Let's start with why bother in the first place?

1) remove or neutralize biological pathogens

2) remove chemical and mineral impurities

3) Make it tast better

4) make fresh water from salt water


In general the options are.
a) boil the water - this doesn't mean distill it just get it hot enough to boil and then use it. This will kill all the bugs - or atleast any we realistically need to worry about including the plague.
b) poison the water This includes the chlorine, iodine and other chemical additives. The idea here is to add enough poison to kill the bugs without adding so much that we kill ourselves. A relatively safe approach since the bugs are vulnerable to a bunch of stuff that we aren't.
c) filter the water - This will remove the bugs if the filter is good enough. If a bug is small enough it will pass the filter but filters have become very small. most of the minerals and chemicals will also be removed by a good filter
d) distill the water - This requires making the water into steam and then condensing it out on a cooler surface and collecting the condensate.


Boiling the water doesn't take too much fuel and will take care of any reasonable bio contaminants but will do nothing about minerals and only a little about chemical impurities and won't drive off the salt of salt water only concentrate it a bit.

Poisoning the water will take care of the bio contaminants and do nothing about chemicals or minerals or salt

Filtering the water will take care of bio, chemical and mineral and if you get a very expensive filter you can make fresh water from salt. (Making fresh water is very hard and will consume a bunch of energy either from your muscles or a battery.)

Distilling water - This requires a bunch of input energy, usually some rather elaborate setup and a bunch of time as well but if you can do this in a precisly controlled thermal environment you will get 100% pure water with no contaminants even from salt water.

If you are packing for a psk the only thing that will fit is tablets.

If you are packing for a BOB the energy consuming options are poor because they also consume a bunch of time. So you have tablets or filters. Filters have no shelf life and address a wider range of issues. A good backpacking filter is small and light as well.

If you are in a longer term mode you might want to build a solar still so that you can be making water when the sun shines without haveing to work for it. This is not the typical survival solar still I refer to here - Those don't work. I am talking about using glass and plumbing to bring a ready source of water to a hot enough temperature to boil and then condense and collect. This presumes a good volume of questionable water readily available from a stream or pond.

If you are in a PSK or BOB situation and your first choice method doesn't work then be prepared to boil water in your cook pot for cleanliness. Won't address any industrial contaminants but will handle the bio nasties.