This link might be useful to you:
https://www.berkeyfilters.com/collections/berkey-water-filter-systems?a_aid=5a5fbcc0b393f&a_bid=55078429
The above filtration units claim to filter out nearly all bacteria and viruses in addition to chemical and physical contaminants.
I don't think you are going to find many people who put untreated water into their RV holding tanks. This is simply an unnecessary and considerable risk in most of the world these days. Sadly most of the world has now become polluted in one way or another.
My RV is an ancient 1990 model. I have never sanitized the tank. There is a clear bit of tubing that runs from the water tank out to a vent that is integral with the fill nozzle on the outside of the RV. This is to allow air to escape when the tank is being filled. This little tube, which of course gets water and water vapor in it, continually grows gunk in it. Every couple of years I'll pull up the bed to get at it and run a small bottle brush through it to get the gunk out.
But, we never drink our onboard water, even when hooked up to city water. It's plenty clean enough for the toilet, hand washing, and taking a shower, but we always have cases of bottled water in the RV for drinking and cooking. We can buy 40-bottle cases of water from Costco for about $2. It's so cheap it's almost free.
If I was doing semi-permanent boondocking, I believe I'd add cases of water to my monthly food treks, and just drink bottled water.
If I had to use water from an unknown source, I'd probably investigate some kind of filtration system like I linked to above. I would filter before the water went into my RV holding tanks.
But, as others have asked, where is your waste water going? Unless your campsite has a septic system, is your waste water going to run off right into the lake you are pumping water from?