Well crap, just read my chlorine treatment (msr sweetwater) will only kill viruses, guess I have been lucky. Time to get a sawyer.
Just read this online. I don't know if it's true but it makes me laugh at all the guys telling me I NEED a filter (not here).
"I have not heard this about AM (Aquamira). Waiting to see what evidence there is either way. Last I read on their site they were waiting for FDA approval to make certain claims about the product anyway. I tried it and didn't like the taste.
As to bleach. If you go that route use unscented. The scent stuff is a poison and will make you sick or worse. And if you follow the recommendation of survival class, CDC, or FEMA you should treat, wait 30 minutes and smell the water. If you cannot smell the chlorine in the water, you have to add the same amount again and wait another 30 minutes and smell again. If you cannot smell the chlorine yet, then you are supposed to dump it and find another water source - that source is too contaminated for bleach to kill it and still be safe to drink. So basic rule of thumb is if you cannot taste or smell the chlorine, you are not using enough.
As to iodine - Basically if you encounter water that is lightly to moderately contaminated and follow the package recommendations, then you are probably going to be fine. And the entire time the iodine is in the water, it is working. So if you take a drink at a half hour, you have less protection than you will when you take another drink from that water 30 minutes later or an hour later - then you are getting a higher protection level than is required by the FDA. When you filter and there is something in the water, it gets the chance to come back as it sits in your bottle. But as to water quality in the back country - there has never been a study of the water on the AT, but from anecdotal evidence (the fact that some people that never treat or filter don't get sick, and the general consensus being that most stomach bugs are probably hand to mouth passing of other diseases) one can assume that the water along the AT is either not contaminated by Giardia or crypto in most places; and in the places it is: the contamination is so low it wouldn't cause most healthy people that drink it to get sick.
To the safety of iodine. You already eat it regularly in salt - read the package, it is iodized. The reason for that is you need iodine in your system to prevent goiters. And a recent article I read said with the low salt craze in America that most people are not getting the RDA of iodine now anyway - so if you increase your iodine intake for a few months it probably won't hurt the average healthy person. Plus you can neutralize the iodine with VitC after it has done it's job.
And as to filters - Roland Meusser, in his book, has data that shows in laboratory controlled tests that filters are only 70% effective against Giardia after they have been used regularly. The stats on filters are only when they are new. Compare that to Iodine treatment in the same study that found the iodine to be greater than 90% effective when used according to the package recommendations. And 99% when given longer periods of time. Plus filters do not stop any viruses - even the filter makers recommend using chlorine or iodine in addition to their filters to protect against viruses. The last big outbreak of illness on the AT was HepA - a virus. I've never heard of a big outbreak of Giardia or crypto on the AT, while there have been many many cases of stomach viruses every year on the AT. Hmmmm....
Anyway, we didn't have filters for years in the back-country and everyone survived without them. Now that filter companies are selling them to backpackers, our water has suddenly become very very dangerous and the battle cry is "I don't want to take any chances" LOL. The best thing you can do is practice good hygiene. If you really don't want to take chances you would bring a filter with iodine and wash your hands like a doctor."