I'm not sure how much these things hurt people if they are not drinking the water from their well (?)

The water around me is generally pretty good- but as I have no filtration or such on the system, we don't drink it. If I were to start drinking it, then I think I would go fairly all-out on it- particulate filter, UV and reverse osmosis. Then the question becomes- would that be enough? Does something like arsenic get removed by reverse osmosis (it's primary function is heavy metal removal and such)?