Here is the link to the people who designed this water filtration system.
Link to their resource page where you can download manuals on how to build this system and larger ones and how to make biochar.
Quick explanation of how the Biosand Filter works:
this isnt the one we built but works exactly the same.
We havent had the water tested yet because we havent finished the biochar stage. We willl post another video once we get the water tested with the results.