Reduce turbidity in rural water tank?
Hello, I hope this isn’t too much off topic.
I’ve lived with my rural home water system for 25 years. I wonder if I can do anything about the excessive turbidity (silty particles in the water).
The water is pumped from a 285′ deep well into a 500 gal. (I think) above-ground concrete storage tank [about 6′ wide and 5′ deep], going through a big spraying arm above the water. It settles to a degree in the tank, and I clean out the bottom of the tank every few years; but it doesn’t settle much, I suppose because the particles are so fine and the tank is not still very much of the time.
The water goes through a pick-up (intake) tube, elbowed about 10 inches above the floor of the tank; then through a shut-off valve, some 1-1/4″ piping over to the pump house 5 feet away, through a check valve, through a pretty big pump, and then in parallel to a pressure tank, through an iron filter (a big cylinder filled with medium that back-flushes every couple days), through a standard paper-filter, and then on to the house plumbing.
The whole thing works fairly well, but requires a lot of attention because all the piping before the filters becomes choked with silt, in particular the check-valve.
My question is, is there some way to settle or pre-filter the water before it leaves the storage tank. Should the intake pipe be higher? If so, how close to the top of the water? Would it help to move the intake point to the side of the tank opposite the spray of well-water? What about a baffle wall of some kind built into the tank? What about a whole new filter of some kind between the intake pipe and the entry into the check valve and pump?
If any knowledgeable person is kind enough to comment, I would sure appreciate it. Thanks!
Replies
I am not a water treatment person but common sense tells me that a simple sediment filter on the well side of the tank would solve a lot of your problems.
At least it would help keep the sediment out of your tank and the subsequent piping etc.
Probably have to be a regular maintenance issue though.
I agree about the common sense, but I wonder if there is some reason that you don't usually see a filter before the storage tank (in my limited experience).Thanks for the reply!Skhu
Alum is what's used in municipal systems, plus chlorine helps too.
It sounds like your system has too much turbulence and not enough settling time to allow the silt to drop out. You need to draw your water from as close to the top of the storage basin as possible. Another possible solution may be to add angled plates into the storage basin. These plates in effect help shorten the required settling time, depending on the nature of the silt and may also provide sufficient barriers to lower turbulence.
Have you spoken to your well installer. They may be able to treat the well to minize the amount of silt. You may be able to adjust your pump height so it draws from a different area of the well depending on your screen location and length. There also may be a filter you could put on the intake side of your pump.
I do not think any type of chemical treatment is appropriate for your system.
Bruce
Thanks very much for these detailed suggestions. How would I learn how to design such plates? I suppose I might have to consult a water system pro. Thanks
Skhu
How much work do you want to do?
We could start from scratch, time consuming , labor intensive, & expensive.
I would use a commercial swimming pool sand filter in line before sediment tank, does require maintenance, but they are easy to clean.
I second the suggestion of a sand filter. Did a quick web search and came up with the following. (Disclaimer: I know nothing about this vendor or these products.) http://www.plumbingstore.com/lakossandmasterfilters.htmlI would guess that with some study you could probably build your own, although it might not be quite as efficient as the engineered versions.
You have a very specialized problem.
Here are some possibilities.
Maybe the media, disk, or centrifical filters with automatic backwash.
http://www.irrigationtutorials.com/filters.htm
But first you should get a sample of the raw water from the well and also from the settling tank and get it analyzed as to the amount and size of the particles.
That information is really needed to design the right filters.
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
You might try checking with a state hydroglist who would know about the water quality.
Or checking with state universities.
Not sure what departments, but start with geogogy.
Edited 10/20/2007 11:30 pm by BillHartmann
I know very little about this situation however, you said:
>> You might try checking with a state hydroglist who would know about the water quality. <<
Not sure I'd take that route... might end up with some government guy slapping a red sticker or other lockout on the system because they found something they didn't like.
BTW - I wonder why the well water is sprayed into the top of the tank? Seems like that is just worsening the situation.
