I would like to experiment with bio-sand filters, and was wondering if anyone knew if there were patents on the whole things or specifics. And I was also wondering if anyone could give me tips on making one. I plan on using clay, sand, and charcoal.
Just follow the principles on this site regarding media size (D10 0.15-0.35mm) and sand bed depth (0.5m) and you’ll be OK, as long as flow rate doesn’t exceed 0.4m3/m2/hour. Flow then dependent on the surface area you have.