Floating Island for nutrient removal
About this good practice
Constructed floating island is an eco-engineering solution applied for water restoration and creation of natural floating riverbanks in the cities. Wetland plants are supported by artificial buoyant mats. Nutrient rich water is treated by bacteria attached on the plant roots performing nitrification/denitrification (release of N2 gas), biological breakdown and detoxification. Roots and installation itself enhance particle retention. As a result increased water clarity, reduced algae and cyanobacteria growth as well as reduced nutrient levels could be achieved. The increased habitat and food availability further enhances aquatic food chain and partly restores deteriorated biodiversity in turbid waters. In addition, floating wetlands provide habitats for aquatic and terrestrial fauna (insects, birds) as well as number of cultural aesthetic services.
Resources needed
The installation of an island was in May 2020. The maximum growth was reached in ~July. For an island there is a need a sum of ~10 000 euros, which they have within LiveLagoons project funds (about the project: http://www.balticlagoons.net/livelagoons/).
Evidence of success
The nutrient removal capacity of the island is the sum of nutrients accumulated in the aerial biomass (stems and leaves) and underwater biomass (roots), nitrogen loss by microbial activity, phosphorus uptake by microorganisms and sedimentation. Our estimates of plant biomass and nutrient content in the harvest from the 28 m2 island installed in the Curonian Lagoon equals to 103g of N and 5g of P/m2. Therefore, the annual removal of 28 m2 could be 2870g of N and 140g of P.
Potential for learning or transfer
The main factor in the implementation of good practice is the goodwill of the local government to allocate the resources and to carry out this type of treatment plant maintenance at a later stage. The natural plant filter reduces water blooms and clarifies the water body. In addition, a new space is created for the local flora and fauna. Constructed floating islands are increasingly applied for water restoration and creation of natural floating riverbanks. Greener coastal cities contribute to nutrient removal capacity. Artificial buoyant mats support wetland plants. Bacteria attached on the plant roots performing nitrification/denitrification (release of N2 gas), biological breakdown and detoxification treat nutrient rich water. Roots and installation itself enhance particle retention. As a result increased water clarity, reduced algae and cyanobacteria growth as well as reduced nutrient levels could be achieved.
Further information
Website
Good practice owner
You can contact the good practice owner below for more detailed information.
Klaipeda University