Filter for iron in water

Here in NH, lots of people with wells have iron in their water. The question often arises as to how to filter this stuff out.

Actually, iron (the red, visible kind) is easy to filter. Because of electrostatic attraction, this type of iron wants to attach to something - anything. You could run rusty water down a 2" pipe (long pipe, very very long) and it would come out clean at the other end.

So, with this in mind, avoid using filters with a small micron rating. Larger is much better to avoid premature clogging.

In my house, I use a 1.5 cu.ft. automatic backwashing filter filled with a medium called "Filter Ag". It has a 20 micron size rating and it works slick. The water is sparkling clean.

Now here's the rub. Water from my well has TWO kinds of iron in it. The first kind is ordinary rust which, as I mentioned, is easy to filter out. The second kind, is disolved iron which is clear. This cannot be filtered out. So what to do?

This disolved iron must be oxidized so that it becomes ordinary rust which can be filtered out. There are several ways to do this: (1) Bubble air through the water. Municipal water systems sometimes do this. Tough for a homeowner though. (2) Add a tiny amount of Chlorox bleach. The bleach gives up oxygen molecules to oxidize the disolved iron and the left-over bleach molecule (minus the oxygen) becomes an ordinary table salt molecule. Since we're talking tiny amounts here, the salt left in the water is trivial - almost unmeasurable.

This is the method I chose and it works. A special chemical injection pump is used for the bleach, plus you need a large (I use 120 gal) retention tank to allow adequate reaction time. This tank is in addition to the regular bladder water tank you need for a well system. All of this is followed by the filter.

(3) You can buy a filter that uses greensand for the medium. This avoids having to use a chemical pump and retention tank but, you have to periodically recharge the greensand with potassium permanganate. Not for me thanks.

I hope this info helps someone.

Well, my pressure tank is "Air over Water." Each time the deep well pump starts it forces a slug of air into my tank. (A "air volume control valve" on the side of the tank bleeds out excess air.) I find myself wondering if that amount of air would be sufficient to oxidize the Fe.

In any case I don't see any real problem to "bubble air" through an air/water tank. If you had a sealed air pump it would take little energy to pump air from above the water and inject it into the supply pipe from the well. The "head" would be about 5' of water or about 3 psi. Alternatively, the intake from the well rather than just filling from the bottom could, say, spray water on the top of the tank. The air volume control valve would have to be shielded to keep it from spitting out water when it operates.

"Around here" many of the schools are still on well water. The standard installation has two tanks. One tank received the water from the deep well pump. It is air/water with the air being at atmospheric pressure. Since it isn't under any real pressure it's cheap to put in a tank that holds well over 1000 gallons. The second tank is the pressure tank on the order of

300 gallons. If homes had such an arrangement it would make it a lot easier to treat various water problems. Chemicals or air can be injected into the main holding tank at low pressure and the deep well pump would be sized to the peak average consumption rather than the maximum consumption.