Water clean-up buoyed by manufactured floating wetlands

Local councils are installing floating wetlands in order to clean-up lakes and rivers and stormwater basins so that marine and plant life can flourish again.

Common pollutants in water bodies include nitrates and phosphates and organic nutrients caused by materials like fertiliser, oil and grease from machinery, cow and dog manure and dust contained in the run-off from stormwater drains and creeks.

Poor water quality can lead to algae blooms and aquatic weeds and, in worse case scenarios, the water can be robbed of oxygen and nothing can survive in it.

Floating wetlands, which originated in the US and came to Australia around 10 years ago, work by creating micro eco-systems using specially designed platforms planted with a wide variety of wetland plants, which also provide a habitat for bacteria to flourish.

The stable, buoyant non-biodegradable platforms contain a mix of fillers like recycled plastic, foam and shredded carpet as the growing medium and there is a water column where the plants’ roots are suspended.

Although the plants absorb some nutrients and heavy metals most of the pollutants are dealt with by bacteria, which converts the nasties into gas or metabolites and renders them harmless. Bacteria can also bind sediment together so it sinks.

Keith O’Donnell is the Managing Director of FIA Technology, a Victorian company which specialises in floating wetlands, and he has worked with a number of local councils across Australia.

Mr O’Donnell said floating wetlands provided an efficient and durable bio-filtration system that removed nutrients and other pollutants from water bodies.

He said popularity was increasing with local councils because they did a good job of improving water quality, they look good and ratepayers like them.

“There’s a big movement in councils across Australia to put in stormwater harvesting projects. When you harvest it you want it to be as clean as possible. There’s certainly a role for the technology in that movement,” Mr O’Donnell said.

“The ratepayers absolutely love them and councils cop so much flack that if they’ve got something that really appeals to your ratepayers then they consider that money well spent.”

He said there have already been some Australian local government success stories, such as the City of Swan in WA, where the council installed floating wetlands to improve the health of the water basin in north Perth.

“They were struggling with phosphates and offered very expensive solutions,” Mr O’Donnell said.

“They now have floating wetlands in and all the pollutants just dipped like crazy, ten per cent of what they were before over two to three years.”

While floating wetlands are not cheap to install, Mr O’Donnell said they took very little maintenance, they did not need extra equipment and they had minimal operating costs.

“You obviously have the upfront capital costs but there’s no other infrastructure. You just float them on top, you don’t have to pour concrete or anything like that.”

In Mildura, Vic, a Smart Water grant in 2009 paid for a large area of floating wetlands on a lake, which is the area’s stormwater basin.

City of Greater Bendigo is another council (not supplied by FIA Technology) that is investing in floating wetlands to improve the water quality of one of its lakes at Gateway Park. If the trial is successful, the council will consider installing similar wetlands in other Greater Bendigo urban lakes to mitigate stormwater run-off.

Cairns Regional Council have also installed decorative floating wetlands, which they introduced for aesthetic reasons and other councils with floating wetlands include Adelaide City Council, City of Bayswater, WA and Redland City Council, QLD.

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