Hey, Bill. Look under "THE LIGHTWEIGHT ZONE >> Lite Gear Talk - Water filter cross -over" on this forum. There's a tremendous amount of excellent advice being discussed on water treatment there.

I would suggest that you use Chlorine Dioxide first, then filter with the Katadyn Siphon filter:

http://products.katadyn.com/brands-and-products/produkte/Endurance_Series_23/Katadyn_Siphon_26.html

The Katadyne Siphon filter works on gravity feed and filters at 1.40 gallons per hour with no pumping. It uses a 0.2 micron medical grade ceramic filter, has no moving parts, and will filter between 5000 and 20,000 gallons of water depending on your raw water's particulates content. You can use the Siphon filter at home for emergency water supply too. Hope this helps, Brum