remediating the aquafer

Due to a certain practice used in oil drilling over several decades, my local aquafer has a chloride plume. It is migrating slowly through the subsoil(large area). I was wondering about possible remedial actions that could be taken. For instance, chlorine when exposed to the sunlight will dissipate. Would that happen to chloride? the difference between the two substances is an extra electron. Could you pump up water from the aquafer into a shallow pool and allow the chloride to evaporate and then reintroduce it to the aquafer? or what plants could be planted with deep roots that could lock up the chloride? I am sure there is information I do not know or have that might be needed to explore fully the different possibilities. I would still like to start a discussion and discover ideas and thoughts on this.

Hey Jennifer

My sympathies with this problem. It is not an easy one. This is really something that the pollutor should deal with but if your garden is under threat....


Could you give some extra information ?

It is migrating slowly through the subsoil

How deep ? Is the polluted groundwater in use for irrigation or is it a problem for plant roots ?
How big and how concentrated is this chloride plume ? Is it just chloride ? How fast will the chloride plume reach your property ?
I can imagine that sulfates etc.... are up as well. Is the water unsafe and/or unusable ? Chloride is very soluble and has the potential to migrate away from its source. Others pollutants may also have been released and move more slowly. The other pollutants - if present - may be more of a problem.

For instance, chlorine when exposed to the sunlight will dissipate. Would that happen to chloride? the difference between the two substances is an extra electron. Could you pump up water from the aquafer into a shallow pool and allow the chloride to evaporate and then reintroduce it to the aquafer?

No, chloride - evaporation is not an option - Salt pans do actually the reverse - In a salt pan, the water evaporates and the salts kristalise and can be harvested. https://en.wikipedia.org/wiki/Salt_pan_(geology) https://en.wikipedia.org/wiki/Salt_evaporation_pond

Groundwaterpollution of this type is difficult to clean up. Chloride will not degrade (biologically or chemically) spontaneously. Active chemical remediation can work but is not cost-effective for large areas or for private individuals. Environmentaly this kind of remediation is also a CO2-producing mess. Most chemicals which you could theoretically use are energy intense to produce and they are not specific. Meaning they may react with other soil components you don't want to loose.

Pumping it up is possible but once up, chloride will not evaporate. Chemical treatment is possible but is usually expensive. Most cases i know of are left to dilute spontaneously after the source has been dealt with.

I doubt very much that much can be done other than containment or placing some kind of reactive wall. Containment works by placing a barrier in the way of the groundwatermovement to prevent the pollution reaching a vulnerable area. It can also be a pumping action to change the flows rate or direction. Containment works best when you can lock the pollutant in. It is difficult to lock the pollutant out.

A reactive wall is a permeable barrier that either absorbs the pollutant or changes it into something harmless.


Peat has interesting properties regarding chloride. So if you have easy access to peat or something similar you may experiment with it.
Peat when flooded with seawater retains salt. That is why during the middle ages salt was extracted from salty peat by boiling. https://nl.wikipedia.org/wiki/Moernering This wiki is not linked to an English equivalent but since it was done in England as well, i suppose there must be one somewhere. This link illustrates the point http://www.nihk.de/index.php?id=2297 You must check if it is effective enough to make a difference - i don't have a clou.


There are plants and plant varieties that can cope with some salt in the groundwater but there are none that i know of that effectively remove salt from the soil or the groundwater. There are usefull plants grown in salty conditions but not much. Check Israeli research institutions for more details.



When you cannot keep the salt groundwater from reaching your garden you may loose lots of plants. Possibly your garden may survive if the salt groundwater is deep enough and you don't use it for irrigation.
If you irrigate with groundwater check the construction of your well. Salt groundwater is heavier than fresh water. Salt water might use the disturbed zone around the well as a conduit to contaminate deep fresh water aquifers (eg under a clay layer). This is usually prevented by sealing the well with bentonite.

If you irrigate from a fresh water layer atop of the salt water layer, do not pump fast or to much because this will encourage mixing of the groundwater layers.


Good luck
Erwin

Erwin Decoene wrote:Chemical treatment is possible but is usually expensive.

That is what I found after searching a bit for articles. I don't see it as something an individual could do, only a community. Of course the responsibility for clean up should be on the polluter, but they usually scamper away.

Possibly a helpful strategy could be to restore the larger watershed so that the aquifer could be flushed with more fresh water.


Some watershed restoration resources:

"Urban water harvesting systems" https://www.youtube.com/watch?v=WymWRDd1OOg

Rainwater Harvesting Basics https://www.youtube.com/watch?v=2iQ-FBAmvBw

http://www.harvestingrainwater.com/

http://quiviracoalition.org/Publications/index.html

http://www.regrarians.org/

Natural Sequence Farming https://www.youtube.com/watch?v=Xo8N38lAgq8&list=PLE-d88mKVNvCLWK0_m46vHoQGXfT5T-S4&index=20

http://www.nsfarming.com/

http://www.watershedartisans.com/Erosion_Control_Field_Guide.pdf

It is a community issue. It is a county issue. I am interested because I want to purchase land and institute permaculture design which even on my comparatively small parcel, would over time hydrate my soils and add to the aquafer. In discussing this with a friend who is a hydrogeologist who works with monitoring the aquafer and helps the county determine what water rights to issue, is telling me about this issue(he tells me about 12 trillion gallons of water is effected by this pollution) is incredulous about the possibility of rehydrating the soil in this way and also that it would be bad for the aquafer. I know that there is other pollutions such as oily residue and heavy metals. I would be concerned about the pH and the affect a high acidity would have on the heavy metals. It would be miraculous to be able to find a reasonably simple solution to this problem. I wonder if there is a market for the chloride.

In my opinion, rehydrating the soil can never be "bad for the aquifer." I'd want to know what the person meant by this. To me it sounds like he's saying "I don't believe in it and it is bad" which is what someone says when they are threatened by a new idea.

With those volumes, nobody will be doing anything anytime soon. Certainly not with expensive chemicals and/or energy intensive and/or labor intensive methods. Did someone inject brine into the earth or did they extract oil from the environs of a salt dome ?


There are industrial processes which can use chloride-rich water ~ think of greywater use to compare what can be done. But not enough to change much of the condition of your aquifer.


I aggree with Tyler. Why would it be bad to rehydrate the soil ? The only valid reason i can think of - just now - not to allow water to permeate trough the soil is if you have a compound leaching into the groundwater. Then you want to keep water away from that compound. That should not be the case in your situation.

If a fresh water layer can be formed or maintained above the salt water you might escape most ecological problems. An other approach that is feasable for small surfaces is to block upwelling, salty groundwater from reaching your topsoil.

I agree with Tyler as well. I am insulting his intelegence, or his years of schooling. I think that is what it comes down to with that situation.
And, yes, brine was used or created in the oil mining process used some 50-80 years ago. I think he said the chloride was 16000 parts per million
enough to kill anything.