The osmosis filter is not a charcoal filter, it is a type of memebrane, that allow water thru but hold onto everything else. My ro system has two carbon filters besides the ro filter, some systems have more and bigger filters. You could make a homemade filter out of just carbon and it would filter the water. Im sure there are diy ideas all over the web for homemade filters, i dont think one the size a water bottle would have much filtering capacity.