Although this blog has a post that teaches you have to manually make water drinkable, you may want to consider investing in a water filtration system that can filter gallons of drinking water in an emergency situation.
The one that I purchased was the Sawyer Point One Emergency Water Filtration, and although it is very simple to use, it can yield over 500 gallons of clean drinking water per day. The manufacturer says it can remove contaminants like bacteria, sediment, and protozoa for up to a million gallons. I used it to filter 10 gallons of water from Sloan’s Lake in Denver and not only was the filtered water very tasty, a chemical analysis of the water showed that it was cleaner than the water I get from my tap.
I would strongly recommend this product to anyone who doesn’t want drinking water to be a concern when SHTF.