Water Purification question???

arby

Hello all,
I have installed a water pump and pressure tank system at my Solar Powered cottage (off grid).
The setup has two huge filters feeding into a UV light chamber and then into the 60 gallon pressure
tank.
I have wired the light to come on when the pump turns on , and off when the pump stops. This usually lasts about 1 minute.
Doing a bit of googling, etc., it seems that the UV light needs to run a minimum of 5 minutes before it is effective.
The recommendation by the manufacturer is to leave the light on all the time. This apparently is like leaving a 40 watt bulb on.
A pretty hefty draw for something that for the most part is maybe used twice or three times a day, if that.
I did a search, but came up empty.
Any ideas, or methods appreciated.
Thanks in advance.

Cariboocoot

Re: Water Purification question???

The first thing I'd do is check the water supply and see if this is actually needed. You're quite right that leaving the thing on all the time would be a strain: 40 Watts * 24 hours = 960 Watt hours, or about twice what a large pure sine inverter uses!

Having it "warm up" for 5 minutes before the pump activates is also not practical; you'd have to estimate time between one pressure and the pump turn-on pressure so that the light would come on at, say, 30 psi and the pump at 28 psi. Pretty problematic since pressure and volume do not automatically equate to time. Unless you have a degree of manual control (I don't allow my pump on until I know there's enough power to run it) it's messy.

So it's back to "do you need it?" If it's a question of guaranteeing drinking water, a separate tap with a ceramic filter may be a better choice (this is what I use, even though it is not technically needed). UV only kills bacteria; the ceramic will take out particles and cysts even.

NorthGuy

Re: Water Purification question???

If you fill in your 60 gallon tank in a minute, you're probably pumping in at 15gpm. You have a good well and a big pump.

The volume of your UV chamber is, say, 2 gallons (I'm wildly guessing here). It means that every piece of water stays in the chamber for 2/15 = 0.13 minute = 8 seconds. This won't desinfect anything. It'll be a little bit better if you connect it after the tank, but then you need some flow-controlled switch, and it still may not do enough.

If you keep it constantly on, it'll do the same for most of the water except for 2 gallons of water that are in the chamber right after the pump cuts off. From the desinfection viewpoint it is absolutely the same.

If you have some bad bacteria in your water that make it undrinkable, you need some serious treatment to get rid of them. Your UV light device will not do it.

If you don't have bad bacteria, then there's no need for desinfection of any sort, and the UV device is useless.

If I were you, I would just remove the UV device completely.

Thom

Re: Water Purification question???

NorthGuy wrote: »

If you fill in your 60 gallon tank in a minute, you're probably pumping in at 15gpm. You have a good well and a big pump.

The volume of your UV chamber is, say, 2 gallons (I'm wildly guessing here). It means that every piece of water stays in the chamber for 2/15 = 0.13 minute = 8 seconds. This won't desinfect anything. It'll be a little bit better if you connect it after the tank, but then you need some flow-controlled switch, and it still may not do enough.

If you keep it constantly on, it'll do the same for most of the water except for 2 gallons of water that are in the chamber right after the pump cuts off. From the desinfection viewpoint it is absolutely the same.

If you have some bad bacteria in your water that make it undrinkable, you need some serious treatment to get rid of them. Your UV light device will not do it.

If you don't have bad bacteria, then there's no need for desinfection of any sort, and the UV device is useless.

If I were you, I would just remove the UV device completely.

You sure you are giving good advice on this ? The lights are rated by GPM .

Thom

arby

Re: Water Purification question???

This is my UV filter specs. Lake water is the source.
UVD320
PRODUCT FEATURES

Flow rate of 10gpm (37L/min) delivers UV dose of 30mj/cm2
Flow rate of 8gpm (30L/min) delivers UV dose of 40mj/cm2




Plus a large sediment filter and a large carbon filter

keyturbocars

Re: Water Purification question???

Do you need to disinfect all the water? Like Cariboocoot said, if you just need to purify the drinking water, then you could have something like a Berky water filter for drinking. The Berkey uses a ceramic filter impregnated with silver. They have been proven to be very effective at removing biological contamination.

http://www.berkeyfilters.com/

Personally, I have a reverse osmosis water filtration system which works very well at purifying drinking water, but it uses quite a bit of water to flush off the R.O. membrane. That additional water usage would mean that your pump would need to cycle on/off more often. Not ideal for an off grid system unless you had lots of extra RE to burn up. If I was in an off grid situation, I'd probably just go with something like a Berkey to purify the water for drinking and use in the kitchen.

