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topic 4630

Demineralization (Water Treatment)


I have a problem with a demineralization system. The conductivity of our pure water increase almost 6 times its value. We have tried to recycle the process several times, but the conductivity still higher. Other than regenerated the anion and cation exchanger, we can not find the problem.

My question is:

Do you think that CO2 can be also the problem or what else you recommend me to look for?

Lorena Ramos
Tampa, Florida


DI tanks start out at 8-12 meg ohm for tanks that platers use, up to 18 MOhm for lab use.

With use, they rapidly lose their ability to give that quality. As they get to loser and lower quality, the rate of decrease in quality slows down. This is just the nature of the beast.

If you think that you have a CO2 problem, take a reading on a beaker full and boil it for 5 minutes. Cover it and let it cool to original temp. If you have a CO2 problem, you will have better quality water when you take the second readings as you have eliminated the ion.

James Watts
- Navarre, Florida


What is the inlet/outlet conductivity of your water?

Is it possible your demineralizer is mechanically malfunctioning? Valves, flappers or chemical delivery system may not be working. Are you drawing the proper volume of chemicals during regen?

How old is your resin? The Anion could become organically fouled or silica fouled over time and may need to be cleaned or replaced.

If the pH of the water is down around 4 you may be seeing CO2 leakage. If it is above 8 you may be seeing Sodium leakage.

John Ring
- Whaton, Illinois, USA


I would like to know the average, minimum and maximum service life of an ion exchanger resin (in general).

What's the frequency in replacing the resin? annually?

How would you evaluate a resin if it's still functional or not by just merely looking at it? Or is it possible?

Dax Bracero
- Philippines


Q:I would like to know the average, minimum and maximum service life of an ion exchanger resin (in general).
A:If your influent is normal quality water, resin may function efficiently +15 years. However, the life of resin depends upon many factors, oxidizing agents in influent may cause very short life.

Q:What's the frequency in replacing the resin? annually?
A:You don't need to replace the resin if it is functioning properly. You may need to add some quantity if the resin is lost during backwash.

Mazhar Shah
- Karachi, Sindh, Pakistan


Please check your degassifier equipment. If you don't have a degassifier then please to purchase one and fit it at the end after the anion exchanger.This would solve your problem of CO2. Then even if the problem persists use the modern resin conductivity sensor which gives you an output in digital format based on the resin exchange capability and the conductivity of the water.

Please respond about my suggestion.

Atmakury Harish
- Hyderabad, A,P, INDIA

September 24, 2008

Is there any effect if I put degassifier before and after the anion exchanger?
I often see some article that they put degassifier between cation exchanger and anion exchanger. Because degasifier can reduce anion exchanger load to exchange the anion content in the water.
I wish some suggestion for this question.
Thank you.

- Indonesia

April 29, 2009

Sir, ours is a dm plant of 600 m3/hr capacity with 6 streams (cation, anion, mb).
Recently we faced a problem in one of our anex, i.e., after regeneration silica is not coming down,whereas pH and conductivity are normal (8.5 & 20 micro mho/cm)
our co2 inlet to anex is 17ppm. sodium from catex is 0.9 ppm?
what could be the reason?

azhagarasan veeraiyan
employee - india

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