Roland Jacques
Premium Member
thanks, but i guees the main question is, has this method reduced your waste water and by how much???? 1:1 or 1: 2 ???
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ro water saving idea
- Thread starter little_squid
- Start date
thanks, but i guees the main question is, has this method reduced your waste water and by how much???? 1:1 or 1: 2 ???
Roland Jacques
Premium Member
Re: Dangit AZ
Re: Dangit AZ
That’s funny Bryan, you sure have say allot over the phone. My head is still spinning lol
Why dose your optimum units make less waste water than other units. And dose booster pumps or permeate pumps give any advantage when used with your RO systems?
Re: Dangit AZ
<a href=showthread.php?s=&postid=7554564#post7554564 target=_blank>Originally posted</a> by purelyh2o
I never get to say anything when your around. Save some brainpower for me will ya..
Im watching this one too...lol
This is a good one!
That’s funny Bryan, you sure have say allot over the phone. My head is still spinning lol
Why dose your optimum units make less waste water than other units. And dose booster pumps or permeate pumps give any advantage when used with your RO systems?
jdieck
New member
Re: ro water saving idea
Cheaper with similar results, buy a second membrane take the waste of the first one as the input of the second one, move the restrictor to the waste of the second one and to the drain, join the product lines of both into the DI stage.
This setup will produce twoce as much product water with the same waste, in other words half the waste with the cost of a second membrane (About $70.00) and no power consumption from the pump.
If you use two high rejection membranes the increase of TDS in the product water is neglegible.
Another saving water tip is that if you are using a pressure tank (Like the ones used for drinking) As the pressure in the tank rises the product water flow decreases but not the waste so you end up producing very little with lots of waste when the tank is 2/3 full or more.
To prevent this install a permeate pump driven by the pressure of the waste, this pump will increase the pressure of the product line maintaining the production rate and filling the tank faster reducing the amout of waste produced.
<a href=showthread.php?s=&postid=7377800#post7377800 target=_blank>Originally posted</a> by little_squid
ok ill try to make this as clear as i canheres my thought i dont recall ever seeing this talked about so here it goes!
get a float valve and attach it to the top of a 5 gallon bucket and attach your tap water line to it.
add a ro pump at the bottom of the 5 gallon bucket to feed the ro unit.
have the waste line of the ro unit drain back into the 5 gallon bucket
so lets say every 5 gallons of water thats pumped thru the ro unit you will get 1 gallon of ro water and then the float valve will refill the 5 gallon bucket with 1 gallon of fresh tap water.
now i could see the water over time in the 5 gallon bucket getting full of impurities but if you emptied the 5 gallon bucket and started with new fresh tap water on a weekly or bi-weekly i dont see any harm.but would save alot of water!
any ideas or thoughts on this set up would be great
Cheaper with similar results, buy a second membrane take the waste of the first one as the input of the second one, move the restrictor to the waste of the second one and to the drain, join the product lines of both into the DI stage.
This setup will produce twoce as much product water with the same waste, in other words half the waste with the cost of a second membrane (About $70.00) and no power consumption from the pump.
If you use two high rejection membranes the increase of TDS in the product water is neglegible.
Another saving water tip is that if you are using a pressure tank (Like the ones used for drinking) As the pressure in the tank rises the product water flow decreases but not the waste so you end up producing very little with lots of waste when the tank is 2/3 full or more.
To prevent this install a permeate pump driven by the pressure of the waste, this pump will increase the pressure of the product line maintaining the production rate and filling the tank faster reducing the amout of waste produced.
