Iron and hydrogen sulphide - is this a crazy idea?

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Jeremy Harris

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OK, I'm a novice at this stuff, and I've spent over a year learning as much as I can about wells and treatment, mainly as they are rare here in England and good advice is really hard to find. I started life as a chemist, so understand the basic oxidation reactions that are used to convert hydrogen sulphide to sulphur that precipitates out and ferrous iron to ferric iron that also precipitates out. This seems to be what all the commercial iron and H2S filter system do, oxidise and then filter out (or just let the precipitates settle out).

I've read a couple of threads on here and looked at the web site, for a venturi air injection device that squirts highly oxygenated water back down the well, which then encourages oxidation in the well itself of H2S and probably ferrous iron ("clear" iron) as well. I've read the mixed views, but nothing seems to indicate that this system doesn't basically work. The downsides seem to be that it uses a small amount of pump water 24/7, so the pump works a tiny bit longer and that the top of the well may get some additional iron and sulphur precipitates, as it injects right at the well head.

This got me thinking. I have an electrical box in my well head chamber (which is what I think you guys may refer to as a "pitless head", a concrete chamber covered with a lid with the well liner sticking up from the base with a cap over where the pipe and cable comes out). This has switched power to it and a water proof connector that connects to the pump cable, to make changing the pump simpler. There's room on the electrical box for a second connector, and the underground feed cable's big enough to supply three or four pumps. There's also some spare room in this chamber, as the 5" well liner comes up near one corner and the chamber is around 18" x 24" internally.

What would happen if I fitted a small air pump, like the quiet sort used for powering an air brush, and connected it to a long length of thin nylon tube with a nozzle on the end, then dropped this tube down well below the pump. If this air pump was then hooked up to the pump feed, every time the borehole pump ran the little air pump would run and oxygenate the water in the well below the pump. My guess is that this would do the same thing as the Sulfur Eliminator, by oxidising the H2S, and maybe the ferrous iron.

In my case my pump is about 60ft below the rest water level, and around 70ft below the surface, so if I ran the nylon hose down to, say, 80ft then I'd need a pressure of around 40psi minimum to get air to trickle out, maybe 50 psi to get loads of very fine bubbles out of something like an aquarium air stone or a very fine nozzle, as really fine bubbles would be needed to get most of them to dissolve in the water and not get sucked into the pump. This sounds achievable, as the small air brush type air pumps chuck out around 60 psi and cost around £60 (~$90?). If it works it seems a lot cheaper than the Sulfur Eliminator for something that would seem to do the same sort of job, oxidise water in the well.

One downside is that some of the precipitate is going to go down the well, but a fair bit may well get sucked up by the pump, as the reaction is a fairly slow one and much of it may well happen in the pipe from the pump to the pressure tank, and inside the pressure tank. This would be helped because the air pump would only be running when the borehole pump is running, so most precipitate is going to form whilst water is being sucked into the pump. A filter would be needed to catch this, but in my case I have one anyway, so all I'd be doing is reducing the oxidising load on it, by making sure it was always fed with pretty well oxygenated water, which would help the media last, I think. I'm already doing this with my break tank (discussed in this thread: https://terrylove.com/forums/index....dvice-please-borehole-supply-in-the-uk.61806/).

Am I crazy for thinking this might work? Feel free to call me a nutter if this is a crazy idea, I'm British, so used to being viewed as eccentric.................
 
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Many of the systems oxidize but speed the oxidation with a catalyst. Many wells have enough oxygen in the water to not add extra oxygen before the catalyst.

A pit is usually a chamber that lets the water, fittings, and casing be below the frost line. They are nice enough in theory, but they are subject to being flooded and letting dirty water leak through the well seal.

A pitless (pitless adapter) is a device that penetrates the casing and allows the passage of water through the casing below the frost line.
Install2.jpg
The casing is then extended above ground to be higher than potential flooding. The wires are brought out of the top of the casing and the top of the casing and the wires cresting the casing are covered by the well cap.


https://terrylove.com/forums/index.php?threads/sulfur-eliminator.51158/ is another system for oxygenating in the casing.
 
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Jeremy Harris

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Many thanks for the clarification, I'm battling with the different names for things between one side of the Atlantic and the other and the lack of expertise over here, so your help is really appreciated a lot. This forum feels like a lifeline to me, given the difficulty I've had over the last year or so in getting hold of even basic information on wells here in England.

