RO/DI Rejection water uses?

[jrossjr79]

Ok, I just got my filters in today for my RO/DI unit. Decided to one last water change in my 55G before I tear it down for the 120 I am getting this weekend. I noticed there is alot of water being rejected, which I expected anyway.

But it got me thinking. Instead of letting all this water just go down the drain, there has to be other uses for it. I know I could use it to water my lawn and plants. But I am wondering if the rejection water is safe to drink or cook with, if it is, how foul of a taste would it be.

Also like to know what other plausible uses there are for RO/DI rejection water. Thought of washing clothes with it, but other than the things mentioned above, I do not know.

[alton]

It is filtered non chlorine/chloramine water.

[jrossjr79]

Thanks Alton, then I guess I am missing the point why it is rejected water. I know it goes through 3 filters before it gets rejected, and the pure clean water goes through the DI Resin. What exactly does the DI Resin take out?

[rrasco]

DI removes the rest of the stuff that can't be filtered with the carbon block or the RO membrane.

I know there have been a few threads on waste water uses.

[Mr Cob]

good questions Joe, right now I'm just watering the lawn.


I think the waste water is just cleaner tap water. So whatever you are already doing with your tap water could also be applied to the waste water if you have a way to implement.

*we don't drink tap water though, we did hook up a drinking water reservoir to the unit but it doesn't come from the waste water

[jrossjr79]

Yes, that is what I read after rrasco mentioned that there are other threads on here about it. Sadly only found one. Decided to take a taste test of the rejected water, and ya, I do not think I will drink it. I know the wife wont, she hates tap water, I dont mind tap water, and this water taste even worse.

[350gt]

I have 2 45 gallon brutes on the outside wall of my garage that collects the waste water.....

I pump it to my grass and trees with a mag 9.5 and a water hose, works great and you can tell where i usually water around the trees, its greener than the rest of the lawn..

[rrasco]

I believe the waste water is dechlorinated but has a higher TDS content. If you think about it, the TDS being removed from the good water has to go somewhere. I'm sure some of it is bound up in the filters and membrane, but I'm willing to bet a good portion of it ends up going out with the waste water. Would be easy to test with a TDS meter, I might do that tonight.

I tried searching for those other threads too, didn't really come up with what I was looking for. Although, admittedly, I didn't try that hard.

https://www.google.com/search?q=site%3Amaast.org+waste+water

[jrossjr79]

I took a TDS reading after buying the unit (bought used from a MAAST member) on both lines. They were both high at the time, but if I remember correctly, the waster water line was significantly higher than the pure water line.

Makes me wonder though, if it is possible to hook up maybe another Membrane with a DI Resin filter as well and daisy chain them to the membrane and have two lines of good water going through. Wonder if this would work?

tap water---> Carbon ---> Sediment--->Membrane --> DI Resin--> Pure Water
.................................................. ....................--> rejected water --> additional membrane ---> DI Resin ---> pure water
.................................................. .................................................. ............................----> Rejected water

hope the small illustration I done makes sense.

[rrasco]

I was referring to testing the tap water and comparing it to the waste water. I would think the waste water would be higher than the tap. The waste water will no doubt be higher than the filtered water.

I don't know exactly the order for them, but I do believe some people run dual membranes.

Also, I believe the sediment filter should go before the carbon block.

[new2dis]

Doesn't the waste water already have higher TDS making it more difficult to clean again?? Wouldn't the life of the second filtration system be considerably lower considering how hard it is working? Just a thought...:confused:

[Mr Cob]

I have taken TDS readings of the waste water and compared it to the tap water before filtration and the waste water was cleaner than the tap water but I still wouldn't drink it.

Joe, interesting idea on double DI...lol, in a month we will see you ask about what to do with that waste water! lol I don't think the cost would be worth it though...I would hate to have to double or triple my DI resin purchases every month

[Mr Cob]

My readings don't line up with the norm... (so take your own readings, lol)

From Air Water and Ice's site:

"The pure water has low TDS. The waste water, however, is normally higher in TDS than your tap water. This is because of the pre-treatment of water before the RO membrane.
"

quoted from:
http://www.airwaterice.com/c=aEvxQx9gX233ifhOgD7GCtovx/category/z.3/

[The_wolfeman]

There are plenty of people who run dual DI canisters and membranes, which result in a lower TDS for extended periods of time.

Drinking and cooking with waste water is actually ok. There have been studies researching the affects of TDS on the human body that have come up with nothing bad to say except for the hardness, which in some cases can dry your skin and hair. Not to mention the hideous stains we all deal with on our bathroom fixtures due to hard water.

In reference to the illustration, I'd be curious to see what the "waste vs tap" TDS results would be. That would be the best way to tell what setup would be most affective. If the waste water is higher you'd be better off using it in a recreational matter due to the fact that it would exhaust your DI resin faster then tap.


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[Big_Pun]

Doesn't the waste water already have higher TDS making it more difficult to clean again?? Wouldn't the life of the second filtration system be considerably lower considering how hard it is working? Just a thought...:confused:

actually no BRS makes a water saver kit where you add a second membrane and the waste of the first goes into second one and then with a wye connection feed both into di filter. your incoming psi must be 65 or more for this to work

what this does is double the amount made in a day and cuts waste water in half

[ramsey]

If you're serious about it, just run DI and skip the RO. Just run your prefilters and carbon, then straight to DI. You'll burn through DI resin a lot faster but you'll have zero waste water and you'll also be able to make pure water way faster. Search around on Reef Central. I've read a few threads about this.

[jrossjr79]

Anyone know how fast I will go through DI Resin if I do it that way? Skipping the membrane all together?

[Big_Pun]

Anyone know how fast I will go through DI Resin if I do it that way? Skipping the membrane all together?

depends on tds coming in, and from pumping in 8 tds and getting a few hundred gallons, im thinking not much. if it was that great idea im sure more people would do it.

[jrossjr79]

TDS going in is 300ppm

[rrasco]

I would try it if you like replacing DI. :P