Roland Jacques
Premium Member
jdieck
im still learning about ROs. moving the restrictor makes it all make sence to me. so the pressure should be the same on your second membrane (or thrid) as in your first membrane.
if so if each membrane has a 4 to 1 rejection. then buy going thourgh 3 membrane you should end up with a close to a 1 to 1 rejection ratio. that sounds real good to me. and the 3rd membrane should be seeing water that is 56% higher in TDS than the first. so unless im missing something, (very possable) this sounds like a very good and practical way of running a RO. and if i use better membrane waste would be even lower.
im still learning about ROs. moving the restrictor makes it all make sence to me. so the pressure should be the same on your second membrane (or thrid) as in your first membrane.
if so if each membrane has a 4 to 1 rejection. then buy going thourgh 3 membrane you should end up with a close to a 1 to 1 rejection ratio. that sounds real good to me. and the 3rd membrane should be seeing water that is 56% higher in TDS than the first. so unless im missing something, (very possable) this sounds like a very good and practical way of running a RO. and if i use better membrane waste would be even lower.
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Roland Jacques
Premium Member
i assume the membrane are relitively free flowing without the resistrictor, Right? by the name "restrictor" it seems that it would responceable for creating the pressure for the membrane to work.
if that is so then the restrictor at the end would make the presure equal in all membranes.
if that is so then the restrictor at the end would make the presure equal in all membranes.
purelyh2o
New member
Well
Well
A restrictor is actualy intended to allow a certain amount of pass through. 400ml per minute 600 etc.. Unfortunately what you will run into is alot of variables that come into play such as pressure and total saturation etc... If you run the drain from the primary membrane into the secondary membrane input you are making that allowance a wild card. The second membrane will also degrade sooner because of the higher TDS levels it is being fed and this will ultimately lead to premature failure of the second membrane due to the in ability to remove the TDS through the drain line at an acceptable rate.
Well
A restrictor is actualy intended to allow a certain amount of pass through. 400ml per minute 600 etc.. Unfortunately what you will run into is alot of variables that come into play such as pressure and total saturation etc... If you run the drain from the primary membrane into the secondary membrane input you are making that allowance a wild card. The second membrane will also degrade sooner because of the higher TDS levels it is being fed and this will ultimately lead to premature failure of the second membrane due to the in ability to remove the TDS through the drain line at an acceptable rate.
AZDesertRat
In Memoriam
I've got to follow this one through to the end. Not to rain on anyones parade but if this works it will surprise the heck out of me. Companies large and small spend untold millions of dollars on research and development of membrane technologies, mine included and we have some of the smartest water/wastewater engineers and operations specialsts in the world on staff and none of us have come up with anything like this.
AnnArborBuck
New member
It takes the pressure that is left over in the waste water to boost the pull the water away from the membrane which increases the osmotic pressure which then drives a more efficient seperation.
http://www.waterfiltersonline.com/pumps.asp
One very key thing that many miss when operating an RO unit is the operating temperature. The density of water goes down as water is warmed, therefore the membrane will be able to process more water with less waste. Just add a coil of pipe before the unit that sits in a water bath that you can use to warm up the water. Easy, cheap, and very efficient.
Also, make sure you back flush your membranes on ocassion to help remove the buildup of scale on the membrane.
AZDesertRat
In Memoriam
You process more water when it is warm but you also pass more solutes through the membrane due to the viscosity meaning higher product water TDS. Its a trade off, do you want more water or better water?
JonnyQuest
New member
Using a booster pump to take the waste water back to fresh water inlet is basically the same thing as completely shutting off the waste water stream with a valve. This will not allow the impurities to leave the system and will plug up and reduce the life of the RO membrane.
A better solution would be to use a storage tank to collect the waste water. A high pressure pump then can be used to recycle the waste water back into the main water line (not running RO system at this time) while water is being used in the house (like during a shower). I believe most homes have a check valve so that the city water cannot be contaminated and an expansion tank is used to account for the water heating up in a hot water tank. Therefore the recycle pump should be used while water is being used in the house so that the expansion tank space can not be completely filled.
I suppose you could add a large expansion tank to the water system which would allow a continuous addition of the waste water to the system via booster pump. When water is used within the home, the expansion tank will release some of the water in has stored and the city water will not be added. A check valve could be used so that the waste water to the expansion tank could not enter the RO filter water inlet.
As others have pointed out these ideas are most likely not cost effective.
