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Posted by calamity on December 10, 2007 at 2:11:41 am EST
In reply to Re: Water purification in extreme conditions posted by Jim S on December 9, 2007 at 9:50:09 pm EST

Perhaps you should investigate "forward osmosis" systems, which apparently rely on osmotic pressure, and the presence of a "draw solution," rather than pumping as required by "reverse osmosis." Because of this, supposedly, turbidity has no affect on the filter. The US Army Center For Health Promotion Web site seems to imply this is a factual claim for the system.

The only such systems I've heard of weigh only a few pounds, cost several hundred dollars, and are made by Hydration Systems Inc. of Albany, NY.

I don't really understand forward or even reverse osmosis, but there are rather technical entries for both technologies on Wikipedia.

I don't have my copy of Kephart with me, but I recall him quoting an Aussie, faced with a dead kangaroo in the only available spring, who relied on charcoal and settling. I don't recall HW Tilman commenting on this subject in connection with his bicycle trip across central Africa.

As for Dr. Rockwell's work having "little bearing on the topic of this thread," one sees that a number of posts above are much-related to experience in filtering water in North America.

While perhaps, as you say, "many of the Loma Prietan articles are often 'summarized' poorly from other sources," I wouldn't know.

Rockwell's paper, last updated four years ago, does consist of a survey of scientific literature, which is of course a standard and necessary form of scholarly writing. The current version of his paper cites more than 60 sources with very clear footnotes.

Dare I say he makes a bomb-proof case that water purity is an extrememly over-blown concern for hikers in the Sierra Nevada, and by implication, many other areas in the US? I carry my filter but rarely, and am not much interested in the thing.

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