Aerating Water to Get Rid of Iron

[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