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Re: RO vs. Ionic Exchange

Andrew is looking for the most practical way to remove phosphate from his
source water:

> I do know that Kent Marine does not recommend using their DI anion -
> resins alone, because the life of the resin is reduced.  Why this is so
> never
> been explained to me.  Any ideas?

In the Kent Marine R/O units which incorporate Inonic Exchange Resins, the
Ionic Exchange column is placed AFTER the R/O membrane, i.e. the water going
into the IEC is already pretty "clean". When you look at the "manufacturer's
specs" for different types of R/O membranes, you will notice that TFC are
generally more efficient than CTA membranes but even TFC can't get 100% of
everything out of the water. The efficiency of either type is influenced by
both the temperature and pressure of the input water. The "effective life"
of the resins in the IEC is therefore going to depend upon a number of
factors and the "manufacturer's specs" can only be used as a guideline.

You will have to determine, for yourself, based upon your conditions, when
those resins need either recharging or replacing. If I'm not mistaken the
Kent unit is a mixed bed one, meaning that both the KATI and ANI resins are
in the same column together.

But however long they last, I can imagine that the water would be pretty
close to very pure coming out of a well maintained and properly operated
unit. I have been happy with my R/O only unit.

James Purchase