High Efficiency RO/DI Systems

[Myka]

I really need to do something about my 1:4 RO production (good:waste). Our water is metered and they use the water use to calculate septic use as well, so double ding!

Anyway, I've been scouring high efficiency RO systems and looking closely at description and pictures. I think the only difference between high efficiency and normal output is a booster pump and an auto flush kit. I believe the idea is simply to push the water through at a higher pressure and the auto flush keeps the membrane running at peak performance. I believe this can be done with typical membranes.

Does anyone know differently?

[Skimmerking]

Mindy those ones that are 1;1 ratio, well the way that its stated that the auto flash kicks in ,however there isn't any power mech's on there that would do that its just a fancy up flush system my system has an extra filter one for 5M-CArbon-1M membrane-DI

[phi delt reefer]

do you think the efficiency could have something to do with how cold our water is? This company is promising 1:2 ratio on their cold water rated membranes;

http://reefbuilders.com/2011/04/07/g...old-membranes/


I just put my hand in a bucket of cold water from the tap for 5 seconds to adjust a heater and my hand started to get numb.


Most of us have good pressure - but Canadian water is frigid!

[Myka]

Originally Posted by asmodeus

Mindy those ones that are 1;1 ratio, well the way that its stated that the auto flash kicks in ,however there isn't any power mech's on there that would do that its just a fancy up flush system my system has an extra filter one for 5M-CArbon-1M membrane-DI

No plugins eh? I know one I saw for sure had a booster pump attached to it. Yours is 1:1? Which brand?

Originally Posted by phi delt reefer

do you think the efficiency could have something to do with how cold our water is?

I get 1:4 ratio with semi-warm water around 75 degrees. If I run straight cold water the flow slows down a lot, although the efficiency doesn't change.

[Skimmerking]

No Mindy I don't have one I still have the original one from 2002 and just add filter to it as i go. i know that mine doesn't give off alot of waste thou. DOW membrane and i still don't have a flush n mine. my water here in the East end its like 850 by the time it gets to me. so I go through 2 membrane in a year,

[Myka]

Originally Posted by asmodeus

No Mindy I don't have one I still have the original one from 2002 and just add filter to it as i go. i know that mine doesn't give off alot of waste thou. DOW membrane and i still don't have a flush n mine. my water here in the East end its like 850 by the time it gets to me. so I go through 2 membrane in a year,

Ew! That sucks. My tap water is usually between 120-160 ppm, so my membranes last a couple years(ish). I'm using a Filmtec 150 gpd membrane. I have a manual flush that I use at the beginning, end, and a few times during the day as I'm filling my reservoir. Takes all day.

[Skimmerking]

that is why maybe you are getting a crappy ratio the 150 gal per day alot of the water is wasted, I found a huge difference in the 50 compared to the 100 saved alot of water and the membrane lasted longer now im getting around 7=8 months out of a membrane on a 50 gal

[Myka]

For me, it's not about saving money so much as saving water. It does annoy me that I get dinged for the septic the same as the water usage though. The savings really isn't that significant, but it mostly pays for the cost of fouling up a membrane quicker. I imagine this is where the auto flush kits come in...hoping they flush the membrane often enough to keep it from fouling.

I think I'm going to try putting a 75 gpd restrictor on my 150 gpd system and add a booster pump. See what happens. I have a year on this membrane already and it is still giving me 2 ppm out of the membrane. Lots of life left, but I think still worth the fun. Hehe

Hmmm...from Reef Central:

Originally Posted by Buckeye FS

We feel it is misleading to tell people they can cut down on waste water by adding a second membrane. Here's why.

First - remember that what folks call "waste water" really would be better thought of as "flush water" in that this water serves the important purpose of internally flushing the surface of the semipermeable membrane to keep the membrane from fouling/scaling.

When you configure a system with two membranes in series (the waste from the first membrane going to the "in" port on the second membrane), for this discussion let's say it's two 75 gpd membranes, the system behaves like you have a single long (75 gpd x 2) 150 gpd membrane.

Now - if you use a proper flow restrictor, that is, one for a 150 gpd membrane, you'll have about a 4:1 waste to product ratio. Sounds familiar, right?

If however you don't change the flow restrictor - meaning you keep using the same restrictor you were using when you just had one 75 gpd membrane, then you'll see a waste to product ratio much lower than 4:1. But remember that the recommendation for a ~4:1 ratio comes from the membrane manufacturer. They are telling you that you need about a 4:1 ratio to keep the membrane flushed and keep the membrane from fouling or building up scale. Run the system with a lower ratio and you will foul/scale the membrane(s) quicker than would have otherwise been the case.

Instead of adding a second membrane to lower that ratio, you could have just changed out your flow restrictor ($4) instead. A much less expensive approach to get you to the same endpoint in terms of saving on waste water.

Now, to confuse things just a bit. Filmtec specs call for the 4 to 1 ratio on the basis of assumptions about the water that will be supplied to the membrane. If you have very soft water you MAY be able to get a decent service life from the membrane running at a ratio lower than 4 to 1 (e.g., 3 to 1). Remember that the waste water from the first membrane is about 25% harder than your tap water.

Bottom line: If what you are after is reduced waste water, experiment with a different flow restrictor for $4 instead of messing around with a second membrane plumbed in series.

As a side note, you can also lower the ratio by increasing the pressure delivered to the membrane (with a booster pump), because flow restrictors are sized assuming you are providing factory spec conditions (50 psi and 77 degrees for Filmtec membranes). Increase the pressure and you'll drive more water through the membrane and viola - less waste water. But as I mentioned above, if you do this (just like over-restricting a membrane) - the lower the waste to product ratio, the shorter the lifespan on the membrane.

Makes sense?

Russ

http://www.reefcentral.com/forums/sh...cient+membrane

[phi delt reefer]

Myka - run the waste water line outside your down spot and just have it run off your lawn/driveway.

Or do they measure your sewage usage by just doubling your water consumption (thats how they do it here in London)

[Myka]

Originally Posted by phi delt reefer

Myka - run the waste water line outside your down spot and just have it run off your lawn/driveway.

Or do they measure your sewage usage by just doubling your water consumption (thats how they do it here in London)

Ya, the septic usage is the same number as the water usage.

As much as it chaps my ass to get charged for something I'm not really using (all that waste water is doing is flushing the membrane anyway) it bothers me more to be wasting fresh drinking water that I don't necessarily need to be wasting.