Purifying water in the field

I am familiar with using a solar still to purify and/or capture water from urine, vegetation, sea water, etc. Is there a field expedient method for purifying water that has been contaminated by, for example, gasoline? I realize that you are unlikely to encounter that in a survival situation, but it is possible.


Petrol products will not mix with water so it is a matter of separation. It would seem to be one of the easiest ways to get water, if needed just stick your head below the gas level and drink.

Maybe not. Gasoline in the US and in Europe has around 1% benzene added as an octane booster. Benzene is soluble in water, to the tune of around 0.8 g/L. There are probably other water soluble toxins in gasoline as well, but the benzene alone will render it undrinkable.

Chemical contamination is probably not solvable by the unequipped person.

Biological contamination is fairly straight forward. Either boil, treat with iodine (drops/tablets), or chlorine (bleach). Time, quantities, and dilutions will be left to the reader as an exercise.

Are filters suitable for removing chemical contamination? I would think a reverse-osmosis filter would do the trick, but I am not sure if things like Katadyn filters do that. Is there a field expedient means of fractional distillation? If a substance like benzene is dissolved in the water, can it be separated through distillation through a solar still? Is there a way to deal with suspended solids or heavy metals?


Activated charcoal will adsorb most organic compounds. It’s quite good at grabbing benzene, for instance. Suspended solids (or turbidity) are usually handled by sand filtration.

I’d go with several levels of activated charcoal. Reverse Osmosis can get rid of a lot as well.

I would go: coarse filter -> fine filter -> ion exchange resin -> charcoal 1 -> charcoal 2 -> RO

At the bottom of the Grand Canyon, we simply had a little pump filter. It may even have been a hand pumped RO unit. Supposedly, it took anything nasty out. I have no idea how well it would work with urine. I think it would be sanitary, but not tasty.

So, if I’m reading this right…

Filter through a bed of activated charcoal, and sand. Probably best in layers? This removes solids, and organic compounds.

Filter and/or treat to remove bacterial/fungal/parasitic nasties?