for water purification.

http://:www.epa.gov/safewater/mdbp/pdf/alter/chapt_5.pdf

1999 EPA document on using it in water purification applications, with pathogen-by-pathogen analysis for various nasties.

Here's the dirty:

Bacteria die nicely at 2 mg / liter

Viruses, it seems, are git-hard and might require as much as 50 mg / liter, however the part of the text talking about this is much more complicated than the bacteria part and I'm less sure that it's comprehensive.

There's no numerical data on protozoa or cysts, apart from noting that they're tough little beasties.

However, it does say:
However, based on the other disinfectants discussed in this report, protozoa are significantly more resistant than viruses; therefore, it is likely that the dosages and contact times required for protozoa inactivation would be impractical


Now, we've there's been a lot of stuff about mixing Potassium Permanganate by color. I've yet to see a really clear chart of concentration vs. color, but from what the fancy fish folks (who use it routinely) a light pinkish-purple is about 2 mg / liter, and that seems to be what most people are mixing at for drinking water.

So, as far as field-expedient water purification goes, it seems that the standard practice is probably just-about good enough for bacteria, but likely to be ineffective against protozoa and cysts, which means giardia and crypto are likely to be untouched, if I read the science correctly.

Somebody want to double check me on this? I may have got it wrong, but it looks like PP is not Strong Mojo as far as swimming evil is concerned.

Which is a shame, because I really do dislike iodine. Schwert's post here:

somewhere down the thread

has some overviews of alternatives.

Hey, let me simply that: potassium permanganate does not appear to be comprehensively effective water purification according to the EPA.

Does anybody have any contradictory evidence? Can we figure this out clearly once-and-for-all?

Muppet,

Totally agree.

If I had no other options then I would give it a go, but if I have any way to boil, filter, iodinate, chlorinate I would use these first.

Too bad really as you can easily carry enough KMnO4 to "treat" many gallons of water.

Yeah, file under "too good to be true." - I'm a little disturbed that so many people seem to be gathering the impression that it's actually a reasonable way to treat water.

It seems like a dangerous myth which could get loose in the wild and be nearly impossible to clear up - I can see people now having the vague idea that it's OK to use for water purification because, after all, it's in lots of kits and people talk about it online.

If I hadn't dug for ages and found that EPA report, <b>I'd probably believe that</b>. Worrying.