Floating Treatment Wetlands:

Keeping our fresh water clean and healthy

Why Do We Need Floating TREATMENT Wetlands?

Freshwater lakes around the world, especially shallow lakes, are in trouble.

Urbanization, waste treatment, landscape changes, agriculture, and natural resource extraction cause runoff of nutrients, contaminants, petroleum products, and organic materials to freshwater lakes around the world.

Biological treatment is possible, however, by harnessing the natural ability of plants and microbes to absorb nutrients (such as phosphorus and nitrogen) and break down contaminants through biological processes known as bioremediation.

The Magic of Wetlands

The use of wetlands for bioremediation to capture and remove contaminants and nutrients is widely practiced around the world.

Wetlands can improve improve water quality of storm water runoff and manage watershed nutrients, as well as treatment of wastewater and other industrial contaminants.

Wetlands rely on natural processes to biologically filter water as it passes through shallow areas of dense aquatic vegetation and permeable bottom soils. The primary mechanisms for nutrient removal is transformation and uptake by microbes and plants, assimilation and absorption into organic and inorganic sediments, and converted into gas through volatilization. Aquatic plants, both above the water and submersed, take up and remove these elements from the sediment and water column into their plant material or biomass.

“Floating cattail islands have been proven to clean the water and improve water quality.”

Jodi Goerzen, Manager of the Seine/Rat River Conservation District

How Do Floating Treatment Wetlands Work?

Floating treatment wetlands (FTWs) or islands are small artificial platforms that allow these aquatic emergent plants to grow in water that is typically too deep for them. Their roots spread through the floating islands and down into the water creating dense columns of roots with lots of surface area.

Not only do the plants take up nutrients and contaminants themselves, the plant roots and floating island material provide extensive surface area for microbes to grow—forming a slimy layer of biofilm. The biofilm is where the majority of nutrient uptake and degradation occurs in a FTW system.

The shelter provided by the floating mat also allows sediment and elements to settle by reducing turbulence and mixing by wind and waves.

The unique ecosystem that develops creates the potential to capture nutrients and transform common pollutants that would otherwise plague and harm our lakes into harmless byproducts.

Want to see how floating treatment wetlands are constructed?

This short video explains all...

How and Where Can You Use Floating treatment Wetlands?

There are many freshwater bodies in which floating wetlands can be deployed in order to improve the quality of water. Here are just a few...

Stormwater Ponds

FTWs can improve the quality of water of ponds in urban and rural neighbourhoods, that otherwise have a tendency to stagnate and accumulate toxins.

Wastewater Lagoons

These second and tertiary treatment lagoons, rich in pollutants, can benefit greatly from the biological treatment afforded by FTWs.

Landfill Leachate and Tailings Ponds

All manner of toxins, contaminants and metals found in these bodies of water can be treated with FTWs.

Sites of Oil Spills

At IISD Experimental Lakes Area, we are currently exploring how FTWs could break down oil constituents after a spill.


For the past decade, our research has explored sustainable water and land management that creates opportunities for economic growth that can also improve the environment. We have shown that, by harvesting cattail, nutrients (such as phosphorus) taken up during growth and stored within the plant are permanently removed from the soil.

Over the last few years, we have deployed a number of floating wetlands in a number of locations in Canada, from the lakes in IISD Experimental Lakes Area in northwestern Ontario to 'real-world' application in Lorette, Manitoba and Assiniboine Park in Winnipeg.

How Effective Can Floating Treatment Wetlands Be?

Some of our results have been staggering!

When we placed a series of FTWs in two lakes at IISD Experimental Lakes Area, we intentionally selected one lake that was high in phosphorus (Lake 227) and one that had normal levels (Lake 114).

We discovered that the cattail plants in Lake 227 had eight times the productivity and five times the amount of roots than those left in Lake 114, and four times the amount of phosphorus. This clearly evidences the effectiveness of FTWs in removing excess phosphorus from lakes.

Want to learn more about the power of floating treatment wetlands?

Visit www.iisd.org/program/water