Treating Urban Runoff in Australia Using Floating Wetlands

Christopher WALKER1,2, Darren DRAPPER3, Peter NICHOLS2, Kristin REEVES2, and Terry LUCKE2

1Covey Associates Pty Ltd, 124 Duporth Avenue, Maroochydore, Queensland, 4558 Australia2University of the Sunshine Coast, School of Science and Engineering, 90 Sippy Downs

Drive, Sippy Downs, Queensland 4556 Australia3SPEL Environmental, 96 Cobalt St, Carole Park, Queensland 4300

*Corresponding author’s e-mail: chrisw@covey.com.au

ABSTRACTOverviewIt is widely accepted that Australia's increasing levels of urbanisation will result in increased

stormwater runoff and higher levels of pollution. Water sensitive urban design (WSUD) has

risen in prominence as a consequence of the need to address stormwater issues in relation to

urban development. Integrating urban planning and management practices to protect and

conserve the urban water cycle and ensuring that urban developments are sensitive to natural

hydrological and ecological processes are key principles of WSUD. Constructed wetlands and

bioretention systems have been used previously to replicate and enhance the environmental

benefits and ecosystem services provided by natural buffer systems (e.g. natural wetlands).

This paper describes the performance evaluation of an innovative solution to treating

stormwater in the form of an artificial floating wetland. Floating Wetlands Treatment (FWT)

systems have the potential to provide greater stormwater pollution removal rates per unit area

compared to constructed wetlands and other treatment systems. A research study is underway

at Bribie Island in Southeast Queensland (SEQ) to assess the ability of FWT to treat

stormwater. The experimental design of the study incorporates an array of impermeable baffles

which directs all of the catchment stormwater runoff through the FWT system, eliminating

short circuiting and allowing the efficacy of the system to be assessed in variable flow

conditions. This approach has successfully eliminated the short circuiting issues experienced in

previous studies. This approach makes the FWT an on-line treatment system and enables real-

time water sampling to be undertaken to accurately evaluate the FWT pollution removal

performance.

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ObjectivesThe objectives of this research project include:

⦁ To evaluate the overall pollution removal performance of the SPEL Waterclean FWT

system in treating;

⦁ Total nitrogen (TN)

⦁ Total phosphorus (TP)

⦁ Total suspended solids (TSS)

⦁ To determine the treatment performance in various flow conditions;

⦁ To evaluate the pollution removal performance of Carex appressa plants by analysing

sediment mass collected on plant roots and by analysing root length and mass.

⦁ To establish the optimal ratio of contributing catchment area to treatment area to

enable FWT systems to be sized effectively.

MethodThe sampling and handling procedures were in accordance with the Queensland Department of

Environment and Heritage Protection (DEHP)’s Monitoring and Sampling Manual (2009) and

the National Association of Testing Authorities (NATA) requirements. All analyses are

completed in the NATA accredited laboratory at the USC. The FWT system was installed in

June 2013 with instrumentation for data collection installed in February 2014, allowing for an

8 months plant establishment timeframe. It was originally proposed to install the data collection

instruments in November, however, site activity delayed this. To date, two storm events have

been captured, however, ongoing issues with the flow meter have caused problems with

triggering the sampling protocols in rain events. In two events, samples were collected based on

time, rather than flow, as the flow meter was not registering flow even though flow was

evident. As part of a troubleshooting exercise, water from the outlet of Lake 1 was pumped

into the inlet of Lake 1, directed at the floating wetlands. This served to test the flow meter and

simulate an event. A number of samples were collected during this exercise, with samples

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collected on 5 and 3 minute intervals at flow rates of 100L/s and 200L/s, respectively. These

flow rates equated to approximately half of a Q3-month event (100L/s) and a Q3-month event

(200L/s) for the contributing catchment. While it is recognized that the existing results are

collected on the basis of time, rather than flow rate, the flow rates in the pumping test were

known.

