Floating wetlands

Floating wetlands — Key considerations

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

What makes an effective floating wetland?

• The establishment of an extensive root mass is very important for the performance of the system[8].
• Desired root length is typically 0.4-0.8 m[4]. Some roots grow up to 1.5m[5].
• A minimum water depth of 0.8–1.5 m should be maintained to prevent the macrophyte roots from attaching to the benthic substrate[4].
• Anchoring should allow the floating mat to rise and fall with changing water levels to avoid the macrophyte vegetation being submerged or roots attaching to benthic substrate[4].
• Floating wetlands require permanent water to maintain the vegetation.
• Plant selection should incorporate local native species.
• The floating wetland should be situated so that it treats most incoming flows and does not promote short-circuiting.
• Detention time - Sufficient detention time is required for sediment settling and microbiological action. Higher hydraulic residence times (HRT) increase nitrogen removal[1][8][11]. One study reports HRT of 5-7 days showing higher rates of removal compared to a 3 day HRT[1].

Suitability and limitations

Trials have been conducted in South East Queensland and other countries[2][6][7][8][11][12][10].

Pollutant removal rates vary depending on the site and the type of water treated. Other factors such as loading rates, pollutant concentration, sediment size, and temperature will also affect removal effectiveness[3][8][9].

Floating treatment systems are suitable for ponds, lakes and slow-flowing waters. While they can tolerate fluctuation in flows and water depth, this variability reduces treatment effectiveness[6][9].

Treatment processes

References

1. ^ a b Boonsong, K & Chansiri, M (2008), 'Domestic Wastewater Treatment using Vetiver Grass Cultivated with Floating Platform Technique', Assumption University Journal of Technology, vol. 12, no. 2, pp. 73-80.
2. ^ Borne, K (2012), Floating Treatment Wetland To Treat Stormwater Runoff, vol. 2, Department of Civil & Environmental Engineering, University of Auckland, Silverdale Pond, New Zealand.
3. ^ Headley, TR & Tanner, CC (2006), Application of Floating Wetlands for Enhanced Stormwater Treatment: A Review, vol. 324, Auckland Regional Council, Auckland.
4. ^ a b c Headley, TR & Tanner, CC (1 November 2008), 'Floating Treatment Wetlands: an Innovative Option for Stormwater Quality Applications', 11th International Conference on Wetland Systems for Water Pollution Control.
5. ^ Hornbuckle, A (July 2016), 'Floating Treatment Wetlands', Presentation to the Treatment Systems in Coastal Catchments Forum.
6. ^ a b 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.
7. ^ Park, J, Headley, T, Sukias, J & Tanner, C (2008), Attenuation of Nutrients in Eutrophic Lake Water Using Floating Treatment Wetlands – Mesocosm Trials, vol. NIWA Client Report: HAM2008-111, National Institute of Water And Atmospheric Research Ltd, Hamilton.
8. ^ a b c d 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.
9. ^ a b Tanner, CC & Headley, TR (2011), 'Components of floating emergent macrophyte treatment wetlands influencing removal of stormwater pollutants', Ecological Engineering, vol. 37, pp. 474-486.
10. ^ Walker, C, Tondera, K & Lucke, T (22 September 2017), 'Stormwater Treatment Evaluation of a Constructed Floating Wetland after Two Years Operation in an Urban Catchment', Sustainability. [online], vol. 9, no. 10, p. 1687. Available at: http://www.mdpi.com/2071-1050/9/10/1687 [Accessed 20 April 2022].
11. ^ a b Wanielista, MP, Chang, NB, Chopra, M, Xuan, ZM, Islam, K & Marimon, Z (2012), Floating Wetland Systems for Nutrient Removal in Stormwater Ponds, vol. SMA 1660 7026, Stormwater Management Academy Stormwater Management Academy Civil, Environmental, and Construction Engineering Department, University of Central Florida, Orlando, FL.
12. ^ Winston, RJ, Hunt, WF, Kennedy, SG, Merriman, LS, Chandler, J & Brown, D (2013), 'Evaluation of floating treatment wetlands as retrofits to existing stormwater retention ponds', Ecological Engineering, vol. 54, pp. 254-265.

Last updated: 10 June 2022