I have the First Need purifier. It gets rid of all biological contaminants (protozoa, bacteria, viruses), but doesn't remove chemicals. I've used Aquamira (chlorine dioxide drops), but the typical 2-4 hour wait time means I have to carry at least an extra quart of water. The quart of water (2.2 lbs) weighs 1 lb more than the purifier (1 lb). Also, I don't like making mountain stream water taste like city water by treating with chemicals. I can always boil or use my backup Micropur tablets if the purifier fails.

I wouldn't trust any portable system to be effective on chemical contaminants. Consider caching or carrying more water.