ro waste water

[scbasser5]

Ok guys and gals,

I have seen several different uses for the waste water coming from an ro filter. I have also read that most ro units produce less waste water if the inlet pressure is higher than most home water supplies have.

Question one, isnt this waste water really only water that did not go through the membrane and flowed straight through the filter. It doesnt have any more negative things in it than tap water correct.

Question two, if there is really nothing wrong with this water why cant it be reused, rather than drained or put to the other uses.

My thoughts were to build a storage tank of some sort for the waste water to flow into, have a booster pump, pump from this tank and increase the preasure into the filter. You could put a float switch on this tank and when the water level falls below useable limits it opens the household water supply into this sump refilling it.

This idea would do two things, I think, one make the ro filter more effiecient since the preassure would be higher, this in its self would mean less waste water. The lesser waste water would flow through the system until it was all filtered through the ro filter. Then you only lose the water required to back flush the system. You would need to drain the backflush water to the sewer system.

Let me know if any of this makes since or is correct.

thanks

 

[StevieladUK]

That idea is not new (but then most ideas are not!).

The waste water does contain more impurities than the input water (after all they have to go somewhere).

But yes - you can keep passing a volume of water over/through the RO until the TDS becomes unacceptably high. Likely to use up your DI quicker - but if your on a water meter it may work out cost effective.

 

[Mind_nl]

Oke so the waste water contains more impurities then your normal tap water. What about building a storage tank to collect the waste water and use it for specific applications in your household like flushing the toilet, watering the garden, etc. Ofcource you would have to change some of the plumbing but in the long run I guess you could be saving a lot of water (=money)

 

[StevieladUK]

<a href=showthread.php?s=&postid=6655523#post6655523 target=_blank>Originally posted</a> by Mind_nl
Oke so the waste water contains more impurities then your normal tap water. What about building a storage tank to collect the waste water and use it for specific applications in your household like flushing the toilet, watering the garden, etc. Ofcource you would have to change some of the plumbing but in the long run I guess you could be saving a lot of water (=money)

Absolutely - I'm sure the garden or pot plants will love the nitrates and phosphates! And as for the toilet - any old water will do!

 

[scbasser5]

StevieladUK, maybe i dont understand the RO process correctly but how doing this use the DI faster? Doesnt the RO membrane have the same rejection rate at all times? I could see the RO membrane expiring before it's time but not the DI.

Yes I am on a meter and hate to see many gallons of water just go down the drain.

Mind_NL, there are several posts in this forum where people are doing just as you say, but having the waste water run to your toilet or washer would mean that your RO would only run when either of these need filling, from what I have seen. Storing the water and using for garden watering seems to make the most since. One poster has his water just going to a drip irragation system in his flower bed.

I dont have a need to water as often as I need the RO water. So I am afraid I will have a surplus. Most of the systems I have seen have 3 to 5 gallons of waste water for each gallon of RO/DI water.

 

[ben&bobbi]

i dump ours into the washing machine. but how can there be "more" impurities in the "waste" water? if the filters filter out the impurities sending them out the "waste" line and the rest through the good line. the impurities will be more concentrated in the waste water.

we are on well water, 2-3 years later, same filters, our water tests out at 4/5 on the TDS.

 

[mbbuna]

<a href=showthread.php?s=&postid=6655649#post6655649 target=_blank>Originally posted</a> by scbasser5
StevieladUK, maybe i dont understand the RO process correctly but how doing this use the DI faster? Doesnt the RO membrane have the same rejection rate at all times? I could see the RO membrane expiring before it's time but not the DI.

if your Tap TDS is 200ppm and your membrane will clean 98% then the DI will have to clean 4ppm. if you keep running recycled(waste) water through the RO, that water will keep going up in ppm. so in time you will have a tank full of 600ppm, 800ppm and so on but the mambrane is still only cleaning at 98% so now the DI has to clean 10ppm, 12ppm and so on

 

[StevieladUK]

<a href=showthread.php?s=&postid=6655677#post6655677 target=_blank>Originally posted</a> by ben&bobbi
i dump ours into the washing machine. but how can there be "more" impurities in the "waste" water? if the filters filter out the impurities sending them out the "waste" line and the rest through the good line. the impurities will be more concentrated in the waste water.

we are on well water, 2-3 years later, same filters, our water tests out at 4/5 on the TDS.

OK - problem with terminology - I meant more as in more concentrated

Quite - the total impurites in the RO and waste are the same as went in (minus chlorine etc inactivated by the carbon prefilter and particulates removed by prefilters).

 

[StevieladUK]

<a href=showthread.php?s=&postid=6655719#post6655719 target=_blank>Originally posted</a> by mbbuna
if your Tap TDS is 200ppm and your membrane will clean 98% then the DI will have to clean 4ppm. if you keep running recycled(waste) water through the RO, that water will keep going up in ppm. so in time you will have a tank full of 600ppm, 800ppm and so on but the mambrane is still only cleaning at 98% so now the DI has to clean 10ppm, 12ppm and so on

Exactly - well put!

 

[scbasser5]

Okies, thanks now that I can understand and obviously overlooked.

But if I back flush my filter with this water then that much of it would go down the drain. Perhaps this is not the best approach.

Ben&bobbi, do you just let the water dump into the washer as the filter process? Then you tub is full when you wash a load of clothes? Or do you only have your RO working when the tub is filling?

 

[mbbuna]

<a href=showthread.php?s=&postid=6655927#post6655927 target=_blank>Originally posted</a> by scbasser5


But if I back flush my filter with this water then that much of it would go down the drain. Perhaps this is not the best approach.

the membrane doesnt hold the impurities, it just doesnt allow them through to the other side where the good water comes out. back flushing just rinses what ever might be stuck to the membrane.

 

[ben&bobbi]

scbasser5
when i see the washer empty, i fill a 5gal bucket. it fills the washer as it processes. if i need water and washer is full, i let it go in the washer outlet tube. then we will wash a load so i can fill another bucket. i usually miss a time or two though!