Performance monitoring of constructed floating wetlands: Treating stormwater runoff during the construction phase of an urban residential development

Peter F Schwammberger; Katharina Tondera; Tom R Headley; Karine E Borne; Catherine M Yule; Neil W Tindale

doi:10.1016/j.scitotenv.2022.161107

Performance monitoring of constructed floating wetlands: Treating stormwater runoff during the construction phase of an urban residential development

Sci Total Environ. 2023 Mar 20:865:161107. doi: 10.1016/j.scitotenv.2022.161107. Epub 2022 Dec 29.

Authors

Peter F Schwammberger¹, Katharina Tondera², Tom R Headley³, Karine E Borne⁴, Catherine M Yule⁵, Neil W Tindale⁵

Affiliations

¹ School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore DC, QLD 4558, Australia. Electronic address: pschwamm@usc.edu.au.
² INRAE, REVERSAAL, F-69625 Villeurbanne, France.
³ Wetland & Ecological Treatment Systems Ltd, Nelson Bay, NSW 2315, Australia.
⁴ National Institute of Water and Atmospheric Research, Private Bag 99940, Viaduct Harbour, Auckland 1010, New Zealand.
⁵ School of Science, Technology and Engineering, University of the Sunshine Coast, Maroochydore DC, QLD 4558, Australia.

PMID: 36587660
DOI: 10.1016/j.scitotenv.2022.161107

Abstract

In the context of climate change and global trend towards greenfield urbanisation, stormwater and transported pollutants are expected to increase, impairing receiving environments. Constructed floating wetlands (CFWs) can improve stormwater retention pond performance. However, performance data are currently largely restricted to mesocosm experiments, limiting design enhancement fit for field implementation. The present 12-month field study aims to fill part of these gaps by identifying limitations and necessary design improvements for CFWs on a large retention pond/lake. Water in a 2.6-ha lake receiving stormwater from a 45-ha urban area under development in subtropical Queensland, Australia, was recirculated during dry weather periods to minimise algal growth and the risks of blooms. Pollutant removal efficiencies of two full-scale CFWs were evaluated during storm events and dry weather periods as a function of inlet and outlet pollutant concentrations, flow and rainfall. Inlet TSS and TN concentrations in runoff during the construction phase of the development exceeded required water quality limits while TP inflow concentrations were low and often below the detection limit. Median pollutant load reduction efficiencies during storm-events were - 20 % TSS, -2 % TN and 22 % TP at CFW1 and 51 % TSS, 3 % TN and 17 % TP at CFW2, respectively. TSS and TN concentration removal efficiencies at CFW1 were low and highly variable, partly due to low inlet concentrations, high flow velocities and short hydraulic retention times (<1 day). However, CFW1 significantly reduced TSS concentrations during dry weather periods. In contrast, CFW2 significantly reduced TSS concentrations during both storm events and during inter-event periods. This study highlights treatment limitations associated to the operational conditions of CFWs at field-scale not identifiable in a mesocosm-scale study. Further research is necessary to investigate treatment performance of CFWs during the operational phase of the development with higher nutrient levels.

Keywords: Best Management Practices; Floating treatment wetlands; Nature-based solution; Pollutant treatment; Stormwater pollution; Urban runoff; Water sensitive urban design.