being cheap

[Rmip]

Anybody thought about tapping the waste water line back onto the tap water line, so that the waste water can be reused and therefore not wasting any water?? The only problem I can thing of is the pressure from the tap pushing water along the waste water line and travelling backward into the system and mess somthing up??

I currently using the waste water for washing machine and fresh water tank.

Any comment?? AJ??
:thanks:
Ray

[ajx22]

Ray,

Reconnecting the wasteline to the RO could be done without messing-up the backpressure (using a back-flow preventer/check valve and a permeat pump) - however, from what I have learned over the past few years about RO - it would not really achieve the desired outcome.

The water that is flushed out of the waste line, contains all the stuff that we don't want in our water (other then what is taken-in by the prefilters) - obviously, the TDS concentrations in this waste water would be much higher then the household water that is feeding the unit - thus making the membranes work harder to try to remove the TDS - that it has already rejected.

Also...the filters are only designed to remove xx% of the contaminates - and the wastewater is meant to 'Flush' out the unusable - so reconnecting this 'rejected' water wouldn't really serve the desired purpose (other then killing the membrane in a quarter of the time - say a few months opposed to a few years).

There are units out there that are designed to do just this...reprocess the RO wastewater...however, they are VERY expensive and large (10' x 3') and in the $10,000.00 ranges. While I'm not 100% versed in 'exactly' what they do...I know that the wastewater needs to be treated to some degree before being 're-filtered' again.

I wish that I could be of more help here...but I don't have an engineer's level of understanding of the Reverse Osmosis process. Maybe someone here who is an engineer can provide some 'scientific' reasons into this.

[piscies75]

this fellow tank of the month on REEF central is doing it. http://reefkeeping.com/issues/2003-12/totm/index.htm

[ajx22]

oops...forgot to mention the Permeat (non-electric/pressure) pump in my first post.

Edit made.

I know that it HAS been done/is done...but I really don't think that you will really get that much more product water - ie. the bang for the buck. Reintroducing this much TDS rich water back into the filter will reduce the usability of the individual filters/membranes - thus decreasing the length of use per filter/membrane - thus increasing operating costs (more often replacements).

I use a stacked RO set-up in order to get more product water and less waste (ie I have x2 RO membranes). My system runs like this:

Feed water - booster pump - 20" prefilter (sediment) - 20" prefilter (carbon) - RO membrane #1 - WASTE line from membrane #1 - INPUT of membrane #2 - PRODUCT line from membrane #1 and membrane #2 - DI stage #1 - DI stage #2 - DI stage #3 - sump/holding vats ---> See image below

This way, the second membrane is technically reprocessing the waste water from the first membrane - thus reducing the wasted 'good' water.

Poor photo of RO membrane set-up:
http://www.aquariumpros.ca/userfiles/ro-membranes.jpg