RO Waste Water Theory

[Guest clownfish4]

I posted this over at reef central.  Any thoughts?

 

http://reefcentral.com/forums/showthread.php?s=&threadid=421976

[Guest Houshan]

Posted this at RC too:

 

Hmm ... I don't doubt you could do it but ...

 

- membranes are made to have peak performance at a certain psi (~ 50 - 65psi). So, you have to be able to control water pressure. I guess you could stick a gauge on there and manually control it through the ball-valve or gate valve.

 

- you might as well find the temp your membrane was made for and heat your water too. I think most are in the range of 70 - 77 degrees

 

 

If you're ultimately trying to save money, I would just get a booster pump and/or heat your incoming water (several ways to do this) - much easier. Raising temp & getting proper water pressure I think would be easier but not as efficient as your method maybe. Which one would be the most cost effective? Seems your method may actually cost more depending on what you already have or need to buy. Most RO/DI units have 1/4" inputs. How many adapters will you need? Lots to think about.

[traveller7]

Why not run multiple membranes in a series to begin with?  The scenario you describe creates diminishing returns in a non linear fashion.

[ctreptow]

HJas Any one looked into a permeate pump to save water. I have seen these pumps around for a while but I haven't tried it yet. I seems to only work on systems with a pressureized tank but it does put your wastewater back to work for ya.

 

Permeate Pump

[Guest Houshan]

HJas Any one looked into a permeate pump to save water. I have seen these pumps around for a while but I haven't tried it yet. I seems to only work on systems with a pressureized tank but it does put your wastewater back to work for ya.

 

Permeate Pump

Yes, they only work on units with a pressurized tank.  I did not want a storage tank and that's one of the reasons I didn't go this way.

 

If I'm not mistaken, the way the permeate pump (about the same cost of a booster pump) works it's magic is by increasing the pressure to the membrane (like what a booster pump does) using the waste water pressure (like how a turbocharger on cars use exhaust pressure) to re-feed the waste water into the membrane.

 

However, really the permeate pump is compensating for using a pressurized  storage tank.  As the pressure increases in the storage tank, it naturally decreases the pressure on the membrane - so you get less product water made (less efficient).  You would not have this "problem" to overcome when using a unit w/o a pressurized tank.

 

All those benefits they list are true but are relative.  Like "save on booster pump life and pre-filter life because your system doesn't see this water".  Yeah, the booster & prefilters don't - but the RO/DI does. :p

 

So, you really gotta be careful with what you read and what it all means ...

 

Hope that helps.

 

- Jose