So i have a large pond on a farm. If anything happens id like to be able to go down, get some water and purify for use in home.
Have well water now, the spring feeds the pond. I mention the farm thing bc of fertilizers and other potential runoff. We dont drink our home water rn but use it for brushing teeth and ice cubes. Its been tested and isnt bad but has some turbidity so its not aesthetically appealing.
There are a lot of things posted here that will filter contaminants and debris. But easiest is gonna be manual filter and bleach.
But I dont know of anything that will take care of possible chemical runnoff.
Best bet is to have manual backup for your well and use bleach to kill of organizms and have some meds on hand to deal with issues related to microbiological contaminants that cant be screened/killed.
Nextbest option if you have space is a catchment system