PURE WATER FROM A MUD PUDDLE
My point here is you can get drinking quality water from almost any source, yes, including a mud puddle.
Actually mud (dirt) is part of a bio filters purification medium, although sand works better.
When you are pulling water from a badly contaminated source, further steps have to be taken in order to clean it.
My favorite method of purification is a solar still. It is easy, cheap (free once it is built) and it produces clean water free of everything, except possible chemical carryover. When purifying water contaminated with traces of chemical elements, distilling by itself will not work. Some chemical contaminants will be driven off with the water when it evaporates.
Another effective way to clean dirty water is to use dirt. This dirt is actually a type of clay. Bentonite. Bentonite clay is used commercially for cleaning wine and beer as well as internal cleansing.
The whole idea is that when a purified clay is pulverized and mixed with water, it bonds with any particle in the water or liquid and settles to the bottom. Other benefits of this method are Bentonite's (clay) ability to bind with heavy metals. Clay is also one of two ways to purify radioactive contaminated water.
If you track these ways back to the source you will find it is Mother Nature doing it's "clean thing". Evaporating water (rain), filtering or bio filtering is Mother Nature's way of cleaning. A lesson for us all!