Perhaps the setup it just to expensive, complicated and not robust enough for the US Army. Doesn't mean to say it doesn't work and the ability to quickly purify water (4hrs is a very long time for chemical purification if your thirsty by which time you could have made a fire*, boiled the water and made a brew, drunk it and done the washing up) with a lifetime capacity of nearly 2000 gallons of water would probably be more than the US army requirement for a water purification system. Oh and no chemical aftertaste like drinking from the local swimming pool.

* I don't think the US Army generally issues any means to get a fire going either to allow the ability boil some water in a mess tin or metal pot and make a brew up, having to rely on chemical heaters, which are pretty restrictive. How on earth you would expect a GI to make a decent cup of Earl Grey with a chemical heater is really beyond me I'm afraid.