I live in a very dry climate, so water is a concern. I keep a MSR MIOX water purifier attached to my bag. It's not very big, and it's great inside my Janus pouch.
Bookmarked this informative review during research — covers four years' use in varying conditions. Positive, with just a couple of minor "cons," none of which are insurmountable. Remains on my to-get list.
I also keep some of those Katadyn Micropur tablets in my bag. Because of how long they take to work, they are my back up option.
not EDC compatible without a large bottle holder probably, but, LIFESAVER bottles are pretty sweet. VERY quick....
Primary in BOB/Jeep kit is First Need purifier with Micropurs as back-up (MP1s are primary treatment in smaller kits ... backed by Frontier filter when kit-size allows). Quick aside for those not familiar, Micropur tabs — if cold, dirty water — take four hours to handle Cryptosporidium, same period the MIOX requires for Crypto.
I have a 2qt canteen (filled with treated water) in the new car kit plus extra AquaTabs and Aquamira drops. I got the idea from my neighbour, prior to the canteen I used to keep Datrex pouches in the car. But I like the canteen/Tabs/Drops idea more.
I carry Micropur tablets and gallon Ziplock bag for emergencies.. Sawyer makes some highly portable "pointzerotwo" products that filter and purify (incl viruses), with million gallon guarantees and back-washable.
I used to EDC an Aquamira Frontier Pro in my bag...which was a GHB(Get Home Bag) at the time. It was an NRA Range Bag, with great organization. I carry a little different configuration of stuff now...no less, really, just different. I liked this for its size and for its different filtering configurations. Hang it to filter by gravity, straw directly from a pool of water, or attach to a standard plastic bottle. Got it for about $12 I think. Got one for each of my Fam of 3 Figured it was good for getting us to water storage and then some. http://aquamira.com/consumer/frontier-pro-filter-system/
I use the Sawyer filter. Its the best all around filter iv found to carry in a bag. I work with ro systems for a living so Iv delt with allot of water filtration systems. I highly remand the Sawyer. http://texaspreparednessgroup.ning.com/page/products-1
How about something like this? LifePack Filter. Using a flavored syrup, it creates Forward Osmosis (not reverse) to make a drinkable electolytic beverage. Not the same as having pure water around, but it will keep you alive. Available in 1l to 20l capacities.
I'm in a very urban area and tend to travel to other heavily urban areas. Thus, obtaining potable water after a disaster is especially critical, given the post disaster pollution and microbes. My EDC bag has the following lightweight , redundant kit, which I believe is very effective: 2 Seychelles advanced water straw purifiers, the only such straws to filter/purify chemicals, bacteria and viruses. Alternatively, one such straw and a Seychelles advanced bottle filter with the filter element dry stored in a zip-lock. That allows me to use the bottle as an everyday water bottle. Backup is supplied by Micropure tablets, coffee filters and the Survial Resources fold up filter holder. I also have two SR ziplock top one litre water storage bags, to increase storage capacity. My kit also contains a 4 way Silcock Key tool to obtain water from outside commercial building outlets.
To reduce chemical pollution in water, i would prefer to use some form of distillation. Heat sources for distillation can be sunlight, fire, camp stove, etc. Distillation is also effective for desalination of sea water. http://edcforums.com/threads/drinking-water-distillation-without-sunlight.97708/#post-1250203
I keep water purification tablets (enough for three refills of my 32oz nalgene) in my EDC along with my buff. The buff is used as a filter during filling, to keep out larger particulate. The tabs take care of the nasties you can't see. I think this method is ideal for EDC. On the other hand, my 72hr kit has a Microworks EX as a longer-term clean water solution.