I know I shouldn't drink seawater (because of the salt it contains), but how can I desalinate it?
You need to distill it - I'm assuming that freezing is not an option (unless you're camping in the extreme latitudes). This is easiest, as the ice on top is almost pure water.
Where you don't have a freezer available - boiling the water, capturing the steam and condensing it back to water will provide pure water.
3This method can be achieved using a plastic tarp or other impermeable membrane (raincoat). Boil water below, with the tented tarp above funneled into a container. Jan 25, 2012 at 14:20
1If no heat source is available and you have a clear plastic tarp, use the solar energy of the sun to evaporate the salt water and capture the condensation. Make sure to angle the tarp and create a wrinkle for the liquid to drain into a container. Jan 25, 2012 at 14:31
Distillation doesn't work 100%, the steam also contains some salt... when I was young I grown crystals and once I got for 1 week away. There was a book near the saturated salt solution where the crystals have grown. When I returned from vacation, it was completely covered with salty coating with crystals. So it doesn't work 100%.– TomasFeb 18, 2012 at 11:18
it might not be 100% but it is better than nothing– HorusKolFeb 21, 2012 at 7:35
Outdoors you can dig a hole and build SOLAR STILL. It is quick and dirty but works very well and it is time tested.
Or you can put big plastic bag over brach with a lot of leaves on it and put rock on the bottom to capture the water. Make sure you don't do it on foliage that is toxic to people.
If you have the bucks you could get a portable Reverse osmosis filter.
Electrolysis turns the salt water into oxygen and hydrogen then recombine them and the result is pure water.
+1 for the solar still: but how do you 'recombine' hydrogen and oxygen? other than combusting the hydrogen?– HorusKolJan 25, 2012 at 22:00
@HorusKol: You burn them, and make a sizable explosion. Hydrogen is dangerous, and the danger arises from particular concentrations, which make it detonate, instead of burning. Also careful with the electrolyzed water. That most likely contains a mixture of bleach and lye. Jan 26, 2012 at 0:55
My recommendation for solar stills is to look for an appropriate dip rather than dig a hole since you'll sweat buckets digging, which rather defeats the object. The latter does not help with sea water. Aug 5, 2014 at 0:33