-- Last Updated: Nov-09-12 8:57 AM EST --
Most convenient is to use gravity flow filters. But you do need something to hang them from like a tree.
Google Sawyer, MSR for gravity flow filters.
Kataydn, MSR, Pur and some others make pump action filters.
I have never carried water with one exception: salt water environs. Filters do work with silty water. Settling or prefiltering takes care of the issue of silt. (Been to the Green River UT and many glacial meltwaters. Glaciers are full of silt)
Five days of water is about 40 lbs per person. Depending on what sort of boat you are paddling and where you can stow it that could affect handling.
I have some 23 years on my MSR MiniWorks..thats seventy days a year. Not everyone likes pumping..though. This unit is easy to clean. The MSR Autoflow backflushes to clear contaminants. Its only got 63 days of use so far in the Yukon.
Of course if you are travelling agricultural country pesticides are a concern. Filters will not remove them. Heavy metals are on the bottom. I don't filter from the bottom. But I also never travel in such developed areas.
Might I ask which river you are going on?
As Chip has said, five days just calls for a little more food..figure 2 lbs a day per person.
Sorry I edited this so Chips reference is below.