On Wed, 12 Sep 2007 23:40:01 -0700, Keith Hughes
wrote:



Richard Casady wrote:
On Wed, 12 Sep 2007 00:44:05 GMT, Jere Lull wrote:

You say that viruses are smaller than sodium or chloride ions? I got
A's in college chemistry, and I have trouble believing it.

Smaller isn't necessarily the issue with retention of ionic species. A
membrane that electrostatically adsorbs ions can still pass much larger
non-polar molecules and materials.

As I understand him from the past, the viruses are broken down to toxic
chemicals that will pass.

Thank you for relaying that little tidbit. I remain skeptical. I may
drop by the local waterworks and look at a few trade magazines. Check
out the ads for the millions of gallons a day RO plants.

Casady

There are a number of studies showing that RO membranes (which are not
absolute porosity filters, but are spiral wound depth filters)

That explains a lot. I have cut open,[ they make a tool just for that]
a number of pleated paper oil filters. With those they seem to either
pass a particle size, or not. Like any sieve, its all or nothing. I
have seen filters made from spiral wound string, for fuel, if I
recall, but they didn't make any claims of micron size. That would be
a spiral wound depth filter? I can see how it could pass some, but not
all, of the same size particles. You could call it an attrition
filter. but clearly it isn't a simple sieve. Photographic filters take
out a percentage, but not all, of the light.I was under the impression
that RO filters were all or nothing,like any sieve. It is good of you
to post some actual information. A newsgroup with news, of all things.

are not 100% viral retentive, or bacterial retentive (especially for Giardia
oocytes, and certainly not for mycoplasma) when challenged with a
significant upstream population. The prevalence of these organisms (and
almost-organisms) in seawater is, however, extremely low, and a 2 to
3-log reduction (about what the literature seems to support) gives a
very high probability of 100% removal. Safer than tap water, by a long shot.

Can you run the stuff through twice and get the same percentage
reduction for the second pass?

Someone mentioned arsenic,and the CRC does list it as a component of
sea water. Three to twenty-four parts per billion. Or mg/ton. About
the same as iron. 1970 edition, your milage may vary.


As for viral proteins being toxic, the only studies I'm aware of have
been done on the common viral pesticides, where no oral toxicity has
ever been observed - doesn't mean it can't happen, but given how rapidly
protein is denature in the stomach, it's pretty unlikely.
That is the reason for having stomach acid isn't it? That and
dissolving "insoluble" heavy metal salts.
For injectables, some hepatotoxicity has been shown in mice injected with
solubilized viral proteins - hence my reluctance to inject RO water
while out sailing...

The DNA/RNA does not appear to be orally toxic either.
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