Iron is a night mare, most here use ozone injection then a settling tank with some times floculant, Green sand lasts 7 to 10 years so long as you maintain it well, they do need regenerating with pot perm (Potassium permanganate).
Yep, that matches with the research I've done on the topic. Main difficulty I see is that getting hold of more than half a pint or so of liquid KMnO4 (and the purity that "Joe Average" can get is a joke... I'm not even sure that the 8% solution that was the only thing I could find when I went looking a couple years back is adequate) is damned hard here in the states anymore, and unless you're a lab or similar, you can just plain forget the crystalized version completely - It's on the list of "things used to make meth", and even asking about it is likely to put you on a terrorist watch list. (Though, there is the concept of "If you're not on a watch list, you're slacking off"...)
Generally the trick is oxidize the iron out,
No question. Filters can't touch the dissolved form even a little bit. Trying is roughly the same as stirring a cup of sugar into a pan of hot water, then trying to filter the sugar out - It just ain't gonna happen, no matter how good your filter is. Gotta convert it to rust for filtration to have even a ghost of a chance.
What a nightmare, just in space alone...
green sand is more for H2S and other smells.
That goes against almost everything I've found - While it IS, absolutely, useful for H2S, everything I'm finding is using diffrerent wordings, but they all come down to the same thing: "If you've got a lot (5PPM or more is apparently considered "a lot", so at 12+, I guess we have "a lot - and then some!") of dissolved iron, greensand and/or manganese dioxide is *THE* magic bullet." Which makes perfect sense to my (admittedly limited) chemistry knowledge - "naked" iron "wants to be" rust, and MnO2 catalyzes the oxidation reaction, turning the dissolved iron into rust flakes that a filter at least has a chance of grabbing.
Metsorb for arsenic and other heavy metals.
Thankfully, we get "none measurable" results on lead, mercury, asenic, and nitrates/nitrites, so that's not an issue for us.
'Bout... Oh, must've been 4 years ago, now, I ran across a unit going under the name "The Iron Eater" - Venturi air injection (optional tank-oxygen or hydrogen peroxide injection adapter available at additional cost. Editorial comment: O2 and/or H2O2 injection ought to do ABSOLUTELY WONDERFUL things for houses plumbed with copper pipe... <eyeroll>) plus a three-vessel series, with the first vessel supposedly loaded with "chunk" manganese dioxide, the second filled with greensand (which, if I haven't misunderstood, is just "smaller chunk" MnO2) and the final vessel loaded with plain old pool filter sand. Theory of operation is the venturi puts plenty of atmospheric O2 (or straight-up O2, or H2O2) into the water, the first vessel, loaded with the "chunk" MnO2 catalyzes the Fe+O2 --> FeOx reaction so that things happen close enough to instantly (no need for reaction and/or settling tank and the associated extra hardware) and depending on flow at any given moment, may "settle" some of the rust out before passing it on to the greensand vessel, where the reaction continues, and the "sand" part starts filtering the rust, then the pool sand does a final filtration. They claimed that dissolved iron would be less than 1PPT when it comes out the other side of the system. Great, by the sound of it - Until you read the price tag - A unit sized to supply our outfit (assuming we don't just keep on running untreated water to the barn/stock tanks) is north of ten grand, and based on their dimensions, would almost totally fill the barely-extant "basement" where the pressure tank, the current(ly not operational ) "(not) treatment" system, hot water heater, and furnace currently live.
When I was in Florida, the well brought up similar water to here, but worse - Don't recall the exact numbers 30 years later, but I'm wanting to say it was carrying 20+ PPM iron and mid-teens PPM sulfur. (Fortunately, as iron sulphate, rather than hydrogen sulphide) Stunk so bad it could gag a maggot. I couldn't stand to get it near enough to my face to try to drink it "in the raw"! The stuff was almost "crunchy" straight out of the well.
There, the well-pump went straight to a dozen or so spray-heads that didn't look much different from (might actually have been, in a previous life) fire sprinkler heads hung about 6 feet above a bug-screen enclosed 1500 gallon tank. (That they had to have a "sewer sucker" type truck come through and pump out every few months due to muck buildup from the rust sedimenting out) After being sprayed into the tank, the water sat "for a while", depending on current usage, and a pool pump sucked it from the tank, then pushed it through a sand filter exactly like a pool filter (wouldn't be a bit surprised to find it was originally designed to BE a pool filter) then through a gizmo I never saw the inside of, but the owner said was about 400 linear feet of made-to-order half-inch glass tubing running back and forth between a pair of 2500 watt banks of UV lights - he called it the UV-blaster - then through a standard "paper cartridge" filter, and finally, to the rest of the place. House had a fancy salt-regenerating softener, while the barn "only" had a charcoal filter cannister. I liked the barn water better - The house water tasted "dead" somehow. (Which I've since found out is a common thing with "soft water" systems - back in Florida was my first exposure to "softened water" after growing up drinking northern Michigan well water - which is pretty universally "fine stuff", even when the only "treatment" is the well-pump bringing it up)
I wouldn't want to pay the power bill for the UV-Blaster... 5KW? Running 24/7? OUCH! My wallet is screaming in agony at the mere thought! But then, at the time, the owner had money to burn - He was ranked as one of the top 20 surgical oncologists in the world. He was a double-specialist - as he put it, "I majored in lady-cancers, with a minor in boob jobs", which I eventually figured out meant carving out breast, ovarian, uterine and cervical cancers, and the reconstructive surgery to fix the damage he did while doing the carving. He was "famous" for being a "one man cancer treatment clinic" - Assuming you were female, he could diagnose it, carve it out of you, and do the reconstructive surgery to make you pretty again. Always thought it was a bit too ironic that his wife (who was the reason there were horses there to be taken care of) died of ovarian cancer that went wildfire on her.
But I ramble... Lemme hit send before this turns into "Gone With the Wind, Part 2"
youtu.be
