Filters are a good first method. In my backpacking experience, you always want two methods of water purification (because any kind of gastrointestinal issue in the wilderness is a really bad time.) On our trips we would take filters, iodine tablets, and equipment for boiling and use the three in combination according to the situation. The one time we only used filters and didn't take the time the boil or iodine, we all got giardia. (Not sure on the spelling but it wasn't pleasant.) Luckily we were on our last day out of the Grand Canyon, so we didn't get sick until we were all back home. Taught us a lesson about water though. I will always use two methods after that experience.
Somewhere in another thread I can't find now, I asked about powdered bleach. I had heard of it but couldn't find it anywhere. In internet searches, I always came up with different forms of powdered laundry detergent - not workable at all for cleaning water.
But, today, I got lucky, I think. Several days ago, I did read that the liquid bleach you purchase for cleaning water should be "Calcium Hypochlorite." Today, I found it in a granular form. Liquid bleach only has a shelf life of 2 years. This stuff is 7 to 8 years. And it is rotatable since you can use it in any way that you would use liquid bleach. http://www.geekprepper.org/disinfect-water-with-calcium-hypochlorite/