sand filter and iron

I was excited to finally have a functional pump in our well, but then I discovered how much iron is in the water.  something like 15 ppm when .3 ppm is enough to stain.  there's some manganese in there as well, but not nearly as much.  I had a local outfit price a treatment setup and it would be upward of $2000 for a basic system with an 85-gallon pressure tank and iron filter, and more than $3000 for a more complete system including a water-softener.

instead, I would like to build a slow sand filter feeding into a large tank at the top of our hill and gravity feeding to the rest of the property.  that way I can skip the pressure tank and iron filter and water softener (I hate soft water).  having read a bit and chatted with a few folks, I believe that slow sand filters are effective at removing iron and manganese, but I'm not sure how much of those metals they can handle.  I think this is going to work, but if I'm going to have to climb up there to scrape the sand every week, I might explore other options.  so what do you think?  great idea?  doomed to failure?

alternately, does anybody have any other relatively simple and affordable ideas for removing iron from our well water?

also, what's the contraption called that would turn a pump on when water gets to a low level, then off when the water reaches an upper level?  mechanical float valve won't do, has to open and close a circuit to control a pump.

Tel - I have no advise on removing iron from water, however when it comes to sand filters the best way I know of maintaining such a system is to purchase one of those large sand-filter units for larger swimming pools. 

Every couple of months you just back-wash the filter (run water through it in reverse) to 'clean' for 10 minutes or so and it's good to go.  Every couple of years you change the sand (I do not know what the rate would be for iron, so these numbers are based on large swimming pool maintenance and would need adjusting for your situation of course).  But if sand filtering will do the job you require then using a sand-filter unit would make it easier.

Anyway, using a unit like this would be a more reasonable solution than having to do sand scraping weekly - IMO.  Of course there is the up front cost of the unit to consider and the equipment to run the water through it (not a drip system).  So as with all things there is a trade off to consider.

I'ts a good thing you hate soft water, because I think the cheapest way to remove iron and manganese would be by raising (got it wrong at first, thanks for spotting it!) the pH with some sort of calcium before it exits the sand filter.

This might mean the sand must be changed more often, or it might not. You could try mixing some limestone chips in with some sand and seeing how well that works. Is there a cheap & easy way to get a general sense of how bad the iron is out of various test systems? You mentioned staining, so I'm imagining something like a little cube of scrap drywall in a quarter cup of water, where you can look at the color after it's dry. IIRC, manganese rust sometimes comes out a bright green color.

Here is a possible solution to the iron in your water.  Might be costly, but no maintenance afterward.


This is an excerpt from the link below.  The image could not be copied and pasted, so I included the link.

"Iron and manganese problems are most likely to develop in water from wells with high carbonate and low oxygen as shown in the middle well in Figure 1. Problems occur when this type of water is pumped to the surface. The chemical equilibrium is changed upon exposure to the atmosphere. The end result is precipitation of iron and manganese compounds in plumbing, on fixtures, and on clothing, dishes, and utensils."

http://www.ag.ndsu.edu/pubs/h2oqual/watsys/ae1030w.htm

Joel Hollingsworth wrote:
I'ts a good thing you hate soft water, because I think the cheapest way to remove iron and manganese would be by lowering the pH with some sort of calcium before it exits the sand filter.

my understanding is that calcium tends to raise pH.  but then, high school chemistry was a while back.  the idea is that the iron stays in the filter, though, yes?  that's what I'm hoping for without any change to the standard bio-sand  filter.  I think I could probably deal with cleaning it once a month, though I would certainly prefer less often.  if that doesn't remove the iron, lowering pH seems reasonable.

supposing I'm mistaken and calcium will lower pH, what's a good and cheap source?  oyster shells?  limestone?

Al Loria wrote:
Here is a possible solution to the iron in your water.  Might be costly, but no maintenance afterward.

looked like all the treatment methods mentioned on that page do require maintenance.  I suppose the back flushing would be automated, but the polyphosphate and chlorination and greensand options all consume some substance that must be replaced.

I think I'm going to go ahead with the slow sand filter.  the filter itself will cost me all of $20 to build, as opposed to hundreds or thousands of dollars for some of the other options.  if it doesn't work, I'll only be out my time.  if it sort of works, I'll look for ways to improve it.

Please post back your set up and results, as I'm sure your experience will be useful to others.