"Not sure I'd take that route... might end up with some government guy slapping a red sticker or other lockout on the system because they found something they didn't like."Possibly. My though was that this type of problem might be common in certain areas and thus they would know about possible solutions."BTW - I wonder why the well water is sprayed into the top of the tank? Seems like that is just worsening the situation."Several possibilities.One is to release gases.Another is mix air into the water. I think that helps with some mineral compounds.And the third is that this if done right the water can drain smoothly down the side of the tank and not stir up the sediment in the tank.Here is another though. Don't know what the cost are or how practical this is.And don't any idea of the well pump rates or the usage rates.But have two main settling tanks. It would require some time clocks, level switch, and motorized valves.But alternate tanks so that one is available to supply water. The other is being pumped into. At the start of the cycle a purge valve is opened and flushed the tank. That would probably use a separate inlet that is down low to stir up the sediment in the tank and flush it out.Then the tank fills. It then sets for a period of time (24 hrs?) allowing more stuff to settle out and reduce the amount that the down stream filters need to handle.Then at the end of that period the this tank now supplies water and the other is being refilled..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Hi - original poster here.Thanks to all for helpful comments.The hesitation I have about installing a new filter between the well pump and the storage tank is, that that would add additional back pressure / stress to the well pump, which is probably sized and designed to deliver water without extra resistance, so it would shorten its life. Particularly if anyone in the future forgot to clean the filter in a timely way. Or is this not really a worry?Lots of good ideas here, thanks again.
Skhu
I don't think that is much of a worry.
Edited 10/21/2007 7:36 pm ET by TomW
There is a worry that in a system like this a filter could serve as a breeding ground for nasties.
If your view never changes you're following the wrong leader
You're correct that problems could result.
Any type of common filter placed between a submersible pump and your tank will become clogged to some degree, sooner or later.......if it's actually filtering any particles. IOW, it would begin to perform the same function as a throttling valve. Although throttling valves can be used without harm to either motor or pump......the end affect of a clogged or overly restricted flow thru a filter would be the same as having an overly restrictive throttling valve in the line. While that won't actually overwork a centrifugal pump motor (would actually put less load on the motor as it's pumping less water)....... it will substantially reduce the flow of water over the motor which is necessary to cool it. And the pump will likely begin cavitating if it isn't moving enough water. If that happens, the pump will become pitted or worse and it's useful life will be dramatically shortened. If the pump overheats substantially, it could swell and seize.
Bottom line....I wouldn't.
Edited 10/21/2007 9:56 pm ET by HootOwl
Hello,
I guess I'm very much a newby to this forum :) Since the present topic concerns well water, I have a question I hope someone will have a helpful suggestion for.
We had a well drilled three years ago, to a final depth of 160 ft, through a lot of sand and the like. The water has been tested chemically and is very hard (550 ppm total hardness), pH pretty close to neutral, no bacteria, so otherwise, manageable. Most of the plumbing is Pex (much to my displeasure....) but wherever the water is in obvious contact with anything containing copper, the fixture soon takes on a sky-blue colour (copper sulfate, I know, proof that sulfur is present in some form in the water). As well, when the house is closed up, as in winter, we notice a very definite sulfur smell in the house when we come back from being outside for a while (but not exactly H2S which I would recognize immediately). And, anything that contains silver is now a very definite carbon black!!
We have enquired with respect the remedies for this situation, but have not received any useful answers other than spending big bucks on a system that will remove iron (which is also present in the water; 5 PPM, which is more than the water softerner can manage without regular "de-ironing"). We hate to contemplate having to spend another couple $K on yet another water treatment system, with no guarantee that it will provide a long-term solution to the sulfur gas (whatever it is).
Any and all feedback is most appreciated!
Thanks
Ted
A pylrolox filter will take care of iron, manganese and a certain amount to sulphur. This can be put in in conjuction with your softener. Whatever you do, you need to have your water tested to figure out what needs to be addressed. I got good informationhad and service from http://www.abundantflowwater.com . Give them a call or send them an email with your water test results and see what they can offer.
Edited 10/21/2007 9:37 am ET by TomW
Thanks, tom. Yes I did have tthe water analyzed, hence knowing the concentrations of the calcium/magnesium (hardness) and the iron. The link you provided has exactly the kind of information I need. Ted
There are lots of sulfurry (sp? HA!) wells around our area. Common solution here is to install a much larger holding tank with an open air top. Supposedly the sulfur dissipates into the air.
I've not tried it, but I've heard positive results from various sources.
We see water treatment systems around here costing as much as $15k. I'd sure try everything else before I'd spend that!
"Doubt is not a pleasant condition, but certainty is absurd."
~ Voltaire