How Floating Wetlands Work

How Harris Floating Wetlands Work

How the Harris Wetlands Water Treatment Solution works - Our system utilises floating mats, wetland plant species, protective cages and anchorsHarris Floating Wetlands technology provides a great opportunity to utilize the powerful benefits of biological treatment without the constraints associated with constructed wetlands and reedbeds.

Our system utilises floating mats, wetland plant species, protective cages and anchors. Water is treated by the oxygenated, bulky mass of roots that hang beneath the raft like a thick curtain. This thick mass of roots provides an ideal surface area for the growth of biofilm that produces a powerful, effective bioreactor for water treatment.

Roots of aquatic plants harbor unique, diverse, and novel microbes.

The design of the system also offers greater flexibility for managing water quality. Unlike a constructed wetland or reedbed which may require about 3% of the catchment area for effective water treatment, floating wetlands are installed (float) on existing water bodies and can move up and down with fluctuating water levels which would be detrimental to a conventional wetland system.

Floating treatment wetlands have become an accepted technology in the UK, China, Japan, U.S.A., New Zealand and Europe, where they are universally valued for water quality treatment, biodiversity, wave energy dissipation and landscape amenity.

Water Treatment

Floating wetlands provide an effective system for the removal of nutrients, suspended and floating solids, heavy metals, COD and BOD, as well as providing supplemental aeration.

Sutton Forest Floating Wetlands installed by Harris Floating Wetlands.

Common applications are:

  • Stormwater management
  • Stormwater and grey water re-use
  • Golf course treatment ponds Leachate from tips, mines
  • Wastewaters from industry and food processing
  • Reservoirs and lakes used for storage and recreation
  • Municipal sewage ponds
  • Dairies, feedlots and piggeries
  • Recreational fisheries
  • Aquaculture water management ponds
  • Landscape amenity, biodiversity, fish habitat, wave dampening and shoreline protection.

Habitat rehabilitation

Campbelltown Wetlands - bird cage protection
The streambank edge is the land immediately adjacent to streams, lakes or other bodies of water, and is a highly productive biological system. In many stormwater ponds in urban areas, the riparian edge is difficult or impossible to re-establish using conventional methods because there is no longer a sloping bank and any attempts to establish within the shallow margins would be decimated by waterfowl – Ibis and Purple Headed Morehen in particular, and European Carp.

The birds pick at the vegetation for nesting material and in search of food near the roots. The European Carp suck up the sediment and undermine the side banks that collapse, adding more nutrients and prevent wetlands or grasses from establishing. The streambank edges can also used to dampen the effect of waves that will be adding to the undercutting of the pond or river banks.

Advantages of using floating wetlands for water treatment

Retrofit existing wetland or detention ponds

It is not always feasible to increase the size of a wetland or install source controls to take account of additional pollutants given the cost of land acquisition or the cost of replacing existing infrastructure. Floating wetlands will reduce pollutants without requiring changes outside of the existing pond or wetland.

Design to target required level of treatment

Floating wetlands are a modular system, so they can be scaled up to meet the desired level of water quality treatment, or removed if water quality treatment is no longer required. We have also relocated mature installed FTWs.

Maintain treatment despite fluctuating water levels

In conventional wetlands and reedbeds, water level management is critical to sustain plants. By contrast, floating wetlands will rise and fall with water levels, which enable it to be used in situations where water levels cannot be maintained at the same level.

Recovery of sediment and sludge

The floating wetlands can be moved around the waterbody, so sludge and sediment could be removed without causing damage to infrastructure. This may be a key advantage when treating waters high in suspended solids which would limit the life of a conventional treatment wetland or reedbed.

Control the growth of algae

Floating wetlands are effective in reducing the excessive growth of phytoplankton and filamentous algae, caused by high levels of phosphorus entering the waterbody. It is generally thought that the reason for this reduction is due to the combined effects of shading and temperature reduction.

Provide a food source and refuge for fish

Floating wetlands are used in recreational fishing ponds to support a biologically diverse range of autotrophic and heterotophic organisms fixed on the root systems.

Enhance landscape amenity

The floating wetland can be sized and designed as an amenity feature. They can be designed as an island, to surround a degraded island or around the margin of waterbodies that are too deep or steep to establish a conventional, shallow wetland.

Installation of a low maintenance treatment system

No extra-ordinary measures are required for maintenance when compared with other water treatment measures. The main requirement for maintenance will be removal of weeds or rubbish.

Recent Floating Wetlands Projects


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