The article was informative, but missed a major water purifier method for anyone with a decent amount of sun. A widely used treatment method to obtain 150F water for 5 minutes or greater temperatures can be seen in all of the myriad of solar heat collectors used throughout the less developed world and even by many in the developed world.
Solar water purifaction: Goes like this generally speaking
Generally said system is a simple tray with its Bottom painted JET BLACK and then one carries stiff aluminum foil(needed for cooking anyways) or cardboard aluminized foil(bulky but far easier to use) that directs the sunlight onto the water tray. This heats the water to the correct temperature without any fuel consumed. The fancy ones have a temperature gauge that turns a color when it reaches 160F, then you time it for 5-10min and viola out pops 2 liters or so of clean water. Weight is generally about a pound when all is said and done for the lightweight systems and for the food solar cooker, an earthenware pot of a couple pounds to pots painted jet black to 10 lbs and several gallons in size.
Generally people have one of these systems running as long as possible during the day to produce enough water. Its doable in a long 1hour lunch break to produce enough water for your entire hiking day for instance. In Equatorial regions getting 20L from one of these systems a day is not unheard of if one is just "sitting".
These system are prolific in Africa/middle east/equatorial islands, etc. Obvious requirement is dependable sun. Also works perfectly well depending on the season very far north. Farthest North I have personally heard is British Columbia. California/Colorado would be simple I would think. Same with the Blue Smmoky Mountains and the EU alps.