With your type of water and daily water usage it all depends on how deep you want to get into maintenance, power requirements, etc.
Typically with your type of water, they put it a greensand filtration system for iron and manganese, followed by an ultraviolet light system to kill the total coliform. You can add sediment filters in between before the UV to protect the life of the UV etc etc. And the add an optional activated carbon filter for flavor and taste and odor.
When you decide to seal your well, start with chlorinating your well. Figure out the static head and how deep( imagine your well a giant pipe full of water), go research online how to calculate chlorine dose. Need to figure out how much water is in that well. Use bleach it's safer. Pout it in, let it for a few hours or overnight. Eyeball it if you don't mind smelling like a pool for a while.
Run your well off and flush out your tanks with that chlorine water.
Then later on Flush your water lines with chlorine, start with a bit more is less with chlorine. Pour it in though the big drums, if not possible pour it down the well again. Open your line long enough to keep the chlorine in the lines. Keep it in there for about 20 minutes, then flush out all your lines.
You have bacteria in your lines since the water lines were probably stagnant in between owner and you moving in. See it all the time.
Now if you want to keep this as primitive as possible you could put it sand filters, 55 gal drums of sand and activated charcoal, you would have to rig it up. If you don't want to use a pump or power you will need a good height difference(head) to push the water through the sand. It's called slow sand filtration that's what they use in water treatment plants look it up. But then when the sand gets bad you will have to shovel out to old sand and put it new. There's also diatomaceous earth filtration. If you get creative you can improvise the whole thing.
If you are able to, get big glass jugs like for home brewing, and sit the water on in good sunlight, that will naturally kill the coliform, at least ,24 hours. Add bit of lemon juice or baking soda, bump the pH up and kill any microorganisms too. You can also buy reverse osmosis system under the sink but you will need a pump for that.
Coliform is weird sometimes it's from septic leaching, manure, etc sometimes it's just decaying foliage down under. So what I'm saying is sometimes it's not necessarily a bad thing. But they use the presence of that to assume that it's bad. So Id say keep the surrounding well head area clean and maybe plant some short root shrubs and stuff around to help with percolation.
Take note of natural springs in nature...ferns birch sycamores berries maples pines etc. they are natural filters. Mother nature knows copy her. She will guide ya strong
Hope that helps. If you have any questions give me a holler.