Neither filtration nor chemical treatment will deal with industrial pollution. A charcoal filter will remove some, but not all chemical pollutants. The easiest solution is to carry in your water in that case.
I agree with Jerry.
Filteration removes suspended ( non dissolved) materials
Boiling kills organisms
Chlorine kills organisms
None of the above will remove industrial ( chemical ) pollutants if they exist in the water. Charcoal will remove some, distillation and reverse osmosis will remove most.
For PSK and BOB, if chemical pollution is a concern , carry your own water. And if chemical pollution is a concern in longer survival situations, I would establish a distillation system or rig some small RO unit.