Blackcherry04

Re: Water Purification question???

What you need to do is install a flow control nipple on the output side of the UV unit to limit it to 8 GPM or less. You should be filtering down to 1 Micron before the UV will be effective. If the suspended solids are larger than what your trying to kill, they do not work all that great as the solids will shield them from the UV light.

The way to control the start of the pump is to install a " delay on make " timer relay on the pump pressure switch to control the 5 Minute delay on the start of the pump.

arby

Re: Water Purification question???

The switch idea I thought of. The problem with that workout is that the water stops flowing
about five seconds after the pressure switch calls for the pump. It only takes one minute and 20 seconds to empty the tank at full tap flow,
so if someone were having a shower, the water would suddenly stop for almost five minutes.
My other idea was to put a timer on the UV lamp for say from 7 in the morning until 10 at night thereby saving some hours of usage.
The under the counter ceramic that Cariboocoot suggested is sounding pretty good.

NorthGuy

Re: Water Purification question???

Lake is an open system. It may be safe now, but get contaminated at any point in the future.

arby wrote: »

Flow rate of 10gpm (37L/min) delivers UV dose of 30mj/cm2
Flow rate of 8gpm (30L/min) delivers UV dose of 40mj/cm2

S, if you get 15 gpm, you get 20mJ/cm². 10mJ/cm² is supposed to kill 90% of everything, so 20mJ/cm² will kill 99%. Probably not enough for drinking if you have a serious contamination in the lake. 40mJ/cm² will kill 99.99%, but 0.01% still remains and can multiply while in the pressure tank. You be the judge if it is good enough for you.

It may be a good idea to install a separate filtering system just for the drinking water. Since you need much less of it, it is much easier to make it really clean and safe to drink. I have a separate tap in the kitchen for drinking water.

At any rate, getting back to the original question, it is totally pointless to keep filter on when there's no water flow through it. The way you have it now will yeild the same result, but without extra energy expense. This is a piece of advice I'm sure about.

arby

Re: Water Purification question???

"At any rate, getting back to the original question, it is totally pointless to keep filter on when there's no water flow through it"

Actually, last night I left the UV on all night, and this morning when I went to get a sample of water for testing, it was a little bit warm.
Certainly warmer than the ambient temperature. I wondered if somehow the water was actually slowly circulating because of the lamp heat.
I could not see what else could have warmed it up,.
The whole setup is in a pump house shed that I built for it out back of the cottage.

mike95490

Re: Water Purification question???

I went around for months, and finally settled on a homebrew (easily & safely done) slow sand filter backed up by an ozone generator. But you need storage for the supply and output of the slow sand filter, which should never, ever stop or go dry.

I'm now looking for LED UV water systems. haven't seen any yet, may decide to roll my own.

I'd use several cheap, easy to replace, whole house style filters before the pressure tank, and a 100% drinking water filter for drinking.

OR - you could place another conventional UV filter in series with the existing one, which with short cycle times, should give you enough light exposure, only while pump is running.

Blackcherry04

Re: Water Purification question???

Your pointing out all the reasons that a off-grid system should have a open loop system and a demand pressure pump. The yield on a 60 gallon pressure tank is less than 20 gallons. The cycling of a large pump eats up way to much power. A 5.5 gpm demand pump will use less than 2 amps and run every thing in a normal house @ 60 psi.

By the way a Ceramic Filter requires really clean water ( Low Solids ) are they will lose flow really fast and require lot's of cleaning.

arby

Re: Water Purification question???

Interesting but too late for me. Bought, paid for and installed.
BTW, my pump is rated at 10 gpm, 1/2 HP.

NorthGuy

Re: Water Purification question???

arby wrote: »

"At any rate, getting back to the original question, it is totally pointless to keep filter on when there's no water flow through it"

Actually, last night I left the UV on all night, and this morning when I went to get a sample of water for testing, it was a little bit warm.
Certainly warmer than the ambient temperature. I wondered if somehow the water was actually slowly circulating because of the lamp heat.
I could not see what else could have warmed it up,.
The whole setup is in a pump house shed that I built for it out back of the cottage.

