Sepp doesn't talk much about dealing with humanure, and so far no one has asked him about it during a
workshop that I've been at. I know he has built 3
pond systems for purifying grey-water (this is the only time he will use a liner), I believe this was for the Princess Nora Von Liechtenstein. I'd imagine he has built some others as well, but this is the only one I've heard of.
As for dealing with human waste at the Holzerhof, the house and infrastructure was already in place when he purchased the property, so I imagine it is on a septic or whatever strategy is standard for the region.