Good luck[size=14pt] ♠[/size]

A float valve can work to turn water on/off electrically too. Mount the float in the water, add a rod to the stem near the pivot point with the other end of the rod operating a micro switch.

rockguy wrote:
A float valve can work to turn water on/off electrically too. Mount the float in the water, add a rod to the stem near the pivot point with the other end of the rod operating a micro switch.

interesting.  how would I set that up so that the tank empties before the pump turns back on?

tel jetson wrote:
looked like all the treatment methods mentioned on that page do require maintenance.  I suppose the back flushing would be automated, but the polyphosphate and chlorination and greensand options all consume some substance that must be replaced.

I was thinking of the well being shallower or deeper as shown in figure 1.  The well would be above or below the heavy iron zone at that point, eliminating maintenance.  The other solutions do require maintenance.

Al Loria wrote:
I was thinking of the well being shallower or deeper as shown in figure 1.  The well would be above or below the heavy iron zone at that point, eliminating maintenance.  The other solutions do require maintenance.

right.  good point.  I did notice that bit, but a new well is well beyond my means at the moment.  I would probably just pump out of the river before I went that route.

in any event, I'm not sure that would really be an option anyway.  being on extremely sandy soil and very close to a river, the water table is pretty shallow.  a well shallow enough that iron is oxidized might be shallow enough that water is out of range during the dry months.  deep enough that iron is bound up with sulfur might mean that hydrogen sulfide is a problem (that's just a guess, as this stuff is well outside my ken).  I will keep those possibilities in mind for the future, though.

I knew it was an expensive option to dig a new well but wanted to put it out there if you were able to do it and did not have the concerns of the sandy soil.  also it is a crapshoot if the water table changes and you have no water with doing a shallow well.

Good luck, and I hope you find a solution that is affordable and low maintenance as well.



Al

well, I built it.  actually, I built two, because I thought the first one didn't work.  turns out that I don't know as much about siphons as I thought I did, and they both work.

the iron is reduced to undetectable (by me) levels, so that much at least is a success.  how long it will take for these things to clog up, I don't know yet.

this is also without any of the goo formed on top that's supposed to do the bulk of the filtration work in a slow sand filter.  I'll try to take some pictures and add some more details later on.

Congratulations on the success! 
It would be nice to see pics.

I had a situation with iron in the water.  This is when I was told that there are different types of Iron.   
http://www.dnr.state.wi.us/org/water/dwg/iron.htm#types
Bacterial Iron is difficult to remove and I had a device put in that literally pumped air into a tank with the water.  Then the water continued on to the water softener where the iron was removed.  I rented both appliances for like $29 a month per each.  I preferred renting that way if anything went wrong, the company (Culligan) would have to come and fix. 
It worked well.  Before that I was noticing rust spots on my sheets and film on my dishes. 

A water softener will remove some types of iron.

As for digging a new well... There is no guarantee.  Mine was a brand new well.

I wonder if the pipes used for the well walls are rusting out, and that is the cause of the iron.

I think the camera just left town for the week, but if it's still here, I'll try to take some photos tomorrow.

erikgreen wrote:
I wonder if the pipes used for the well walls are rusting out, and that is the cause of the iron.

there's a lot of iron in this water.  if it was coming from the well housing, I don't think there would be a well housing left by now.  a reasonable idea, though, and that may well contribute to the iron load in some well water.

took some photographs.

here's the second filter I made.  the first one is pretty much the same, but in a smaller barrel.

that's 1/2" polyethylene pipe on the ground with 1/4" line feeding up into the top of the filter.  one end is connected to the well and the other end is connected to a couple more barrels uphill.

closer view of the top:

you can't really tell what's going on inside the filter, but the designs at www.biosandfilter.org are pretty close to what I did.  it's a little hard to see, but just downstream of the outside fitting, there's a little drip irrigattion emitter.  I put that in to break the siphon that was emptying the filter too quickly into the 550-gallon tank just downhill from the filter.

to make a good seal through the wall of the barrel, I used a brass fitting sold as a drain for swamp coolers, which didn't show up in the photograph.  the outside of it is cut with 3/4" male hose threads and the inside has 1/2" female pipe thread.  there's a gasket and a nut to secure it.

this picture also gives a good idea of the amount of iron I'm dealing with, as this thing has only been in operation for a couple of weeks.

