Re: RO......chemistry

["David A. Youngker" <nestor10@mindspring.com>]

From: Mike Jacobs
Sent: Monday, March 22, 1999 10:34 PM

>Folks...................I think we need one of you chemist guys to answer
this!!!
>
>My experience with RO's is that they...produce water that is soft
(distilled water almost) in terms of hardness but the pH always seems to be
in the middle to low 6's immediatly after the RO unit operates.  After the
water sits for a day or two in my 55 gal barrels, the pH rises to neutral
(7.0)...............from there your pH can be easily adjusted...The probem
of course is the pH crash since there is a lack of alkalinity......(buffer)
to stop the pH from crashing.  SOOOOOOOOOOOOOOO...regardless the type of RO
unit the pH is not really DIRECTLY affected...jump big time if I'm incorrect
on this one.  I would really like to know...

Mike -

I'm not a chemist by profession, but I've been working with some analytical
chemistry texts and references from CRC and the like to produce the
chemistry section of my site.

There is, of course, an introductory page explaining acidity, buffering and
so on. I am also working on specific areas in some detail. Right now, I have
a page on reconstructing Lake Tanganyika water types (as an extreme) and a
page on bicarbonate/carbonate buffering. In the works are several other
pages, in particular the specifics of peat treating your water.

But you might find the page on buffering interesting. Almost everyone is
familiar with the KH/pH/CO2 table presented by Erik on the Krib, as well as
the work originally presented by George Booth in his CO2 injection article.
That table essentially helps you determine your CO2 levels based on pH and
KH values. I took a different approach - I broke down the effective range of
each stage of the carbonic acid cycle and illustrate the effects of
buffering. But the math involved and presented can be used to determine or
establish a pH within those ranges.

One of the things holding me up on the peat section is not the actual effect
of peat in softening and acidifying your water - general guidelines can be
established through a set of empirical data gathered in the testing of
various water samples. I say "general" because, of course, each source and
individual sample of peat varies so greatly. But it can be shown that peat
has a good deal more influence and works with a bit more rapidity than a lot
of people realize. And there's also the effects of the anions remaining
after peat treatment and its subsequent softening and acidification.

What I'm trying to establish now are some working parameters for designing
the same type of experiments in using the humics within peat as acid buffers
when dropping below pH values of 6 or so. Here I'm working with water that
doesn't need softening - RO and rain, for example. I'm trying to isolate the
effects of the humics *outside* of anything other hardening or buffering
agents. After all, once peat does acidify the water, the carbonate buffering
system is totally exhausted anyway, so there's no real useful purpose in
starting with harder water initially.

That's the direction I'm headed for, at any rate...

-Y-

David A. Youngker
http://www.mindspring.com/~nestor10
nestor10@mindspring.com




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