It's been years, and I don't know what it's called, but about 30 years ago I used to install septic systems. We were once hired to install some type of natural filter type setup. Going off memory it consisted of us creating walls as if we were pouring a basement. Then we layered various grades of sand and a layer of charcoal somewhere in it. All water was run through it and it came out clear and clean. I'm sure a set up similar could have a steam run through it with clean water coming out the other side like it was a spring