If you left it for 12 hours at 40W this is 480Wh. This is enough to heat 15 gallons of water by 13F. You could feel it. The water certainly will circulate some, but it'll be rather chaotic and chances that all the water comes through the chamber are none. But bacteria multiply faster in warmer water.

You said that you can empty your tank from the tap in 1 minute 20 seconds. If it is 15 gallons in there, you would need either high pressure or an oversized tap. Did you try to measure how much water comes out of the tank when you drain it? If your pressure is not set correctly, you may not be using the full capacity of the tank.

David and Laura

Re: Water Purification question???

Water treatment, we've discovered, is very complex — more complex then off-grid power generation, in our experience.

We take our water from a nearby lake, passing it through three different sizes of ceramic filters before passing it through a UV filter. The UV filter turns on two minutes before the pump starts, and there is a pressure regulator that ensures that water flowing through the UV filter has sufficient time for UV exposure. From this point, the water goes into a pressure tank, and through a final sub-micro filter bank before being used for drinking.

Sadly, this system hasn't worked very well at all, for several reasons:

1) Our water has a high tannin content, which reduces the effectiveness of the UV system
2) When the pump isn't running, untreated water that has not yet passed through the UV system can circulate with treated water, which results in contamination (despite check valves). This is one of the main reasons why they recommend that the UV light must remain on at all times.

We're looking at two options to replace this system:

1) A slow-sand filter (which would require continuous water flow, and thus would require more electricity for pumping).
2) The Sawyer home filter product

http://www.sawyer.com/sawyersaves/products-homeunit.html

https://www.sawyersafetravel2.com/product_info.php?cPath=1&products_id=80

Now that we've got our power system largely completed, fixing our water system is going to be our big project for 2014.

icarus

Re: Water Purification question???

Have you tested the water to see what it is y are trying to "purify" as has been suggested, knowing what the target is, (if anything) can lead to a design to purify as needed, either through filtration, UV or Chlorination. If yr water is "pretty clean" spending the money and energy to purify all the water for the showers and tubs, and gardens etc might not be the right choice. Simply purifying the water thaqt you are going to ingest might be very much easier and cheaper.

We draw from the lake and have essentially pure water from a biological point of view (-as well as the water chemistry is very good as well) we don't have to do any purification at all, but at some times of the year the water can get sort of "fishy" smelling due to algae. We simply use a Brita filter and it is fine.

When we used to have a large central tank (serving multiple buildings and many seasonal users) we would use a chlorine injection system, simply to pass health regs, and to keep algae from growing in the tank in the summer heat.

Tony

arby

Re: Water Purification question???

I have sent in some samples and awaiting the results. Over the years I have drank this lake water several times with no adverse effects, but apparently that is a dangerous game.
Many years ago the Ministry was in our small lake and said that there were coliforms in the water. For drinking water we have always brought in either bottled water or city water. For everything else we have a cistern pump on the kitchen counter fed from the lake. The pump has worked so well over the years that we are reluctant to remove it and switch to this modern new fangled submersible pump thingy. )))

Blackcherry04

Re: Water Purification question???

I'v used surface water for 30 years ( Lake ), any water that will grow algae will grow many other things that will kill you. One thing about Chlorinating the water is, it's fool proof and easy to test. Chlorine requires contact time. I'v got UV and Ozone and 20 different kinds filters of every size. RO membranes are good and some Sub-micron filters, but as was said any by-passing of them is the same as having no treatment.

I do batches of 100-500 gallons at a time, and never let it infect the house system. Once the batch is tested I transfer it to the main tank. My water source gets turbid at times and has to be flocculated to settle the solids, mostly clay.

Surface Water changes very fast, as a user you have no idea what creatures are sharing it with you, one family of beavers can contaminate a whole water shed overnight.

.

Endurance

Re: Water Purification question???

I have been drinking lake water for a few years now. Like some have suggested, I went with a split system to fully treat only the water I drink. I draw lakewater with a pump that goes to a pressure tank. From there, I filter all of my water to 5 microns with a pleated sediment filter. From there, my system splits. I don't give any further treatment to the bulk of my water that I use for flushing toilets, washing dishes, and showering. But for the water I drink, I treat the water with a 1-micron carbon block filter and UV light (a Sterilight S2Q-PA) that treats 3 gpm and consumes 22 watts of power. I leave the UV light on all day, but shut it off when I go to bed. I figured my energy budget for the 22 watts my unit draws, so I don't feel bad about leaving the UV on all day.