Results

The preliminary results to date show substantial promise, particularly as the FWT system

represents 0.1% of the contributing catchment. In an event collect on 14 May 2014, the FWT

demonstrated pollutant concentration reductions from the inlet to the outlet of 56.1% for TSS,

27.1% for TN and 83.33% for TP. The results from the pump test sample collection found that

the average pollutant concentration reductions from the inlet to the outlet of the system in a

100L/s flow rate were 96% for TSS, 41% for TN and 91% for TP. In the 200L/s flow rate, the

average pollutant concentration reductions from the FWT inlet to outlet were 68% for TSS,

13% for TN and 63% for TP.

ConclusionsThe interim study results suggest that the SPEL Waterclean FWT system trialled in this study

may offer an innovative approach to urban stormwater treatment. The modular nature of the

device allows for flexibility in design and construction, and easy maintenance. Providing study

results continue in a positive trend, this new system may establish itself to be a valuable

addition to the diversity in approaches available to land developers, and ultimately local

governments, suitable for at-source stormwater treatment.

KEYWORDSFloating wetlands; stormwater pollution; urban catchment runoff; nutrient removal

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INTRODUCTIONUrban development in Australia has increased substantially and it is widely accepted that as

urban development continues, stormwater runoff volumes and pollutant loads will increase in

tandem. Water Sensitive Urban Design (WSUD) has become a prominent approach to

managing and mitigating the effects of urban runoff. The key principles of WSUD are to

integrate urban planning and management practices to protect and conserve the urban water

cycle and ensuring that urban developments are sensitive to natural hydrological and ecological

processes. Constructed wetland, bioretention and other vegetated/detention systems (e.g.

vegetated swales and sediment basins) have been the principal approaches used to treat

stormwater runoff, though in recent years, proprietary devices (e.g. gross pollutant traps and

filter cartridges) have also been utilised to treat stormwater runoff. This paper describes a

research study that is underway in SEQ to assess the potential for floating wetland treatment

(FWT) systems to be a new means of treating urban runoff in Australia

FWT systems have been used in aquatic enhancement projects for over 20 years internationally

to treat effluent and to provide and/or improve water habitats (Burgess and Hirons, 1992;

Kerr-Upal et al., 2000; Headley and Tanner, 2008; Sukias et al., 2011). A number of early

FWTs provided habitat for aquatic waterfowl (Kerr-Upal et al., 2000), while other projects

focused on the removal of total suspended solids (TSS) pollutants from mine tailings (Burgess

and Hirons, 1992; Smith and Kalin, 2000).

FWT systems simulate the naturally occurring water treatment processes that take place in

natural floating wetland islands. Natural floating wetlands develop when large quantities of

floating organic matter, sediment, and wetland plants combine to form a buoyant island. This

provides an ideal surface for rooted macrophyte species plants to grow. Artificial FWTs are

supported by a floating medium, typically comprised of woven plastic, matting, or fibreglass,

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where plant roots grow directly into the water column, similar to a hydroponic system. As the

plant roots grow through the floating medium and into the water below, they provide an

extensive surface area for biofilm to grow on the root hairs (Figure 1). Biofilm coverage is an

essential requirement for the removal of nutrients from stormwater (Borne et al., 2013;

Winston et al., 2013), as it helps remove nutrients (particularly nitrogen) from the water

through nitrification/denitrification processes, and is ultimately taken up by the macrophytes.

Phosphorus can be retained through binding processes that occur within the biofilm (e.g.

adsorption) and uptake of orthophosphates is achieved by vascular macrophyte species.

Figure 1 - Floating wetland schematic (Image courtesy of SPEL Waterclean)

Research in the United States (Stewart et al., 2008) and New Zealand (Sukias et al., 2011) has

found that FWT can provide an effective, low cost and low maintenance means of treating

domestic and agricultural wastewater. Sukias et al. (2011) found that FWT were capable of

reducing TSS by up to 81%, total nitrogen (TN) by up to 34%, and total phosphorus (TP) by

up to 19%. However, the number of studies on the performance of FWT in treating urban

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stormwater runoff is limited.

