If your drinking water from groundwater or if you are out camping and run out of bottled water and are force to gather water from a natural source. You can use this way to purify water. you can use  bleach with 2 drops for every liter on water and let it stand for 30 minutes before drinking. But you must use unscented bleach. For some viruses that are very resistant to chlorine, it takes a while. Allow chlorine bleach to react adequately with these viral bacteria.
And chlorine is also in the form of tablets. When you need purified water in the wild, you can put the tablets directly into the water without measuring the amount of chlorine.This is a very well and convenience way to purify water.