11th January 2017 at 9:09 pm #914
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.
Re. the patents, I don’t believe there are any.