Shock chlorination for iron?

[mbmarsh]

I've got a good well, 125 feet, refill 25 gpm, 85 feet of water; had the water analyzed several times, there's about nothing in it--very soft, slightly acid, small amount of iron (0.1 ppm). Had a new pump put in five years ago, soon after I moved into this now-18-year old house.

But about six months ago, I started getting discoloration in the water--very noticeable. Before that, there had been no trace of it. I hired a plumber who installed a Big Blue 10 inch filter. With a 30 micron filter, that helped a lot, but not enough; subsequently I went to a 1 micron pleated cellulose filter. Again, a big reduction; but the water, sometimes, is still hazy, and if allowed to stand will deposit a "scum" on the bottom of a glass. When I change filters, the housing contains a lot of orange "mud." So I installed a 0.5 micron String Wound PolyPropylene Filter; still the same problem.

So I called out the company that installed the pump. The specialist looked at my used, orange, filter, took a running water sample directly from the pump head (1 ppm iron, he said), and told me I had lots of bacteria living down in my well (my analysis had said "no iron bacteria") and prescribed a metering apparatus to sit atop the pump and inject a dissolved pellet of chlorine/bromine every morning at 2 AM, to kill the bacteria. He is so sure that this will do the job that he guarantees it--my money back. But that's the rub--it's a LOT of money.

There was mention of shocking the system--essentially pouring Clorox down the well; I read up on it, and it sounds like something I could readily do. While I was waiting for a weekend with time to do this, I investigated the nature of the orange mud. I took a sample from the used filter; I also took a sample scraped from the wall of my toilet tank reservoir. I treated both with fairly strong muriatic acid; overnight, both dissolved entirely. This suggests to me that it's nothing but "rust."

Now, where is it coming from? Best I know, there is no galvanized pipe in the system, so that's probably not the source. Is it in the well, in the ferrous (water-soluble) form? If so, were I to take a sample directly at the well head, it should be colorless and clear; then if allowed to stand open to the air, a precipitate should form as the ferrous is oxidized to ferric oxides. I'll do that soon as I can.

That's step one. Next step would be to shock chlorinate. That should do two things: Kill all the iron bacteria down there, if there are any; and oxidize all the ferrous iron to ferric iron, and precipitate it in the well, to be flushed out when I flush out the chlorine. Next, I wait. If there is no iron bacteria in the well, then this treatment should have almost no effect, since as soon as the water in the well is replenished from the aquifer, I'll have ferrous iron back in the system, and it will go back to falling out in my pressure tank and collecting on my pleated filter.

BUT, if there _is_ iron bacteria in the tank, this chlorination should remove it, and it should be weeks or even months, before it reappears--and so for that period, I should see no precipitate.

OK, so that's great theory; does it make sense to folks who know what they're talking about? Thanks for your expertise.

 

[bimr]

Iron bacteria is common in a wells. Iron is common in a wells.

You can disinfect the well to rid yourself of the iron bacteria. The iron bacteria may come back since it is difficult to remove the bacteria completely.

You may have iron by itself after you disinfect the well.

The iron is soluble in the well (clear solution) and will turn insoluble (red water) when exposed to air.

Go to a library and have them obtain the book titled "Handbook of Ground Water Development" by Roscoe Moss Company. Some of the chapters are online.

 

[mbmarsh]

Time for a follow-up. I chlorinated that well, April 22nd: 3 quarts of Clorox into about 125 gallons in the well, circulated it well for over an hour, let it stand for 12 hours, ran it out into the woods for at least 1000 gallons; the first effluent was very orange indeed; gradually it became very turbid yellow, then less and less so; finally it didn't smell like chlorine, and wasn't more than slightly turbid, so we began using it in the house. After two days I tested with some iron strips, and got virtually no iron; but I also tested for chlorine, and it was still 1.5ppm; not until five days went by, watering the garden some, doing laundry, etc. was chlorine undetectable. So was iron, though my filter continues to collect a small amount of "mud."

Meanwhile, the water got less and less turbid, until yesterday I could not distinguish it from bottled water. Which is great--but how do I interpret this result? I never saw any of the other signs of iron bacteria--no slime, no smell; yet this drastic removal of what appears to be rust should not have lasted this long unless I had iron bacteria--if all I'd done was oxidize ferrous ("clear water") iron to ferric, in the well, it would have long since been replaced by more ferrous water. I guess I should count my blessings, and hope for a long remission before the hypothetical iron bacteria become fruitful and multiply. Any ideas?

 

[bimr]

You should have your well water tested for coliform bacteria. Have you had a water analysis prepared? If not, you can do that as well.

Otherwise, you can continue torun your well with periodic monitoring for iron.

 

[MEM1]

Testing your water for coliform bacteria is a good idea, but keep in mind they are most likely present if you have other bacteria there. Coliforms are an indicator bacteria. They indicate the possibility of other more harmful bacteria being present. What you have is a moderate level of ferrous iron in your water. When oxygen is introduced, the iron changes to ferric iron (rust). You need to reduce the ferrous iron in your water. This is usually done with the introduction of a polyphosphate solution. Adding a polyphosphate will sequesture any magnesium and iron in the water. However, I have seen this done with public water supplies, I have never seen it done in a residential setting.

 

[bimr]

Yes, polyphosphate is sometimes used for the purpose of sequestering.

However, there is more art than science in the application and it is difficult to prove quantitatively that the chemicals work.

If your well is clear, you should not attempt any further measures.

Every well must be tested periodically to determine if microorganisms are present. The indicator test is the coliform bacteria test.