Perhaps the most effective way to make sure that the water you are drinking is free of contaminants, is boiling it. This is because boiling water kills everything that could possibly be lurking in it. Water only needs to be at a rolling boil for approximately one minute before it is drinkable. The only downside to this of course is that you have to wait until it cools down to drink it.
Backcountry firefighters and trail cutters alike will tell you that a small bottle of bleach can go a long way when it comes to having clean water to drink. It only takes 8 drops per gallon to turn unpotable water into a drinkable delight. After applying the 8 to 1 ratio, allow the water to sit for 45 minutes. Then you’re good to go. It is wise to pack a small travel-sized bottle of bleach with you on your adventures into the wild, or in your bug-out-bag for when SHTF.
Liquid iodine works a lot like bleach, however the drawback is that you need quite a bit more per gallon of water… twice as much to be exact. If you find yourself in a survival situation and all you have is iodine, then by all means use it. It works. However, the other potential drawbacks include safety precautions for anyone who is allergic to shellfish. Most folks who have shellfish allergies are also allergic to iodine. Also, pregnant women or women who are nursing are advised against drinking iodine-treated water. Similar to bleach, after applying iodine to the non-potable water (16 to 1 ratio), allow it to sit for 45 mins before drinking.
Most water purification tablets are chlorine dioxide. While you can find some that are made with iodine, the majority on the market today are not. Tablets are a good idea if you find yourself in a situation where you can’t make fire to boil your water. That said, it takes 8 tablets to purify a gallon of water. Given that the bottle only contains 50 tablets, a prepper trying to secure water purification through this method would need to buy quite a few bottles. Similar to the other chemical treatments of water listed above, it takes 30 minutes for the tablets to do their job.
Lightweight, not very expensive and capable of filtering more than 250 gallons of water, a survival straw is a great way to purify water in a pinch. Some straws can even be connected to water bladder hoses, so you can fill your CamelBak with river water and have every sip instantly filtered. Not only is there no wait time for water purification when you use a survival straw, but it is also the most portable and long-lasting option.