP sludge issue. Many AMD sites dispose of the alkaline rich sludge back in the deep mine as an EPA Class 5 well. This is beneficial to the mine pool in that the excess alkalinity treats the generally acidic mine water. The near mention of treating any fluid related to O & G along will the AMD would put an end to Class 5, even if the testing can confirm that the sludge would be safe for disposal. Disposal of AMD sludge in a drying pond or refuse pile would also be out since the material would be reclassified. The cost of alternate methods (landfill) would be way out of range since 99% of the sludge would be AMD.

I agree with you. The potential long term liabilities in any of these cases are overwhelming. If an O&G company wants to take an ARD stream (treated or not - and we know there are plenty of legacy mines discharging untreated waters to the environment), why not let it? Based on previous comments, not many ARD waters would be suitable for this application anyway. Conversely, if produced water from O&G operation would help these legacy sites treat the waters, why create regulations that make it so difficult? The alternative is that these waters never get treated (or barely treated) and the ARD is discharged to the streams, while the produced water is pumped back underground at much shallow depths (thus creating many more potential issues with drinking water contamination that fracking itself).

Please correct me if I'm wrong, but I think it was Newmont a few years back that proposed to cleanup some waters from legacy sites adjacent to Newmont's properties near Elko. The EPA's position was that if a mining company laid its hands on that water, they'd be liable for its treatment in perpetuity and would have to treat it to below the discharge standards. Which of course was not in line with Newmont’s intention as a good neighbor that just wanted to reduce the historical pollution at their own dime?

It's easy to vilify the mining and O&G companies because of a century of unregulated discharges. But I think there has to be a common sense in some of these regulations.

Interesting debate, and good article - thanks for sharing.

I agree with both sides, as there are plenty of pros and cons to think about, but my take away from the end of the article is that the water to be reused would still be treated to some degree prior to reuse perhaps to a lesser quality than new regulations coming into play might propose, but treated all the same.

The main benefits I could see would be that clean water sources would remain in their natural states because discharges (treated or not) would not be added to them, and would also not be consumed by the frac operations because they have another source, leaving it for alternate users and nature.

Is this really a cost-benefit to the mining companies or the O&G operators - that depends on the upgrades that would be required to meet new limits, and the distances at which each source might come from, I guess.

If sulfate is the issue, consider using a "loose" RO membrane to reject the sulfates and use the permeate for fracking, rather than fresh water. The concentrate could be treated with produced water, use the barium to precipitate the sulfate, then clarify and combine with the permeate.

Sludge needs to be evaluated using USEPA 1313 to determine the pH stability range. Use of ARD underground mine pools for disposal is likely not sustainable, due to re-dissolution at the lower pH range.

Using alkenes rather than water fluids makes sense, indeed.

The limited miscibility would help to reduce water contamination.

Is this another topic? 

Agreed, let’s keep the alkenes out of the ARD where possible!

There are issues with liabilities that should be considered from a standpoint of transportation of the AMD from one watershed to another that would normally have been impacted by AMD or is in a more pristine watershed. Another is should mine water be drawn down in an area from an AMD discharge there is the possibility of mine subsidence upstream or around the perimeter or surface area of the land above the mine pool complex. Mine pool complexes, like the ones that I work in throughout North-eastern PA are very hydro geologically complex. If a subsidence should occur, upstream of a discharge location, who is liable for the damages? It may not happen right away. What if the mine pool is backed up or dammed? AMD then could fill the base flow of streams and possibly lead to flooding or the creation of new discharges at other abandoned mine locations. My environmental organization has taken a stance on a particular Senate Bill 411 in PA against it because of various liabilities concerns and the lack of emphasis on assisting the communities where the AMD would be withdrawn by not providing any incentives to reclaim or assist those communities.

I think this is very interesting your experience with acid water. I am working in mine with this lind o water. Could you send me that information related to this issue?

Re tasking AMD is certainly practical. We are building and operating plants that convert the AMD into potable quality water that is used for agriculture and mine processes. So there is no reason why it couldn't be used for fracking. The contaminants are converted into useful products which we sell and share the revenue with the mine. No imported chemicals and no stored wastes.