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View Full Version : Reverse Osmosis 1:1 waste ... how?


sfsuphysics
01/20/2010, 11:46 PM
Spectrapure came out with their "ultra-high efficiency" module, which claims a 1:1 waste water ratio via some "microprocessor <technobabble> which automatically flushes the membrane.... tds creep eliminated...etc" But at over $1000 for a unit I can't even come close to justifying the cost.

Now AquaFX is coming out with a similar unit that claims 1:1 as well. In fact looks identical to the spectrapure as far as what they have "microprocessor control.... <etc>" Their unit is a hair under $400, which I could justify the cost.... if I was buying my first unit.

Now my question is how does it get that 1:1 ratio. I don't think the prefilters matter, the booster pump I have one anyways, while it does reduce my waste I don't think I'm anywhere close to 1:1. Could it be the membrane? The microprocessor controller dohicky? If so where can I get these parts to retrofit my unit I already have?

sedor
01/20/2010, 11:59 PM
Could be some sort of upgraded membrane. That is what is doing the bulk of the work in a regular RODI. My question is would the waste water trickle out like the pure, or would it increase the output of the pure water drastically? 1:1 sounds to me like a marketing scheme, although I can't speak directly against the product because I have absolutely no experience with it.

Goodwood
01/21/2010, 01:40 AM
A 1:1 ratio can be created by using 2 membranes. The waste from the first one goes into the second. You can use two 75 gpd membranes and have a 150 gpd system.

65 psi or a booster pump is required for this theory to work.

sfsuphysics
01/21/2010, 11:13 AM
Sedor: Yeah I wonder about that. It also says they back flush when they start up and when the system shuts down. I'm wondering if that 1:1 is during production and when it starts/finishes the backflushing brings that back up.

Goodwood: How would that work in theory? Lets say you have a 4:1 ratio, the 4 parts goes into a new membrane, but wouldn't that one also have a 4:1 ratio? so every 4 gallons of good water you get 16 gallons of waste water need to be produced, which means the first membrane needs to also need to produce 4 gallons to make those 16 gallons of waste water, at the most that would be 2:1. But yeah the pressure issue might become problematic unless you put a booster pump after the first membrane.

Goodwood
01/21/2010, 02:27 PM
My ration is around 2.5:1 with one membrane, so in theory you are correct. It's all about using the best membranes and having more like 80+ psi. Your looking to get at minimum a 50% reduction in waste or better. In a perfect situation you could get 1:1 but, that won't be the case for most.

Marketing............

Wilberheim
01/21/2010, 02:47 PM
Look into vertex Ro/DI units too. clain 1:1 or better for like 500 bucks or so.

sfsuphysics
01/21/2010, 03:29 PM
I don't want a whole new setup though. If I have to buy some "high efficiency" membrane, fine, if I need some controller then fine. But I really doubt the prefilters are any different at all.

That being said, while I can see the multi-membrane approach can reduce waste further, there is that added expense of additional membranes including replacements, besides of which there aren't any in the pictures of these HE units.

Although I think the theory could be flawed because the waste output depends upon the regulator that's used which puts back pressure on the system, if you plumbed that directly into another membrane you'd change that pressure, and it probably wouldn't work as advertised.

Goodwood
01/21/2010, 04:45 PM
Mike, your correct. The unit brand name means nothing, it's all about the membrane. I have found "Dow Filmtec" 75 GPD to be the best. I use the cheapest prefilters I can get while still getting 0 TDS out of the membrane before the DI. The key is backflushing your membrane for 5+ mins. before each use. My PSI is 85-90 which actually makes about 120 GPD on a 75 GPD membrane.

If you're really interested BRS sells the upgrade "2 membrane" kit for a fraction of the cost discussed here.

sfsuphysics
01/22/2010, 12:29 PM
Thanks I'll give BRS a looksy.

kc350twin
01/22/2010, 12:37 PM
Filter guys sells a upgrade kit for $80 or so. You also need a booster pump. My Aquafx already had it so it was a simple upgrade for me.

sfsuphysics
01/22/2010, 09:14 PM
Yeah seems almost like a no brainer upgrader too, yeah it cost more but you get twice as fast water production and half the waste. BRS doesn't make any claims to how much waste output just say a 50% reduction, and after talking with the owner of BRS he basically told me what I thought those that do claim 1:1 could very well be talking at "optimal" conditions so like 70F water at 95 PSI, etc.

Also unless my thinking is wrong, membrane replacement should be twice as long now assuming you make the same volume of water, since each membrane will only get taxed half as much in that same time.

connecticut cichlids
01/22/2010, 09:42 PM
I'm using the Ocean reef miser from The Filter Guys. I've had the unit over a year now, in the winter time, with 78 psi, I get 1.25 waste, to 1 good. In the summer time when the temp rises, easily 1:1. That's how good this unit is. No booster pump, as my street psi is very good. This dual membrane unit is well under $400. Take a look at it!