RO SYSTEM

[Uppy]

HELLO TO ALL! IM NEW HERE! I JUST HAD A THOUGHT... WHY CANT YOU RE-FILTER THE WASTE WATER? WHAT IM THINKING IS IF YOU HAD TWO CONTAINERS/BARRELS, ONE THAT WOULD HOLD UNFILTERED WATER AND A PUMP TO FEED THE RO UNIT AND THE OTHER BARREL WOULD HOLD THE FILTERED WATER. COULD YOU NOT JUST DIRECT THE "WASTE" WATER BACK INTO THE UNFILTERED BARREL AND LET IT GO THROUGH THE CYCLE AGAIN? MABEY IM NOT SURE HOW A RO FILTER REALLY WORKS, BUT IS THIS POSSIBLE?http://www.kwas.ca/forum/images/smilies/017.gif

[Pamelajo]

Can't answer your question, but wanted to Welcome you to CAC!!

[OldMan]

Let me echo the welcome to the forum Uppy.
You have posed a great question because it shows you are really thinking about what can be done to minimize the impact of tank water consumption. An RO works by forcing water uphill against osmotic pressure. The higher the pressure gradient, the more water you can force through the membrane in the wrong direction and get almost pure water. What is left behind must be removed and replaced with water that has less concentrated impurities so that the pressure can again overcome the osmotic pressure. A typical home RO is only designed to run at less than 75 psig. That limits how much the concenrtration on the inlet side of the RO can get before you stop making good water. If you had a membrane and pressure vessel rated in the thousands of pounds, you could get a larger fraction of the water out as pure water and reject a smaller part. That is a principle used in a commercial water purification system. If your RO is set up right, the reject water is just concentrated enough that you get good performance without wasting any water that you don't have to. That means that if you send it through again, in theory, you will not get any more pure water from the RO because it is already operating at its optimum pressure vs. impurity concentration. There is no such thing as a perfect setup so you will get a little water but not much. One pass gets most of what is available at your pump pressure.

[blainep]

Welcome Uppy !

An interesting idea, I'm not sure if it would be feasible or not.

You would need to pre-filter the water to get suspended particles out of it, or else you would plug the RO unit membranes pretty quickly.

Maybe we have an experienced RO person to shed more light.

[thegrandpoohbah]

Like OldMan said, you can't really get any more RO water out of the waste water (at least not with the commercially available units). However, you could run the waste water through a distiller to get pure distilled water. I wouldn't go using distilled water to completely fill a fish tank. But it would be useful for topping off water lost through evaporation.

[Uppy]

Wow great info guys/gals! I was just thinking that I could mix tap water with the waste water to lower the concentration of the waste water by half, maybe. Also could I just tap my waste water line back into my tap water in feed pipe/plumbing? Just a little brainstorming going on here:Think: Thanks all! Jason.

[OldMan]

If you tap the waste back into the supply line, it will be at the same pressure that the newly arriving water is. No difference in pressures means no flow to waste and a very short period of water production. The 50 / 50 blend would need a higher waste flow rate because the starting concentration for the RO would be higher. If it somehow worked out, that would be the same as just cutting back the waste flow. Adjusting the waste flow, on an RO system designed for it, is something that should be done to try to get near that ideal ratio of waste to product while maintaining product quality. It is a fine tuning that only some RO systems can use.

[Uppy]

Hello! Well, I guess it sounds like a no win situation. Too bad! Im the type of guy who is always trying think of ways "to make it better" or cheaper::D: Just thought I would look into this one a little. Thanks for everybodys thoughts! Jason.

[CACAdmin]

Ways to conserve water use is always good to explore. Even if this idea isn't workable. You never know, you might come up with something else. Brainstorming ideas here is great... more minds to see if it's do-able. Some of the best DIY stuff comes from 'What if?' or 'Would this work?'

[OldMan]

I agree completely Jay. You can only win if you are willing to play. Sitting on the sidelines is a sure way to never win IMO.

[jewels]

Good question UPPY
I like pondering ideas ( when I am not @ work )
While we are brainstorming,,,
RO water is valuable to some species, as they enjoy water with less mineral content then you find in your local supply.
Now consider this.
There are species out there that are looking for mineral content much higher then found in your tap.
A typical home RO unit harvests about 20% and passes the rest. This leaves 100% of the available minerals to be found in the remaining 80% of the "dumped"
Super.
One part for the Softies 4 parts for the Rift Lakers.
Why not?:idea: