Floating wetlands

Floating wetlands

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• Overview
• Key considerations
• Planning and design
• Construction and operation
• Links and references

Other name/s

Floating wetland, Floating treatment wetland

Description

Floating wetlands consist of a suspended matrix planted with wetland plants. This facilitates microbiological and plant processing of nutrients.

Floating wetlands work by encouraging settling and biological processing of suspended sediments, particulate and dissolved nutrients and pollutants and also by directing the water through the suspended root mass[1].

The potential mechanisms that provide treatment in floating wetlands are known but the precise contributions are uncertain[1][3][4][6][7][5]. Plant roots are believed to play a major role in treatment processes within floating wetland systems as the water passes directly through the extensive root system hanging beneath the floating mat. The roots release enzymes, develop extensive biofilms and promote flocculation of suspended matter, at the surface of the submerged plant organs[1].

Other processes that may be important include plant uptake of nutrients and metals if harvested[3][4][6][7], enhancement of anoxic conditions in the water column beneath the floating mat, which promote microbial processes such as denitrification, and promotion of settling and binding of contaminants in the sediment pool[1].

Floating wetlands can be used in existing water bodies or waterways or in a purpose built pond. As they can be used in existing water bodies, they are particularly suited to locations where there is limited space for a constructed treatment wetland or similarly large treatment system.

Highly variable flows are likely to reduce the effectiveness of the treatment[2].

The actual cost-effectiveness of a floating wetland will depend on the specific site conditions and project objectives and needs to be considered relative to other treatment systems or management intervention options. Refer to cost considerations for more information.

Services and benefits:

• Water treatment (sediment, nutrients and pesticides)
• Habitat
• Amenity

References

1. ^ a b c d Headley, TR & Tanner, CC (2006), Application of Floating Wetlands for Enhanced Stormwater Treatment: A Review, vol. 324, Auckland Regional Council, Auckland.
2. ^ Nichols, P, Lucke, T, Drapper, D & Walker, C (2016), 'Performance Evaluation of a Floating Treatment Wetland in an Urban Catchment', Water, vol. 8, p. 244.
3. ^ a b Olguín, EJ, Sánchez-Galván, G, Melo, FJ, Hernández, VJ & González-Portela, RE (2017), 'Long-term assessment at field scale of Floating Treatment Wetlands for improvement of water quality and provision of ecosystem services in a eutrophic urban pond', Science of the Total Environment, vol. 584-585, pp. 561-571.
4. ^ a b Pavlineri, N, Skoulikidis, NT & Tsihrintzis, VA (2017), 'Constructed Floating Wetlands: A review of research, design, operation and management aspects, and data meta-analysis', Chemical Engineering Journal, vol. 308, pp. 1120-1132.
5. ^ Sharma, R, Vymazal, J & Malaviya, P (July 2021), 'Application of floating treatment wetlands for stormwater runoff: A critical review of the recent developments with emphasis on heavy metals and nutrient removal', Science of The Total Environment. [online], vol. 777, p. 146044. Available at: https://linkinghub.elsevier.com/retrieve/pii/S0048969721011116 [Accessed 20 April 2022].
6. ^ a b Tondera, K, Blecken, GT, Chazarenc, F, Lucke, T & Tanner, CC (2018), 'Chapter 2 Treatment Techniques for Variable Flows', in K Tondera & et al. (eds), Ecotechnologies for the Treatment of Variable Stormwater and Wastewater Flows, Springer.
7. ^ a b Wang, CY, Sample, DJ, Day, SD & Grizzard, TJ (2015), 'Floating treatment wetland nutrient removal through vegetation harvest and observations from a field study', Ecological Engineering, vol. 78, pp. 15-26.

Last updated: 19 April 2022