Clogging and Heavy Metal Removal Efficiency of Stormwater Infiltration Systems for Stormwater Management
(2004 – 2008)
Sebastien Le Coustumer
Note: This PhD thesis was undertaken as part of an international collaboration between the French University INSA de Lyon (OTHU, Field Observatory for Urban Water Management) and Monash University (FAWB – Facility for Advancing Water Biofiltration). It is the result of 3 years and 9 months of work, time equally spent in Australia and France. Whilst the original thesis manuscript is written in French, the abstract is translated, and 5 out of 6 journal publications were published in English.
Whilst infiltration techniques such as infiltration basins or biofiltration systems have been widely implemented in the last few years as a source control technique to manage stormwater runoff in urban areas, there are still substantial questions over their long-term performance and sustainability.
Through both field studies and laboratory experiments, this thesis examined two issues of particular importance: (1) the pollutant removal capabilities of the systems, and (2) the potential for clogging that leads to a decrease in hydraulic conductivity and system performance.
The pollutant removal efficiency of the systems focussed on heavy metals, because of their high concentration in stormwater and their impact on receiving water bodies. High concentrations of copper, lead and zinc were measured at the surface of all of the field systems. A marked reduction in concentration with depth was measured, with background concentration reached at a depth of 300mm, suggesting that there is very little risk of heavy metals leaching to groundwater from stormwater filtration systems. Importantly, despites change in the systems (reduction of hydraulic conductivity, plants growth, diminution of soil’s pH…) no reduction of performance was measured over time.
The reduction of hydraulic conductivity ranged from a factor of two to three for the different sites / laboratory tests. The results clearly showed that systems subject to high sediment and hydraulic loading were more prone to clogging. One of the significant findings is that vegetation, when carefully selected, may reduce clogging and restore initial hydraulic performance, through its role in creating macropores.
These results will improve infiltration system guidelines and will help to generalise the implementation and the use of infiltration technologies as a robust technique to manage and treat stormwater runoff.
Le Coustumer S.M. (2008) Clogging and Heavy Metal Removal Efficiency of Stormwater Infiltration Systems for Stormwater Management – Colmatage et rétention des éléments traces métalliques dans les systèmes d’infiltration des eaux pluviales. PhD Thesis, Department of Civil Engineering, Monash University – INSA de Lyon, France. PDF (7.9MB)
Other publications (link)