Aerating Water to Get Rid of Iron

[smallpooldad]

Am lead to believe, after reading a while back an American Ground Water Association article, that aerating water by passing bubbles through it releases Iron and other minerals into the air, therby removing Iron from the water. Is this true?

If so, then what size/sort/strength pump and how many lines and outlets would be needed in pool that is 32' x 9' with 9000 gallons? How long should it take in hours?

I realize this a weird question, but any solution for those of us with Iron issues is helpful.

Aloha

[chem geek]

Am lead to believe, after reading a while back an American Ground Water Association article, that aerating water by passing bubbles through it releases Iron and other minerals into the air, therby removing Iron from the water. Is this true?

This doesn't sound right to me. The iron that is in water is an iron ion (when dissolved) or typically a solid iron oxide when stained (precipitated) on plaster. To aerate iron or other minerals, they would have to be in some sort of gaseuos form and I just don't see that happening. If you can find the article, post a link and I'll take a look at it.

Richard

[smallpooldad]

Chem Geek,

This is what was written. A little too far above my little head but maybe you can decipher some goodies from the articles that may help the iron challenged.

Aeration

When aeration is used as a pre-oxidizer it is generally done with either an air inductor or an air pump.

An air inductor is a venturi installed inline. The water flowing through the inductor creates a vacuum and sucks air into the water line. The faster the water flows, the more air induced into the water.

Watch for pressure drop and perform routine maintenance of the inductor, as they will clog with iron over time.

The air pump method allows more air induced into the water, as a mechanical pump is used to force air into the water. A contact tank is often used.

This method has proven effective with the only cautions being maintenance to the pump and injection fittings.

Here is the link:

http://www.pwgazette.com/ironremovalrules.htm

and here it discusses aeration on page 3 of the pdf:

http://www.amtrol.com/pdf/Removal.pd...0removal%22%22

and here:

http://www.cdc.gov/nasd/docs/d000901...1/d000981.html

and here:

http://www.chennaimetrowater.com/ironrem.htm

Looking forward to your thoughts.

Aloha

[darenjones]

this looks like it would apply more to water treatment, not a pool set up. This is similar to what we use in my industry to treat well water into the home.
just my 2 cents...

[chem geek]

OK, now I get what is being said. Essentially, by introducing oxygen through aeration into the water, the oxygen oxidizes the iron from the ferrous ion, Fe(2+) to the ferric ion, Fe(3+), that they claim is solid. Technically, it is an ion and isn't solid, but what happens when combined with oxygen is that it forms ferric oxide, Fe2O3, also known as rust which is, of course, solid.

So essentially, through aeration, especially using pure oxygen (since the pool should already be saturated at the oxygen level of air already), you can precipitate the iron in water causing solid rust that can be filtered. Unfortunately, the conditions that make this happen, including higher pH, also cause such rust to deposit onto your pool surfaces, causing staining. So yes, aeration with oxygen and raising the pH will cause the metals in your water to come out of the water as solid, but though some of this will get caught into your filter, some of it will also get "caught" into your plaster as a stain. Some of the references you gave talk about pre-oxidation using aeration using regular air, but that is for water that is low in dissolved oxygen as might be found in wells, but not in pools.

This is essentially what darenjones said -- this procedure may work well in a water filtration system, but it isn't good in a pool unless you don't care about stains! Now I suppose it would be possible to have some sort of oxygen aerator injector in a pipe before the filter, but it had better be designed properly so that you create all the rust and have it filtered all out otherwise you could end up putting rust into your pool (though it may be "loose" and not adhered to the pool surfaces).

Last, but not least, is that the levels of iron that these articles are talking about is generally much higher than found in most pool water. However, if you have well water that is high in iron, then it is true that aeration and high pH (8-8.5) plus filtering to remove iron oxide (rust) makes sense BEFORE you introduce such water into your pool (you should restore the pH back to around 7.5 before adding the water into your pool). So, using a device like darenjones described that is used to remove iron from well water going into a home might make sense before adding such water as fill water into your pool.

Oh, and one more thing. Chlorine is also an oxidizer so high levels of chlorine and high pH (which liquid chlorine produces in combination) will generally precipitate metals so usually your pool won't have a lot of iron in it because if it did, then you would most likely precipitate it as stains over time unless you kept your pH low [EDIT] OR if you used a sequestering agent which essentially keeps metal ions dissolved in solution and helps prevent their precipitation even at higher pH or in the presence of chlorine or oxygen. [END-EDIT]

Richard

[smallpooldad]

Saved again by the Pool Forum.

So this idea is "Very interesting, but stupid."

As the little German Corporal used to say on "Rowan and Martin's Laugh-in" (circa 1960's); my father was German captured by the Brits in North Africa. After 1945/6, he loved his English prison so much he stayed there the rest of his live, well not in prison, . So I got much amusement out of this little ditty as it sounded so much like him.

His other favourite but ridiculous saying, which always made me laugh, was "Bloody foreigners," when talking about non-Brits. He said this in his usual heavy German accent. I think my ancestry affects the way I think, always probing technical solutions to problems.

So much for that idea.

Aloha and thank you all for stopping me buy 200 yards of PVC and a massive pump.