What I have is a concrete chamber that is partly below ground level, with a drain in it that connects to the house soak away rain water drain, to keep it dry. The chamber has a sloped and shaped concrete base that leads to this drain, to help any water that gets in there drain away. To top of this chamber is just above ground level, high enough to stop any rainwater or run off getting in. Inside the chamber I have the 5" well liner coming up through the concrete in the highest corner of the floor of the chamber (again so water runs away from it if it gets in there) and a plastic conduit that takes the underground MDPE water pipe to the treatment plant shed and also the underground steel armoured power cable from the pump switch, also terminating in the shed. The armoured cable is good for 30 amps (240V) and terminates to a watertight box screwed to the inside wall of the concrete chamber. That has a waterproof connector on it that connects to the pump cable. The concrete chamber has a steel lid, just like the standard drain manhole covers we use here. The top of the well liner has a plastic cap fitted over it, with the pipe and cable coming out from under that, so it sounds just like the system you've described.

We don't really have a ground frost problem here, but as the well is in the middle of what will be our garden having this slightly raised concrete chamber means that my wife can include it as some sort of "feature", maybe replacing the steel lid with one of those steel drain lids you can get here that take decorative stone blocks or paving, to make it look more "natural" (I am NOT a gardener - I leave that to her!).

The thread you kindly linked to was one I had read, and to be honest it was what gave me the idea of using well air injection. I had thought of just buying a Sulfur Eliminator as the easy way out, but the price, together with shipping and import duties and taxes here would be pretty high, probably well over $600 for the basic model maybe more by the time the shipping company had taken their import handling fee.

Our well water has a pretty low dissolved oxygen content as it comes up, which is one reason why I'm attracted to the idea of a something that helps increase this before the water gets to the filter system. Oxygen dissolves pretty readily in water under pressure, so it seems to me that generating lots of very fine air micro bubbles 20 ft or so below the pump, but only when the pump is running, might just be an easy, and relatively cheap, way of increasing the dissolved oxygen in the water that's pumped up, helping the catalyst in the filter do it's stuff.

Part of my thinking is influenced by the way I feed water to the break tank I have at the moment. I made a very DIY ozone injector as an experiment, using a cheap Chinese (ebay) bare ozone generator (basically just a very high voltage power supply and a couple of ceramic plates with electrodes either side as a corona discharge generator). I machined up a venturi eductor, using off-the-shelf PVC pipe fittings and a stainless nozzle brazed to a brass inlet fitting. This works really, really well, far better than I ever expected it would, and is still in use.

The borehole pump feeds water at around 4 bar (~ 60 psi) to the nozzle, which is around 1/8" in diameter. This then squirts down into a machined up Delrin (acetal) venturi that I turned up to fit inside a PVC pipe , with a thin stepped edge to rest on the top of the pipe. The pipe is cemented into the bottom of the tee to hold the venturi in place. At the top of the tee I have a cemented in 3/4" threaded adapter and that takes the brass pipe fitting (from the pump flexible hose) with the brazed on stainless nozzle, with the nozzle just in the narrow mouth of the venturi. The side arm of the tee leads out and then up to a 1" pipe that draws air from the alloy box that contains the ozone generator, with a small computer fan on the other end of the alloy box to give a bit of added air circulation around the ozone generator plates (they get hot in use). The ozone generator is powered from the pump switch, so every time the borehole pump runs to fill the break tank back up to the float switch cut off level, the venturi eductor draws in loads of air and ozone. I used a short length of clear rigid PVC pipe below the eductor to see what is happening and it's pretty amazing. What flows out is high velocity white foam, down the pipe and under the path around our house to where I have the break tank temporarily located (it's in the way, which is why I want to get rid of it, we're short of space).

The feed pipe runs down from the top of the tank inside a 6" pipe that is resting on the tank bottom, so the aerated water goes down to the bottom and the bubbles come out and float up, with the water running over the edge of the 6" pipe like a weir so that there is minimal disturbance to any fine sediment at the bottom of the tank (the 1hp house supply pipe draws from around 1/3rd of the way up from the bottom of the tank, so it gets clear water). I can smell ozone inside the break tank when it's running, rather than just the smelly hydrogen sulphide that I could smell before, and the break tank water stays crystal clear (maybe because the ozone helps to sterilise it). I strongly suspect that this ozone system is taking out much of the ferrous iron as well as all the H2S, as the clear length of rigid PVC pipe I have under the eductor is now stained orange with ferric iron, which I think may be a good indicator that it is oxidising efficiently (given the reactivity of ozone and the vigorous aeration from the eductor I'm not that surprised).

Apart from the problem of the break tank blocking the path around the back of the house, and having nowhere else to put it (I can't even bury it, as we have a big retaining wall and the structural engineer is adamant that we can't dig a hole anywhere near it), I also suspect that the ozone is going to damage the pipes eventually. As well as the rust staining, the pipe looks to be going milky, so I have a feeling that this wouldn't be a good long-term solution. It was a very fun experiment, though, and gave me a lot of confidence that I could engineer a water system that would work and last, provided I could just get hold of the knowledge needed. This is, I guess, mainly why I joined this forum last year - the knowledge is certainly here OK, and I'm really glad people are so keen to help and share it. I just regret that I'm not really able to contribute much in return, yet.
 
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