Self Contained Mobile Biodiesel Processing Trailer

What is the purpose of the polishing column? What does it do? Is it used in the drying process?

Is this tool going to be updated? Dorn, are you the primary source of this info or are you uploading this for another person? I love the concept, especially something smaller, and think it would be easy to scale b/c of its modularity. Looks like no updates since 2012...