There is a distinct lack of knowledge regarding the ability of FWT systems to improve urban

stormwater runoff quality. Although a number of recent studies have looked at using FWT to

treat runoff from urban, non-residential settings (e.g. major roadways and parking lots) (Borne

et al., 2013; Winston et al., 2013), there have been limited studies on using FWT systems to

treat TSS and nutrient loads associated with urban residential stormwater. Filling this

knowledge gap is critical to expanding options when it comes to urban stormwater treatment

and advancing the principles of WSUD. In Australia, stormwater treatment systems can often

take up substantial areas of valuable development land. This is compounded when

detention/retention systems are required. Stormwater treatment systems are not credited within

infrastructure agreements in Australia (Leinster et al., 2009; Leinster et al., 2010), so the area

required for stormwater treatment is essentially removed from the development footprint, thus

reducing the potential economic yield per hectare.

Many stormwater treatment systems, such as bioretention basins and constructed wetlands,

function best when ‘offline’, with extended detentions depths minimised and high flows

bypassing such systems (Water by Design, 2012a; Water by Design, 2012b). This often

requires detention/retention basins to be separate from treatment systems. FWT has the

potential to substantially reduce the footprint required for stormwater treatment compared to

other systems for two main reasons. Firstly, the hydroponic nature of root development allows

more contact between roots and polluted stormwater which provides a greater surface area for

biofilm growth. FWT systems therefore have the potential to provide significantly greater

stormwater pollution removal rates per unit area compared to constructed wetlands. Secondly,

FWTs are not affected by variations in extended detention depths, as the floating matrix rises

with the water level during storm events. This factor allows detention and treatment systems to

be combined on a large scale with minimal impact to treatment efficacy, and subject to system

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design, with virtually no impact on flood storage capacity. This could substantially reduce the

stormwater treatment footprint on residential development, thereby increasing lot yields per

hectare.

This paper describes a study that is currently underway to assess the ability of a large-scale

FWT to treat stormwater runoff from an existing urban development in SEQ. The experimental

design of the study incorporates an array of impermeable baffles which directs all of the

catchment stormwater runoff through the FWT system. This approach has successfully

eliminated the short circuiting issues experienced in previous studies. This approach makes the

FWT an on-line treatment system and enables real-time water sampling to be undertaken to

accurately evaluate the FWT pollution removal performance to be assessed in variable flow

conditions

METHODSSite DescriptionThe FWT monitoring site is located in an existing lake, Lake 1, (Figure 2) within the Bribie

Lakes development at Bongaree, Bribie Island, Queensland, Australia. The development site is

zoned residential and has an area of 42.3ha, which is being developed into a 600+ residential

lot development. An existing, developed urban catchment area of approximately 10 ha also

discharges into the study lake (Figure 2). The time of concentration for the external catchment

draining to the FWT is estimated to be 15 minutes. The 1-year ARI, 15 minute intensity

frequency duration (IFD) value (I1y,15min) at Bongaree is 77 mm/h (BOM, 2013). Subject to the

outcomes of the current research, the FWT will eventually treat runoff from the site prior to it

discharging into a larger, central lake of the development.

The study FWTs are constructed using four layers of recycled plastic fibre, with inserts of

marine grade foam to provide buoyancy. This matrix is then covered with a coconut jute mat

and the plants (Carex appressa) are installed in circular holes at a density of approximately

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three plants per square metre. Each individual module of FWT is approximately 9.2m2 and

there are a total of 11 modules, yielding a total FWT surface area of 101.2m2. Six plants

contained within metal planter boxes have been placed through the middle of the FWT. These

will be removed from the FWT at different times during the study to assess root growth and

allow for harvesting to determine biomass and pollutant retention.

The experimental design also incorporates an array of impermeable baffles (Figure 2) which

directs all of the stormwater runoff through the floating wetlands, eliminating the short-

circuiting problems experienced in previous studies. The impermeable baffles allow the

treatment performance of the FWT to be assessed under a range of flow conditions. Three

autosamplers have been installed at the inlet, middle and outlet of the floating wetland

(Samplers 1, 2, and 3, respectively). The autosamplers are triggered by flow and

rainfall.

