by bensonng » May 3rd, 2011, 11:38 am
Yes, no portable filtration system will take out chemicals form runoffs, and such...
Here is a break down of what filtration size you may need for each of type of "bugs" :
Protozoa - 1.0–4.0 microns
Bacteria - 0.2–1.0 microns
Viruses - down to 0.004 microns
I been using a katadyn mini for about 15 years for fishing (clean water streams), and a larger Sweetwater for backpacking. The katadyn mini is slower, but its small and light weight (the ceramic depth filter will last for hundreds of gallons of water), its design well, and comes with a cleaning kit built-in to the filter housing and filter down to 0.2 micron. And it fits into a small pocket in the back of my fishing vest. For anything that is smaller, I use the Katadyn Chlorine Dioxide Tablets, but it takes 4 hours for it to work, its one of the best tasting tablets around (if you can call any of them tasty).
There are filters out there with a secondary iodine filter that will take out Viruses (some people are allergic to Iodine), such as PUR Scout. Most of the filters are for bugs, not chemicals, carbon filters will take out some larger size compounds, but not all.