I cant say Ive used the Aquamira Frontier ($10; aquamira.com) yet, but its certainly worth a look. The device is simplicity itselfbasically, a straw with a filter attached. Unfurl the straw, stick it into a water bottle, and sip. The unit is billed as capable of removing nearly all giardia, cryptosporidium, and other nasties. Its not a purifierviruses and very small bacteria can get throughbut you could use it in conjunction with something such as MSR Sweetwater Purifier ($10; msrgear.com) for nearly total protection from water-borne badies.
Drawbacks? Well, yes. Even Aquamira bills it as more of an emergency" filter, or as a backup to a larger filtering unit such as a Katadyn Pocket Filter ($229; katadyn.com). It also is limited to about 20 gallons of filtering. Enough for one person for a week, certainly. The other drawback with gadgets like this is that they tend to force you to sip," rather than drink."
My own preference is the MSR Miniworks EX ($85) which I find to be effective, sturdy, and easy to use. It does weigh nearly a pound, so thats an issue. But it can filter a lot of water in a fairly short period of time.
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