reservoirs:

these are uphill of the filter.  I turn the pump on for fifteen minutes to fill these up, then they gravity feed back down the same 1/2" tubing and into that 1/4" tubing to feed the filter.  I stabbed a hole in the top bung of the white barrel for air and drilled holes in the top bung of the black barrel.  most of the bungs I've seen for poly barrels have a knock-out in the middle so a 3/4" NPT fitting can be threaded in, which is very handy.

the tube and fittings I used are designed for drip irrigation.  probably not the most durable option, but it was much cheaper and I had a bunch laying around anyway.  including the tubing, I believe I spent around $20 on the plumbing.  I bought a 50-lb bag of washed rock and a 50-lb bag of washed coarse sand for $5 each.  those go in the bottom.  I got about 1.5 cubic yards of fine washed sand from the local ready mix concrete plant for free because they were trying to get rid of it.  spent a day rinsing everything that went into the filter, as there was still a lot of dirt and dust on the sand and gravel.  that probably wasn't necessary, but I didn't want to clog up right away.  I used sand I dug out of the ground without washing it for the first filter I built, and it turns out to work just fine, though it isn't hooked up right now.

this second filter is working pretty well, as far as I can tell.  haven't had the filtered water tested, but the iron taste is gone.  there's still a fair amount of work to do to get the whole thing through freezing weather, but I'll probably save that until the very last minute...  I'll probably paint all the barrels at some point as well to protect the plastic form UV degradation.

suggestions for improvement would be appreciated.

edit: changed photo urls

Nice work.

The sand filter will take out much of the particulate iron (and manganese).  If you wanted to take out some of the dissolved iron, you could use some zeolite or green sand in place of the washed sand.  It would cost more but would be more effective. 

Also, if you bought the components yourself you could do a treatment system for half of what you were quoted.  If you used some fine particulate filters you could probably go even cheaper.  If you remove a good share of that 15 ppm as particulate iron, the treatment system doesn't have to take out as much.  IMO many of the water treatment contractors are ignorant at best and thieves at worst.

Next time you send samples off for lab work you may want to run total iron and dissolved iron on the raw water to get a better idea what you are actually having to treat.

how about ozonator this is what  i am plan for rain water collection/storage. it wont remove it but it will oxidize it and can be filtered out easier or will settle out. and in my case it kills viruses bacteria protozoa and cysts and doesnt salt the water(drinking salt water is still bad right?)

sticky_burr wrote:
how about ozonator this is what  i am plan for rain water collection/storage. it wont remove it but it will oxidize it and can be filtered out easier or will settle out. and in my case it kills viruses bacteria protozoa and cysts and doesnt salt the water(drinking salt water is still bad right?)

I don't know much about ozonators.  it wouldn't surprise me to find out one would work well in this application.  my own preference is for biological solutions ahead of technological solutions.

my sand filter is working pretty well so far.  microorganisms, if they're present, should also be removed by a well-designed slow sand filter.

Ozonation will help the iron precipitate out.  Just how much depends on residence time before and through the sand filter.

Ozonation isn't cheap though.

I think generating ozone to oxidize dissolved iron is overkill. Aeration should be enough.

I had forgotten this until now, but some of the earliest forms of life survived by oxidizing dissolved iron. These mostly died out in the oxygen catastrophe (when photosynthesis was developed), but they still have an important place in the soil ecosystem and quite a few other niches. Some of these microbes will certainly find their way into the biofilm, and they should thrive in that environment, making enzymes that speed up the process of iron precipitation (and nourish the microbes in the process).

A biofilm filter plus aerated water should produce (edit) iron oxide out of your dissolved iron, the same way iron ore was laid down in (edit) the distant past. All that extra material might make it clog more quickly, but it should work fine if you can get around that limitation.

Thanks for setting me straight, Ardilla! I like to learn about geology and biochemistry, but haven't gotten around to learning much of either, yet.

Your chemistry is a little off but the idea is correct.  Magnetite is generated in anaerobic conditions not aerobic.

The aerobic conditions make a variety of iron hydroxides and hydrated Fe(III) oxides (which can be physically filtered). 

Magnetite deposits were created in the Precambrian before the oxygen catastrophe.  Now that our atmosphere has oxygen, the oceans no longer precipitate magnatite and and chert...