Figure 2 - Floating Wetland Treatment System study site.

Sampling Protocol: Minimum Requirements

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In order to assess the efficacy of the FWT in treating urban runoff, the protocols and

parameters shown in Table 1 will be used to ensure qualifying stormwater flow events are

captured and standardised, and that repeatable sampling methods and procedures are utilised.

This method has been developed in conjunction with the study partners, University of the

Sunshine Coast (USC), Covey Associates and SPEL Environmental, based on the protocol

development methodology prescribed by the United States Environmental Protection Agency’s

(US EPA) Stormwater BMP Monitoring Manual (US BMP Database, 2009) and Auckland

Regional Council’s Proprietary Device Evaluation Protocol for Stormwater Quality

Treatment Devices (Wong et al., 2012).

Table 1 - Sampling protocolRequirements Criteria Details

Minimum Qualifying Events 15Min.2mm Rainfall Depth within 30 min.Min. 15 min. Storm Duration Min. 6 h

Antecedent Dry Period

Hydrograph sampled Minimum of the first 60% of event hydrograph

Min. Composite sample 1.6L Min. 8 sample aliquots

Three Water Sample locations (Refer Figure 2)

1. 300mm upstream of FWT2. Centre of FWT modules

3. 300mm downstream of FWT

Hose to extend 200mm below the base of the FWT matrix.

Sample method ISCO GLS Auto-samplers To be collected within 2 hours of storm end.

Flow-weighted samples Every 19,200L Sontek IQ Plus at FWT outlet. Automatic logging. Calibrate annually

Plant growth analysis Measure stem height & root lengths Record and Photograph every 3 months.

Rainfall monitoring Pluviometer (0.2mm increments) Automatic logging. Calibrate annually

Flow measurement Sontek IQ Plus at FWT outlet. Automatic logging. Calibrate annually

pH & EC Handheld probe Calibrated to manufacturer’s specificationsTotal Suspended Solids (TSS)

& Total Dissolved Solids (TDS)

APHA (2005) 2540 C & D HDPE or glass bottles, Cool to 4oC, max. hold time 24 hours

Total Nitrogen & TKN APHA (2005) 4500 N HDPE or glass bottles, Cool to 4oC, max. hold time 24 hours

Ammonia N APHA (2005) 4500 NH3 HDPE or glass bottles, Cool to 4oC, max. hold time 24 hours

NOx APHA (2005) 4500 NO3 HDPE or glass bottles, Cool to 4oC, max. hold time 24 hours

Total Phosphorous & Orthophosphate APHA (2005) 4500 P HDPE or glass bottles, Cool to 4oC, max.

hold time 24 hoursParticle Size Distribution

(PSD)Laser Diffraction (Malvern

Mastersizer 3000)Continuously stirred, without chemical

dispersion or sonicationLaboratory Certification NATA registered for all parameters

except PSD --

QA/QCRandom duplicates and blanks in

accordance with the relevant Australian Standard.

--

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Sampling Protocol and HandlingThe sampling procedure and handling are in accordance with the Queensland Department of

Environment and Heritage Protection (DEHP)’s Monitoring and Sampling Manual (2009) and

the National Association of Testing Authorities (NATA) requirements. All analyses are

completed in the NATA accredited laboratory, Analytical Services, at USC.

Data AnalysisTo analyse the data sets, the parameters listed in Table 2 will be used.

Table 2 - Data analysis methodRequirements Criteria Details

Percent Removal based on mg/L data table

Arithmetic mean, and median comparison of influent vs effluent

concentrations for:

⦁ Sampler 1 and 3

⦁ Sampler 2 and 3

Identify % removal for each event AND removal efficiency based on mean and median concentrations

across all qualifying events.

