I recommend the Sawyer Squeeze filtration system. Either full size or mini. See links below. Use chlorine tablets after filtering through Sawyer to ensure virsuses are destroyed. This system is lightweight, packable, and effective.
@burrmsp Just remember that the Sawyer Sqeeze is a filter and not a purifier as there is a huge difference and these terms are not synonymous. You would have to use some other purifying medium such as chemical purification or UV light to purify the water after you filtered it with the Sawyer Sqeeze if you are looking for purified water.
Depending upon what you’ll be doing and if you can take the weight/size hit, I really like the MSR Guardian Purifier. It is crazy expensive and comparatively large for lightweight travel, but it is reliable and fast and great if you’re not wanting chemical treatments for all your water while you’re away and if you are going to be getting water from cloudy/sediment filled sources where it’s hard to trust a UV treatment device.
Also, just remember that with any hollow fiber purifier or filter (such as the MSR or Sawyer) you cannot let it freeze after you have used it once. If you do, you can no longer trust that it is blocking the contaminants they are designed for because the residual water that remains freezes which can “break apart” the hollow fibers and increase the size of the pores which then allows the viruses, bacteria, and other contaminants to pass through to your water.
Hope this helps
If real purifying is needed (Erik is right!), I'd probably dig out my old First Need filter. Heavy and bulky, and not at all cheap, but it really can turn municipal or industrial waste into drinking water. For a little while. At the time I got mine some years back, it was the only device certified as a purifier by EPA. WAY overkill for most water sources, though.
Depends on the water source. The Steripen only disinfects; that is, it's good for bacteria and protozoa. Can't touch any dissolved contaminants, either, nor suspended solids. In fact, cloudy water will inhibit its actions. But if your water souce is clean, it has a lot going for it. And they have a lot of serious cool factor!
I recall (I think) that the early ones were prone to breakage is dropped. You'd mentioned durability, so apparently they fixed that?
Depending on what your doing and budget. camping near a stream or hiking for the day and need a filter. Katyden and Sawyer are very good products. One of the best ones that I have found is www.berkeyfilters.com This product will filter streams, lakes, rivers, and stagnet water. They have a sports bottle for $32 or the Go Berkey kit for $159 that's good for travel.
Good luck and drink safe