A better solution would be to use a storage tank to collect the waste water. A high pressure pump then can be used to recycle the waste water back into the main water line (not running RO system at this time) while water is being used in the house (like during a shower). I believe most homes have a check valve so that the city water cannot be contaminated and an expansion tank is used to account for the water heating up in a hot water tank. Therefore the recycle pump should be used while water is being used in the house so that the expansion tank space can not be completely filled.
I suppose you could add a large expansion tank to the water system which would allow a continuous addition of the waste water to the system via booster pump. When water is used within the home, the expansion tank will release some of the water in has stored and the city water will not be added. A check valve could be used so that the waste water to the expansion tank could not enter the RO filter water inlet.
As others have pointed out these ideas are most likely not cost effective.
purelyh2o
New member
Water temp
Water temp
Very true,
Flushing the membrane is a very important feature at any temp or pressure. The one problem I see happen fairly often when adjusting the temp on the system is that when you go above the 75 degree point you begin to lower the rejection rate of the membrane. The opposite is true when you lower the temp so it is a toss up really as to what is more important to you, Performance or production.
Water temp
Very true,
Flushing the membrane is a very important feature at any temp or pressure. The one problem I see happen fairly often when adjusting the temp on the system is that when you go above the 75 degree point you begin to lower the rejection rate of the membrane. The opposite is true when you lower the temp so it is a toss up really as to what is more important to you, Performance or production.
AZDesertRat
In Memoriam
You're slippin!
jdieck
New member
Actually there is a limit, the more membranes you add the system is more sensitive to pressure drops so there might be some degradation of capacity at some point. Also the more membranes you add the more the product purity degrades. I would say the for this to work you need high rejection membranes and not to use more than three.
jdieck
New member
Re: jdieck
Re: jdieck
By moving the restrictor to the waste ouput of the second membrane both membranes will have basically the same back pressure at the inlet.
Re: jdieck
Actually it is the same restriction for both. Remember, the function of the restrictor is to present a barrier to the flow of waste water so the pressure in the inlet of the membrane is withing the specifications of the membrane to filter optimally
By moving the restrictor to the waste ouput of the second membrane both membranes will have basically the same back pressure at the inlet.
jdieck
New member
Re: Well
Re: Well
Lets run some excercise here:
Tap water 400 ppm TDS
Two equal capacity high rejection 98.5% membranes
Restrictor for a 5:1 ratio
One membrane will waste 5 gallons for every gallon of product so require 6 gallons of feed.
The same 5 gallons of waste will pass trough the restrictor using two membranes but by effectively doubling the membrane area there are 2 gallons produced so require feed of 7 gallons.
How the TDS will be affected:
7 gallons of 400 ppm enter the first membrane and 6 get out.
The product TDS of the first membrane is:
(1-.985)*400=6 ppm
The TDS waste output of the first membrane is:
(6*400+400*.985)/6=2794/6=466 ppm
So the TDS of the product of the second membrane is:
(1-98.5)*466=7ppm
So the tds of the combine product is (6+7)/2=6.5 ppm
And the TDS of the overall waste will be:
(5*400+466*.985)/5=2459/5=492 ppm
In summary:
With one membrane:
Waste 5 gallons per gallon of product
Product tds 6 ppm
Waste tds 466 ppm
Production 75 gpd
Waste 375 gpd
With two membranes
Waste 2.5 gallons per gallon of product
Product tds 6.5 ppm
Waste tds 492 ppm
Production 150 gpd
waste 375 gpd
If we use say 75 gallons per day we operate the system half the time with two membranes effectively save 375 gallons per day of water consumption at a penalty of 1/2 ppm increase in the TDS of the product which equals to an 8% increase (6.5ppm/6ppm=8% incr) in the consumption of DI cartridges.
If we use two low rejection (90%) membranes the increase in TDS of the combined product water will be from 40 ppm to 43ppm also ~8% but it is to note that although the increase in DI consumption is the same in % we will be adding insult to outrage because at 40 tds we are already using about 7 times more cartridges (vs 6ppm) so adding another 8% will be just making a bad situation worst.