Statistical Evaluation of Data Sets Box and Whisker plots with Outlier identification

Use recognised methods for identifying and excluding outliers

Statistical Evaluation of Significance Compare raw and log-transformed data sets for influent and effluent

samples at 90% confidence interval

CURRENT STATE OF RESEARCH STUDYThe research study site was intended to be made operational in November 2013, as the plants

had rapidly reached maturity, however, some earthworks construction was still required on the

banks of Lake 1 (e.g. re-profiling of the banks, removal of tree stumps) and existing drainage

lines on site needed to be re-directed to ensure that no runoff from the existing developed

catchment bypassed Lake 1. These works were delayed by wet weather and other civil

construction activity occurring on site. Due to these delays, the site became fully operational in

February 2014.

There have been ongoing issues in the event monitoring, specifically in relation to the flow

meter (Sontek IQ Plus). To date, the flow meter has failed to record flows in four events, one of

which was a Q100 event. Due to the issues with the flow meter, two events in May and July

were captured on time-based intervals (10 minutes between samples) rather than by flow-

weighted samples as intended.

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A pump flow test was also conducted 3 July 2014, where water was pumped from the Lake 1

outlet, approximately 25m from the FWT outlet, into the inlet of the wetland at a distance of

approximately 3m. Water samples were collected at 3 and 5 minute intervals by all three

autosamplers, at flow rates of 100L/s (6 samples collected) and 200L/s (17 samples collected)

respectively. These samples were tested individually, rather than combined to form a

composite, as would typically be done. It was considered that this would provide a useful

assessment of the pollutant concentration reduction in a simulated event. A rhodamine dye test

was also conducted at a flow rate of 200L/s to estimate the hydraulic residence time (HRT).

While this was a simulated flow event, it was conducted in the field using real stormwater

runoff detained within Lake 1, rather than artificial stormwater.

PRELIMINARY RESULTSThere are two sets of results that have been assessed to date, one from an event sampled on 14

May 2014 and the other from the pump tests conducted on 3 July 2014.

Results – 14 May 2014

On May 14, approximately 11mm of rain fell over a period of 2.5 hours, which was recorded

by the site pluviometer. As the flow meter was not recording flow or triggering the automated

samplers, it was decided to collect samples on a time-based interval (10 mins), rather than

flow-based. The minimum 8 samples aliquots per autosampler were collected over an 80

minute period and were transported to USC for processing and storage. The results from the

analysis are provided in Table 3.

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Table 3 - Composite sample results from 14/5/14Sampler (n=8) TSS (mg/L) TN (mg/L) TP (mg/L)

S1 (Sampler 1 - Inlet) 41 1.18 0.03S2 (Sampler 2 - Middle) 12 0.56 0.005S3 (Sampler 3 - Outlet) 18 0.86 0.005

MUSIC urban residential range (mg/L) 61.7 - 372 1.07 – 3.09 0.162 – 0.708

Based upon the results outlined in Table 3, the FWT demonstrated pollutant concentration

reductions from the inlet to the outlet of 56.1% for TSS, 27.1% for TN and 83.33% for TP.

Results – 3 July 2015 (Pump Test)The pump test was conducted to assess three separate, but linked, issues. First, to test the flow

meter in controlled conditions,; second, to utilise a rhodamine dye to determine the hydraulic

residence time through the FWT in a simulated Q3-MONTH event (200L/s flow rate); and third, to

utilise the dye to determine if there were any breaches in the impermeable baffles that may be

affecting flow readings at the Sontek IQ Plus. While the above issues were being tested,

samples were collected by all three autosamplers at 10 minute intervals, with 6 samples

collected at a flow rate of 100L/s and 17 samples collected at a flow rate of 200L/s. The

average pollutant concentrations for the 100L/s and 200L/s flow rates are summarised in Table

4.

