Floating Wetland Islands are designed around the same principles as a wetland: utilising the natural processes of plants and microbes to improve water quality.FWIs are man-made floating islands, designed to enable plants and microbes to live in ultra-high concentrations, exponentially higher than those found in naturally occurring or constructed wetlands. Beneath the FWI, a hanging network of roots, rhizomes and attached biofilm is formed. This provides a huge active surface area for biochemical processes, as well as physical processes such as filtering and entrapment. The general design objective is to maximise the contact between the root/biofilm network and the polluted water. I have a LOT more information on this idea if you are interested. You can give me a thumb-drive and I can transfer it.