Household bleach is fairly effective, but tastes like a swimming pool, and has a strong residual.
Clear water instructions are:
Add two drops of bleach per quart/liter of water. Stir well. Let the mixture stand for a half hour before drinking.
If the water is cloudy with suspended particles:
Prefilter the water as best you can. Add four drops of bleach per quart/liter of water. Stir extra well. Wait a half hour. Then plug your nose and drink.
If you have the chemistry skills to deduce the molar equivalents, you can neutralize bleach with hyrogen peroxide, which will form salt. Yummy!
Not a very popular method, as you can imagine.