Table 4 - Sample results from 3/7/14 (Pump test)Flow Rate (L/s) Sampler Average Concentrations

TSS (mg/L) TN (mg/L) TP (mg/L)100

(n-6)S1 302.67 1.68 0.11

(n-6) S2 137.83 1.16 0.06S3 9.33 0.93 0.01

200(n=17)

S1 79.35 1.09 0.04(n=17) S2 86.53 1.07 0.04

S3 23.47 0.94 0.01MUSIC urban residential

range (mg/L) 61.7 - 372 1.07 – 3.09 0.162 – 0.708

Based upon the results in Table 4, the average pollutant concentration reductions from the inlet

to the outlet of the system in a 100L/s flow rate were 96% for TSS, 41% for TN and 91% for

TP. In a 200L/s flow rate, the average pollutant concentration reductions from the FWT inlet

to outlet were 68% for TSS, 13% for TN and 63% for TP.

The rhodamine dye test was conducted in a simulated flow rate of 200L/s, which equates to a

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Q3MONTH event. The dye was observed exiting the FWT system after approximately 8 minutes,

giving an estimated HRT of 8 minutes, for the test configuration, in the frequent flow event.

During the dye test, it was observed that there were some minor repairs required to the

impermeable baffle, as trace amounts of dye were noticed escaping at the top edge of the FWT

system. Whilst this will not adversely affect the function of the FWT, it may influence the

accuracy of the flow measurement.

DISCUSSION OF PRELIMINARY RESULTSThe preliminary results suggest that the FWT system has the potential to effectively remove

pollutant loads from stormwater runoff. The results also show that the efficacy of the FWT

appears to be inversely proportional to flowrate similar to existing stormwater treatment

measures (i.e. the greater the flowrate, the less effective the treatment). However, the results

outlined in this paper are preliminary only and should be considered in this context. Two

sample sets cannot be considered to be representative of stormwater treatment efficacy,

particularly as these two sample sets were collected on time-based intervals, rather than flow,

and one of the sample sets was a simulated event.

Although simulated, the pump test provided a valuable insight into the effectiveness of the

FWT in treating stormwater over time and under variable flow conditions. Figure 3 highlights

the differences in water clarity observed between some of the water samples taken during the

pump test. The left hand bottles in Figure 3 contain the FTW inlet water samples collected

from Sampler 1. The water in the middle bottles were collected from Sampler 2. The water in

the right hand bottles shown in Figure 3 were from Sampler 3 located at the outlet of the FTW

(Figure 2). It is clear from Figure 3 that the clarity of the water samples improved as it

travelled further along the floating wetland.

The study is ongoing and we are continuing to optimise the testing methodology and fine-tune

13

the equipment operational issues. The initial results are very encouraging and we will update

our research findings as the research progresses. However, based upon the results of similar

studies by Borne et al. (2013) and Winston et al. (2013), it is anticipated that the study results

will continue to show an improvement in the quality of the urban stormwater runoff achieved

by the FWT.

14

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Figure 3 – Samples taken during pump test on 3/7/14. Left hand bottles were from Sampler 1 (FTW Inlet), Middle Bottles were from Sampler 2, Right hand bottles were from Sampler 3 (FTW Outlet)

LESSONS LEARNED This research study was originally planned to commence in November 2013. However, there

were a number of unforeseen events which delayed the start of the project. The study was

established within an active construction site with its own deadlines and constraints, many of

which impacted the installation timeframes for the FWT. Bulk earthworks construction was

ongoing during the trial installation and the batters of the study lake needed to be re-profiled for

future landscaping. These works would prevent the installation of the FWT and were in turn

delayed by sporadic rainfall. It was difficult to anticipate these constraints. Therefore with any

research study in a similar setting, it is critical to be flexible with start times and research

budget. Timing of outputs, and similar, should not be reliant on a firm commencement date. As

a conservative estimate, it should be assumed that any studies timeframe can be at least

doubled. These delays can be due to sporadic weather events, on-site construction activities, or

availability of relevant personnel.

