no agreement that carrying clean water is preferred, but should one find themselves with only a "straw" and an empty bottle (ie: your other purifiers are lost or broken), bacpacjac's concept sure looks like a smart way to get by.

Lifestraw would work well with a SODIS system.

Carry the untreated water in a two liter clear pop bottle in the
sunshine and the UV will dispatch a good number of any bacteria in the water. Then the lifestraw would get any remaining.

FYI - a 2-page discussion on some of the negative aspects of using the SODIS system can be found in this thread:

http://bushcraftusa.com/forum/showthread.php?p=1045130#post1045130

If you happen to be carrying only untreated water for use with your LifeStraw and then come upon an emergency need for medical irrigation, what's wrong with dropping about a cc or more of liquid iodine into your untreated water? (borrow the iodine from the medical supplies you are carrying) The water would be safe enough for irrigation use in a few minutes.

Of course, who wouldn't prefer to have unlimited clean water available at all times? But I see no reason to limit yourself to only one method of water treatment. Carry iodine (itsy-bitsy small and lightweight). Carry MicroPur (itsy-bitsy small and lightweight). Carry a LifeStraw (a bit larger than the first two things, but much lighter than a conventional pump filtration device). Carry equipment for boiling water. Carry a pump filter too if that's what you prefer. But I think I would feel comfortable enough leaving that out for BOB use. Two chemicals, fire, and a LifeStraw sounds like a decent enough group to take care of my anticipated needs. For something that in all reality I will most likely never use, just keep it in my BOB, I figure the LifeStraw at $19 is a suitable enough replacement for a pump filter at $80+. I wouldn't knock someone who wanted to carry a pump filter though. We all make choices based on what we foresee as our potential needs.

I don't think SODIS works at my 40 degrees north latitude. But that is something that would be useful near the equator.

That has certainly be suggested in the past, although now we're getting away from the Lifestraw and onto wound care.

Keep a ziploc or other small plastic bag handy, drop some chemical treatment into the water and put a pin prick in it so make an ad hoc wound irrigator. I think the last time the idea came up, someone was asking about dropping those povidone-iodine wipes into some water for this purpose.

No negative things about SODIS in PET bottles so far in tests.

For example-

"Negative genotoxicity results were obtained for water samples that had been in PET bottles and exposed to normal SODIS conditions (strong natural sunlight) over 6 months"

Journal of Water and Health

http://www.iwaponline.com/jwh/008/jwh0080712.htm

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"A simple water treatment process called SODIS (solar water disinfection) consists of filling polluted
water in PET bottles that are exposed to sunlight for 5–6 hours. However, sunlight does not only
destroy disease-causing microorganisms found in the water but also transforms the plastic material
into photoproducts. Laboratory and field tests revealed that these photoproducts are generated at
the outer surface of the bottles. No indication for migration of possible photoproducts or additives
from PET bottles into water was observed with the applied analytical methods."

From Journal of Water Supply: Research and Technology—AQUA | 50.3 | 2001

SODIS doesn't sterilize water, just reduce the load of
living pathogens. Higher latitudes reduce the effectiveness, but when combined with other water purification methods might be useful in many situations.

"Since the early days of SODIS it has been widely accepted that SODIS only works in the “35 degree window,” that is, the region between 35° North latitude and 35° South latitude. There is plenty of evidence that the “middle” of our planet gets the most direct sunlight (which is, of course, intuitively obvious), but there has been very little investigation into the relative effectiveness of SODIS at different latitudes. It is known that latitude is not the only factor effecting solar intensity (geographic and climactic factors, as well as altitude are also important), and that solar intensity is not the only factor effecting SODIS (temperature can be an important parameter as well), so the 35° window is probably a simplistic approach. In fact, there is evidence that even at latitudes north of 40°, SODIS can be effective, at least in the summer months. Sunlight intensity in Toronto on June 21 is higher than at the equator."

http://www.waterschool.com/faqs/

great info clearwater. thank you!