I haven't had to use a flow restrictor since the "candy cane" dispensers I use for drinking water can't flow more then 3 gpm at the pressures I have on my system. When I wash dishes, I wash and rinse dishes in lake water then give them a final rinse with purified water.

I considered wiring my UV light to my pump with a time-delay relay that wouldn't let the pump run until the UV light had been on for a few minutes. Something like that might work for you, but seemed overkill for my system.

Blackcherry04

Re: Water Purification question???

UV light works, but the only problem is there is no residual in the system. It's easy to get infected and cross contaminated. The half life of Chlorine is 30 days in a closed environment. If I was only depending on UV light , I'd get it tested often, our health department does it free here.

Once your plumbing gets black algae in it, it's hard to get rid of. It will plug the shower heads and cause flushing problems in the toilets. Been there and done that, it's what led me back to chlorine after several years.


Research has confirmed that UV effectiveness
is relatively insensitive to temperature and pH
differences. In addition, researchers found that
UV application does not convert nitrates to
nitrites, or bromide to bromines or bromates.
Recent pilot studies show that UV-treated drinking
water inhibits bacterial growth and replication
in the distribution system; however, conditions
within distribution systems, such as leaks, still
require additional residual disinfection (e.g., free
chlorine).

UV radiation is not suitable for water with high
levels of suspended solids, turbidity, color, or
soluble organic matter. These materials can
react with UV radiation, and reduce disinfection
performance. Turbidity makes it difficult
for radiation to penetrate water.
Disadvantages of UV disinfection include:
• No disinfection residual;
• No technical database exists on how well
UV systems perform for various water
quality conditions; and
• No standardized mechanism measures,
calibrates, or certifies how well equipment
works before or after installation.
Systems also should consider using different
kinds of microbial testing. Laboratories typically
test for total coliform to judge microbiological
activity in drinking water—but coliforms are
sensitive to UV light. Because of this sensitivity,
microbial tests for UV treated finished water
should include a Heterotrophic Plate Count
(HPC) test. HPC microorganisms may provide a
better disinfection assessment than the UV
sensitive coliforms.

silvertop

Re: Water Purification question???

We use a homemade Berkly, it uses two chambers like a Berkly and a ceramic and silver replaceable filter very low cost and you could filter creek water if you had to! You can find plans on line for this type of filter. We would never go back to tap water or Brita type counter filters, they don't purify like you think........

Photowhit

Re: Water Purification question???

I have a friend who used a 2 bucket system for years in Alaska, he just ran creek water through the system and drank freely, no chlorine. I've read the literature with Sawyer, who's .02 and .01 micron filters filter out pretty much every thing, and even they suggest only a .1 or .2 micron filter is needed in North America, since we don't have anything smaller that will harm you.

This, of course, is for drinking and cooking water, and these systems are what is sent to 3rd world areas to ensure clean drinking water. I purchased the Monolith filter here, and picked up a couple food grade buckets from a bakery. They are slow and require cleaning when flow slows down, suggested every month. I've been happy, but I am on county water and just wanted to use one instead of an expensive(and useless) Brita system I have been using. The carbon taste filter will not be effective after a 9 months to a year, but the filter will work until cracked or worn through.

Ralph Day

Re: Water Purification question???

A timer to keep the uv light on works best for us. On at 5:30am (before anyone is awake), and off at 10:30pm. Toilet is not flushed or regular tap water run during the "off" time. If company is around we'll trip the timer to "on" all the time to prevent any boo boo-s. Again, if someone is ill and up in the night regularly (or over-regularly) the timer gets tripped "on". The uv is rated at 12gpm, the pump about 2.5gpm. Any fixtures nowadays are 2gpm or so, you shouldn't be able to use more than the light can sterilize. (doesn't really kill the critters, just renders them incapable of replication IIRC).

Drinking water system is separate, charcol filter and ceramic (Rainfresh brand). Someday I'll have to put the Kill a watt on the uv light and see it's consumption. It works on all but drinking water 90% of the year rainwater collected in 3K gallon tank.

Ralph