Equipment faults are often common in storm event sampling and this study has been no

exception. The research team is currently investigating alternate means to record flow data and

have this approach be a trigger point for sampling to commence. The current approach in

which a Sontek IQ Plus triggers the sampling once a 0.03m/s velocity is recorded, in tandem

with a minimum of 2mm of rainfall in 30 minutes, with a 19,500L flow-weighting, is not

working as the flow meter is failing to record any flow velocity. This has led to at least three

rainfall events being missed and having to rely on time-based sampling rather than flow-based

intervals. An alternate approach is required where flow velocities through the FWT can still be

profiled, so this can be correlated to pollutant reduction performance.

Effective communication and collaboration between industry and research partners is also

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critical. While there were delays to commencing the research study, all parties involved were in

regular communication so all stakeholders were quickly aware of said delays and able to adapt

as required. This also proved to be extremely valuable in refining the research method, as all

parties were able to effectively build an approach that would yield meaningful and valuable

outcomes to all stakeholders. In addition to effective communication, it is also advisable to ask

for as much help in the design from recognised experts as possible. While refining this research

study, we found a number of internationally recognised experts were generally quite willing to

share their experiences and offer valuable advice. Input and constructive criticism from outside

parties should be welcomed to realise a useful and robust outcome. This can help the study to

adapt to unforeseen circumstances or approaches/methods that may have been overlooked.

It was critical to design this research study to be as flexible as possible. Presently, there is no

standard approach or method for trialling proprietary stormwater treatment products within

Australia. The lack of a standardised method can create difficulties, as it is not possible to

cater for every eventuality. Therefore, it is critical that the approach taken be adaptable. As

there is little data on the efficacy of floating wetlands in treating urban stormwater, this study

design has made allowance for additional floating wetland modules to be installed in the system

at a later date if required. This will allow the results to provide a better understanding of

floating wetland area requirements in a variety of catchments.

CONCLUSIONThe paper presents initial findings of an investigation into using floating wetlands to treat

urban stormwater runoff in Australia. Preliminary test results of a real rainfall event showed

that the FWT system reduced average pollutant concentrations from the inlet to the outlet of

56.1% for TSS, 27.1% for TN and 83.33% for TP. Simulated pump testing results

demonstrated average pollutant concentration reductions from the inlet to the outlet of 96% for

TSS, 41% for TN and 91% for TP at a flow rate of 100L/s. During a test using a flow rate of

17

200L/s, the average pollutant concentration reductions from the FWT inlet to outlet were found

to be 68% for TSS, 13% for TN and 63% for TP. The study results suggest that floating

wetlands may offer an innovative and cost-effective approach to stormwater treatment.

The study is ongoing and we are continuing to optimise the testing methodology and fine-tune

the equipment operational issues. The initial results are very encouraging and we will update

our research findings as the research progresses. However, based upon the results of similar

studies it is anticipated that the study results will continue to show an improvement in the

quality of the urban stormwater runoff achieved by the FWT. Once the initial teething issues

are taken care of, the results of this research study will be of significant interest for developers

and local government authorities both in Australia and internationally.

ACKNOWLEDGEMENTSThe authors of this paper would like to acknowledge the developer for the site, Mr Ty Wardner

of Wardner Developments, for his encouragement, support and use of the development land for

this research project. We would also like to acknowledge Moreton Bay Regional Council for

their interest and support of this project. Last but not least, we would especially like to thanks

Mr Darryl Sullivan and Mr Michael Nielsen from USC Analytical Services for all their help

and support.

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Presenter’s BIO

Chris Walker moved to Australia in 2002 from New York to study at the University of the

Sunshine Coast, completing a Bachelors of Environmental Science (Marine Specialty) and

followed with an Honours Degree at Queensland University of Technology. The Honours

degree was the start of his research into stormwater and water sensitive urban design. This

research continued in a PhD study at the University of the Sunshine Coast. Chris has been

employed at Covey Associates since 2007 as the Senior Environmental Scientist and is also the

Environmental Manager for the company. Chris’s role sees him involved in a wide range of

development projects, both in Australia and abroad.

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Burgess, N.D. and Hirons, G.J.M. (1992).Creation and management of artificial nesting sites for wetland birds. Journal of Environmental Management, 34 (4), 285-295

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