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Results: Bioretention filter media testing

Results: Bioretention filter media testing


*** about ***

Thousands of bioretention systems have been constructed in Australia since the first systems were built in the very early 2000s. Some have stood the test of time. Others have not. There may be multiple reasons for this. 

Bioretention systems needs plants to function. This is fundamentally what sets them apart from sand filters. Bioretention systems must also contain appropriate filter media to support the plants and facilitate pollutant removal. Systems with inappropriate filter media may not grow plants and may leach pollutants rather than capture them.

Many of the bioretention systems that have not stood the test of time have lost all of their desirable vegetation. I speculate that there are two leading causes of this. Accidental killing of the plants through inappropriate maintenance (e.g. herbicide overspray, misidentification, accidental dispersal of weed seed etc) and death due to inhospitable filter media.

In 2015, I (while working for Healthy Waterways) engaged two final year Griffith University students, Nem Krco and Karan Braich, to investigate the later of these causes. They identified a number of interesting trends. In 2017, I engaged another Griffith University student (Calen Murray) to undertake further investigations.

Filter media was sampled at six sites in early 2015 and again at the same sites in mid 2017. Various filter media parameters were tested, including:

  • organic matter content
  • particle size distribution
  • pH
  • electrical conductivity
  • measures of vegetation 

In late 2017 I returned to five of the sites to collect more media and investigate water holding capacity.

To find out more about the research and it's results, download the data and watch the videos below.

If you want to know more, feel free to contact us.

Jack Mullaly

*** 2015 AND 2017 WORK ***

*** Snapshot ***

6 bioretention systems.

216 samples.

Testing in 2015 and 2017.

Lots of interesting results.


*** Download the 2015 and 2017 data ***

Click the link above to download the data.

*** Late 2017 work ***

*** Snapshot ***

5 bioretention systems.

30 samples.

Investigating water holding capacity and available moisture for plant health.


*** Download the Late 2017 data ***

Click the link above to download the data.

*** The sites ***

Outlook Drive


The WSUD Map ID # B00162

Featured in Ideanthro episodes 50160 and 188



Boambillee Drive

(one of the bioretention basins at Coomera Waters)

The WSUD Map ID # B00043

Featured in Ideanthro episodes 1, 3 and 184.



Zeus Circuit 

(one of the bioretention basins at Coomera Waters)

The WSUD Map ID # B00044

Featured in Ideanthro episode 185.



Pendragon Drive

(one of the bioretention basins at Coomera Waters)

The WSUD Map ID # B00045



Hoyland Street

The WSUD Map ID # B00005

Featured in Ideanthro episodes 106 to 112.



Tilley Road


The WSUD Map ID # B00028

Featured in Ideanthro episodes 4182326, 2845 and 49.