40 Gallon - Filter media

[JohnHuff]

After breakfast and posting that phosphate removal thread, I did find that people are using something like that for their septic tank system. It's called Johkasou (probably my Japanese namesake, heh-heh.)

http://www.jeces.or.jp/en/technology/operation-maintenance.html

Though in the US, I would probably build it above ground for easy maintenance.