RODI waste water

cla337 · #1 07/08/2007, 11:23 AM

I've been told that for every 1 gal of filtered water, 5 gal of waste water is produced.

Can someone confirm that.

It's such a waste unless you have a yard to water and a car to wash with it.

Musho3210 · #2 07/08/2007, 11:42 AM

i can confirm that. I use it for plants, dishwashing, cleaning the floor. You can use it for anything really, its just concentrated tap water, just keep away from fish. Its gone through a few carbon stages so its dechlorinated and drinkable, might not taste good though.

flyyyguy · #3 07/08/2007, 11:46 AM

i think the norm is more like 4 to 1...but yeah......there is a lot of waste.

Its kind of funny. Even though my source water is only around 50 tds to begin with ...i still have nearly a 4 to 1 waste/product ratio

Do you have a washing machine???? You can use the waste water to fill that up as well.

cla337 · #4 07/08/2007, 07:07 PM

I rent a livework warehouse. It's pretty urban here. I don't have anywhere to store it for car washing or etc. The plus side is that I don't have to pay for this water. It is extremely wasteful. I need about 10 gallons of top off per week. That's 40 or so gal of waste per week. The building only has a 1 small washing unit that you gotta put quarters in. If only I had a house.

Just to confirm, the RODI from the LFS results in the same waste? Or are there different methods for large scale systems?

customcolor · #5 07/08/2007, 07:11 PM

could the waist water be any good for fresh water fish?

flyyyguy · #6 07/08/2007, 07:12 PM

If you are only wasting 40 gallons per week you wouldnt feel so guilty if you knew how much some people are pouring down the drain.

I salvage more than half of my wastewater and Im still dumping an average of 200 gallons per week down the drain

The Grim Reefer · #7 07/08/2007, 07:35 PM

If it really bugs you there are options. If water is in short supply where you live you could add a second RO to the first RO waste line which will cut down on the waste some or, Remove the RO and go with dual DI units instead. I run a 5 micron, 1 micron sediment filters, Catalytic carbon, .6 carbon block then the 2 DI's. With the water flow throttled back to about 5 gallons an hour I get 1 TDS. We will see how long the DI lasts. Water is in pretty tight supplies around here right now and with the unit in the basement there was really no way to pipe the waste line to the yard. My one consession to being green.

besimon · #8 07/08/2007, 09:02 PM

wow...4 tp 1? My rodi unit is about 2:1 waste water.

poppin_fresh · #9 07/08/2007, 09:15 PM

Some of the new units are claiming less waste/good ratios. I personally divert my waste to the backyard during the warmer months. Dumping a lot of waste water down a septic system can cause problems. 40 gallons a week however, is not very much. Thats essentially a shower and a few toilet flushes.

cla337 · #10 07/08/2007, 09:47 PM

Well, it's only 40 if I choose not to make my own salt water and only use it for top off.

I guess in the mean time I'll forgoe a shower and flushing pee.

ColinPopcorn · #11 07/09/2007, 04:53 AM

A booster pump can greatly improve the rejection ratio, especially for those of us on wells. Mosr R/O units are at peak efficiency around 65 psi.

Ewan · #12 07/09/2007, 07:40 AM

Quote:

Originally posted by ColinPopcorn
A booster pump can greatly improve the rejection ratio, especially for those of us on wells. Mosr R/O units are at peak efficiency around 65 psi.

Ditto. Big time.

I have an aquatec 8800. I'm on a well with 35psi at the faucet, and my aquatec boosts it to 100psi. The product water streams out as fast as my waste water used to. I run my RO/DI for a fraction of the time that it used to take. I can fill a 5 gallon jug in less than an hour.

To put it in perspective, I used to work a 10 hour shift several years ago, and I used to set up my RO in the shower to make water while I was at work. If I came straight home after work, it would just be approaching the top of the container. This was a 25GPD bare-bones, on a 30PSI well. Now I have a 100gpd, dual DI, and a booster pump. I am very pleased with my water production. I store 10 gallons of waste as well, and use it for the first cycle when I wash my filter socks.

Can't beat a booster pump. RO/DI are meant to work under pressure, and usually our household pressure is inadequate for optimal operation.

BeanAnimal · #13 07/09/2007, 09:39 AM

Quote:

Originally posted by besimon
wow...4 tp 1? My rodi unit is about 2:1 waste water.

