A floating wetland occurs when mats of vegetation break free from the shore of a body of water. Ecological engineers from St. Francis University in Pennsylvania and the University of Oklahoma believed that the floating wetlands show promise for water treatment. To test this theory they engineered four different floating treatment wetland designs using different materials and wetland plants.

A red-winged blackbird on the one of the floating treatment wetlands.A red-winged blackbird on the one of the floating treatment wetlands.For the designs, the researchers used materials such as drainpipe, burlap, mulch, utility netting, and reused plastic bottles. They planted them with two wetland plants, cattail, and common rush.

Fully treating wastewater requires processing the nitrogen it contains. The study shows that these floating wetlands might be able to do that.

Researchers say they believe that the processes that allow the wetlands to affect the water derive from a combination of different factors. Although the plants themselves could be taking up some contaminants in the water, William Strosnider, one of the researchers, says that microbes may have the biggest effect.

The base and roots of the floating wetlands are a good place for microbes like bacteria to thrive. They carry out processes that break down or absorb pollutants such as nitrogen and phosphorus.

In order for floating treatment wetlands to be successful they will require high coverage. The goal of the researchers is to get the wetlands to sustain themselves with minimal maintenance. Rather than relying on plastics or Styrofoam to function, the goal is to build wetlands that can grow and remain floating all by themselves.

The floating wetlands could help treat municipal wastewater by enhancing nitrogen removal and could manage algal blooms by helping to regulate water temperature and solar radiation. Algal blooms are a difficult issue for drinking water reservoirs and coastal ponds. Algae can clog water filters as well as result in lower levels of oxygen in the water, which can kill fish.

These wetlands can also provide habitat for fish below the water and insects, water birds and others above the water. "The area directly beneath the floating wetlands is high quality habitat, as small fish and amphibians can use the maze of roots to hide from predators," says Strosnider.