Double Pass R/O and DI

Depends on your needs. This might help...

https://www.labconco.com/articles/whats-the-difference-between-ro-and-di-water-pur

Yes, and no.

Is it worth it? I can't see how it could be.

Two things are not defined.

Ratio of DI water to filtrate.

What is your water usage?

Thanks, for your comments. Our Double pass has an output of 480 gal/hr. Of the we are using approx. 150 gal/hr. We have a reading of 3.4μs. We use this water to clean plastic lenses in our operation. We use to use a single pass R/O with DI bottles following it and had a 10 to 18.5 meg ohm reading. We do not use the single pass because our water needs have dropped.

thanks for your help,

Tom Daugherty

How are you measuring the conductivity?

18.5Mohms sounds suspicious to me,which is .054054 uS.

18.2Mohms is usually the max achievable from a DI filter.

This is VERY pure.

Are you using a traceable measuring standard,or a DVOM?

Check your measurement against a lab standard solution for reference at 25C.

Here is a link that may be helpful:

http://pro-analitika.hu/characteristics_of_deionized_water.pdf

I'd say you're looking for a rotating worker/polisher setup using mixed bed DI tanks to get the best purity. With the double pass RO feeding it you should get a reduced degradation slope compared to single pass so the bottles will last longer and the overall purity will tend to be more consistent. If you want maximum purity it will need to be a three tank system, rotating the 2 polishing stages into the worker.

It's definitely feasible and if you want that quality of water, in my experience also the most practical for the usage levels mentioned.

See this for the reason for my doubting your measurement methods.This chart is from the link I provided in my previous link.

Before you can control anything accurately,you must measure it accurately.

The measurement you provided exceeds the nuclear purity standard,which is the currently highest achievable.

You haven't mentioned your goal...What is your goal?

What is the end use of your water?Laboratory,potable,nuclear?

There are different requirements for different purposes.

De ionized water is usually used as a final polishing of potable water.

RO is usually used first to remove up too 90-99% of contaminants.

DI filters use a molecular ion exchange process to remove inorganic contaminants,and is normally used as a final treatment,so injecting this into a RO output is pointless if your goal is ultra-pure water.

The resins in the DI filter will eventually need replacement depending on how much residual contaminants there are in the water entering the DI resin bed.

Do your homework,and study and understand the water treatment process for your application.Lots of good info on google,including free water treatment sample tests and courses.

The more you learn,the faster you will move up,as most grade level promotions are test and experience based.

Good luck.

We use this water to clean plastic lenses in our operation.

#5

I really wonder if adding additional filter with the same specs(micron size or any) in series would be a difference and beneficial, much more the addition of dilution.

A1) Yes.

A2) The forum doesn't get involved with the economics of equipment operation, as it is usually a commercially sensitive area, and unwise for publication in a global internet forum.