This is an email exchange with (one vendor, ****) describing potential problems with EDI (or just ****?)'s technology. The Sales Manager wanted to encourage us to use their unit for polishing (clean feed to the EDI to produce 16+ Megohm water), not recycling.
Author:****
Date: 7/28/98 4:24 PM
Subject: Re: *** Electrodeionization Technology
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Dear Russ:
Thanks for your email. Our current requirement is to feed RO permeate water
to the***** system, with a conductivity of less than 62 micromhos/cm. In
addition, hardness must be <1 ppm as CaCO3 and SiO2 must be less than 1 ppm.
There are other important parameters for the feedwater that we have listed in
our literature.
We understand your desire to recycle as much water as possible, but EDI is a
polishing technology. EDI has been applied in high feed water conductivity
situations before and it has not fared well. We recommend sticking with the
feed water quality parameters described above and in our literature. If the
feed water conductivity is too high, there are some electrical problems that
can arise. Hence, our water quality requirements as listed above.*****l is
capable of delivering 16 megohm-cm water, but if you don't require product
water of that quality, simply lowering the amperage of the unit will reduce
power consumption and lower the resistivity of the product water.
We'll be happy to discuss this issue with you further.
What is the current status of your project? What is your planned schedule?
How can we assist in your project efforts? We look forward to hearing from
you.
Sincerely,
******
Sales Manager
(my contact) then had the R&D Manager throw in his opinions on the subject. My comments are inserted
.______________________________ Reply Separator _________________________________
Subject: Application of **** for your Recycle/Reclaim project
Author:******: 8/8/98 6:02 PM
Dear Russ:
Below are some comments and questions from our R&D Manager, Dr.#####r, regarding your comments on applying*****l to higher-than-specified feed water conductivities. We would very much appreciate your return comments. With your comments, we can then determine the applicability of*****l to your project.
These are (R&D guy's) comments and questions:
1) With the very limited information on Russ' process configuration and water composition, conductivity, etc, I cannot comment on the prospects fo r****... is there a system in place already? Is *****l to replace an existing DI unit, thereby reducing process design flexibility to near zero? is there an RO in place already?
>>There is a system in place--mixed beds. The *** will replace these units. I don't know if it will reduce process design flexibility, or increase it, or no change.
2) While Russ' stated interest in applying **** to recycle reclaim is encouraging, we know that a SYSTEM approach is needed, especially given the complexity of deciding where the resulting reclaimed water is to be re-introduced into the UPW plant; for example, **** might not be needed if the reclaimed water is to be returned to the RO feed or product tanks.
>>There is a system in place, and the water is returned to the RO product tank. **** in the recycle might not be needed 3 years from now if we replace the primaries with **** that has the capacity for all this contamination. For now, the phase-in of this technology is best done by replacing components with similar function.
3) We should think carefully about trying to apply *** as an alternative to RO or electrodialysis for that matter, rather than for the mixed-bed-type deionization for which it was developed.
>>The EDI will replace only a cation-anion, 2-bed setup. There is no RO or EDI in this train. We would consider an RO on the recycle water as a method to lower the contamination to a level the EDI can handle.
4) At higher conductivity feeds, and hence higher concentrate loop conductivities, we anticipate that parasitic shunt current effects in the stack will be problematic. Also, please recall that the current requirements of an EDI device increase as the feed conductivity increases; at some elevated concentration, other deionization methods (RO?) will be more effective.
>>The higher feed and higher brine loop concentrations are part of our experimental matrix. I've asked the various EDI vendors to help me narrow the choices by giving me their best estimates on feed conductivity limits, brine limits, and brine gpm requirements. If RO is necessary for your *****l, and RO has technological benefits over a competitor's EDI configuration, then I'd like to know about it.
>>I'm intrigued by using RO ahead of EDI, but I would need to know if it could handle, say, 1000 us of sulfuric acid without membrane loss. The application to this recycle stream is very attractive, in that there are virtually no cations besides ammonia and H+. Membranes won't plug.
Russ, these are(R&D guy)'s comments on some questions that I posed to him. Please advise your comments. Then we can figure out where****l fits into the picture for you.
Best regards,
^#^%$%^
Sales Manager
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>>Note: Here's a reply back from (sales guy)
Author: **
Date: 8/20/98 6:08 AM
Subject:*****l for your Reclaim Project
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Dear Russ:
Thanks for your return comments on our questions. I will give you a call to
discuss your project in more detail, but our comments are as follows:
1. All EDI technologies are best applied as polishers downstream of an RO
system or on a low conductivity water with consistent product water quality.
In the early days of EDI, the first generation vendors applied EDI on raw
waters, softened waters, and waste waters with high conductivities. The
results were not good.
2. Your goal to replace your cation/ anion train with an EDI unit is not
recommended. High conductivities and big pH swings will not give you the
results you are looking for.
3. With an RO in place, the high conductivity, particles, bacteria, silica or
other contaminents will be reduced to acceptable levels for an EDI. We are
confident that Bob Donovan's (researcher at SNL) testing will confirm this.
As mentioned, I will give you a call to discuss.
Best regards,
#&$%#
***** company