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Old 07/28/2006, 06:28 PM   #1
SpectraPure
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Ro Rejection Differences... Why The Different Ratings For The "same" Membrane???...

There is some confusion on RO membrane GPD ratings we would like to explain.

We have been testing our RO membranes for over 20 years to the industry
standard of 60psi. This is a significant amount of data for us to draw upon
when we share performance characteristics with our customers, help them
troubleshoot production problems, or back up our ratings claims for that
matter.

For example, the Filmtec 75GPD membrane that is so popular is rated 75GPD at 50psi. When we test it at the industry standard of 60 psi, the rating is 90GPD. The production rate of RO membranes is directly proportional to the applied pressure, thus the rating difference; this is why we sell our membranes and systems as 90 GPD (at 60 psi and 77F).

As a note, there are many other membranes that we frequently use besides
Filmtec with as good or superior performance, and those manufacturers use
the 60psi standard.

Unfortunately, most customers in the USA have less than 60 psi (or even 50 psi) available, let alone the 77F water temp that is used in the rating
process (average water temp is more like 50F across most parts of the
country). In these cases a pressure boosting pump can obtain higher
production rates. If you live in Hades (Phoenix in the summer) the 77F is
not much of a limiting factor as far as production goes. But for our
customers in upstate New York in January, it is a huge factor. Perhaps to be more realistic we should all rate membranes production on systems at 40 psi and 50F, although I doubt our competitors would drop their rating convention in this highly competitive market seemingly driven by perceived cost per gallon production rate.

Even more astounding, is that with the membranes that we hand-select and
test to insure rejection greater than 98%, we typically see production rates
exceeding 100 GPD at 60 psi (and 77 F) !!

If you look back at their literature, Filmtec started the 50 psi rating as a
sales gimmick wherein they stated that FILMTEC membranes have the same production at 50 psi as the competitors membranes do at 60psi. Great way to snag customers, but it requires customers to look at the production rate charts and how they are derived to really compare membrane production rates.

Also, in our hand-selected and -tested Filmtec 75gpd membranes, we can make sure that you are purchasing greater than 98% rejection (look at their spec on the DOW website, 96% is the bottom range of the guarantee! They are not all 98% like many think!....
http://www.dow.com/liquidseps/prod/tw30_181275.htm

Why is 1 or 2% so important?? A 2 % increase in rejection from 96% to 98% can double your DI cartridge(s) life. Over the life of the membrane that can save you big $$$ in DI cartridges! That is why our hand selection and proprietary testing (we reject more than half that do not meet our SPEC of >98.0% rejection) is worth the extra cost. Who else labels their membranes with actual rejection rate on the so called "the same" membrane?

Hope this helps explain the different ratings that you see for what appears
to be the "same" membrane.

Scott
SpectraPure, Inc.


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Old 08/02/2006, 09:08 PM   #2
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Real good info. You should have this stickied!

Thanks Scott.

Tom


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Old 08/15/2006, 11:56 AM   #3
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Quote:
Originally posted by Tomzpc
Real good info. You should have this stickied!
Done...


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Old 02/27/2007, 11:34 AM   #4
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Re: Ro Rejection Differences... Why The Different Ratings For The "same" Membrane???.

Quote:
Originally posted by SpectraPure
There is some confusion on RO membrane GPD ratings we would like to explain.
{snip}
That is why our hand selection and proprietary testing (we reject more than half that do not meet our SPEC of >98.0% rejection) is worth the extra cost. Who else labels their membranes with actual rejection rate on the so called "the same" membrane?
That's very interesting! So do you mean that you physically hook up each membrane in a test fixture and run water through it to establish an accurate rejection ratio? I find this technique interesting and would love to hear or read more on how this testing is performed. In man-hours, test equipment, etc, how much do you calculate that this testing adds to the retail cost of the membrane?

Also, how do you dispose of those rejected membranes? Does DOW take them back, or is there an industrial market for them?
By the way, I really enjoy these more technical posts (or factoids) that you make on here!
Guy


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Old 02/27/2007, 11:55 AM   #5
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each "S" membrane is individually tested. Rejected membranes are sold to another, far less demanding market. The difference in price reflects some of our investment to perform the testing. The price difference bewteen an untested and a tested membrane is lost in the savings if you obtain 1 or 2% improvement in rejection as your DI stage(s) life is drastically improved. Even our untested membranes are subjected to a proprietary process which increases their rejection ratio over the units purchased by other vendors from the same supplier. So, those who claim that all membranes grom a particluar vendor are the same may not be aware of our process by which we routinely see our average rejection increase over non treated units. DI cartridges are one of the highest operation cost factors for your system per gallon of water produced, thus our customers tell us the extra price paid is well worth the return from savings on Di. Others just want the best to take water production quality out of the equation as much as possible from their aquatic environment maintenance equation.

bh


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Old 05/23/2009, 10:25 AM   #6
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I'm assuming that this means that the MEM-900 membranes are originally, or otherwise, labeled as 75 GPD since they are spec'd at 50 psi by the manufacturer.

Is this correct?

What rejection rate should I expect from your "Standard" membranes?
I guess I never payed attention to you having both "Standard" and "Select" membranes.

I hope the "Standard" membranes aren't your rejects from the "Select" process.


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Old 05/26/2009, 11:07 AM   #7
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Lutefisk-
our membranes are labelled as 90GPD at the rated pressure. The membranes are produced to our specifications, and subsequently proprietarily treated and each one tested in house. Our spectra-select membranes have a guaranteed minimum rejection rate of >98%. Typical value is 99%
Our standard membranes are also treated similarly, but are batch q/c tested for our specification of minimum rejection of 96%. Typical value is >98%.
The standard are not rejects from our process, they just do not go thru the same rigorous individual testing that the standard membranes go thru. The standard is an excellent membrane, the -s selects are often referred to as "cherry picked" due to the lengthy testing process to guarantee the rejection as >98%. The standard membrane receive batch q/c testing which has given us the ability to screen batch issues, but not sufficient resolution to guarantee rejection above 98%.

