For all you folks out there, keep on chugging your DI water.
I don't think that water passed through De-ionizing columns is rated or
intended for human consumption.
I'll drink water from my usual, time tested sources. Thanks.
Bill Kasprzak
Moog Inc., Systems Group, Process Engineer
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Ellis
Sent: Wednesday, December 08, 2004 2:00 AM
To: [log in to unmask]
Subject: Re: [TN] DI Water
Let me add my CYP 0.02 worth. If you take potable tap water, pass it
through a new mixed bed DI column, and drink it, it will not harm you in
any way. It'll taste bloody 'orrible, but that's another story.
If you do the same with a column that's been in service for some time,
then there is a risk of excess micro-organisms of unknown species having
proliferated in the resin bed. I've seen DI columns in clear plastic
tubes turn green with algae and the chlorination of tap water does not
prevent it. Probably the same applies to some bacteria, a few of which
may be harmful.
I disagree with the guy who said that DI water could not be better than
2 megohm-cm. Let me quote facts:
1. RO does not deionise: it removes all dissolved impurities by a factor
of about 10 to 20. If your water starts with a conductivity of, say, 300
µS-cm (typical for a medium quality tap water), it'll have a
conductivity of 15 - 30 µS-cm after a single RO stage and non-ionic
dissolved material will also be removed in about the same proportions.
To prepare potable water from sea water in a desalination plant, it will
require two- to three-stage desalination, UV microorganism murder and
remineralisation.
2. Distillation is not a very effective way of purification, despite
popular belief. It, too, will only remove dissolved solids by a factor
of about 50 to 100 per stage. This is explained by the fact that boiling
water produced bursting bubbles on the surface and these throw minute
droplets of water + impurities into the steam. The water in these
droplets evaporates and the impurities float around as an aerosol and
get partially washed out by the condensate. In addition, the
constructional materials of the still tend to dissolve slowly in the
distillate. The distillate will also pick up CO2 from the air if it is
allowed to trickle into the receiver. Even triple distilled in quartz
water, which is the purest you will find, will rarely have a
conductivity better than 0.2 to 0.5 µS-cm and is usually complemented by
a mixed bed DI column to bring it down to typically 0.06 µS-cm
(so-called "18 megohm" water). Distillation is horribly energy-intensive.
3. DI water produced by simply passing tap water through separate cation
and anion beds, followed by a "polishing" mixed bed DI column will have
a conductivity as low as 0.06 µS-cm but will still have almost its full
complement of non-ionic dissolved solids. If subsequently passed through
two carbon columns (different adsorption characteristics) and UV
irradiation, followed by a 0.1 µm mechanical filter, it will be
practically the same as the purest "18 megohm" water. This is what is
used for semiconductor production, except that it is preceded by a
single stage RO, as well.
Brian
David Tremmel wrote:
> Dear Technetters,
>
> As a joke, someone asked me what would happen if they drank DI water and
it
> started me thinking. Is DI Water potable?
>
> Thank you,
>
> David Tremmel
> Belmont Trading
> 3160 MacArthur Boulevard
> Northbrook, IL 60062
> (847) 412-9690, Ext. 345
> (847) 858-5540, Cellphone
>
> _________________________________________________________________
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