Re: Well
Lets run some excercise here:
Tap water 400 ppm TDS
Two equal capacity high rejection 98.5% membranes
Restrictor for a 5:1 ratio
One membrane will waste 5 gallons for every gallon of product so require 6 gallons of feed.
The same 5 gallons of waste will pass trough the restrictor using two membranes but by effectively doubling the membrane area there are 2 gallons produced so require feed of 7 gallons.
How the TDS will be affected:
7 gallons of 400 ppm enter the first membrane and 6 get out.
The product TDS of the first membrane is:
(1-.985)*400=6 ppm
The TDS waste output of the first membrane is:
(6*400+400*.985)/6=2794/6=466 ppm
So the TDS of the product of the second membrane is:
(1-98.5)*466=7ppm
So the tds of the combine product is (6+7)/2=6.5 ppm
And the TDS of the overall waste will be:
(5*400+466*.985)/5=2459/5=492 ppm
In summary:
With one membrane:
Waste 5 gallons per gallon of product
Product tds 6 ppm
Waste tds 466 ppm
Production 75 gpd
Waste 375 gpd
With two membranes
Waste 2.5 gallons per gallon of product
Product tds 6.5 ppm
Waste tds 492 ppm
Production 150 gpd
waste 375 gpd
If we use say 75 gallons per day we operate the system half the time with two membranes effectively save 375 gallons per day of water consumption at a penalty of 1/2 ppm increase in the TDS of the product which equals to an 8% increase (6.5ppm/6ppm=8% incr) in the consumption of DI cartridges.
If we use two low rejection (90%) membranes the increase in TDS of the combined product water will be from 40 ppm to 43ppm also ~8% but it is to note that although the increase in DI consumption is the same in % we will be adding insult to outrage because at 40 tds we are already using about 7 times more cartridges (vs 6ppm) so adding another 8% will be just making a bad situation worst.
AZDesertRat
In Memoriam
It sounds good in theory but I would like to see a long term pilot test to prove it out. I am still skeptical.
AnnArborBuck
New member
Re: Re: Well
Re: Re: Well
Your math is off here and I don't have time right now to correct. First off, the pressure will not be the same on membrane 2 as it is on membrane 1 so you can't assume the same flow rate. Also, if you put 7 gallons into membrane one that will produce ~1.4 gallons of product while membrane 2 would produce 1.12 gallons of water (assuming equal pressure across both membranes which isn't true). Since your reject ratio is a function of TDS,Pressure, Temperature, and the membrane as you lower the pressure on membrane two your ratio is going to get worse then the ration on membrane one. I would bet that you would probably be running more around 1 to 8 or 1 to 10 on the second membrane, not the 1 to 5 that you will get on the first membrane.
In typical industrial setting to reduce waste they will recirculate some of the waste water back into the membrane, so in your case instead of having a TDS of 400 entering the membrane (raw water) you would recycle the water back into the membrane via a pump giving a TDS of around 450 (this is the key here, pressure, pressure, pressure).
Re: Re: Well
Your math is off here and I don't have time right now to correct. First off, the pressure will not be the same on membrane 2 as it is on membrane 1 so you can't assume the same flow rate. Also, if you put 7 gallons into membrane one that will produce ~1.4 gallons of product while membrane 2 would produce 1.12 gallons of water (assuming equal pressure across both membranes which isn't true). Since your reject ratio is a function of TDS,Pressure, Temperature, and the membrane as you lower the pressure on membrane two your ratio is going to get worse then the ration on membrane one. I would bet that you would probably be running more around 1 to 8 or 1 to 10 on the second membrane, not the 1 to 5 that you will get on the first membrane.
In typical industrial setting to reduce waste they will recirculate some of the waste water back into the membrane, so in your case instead of having a TDS of 400 entering the membrane (raw water) you would recycle the water back into the membrane via a pump giving a TDS of around 450 (this is the key here, pressure, pressure, pressure).
