
“When obtaining water to be purified for drinking, avoid (if possible) water which is cloudy. Perhaps there is another nearby access to the same body of water which may be clear.
If scooping water from a pond, etc., try not to disturb the bottom so as not to disturb and pick up dirt or other debris into your water container.
If the water appears cloudy, filter it before treatment. Use a conventional water filter, or any cloth or such filtering material to catch the floating particles as you pour from one water vessel to another. If the water is very cloudy or has a dirty appearance, let it settle in a container for a time, and then gently pour off or scoop the water near the top which will be clearer.
One best way to purify water for drinking is to boil it for 1 minute.
Once the water has reached a rolling boil, it has become safe to drink.
Note that if the water source had been contaminated with chemicals, boiling it or otherwise treating it will NOT assure that the chemical is removed.
Know your water source as best you can.
Use regular household bleach, which the only active ingredient is ‘sodium hypochlorite’.
For many years, regular bleach contained a concentration of 5.25% – 6%.
Note that newer liquid bleach may contain a concentration of 8% sodium hypochlorite (about a third more than the original bleach formula), but is still okay to use with the same quantities from the chart below, given the relative margin of safety.Note that bleach will lose its potency over time. Generally, 6 months to a year after its expiration date may result in half strength.”
http://modernsurvivalblog.com/survival-kitchen/bleach-water-ratio-for-drinking-water/