Lake Taihu experienced its worst ever algal bloom at the height of summer 2004, pushing researchers to search for new solutions. They decided to try a new technology, floating wetlands, that are designed to remove nutrients that fuel algal blooms. An ambitious aspect of the project was to launch the world’s largest aquaponics system, over 4 acres in size, using new technologies in combination with old world bamboo that is used in traditional Chinese building. Experiments growing rice on fish ponds provided a foundation for scaling up to lakes and larger water bodies for earth and water repair. The AquaBiofilter team was invited to participate in the project in regards to project design and evaluation.
Floating island and wetlands technology is part of the new wave of products that biomimics nature, using biomaterials and plant biology to remediate and restore nature’s balance with non-toxic and sustainable processes. The concept was adapted from natural wetlands that process nutrients and pollutants with soil and plants. Mature wetland ecosystems often develop self-sustaining floating wetlands that mop up pollutants. The benefit of floating wetlands over sediment rooted wetlands, is that they rise and fall with the water level, which means plants don’t die off and don’t release nutrients back into the water, which on its own is a compelling reason to utilize floating wetlands in dams, lakes and ponds. When also considering its excellent habitat provision and ecosystem restoration aspects, it is increasingly being utilized by land and water managers. The problem with many dams and lakes is that they experience variable water depths throughout the seasons, and expeience poor water quality or ecosystem dysfunction such as algal blooms, fish kills and aquatic weed overgrowth in summer. Most lakes and urban wetlands are highly modified or recently built, with polluted inflows, making it necessary for management intervention. Floating wetlands take the best of what nature has developed naturally to tackle pollutants that run-off from farming, urban and industrial areas. Floating wetlands are up to x200 times more efficient than conventional constructed wetlands, and don’t suffer the die off problems and nutrient release that free floating aquatic plants or conventional wetlands experience. For these reasons, floating wetlands are often the best management approach for open water bodies including lakes, ponds, aquaculture systems, waste water lagoons and even estuaries with marine waters. Often the only end of pipe alternative is emptying and dredging an entire lake or pond, which economically and ecologically is very problematic.
The floating wetlands provide fish habitat in the root zone, protection from predatory water birds, spawning protection for frogs and eels, and nesting sites for endangered water birds. In some circumstances such as aquaculture ponds or lakes, they are ideal for the growth of food crops, which brings another yield to fish farmers, and prevents building up of nutrients, with plant roots uptaking excess nitrogen and phosphorus, assisting with denitrification underneath the raft. Floating wetlands and islands are multi-functional design elements that stack uses vertically and horizontally, preventing and eliminating algal blooms and fish kills. If farms dedicated just 1% of their land to water quality improvement ponds with floating wetlands, at the landscape point where nutrient laden farm runoff leaves the property, modeling demonstrates its possible to eliminate algal blooms and associated fish kills, preventing inshore marine dead zones. Tom’s vision is for nearly every farm to have it’s own water quality improvement ponds with floating wetlands of some kind. Lake cultures of lake Titicaca use woven reeds to construct floating reedbeds and provide a natural prototype for floating wetland ecosystems. Modern construction methods and materials provide long lasting, durable and non-toxic materials to maintain treatment effectiveness over time.Lake Taihu has extensive aquaculture industry that suffered mass die offs and threatened the future of the industry. The research team chose plant species that would beautify the lake, and also provide rapid root growth which serve as habitat for native fish to spawn and provide refuge from the toxic algal bloom.
Three months after project implementation, the water cleared completely with no visible algae and water transparency improved by 250%. The plants had soaked up the excess nutrients, cutting off the nutrient supply that algal blooms require to grow. Roots exert a strong biofilm that captures nutrients and pollutants, and de-nitrifies the water allowing natural balance to be restored.
Some 2000 square foot of Aqua Biofilter provides a root biofilm surface area of 1 acre, due to the vastly increased surface area of root zones compared to plant leaf and stalk zones, delivering incredible rates of nutrient and pollutant removal, at zero cost once installed. The lack of operational expenses makes the technology attractive to local governments and water managers who need quick results at an affordable price. The benefits of floating wetlands go beyond improving water quality, by also serving as habitat for diverse water fauna, enabling the kickstarting of the restoration of aquatic ecosystems.
AquaBiofilter CEO Tom Duncan has done some interesting floating wetlands projects including growing rice on floating reedbeds, growing herbs on aquaculture ponds. growing samphire and marine salt marsh on estuaries in Sydney Harbor, and installing habitat islands on Local Government owned lakes for bird watchers and recreational fishers. The project below is massive in scale, with large floating wetlands with Chinese characters written with plants, in urban developments on waterways in mega cities to promote water treatment and conservation for urban waterways. The project also incorporated a biodigester to improve water quality, recycle biomass and produce local heat and power. The retrofit of mega cities with floating wetlands and biodigesters is one way to rapidly reduce end of pipe impacts on urban waterways, and increase the livability of a world that is rapidly urbanizing with dramatic impacts on waterway and receiving marine waters health.
For further information on small scale systems, visit Aquarium Garden DIY Aquaponics Kit