To cleanse water of chemical impurities (like PCBs) what to do?

Hm... correct me if I'm wrong but I think that distilling would do the trick. Since the water molecules evaporate and are carried elsewhere and condensed, it makes sense that bulkier molecules with higher heats of vaporization would be left behind. I'm not sure if this applies in every single case, but it seems like the most viable solution to me.