We have had in house q/c of membranes since opening in 1985 which has given us great insight into membrane specification and performance.

Rejects are sold to another market where rejection is not a critical factor, or returned to the OEM.
bruce

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Old 05/26/2009, 11:11 AM   #8
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Thanks!


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Old 09/02/2009, 04:17 PM   #9
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Note our membranes are on sale-


http://www.spectrapure.com/email/cu...eciation.html#1

bruce


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Old 09/03/2009, 10:11 AM   #10
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sorry, bad link. try this-

http://www.spectrapure.com/email/cus...ciation.html#1


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Old 12/31/2013, 12:44 PM   #11
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Our best just got better...

Hello-
I wanted to take some of your time to explain and clarify why our new membranes with 99% typical rejection are so important to your RODI system water production cost of operation. I will also explain why our 99% rejection membrane performance is unique, and when you might want to change your membrane to operate your system at low cost so as to produce high quality water at the lowest cost.

History:
In the old days, vendor specs for the "best" membrane were >96%, and 98% typical.
Of course there were a few with much better rejection in these large batches of membranes so SpectraPure® individually tested each of these membranes to select only a few having the best performance to sell as our "SpectraSelect™” >98% rejection (guaranteed). Those that did not make the grade were used in less critical applications, or if below the manufacturers spec, returned to the supplier.
Around this same time, SpectraPure also developed an in house proprietary treatment process to enhance rejection, increase production, and decrease rinse up time. We still use this process today, regardless of what membrane source material we use as the benefits are substantial for high purity water production.
These original SpectraSelect membranes could easily provide a customer with a 2% rejection increase over the bottom end of the specification of the leading membranes of the day (96% rejection being the bottom end of the typical spec, and >98% rejection being our treated, individually tested and verified guarantee).
Case #1
You may ask why 98% rejection vs. 96% rejection is important, and how could such a seemingly small 2 % increase could possibly save you money in operation costs.
Case#1 Impact of going from 96% to 98% rejection on typical feed
Raw Water TDS (270) 96% rejection (10.8) 98% rejection (5.4) Improvement 200% DI Life DOUBLED

In this case, going from 96% to 98% rejection increase cuts in half (10.8ppm down to 5.4ppm) the ionic load passed on to the DI section of your RODI system. Cutting this load in half in effect DOUBLES the life of the DI section. In other words, cuts in HALF your DI costs.
Now, the best just got better
Our new 99% rejection SpectraSelectPlus™ membrane blows away the competition. It is simply the best available membrane for the money.
http://spectrapure.com/AQUARIUM/MEMB...PD-RO-Membrane
Our newest membrane is treated with our in house proprietary process to enhance rejection, increase production, and then individually tested to guarantee typical 99% rejection, and a minimum of 98%!

Is a one percent increase over our old SpectraSelect membrane really worth it you ask?
Refer to case #2 below; showing a one percent increase at these high levels of rejection DOUBLES the life of your DI! Or in other words cuts your DI costs by half!
Case #2 Impact of going from 98% to 99% rejection on typical feed
Raw Water TDS (270) 98% rejection (5.4) 99% rejection (2.7) Improvement 200% DI Life DOUBLED

The Competition
As usual, there is a competitor offering a “me too” “99%” rejection membrane, but looking closer, their spec is a minimum of 97%. Again, our SpectraSelect membrane has a minimum of 98% rejection, or at least one percent more than this competitors membrane. Refer to case #3 below In the case of going from 97% to 98%, this is a minimum improvement of 1.5 TIMES the life of the DI section. Still a significant cost reduction.

Case #3 Impact of going from 97% to 98% rejection on typical feed
Raw Water
TDS (270) 97% rejection (8.1) 98% rejection (5.4) Improvement 150% DI Life One and a half

But what if you only have 97%rejection and you go to 99% with the SpectraSelectPlus?
Case #4 shows if you go from the minimum competitor rejection spec of 97% to our typical SpectraSelectPlus™ 99% rejection, a TRIPLE life increase in your DI. Triple!

Case #4 Impact of going from 97% to 99% rejection on typical feed
Raw Water TDS (270) 97% rejection (8.1) 99% rejection (2.7) Improvement 300% DI Life TRIPLED


What if you only have 96% rejection, what will 99% rejection do for your operating cost?
To answer the question of those whom have the fairly typical industry standard 96% rejection membrane, a 99% rejection membrane will quadruple Your Di life. Let me repeat, quadrupled. Please to case #5. This is a strong case for keeping the best membrane in your system possible. Rejection performance pays huge dividends in DI life!
Case #5 Impact of going from 96% to 99% rejection on typical feed
Raw Water TDS (270) 96% rejection (10.8) 99% rejection (2.7) Improvement 400% DI Life QUADRUPLED

When should I change my membrane?
The flip side of this question is when should I change my membrane? Refer to case #6 which shows the impact of your rejection degrading from 98% to 95%, DI life is cut in half.
Case #6 Impact of going from 98% to 95% rejection on typical feed
Raw Water TDS (270) 98% rejection (5.4) 95% rejection (13.5) Increase in Ionic Load 40% DI Life >HALVED


Note: these calculations assume no CO2 which is not removed by your RO membrane, which can significantly degrade the life of your DI. High pH, or contaminates such as chloramines will also affect performance. The typical calculation charts shown reflect the IONIC load improvements relative to each Rejection Improvement.

I hope this helps you better understand why/how your RO membrane rejection is a prime driver in your RODI water production cost.
Bruce


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