Then it is not likely running as it should be. You are pushing more through the membrane, meaning lower rejection, meaning higher resin usage (much higher). Not cost effective

fours2many · #14 07/09/2007, 10:07 AM

Hmmm, My ro/di unit is about 2:1 waste water as well. No problem with my DI being used up early either.

If you are that conservitive, you could always save the waste in 5 gallon buckets and use that water to flush your toilets.

I use mine in the washing machine. I have to wash clothes anyway, so I just do wash when I have to make water.

Do you have any plants that need watering? Heck fill a 5 gallon bucket with waste and wash your car. It is better than letting it run down the drain, worse yet a septic tank.

BeanAnimal · #15 07/09/2007, 10:31 AM

fours2many,

What is your input TDS
what is your RO only TDS
What is your RO/DI TDS

What type of membrane do you have.

Given those answers, I (or many of us) can tell you how well your unit is performing.

aznlmpulse · #16 07/09/2007, 10:37 AM

I use a kent marine maxxima and it "supposedly" has a 3:1 ratio. So I'll say it depends on your unit.

BeanAnimal · #17 07/09/2007, 10:53 AM

It really does not depend on the unit. The RO membrane is designed to work at a specific temperature, pressure and waste ratio.

As the waste RATIO decreases, the REJECTION decreases as well. In a nutshell, more of the bad stuff is FORCED through the membrane instead of being rejected by it. The lower the rejection, the higher the output TDS and the more the DI resin has to remove.

aznlmpulse · #18 07/09/2007, 11:31 AM

so........it does depend on your unit.

RichConley · #19 07/09/2007, 11:59 AM

I wouldnt worry about 40 gallons per week. Thats, in most cases, what you're using in an 8 minute shower.

BeanAnimal · #20 07/09/2007, 12:04 PM

Quote:

Originally posted by aznlmpulse
so........it does depend on your unit.

NO it does NOT depend on your unit. Your looking at it from the wrong perspective. The membranes (any of the good ones) are rated at a 4:1 waste to product ratio. The UNIT needs to be tuned to provide that ratio for optimum performance.

aznlmpulse · #21 07/09/2007, 12:49 PM

BeanAnimal, I was obviously trying to get a rise out of you. You're very easy to aggravate.

I understand what you're saying about the membranes being the biggest factor. I'm sure the higher gpd rated membranes don't waste as much, and I agree that higher production is not a good thing. I personally use a 24gpd unit. It's slow as hell, but it makes me feel better.

BeanAnimal · #22 07/09/2007, 12:54 PM

I am not aggravated at all. Just trying to make sure that folks understand what is going on.

Actually the higher GPD membranes waste more. They still run at 4:1 but their rejection rate is lower and therefore teh "waste" is in the DI resin.

With regbard to the better membranes (DOW FILMTEC) the 24GPD and 75GPD membranes will operate at the same efficiency.

The operating efficiency is a matter of the flow restriction (waste ratio) and the operating pressure and temperature.

For optimum performance we would want to tune the unit to run at a 4:1 waste at 70 degrees or so, with at around 65 PSI input pressure.

Enjoy

somethingphishy · #23 07/09/2007, 01:02 PM

"I have an aquatec 8800. I'm on a well with 35psi at the faucet, and my aquatec boosts it to 100psi."

you might want to check the company to see if 100psi to too much for you r/o...not really sure why but as for my r/o kent maxima they say optmial psi is in the 60-75 psi if i recall correctly..

flyyyguy · #24 07/09/2007, 01:05 PM

Quote:

Originally posted by BeanAnimal

For optimum performance we would want to tune the unit to run at a 4:1 waste at 70 degrees or so, with at around 65 PSI input pressure.

Enjoy

70 degrees?? really

I know enough about ro/di units to always achieve zero tds, which is good enough for me.

But im curious, how exactly does using 40 degree water(for instance as that is pretty much what my well is) affect how a ro/di unit operates??

Does it just simply slow it down as less water pressure will??

BeanAnimal · #25 07/09/2007, 01:13 PM

ZERO TDS is not the end-all, beat-all goal.

1) Water can be BETTER than 0 TDS (up for debate if it needs to be)

2) IT IS THE COST TO GET TO 0 TDS that counts.

The colder the water, the higher the waste ratio for the same flow restriction

You can certainly adjust your flow restriction to provide better efficiency if your water is always that cold.

Low pressure also produce more waste, as the membrane is not operating at optimum throughput.