Sustainable soils for enhanced biofilter water quality performance

The aim of the project is to identify biofilter substrate (=soil) mixes that meet three potentially-conflicting criteria: they should be predominantly locally-sourced; they should meet the growing requirements for the vegetation they support; and they should play an active role in filtering out key stormwater pollutants through adsorption processes, particularly heavy metals.

The substrates used in vegetated SuDS (green roofs, rain gardens, biofilters receiving road runoff etc.) are typically imported, highly-engineered mixes, optimised to meet plant survival and water quality treatment objectives. However, the carbon footprint associated with removing native urban top soils and replacing them with these new mixes is high, and can potentially be reduced by making better use of in-situ material. The research challenge is to minimise the use of soil improvers/amendments whilst still meeting the needs of the plants and attaining high levels of pollutant removal. The PhD project will uniquely focus on real urban soils, specifically a typical garden soil and two soil types that have been ‘compromised’ as a result of previous land-use pressures. Laboratory column tests will be used to characterise the soils and to identify how the non-amended soils perform with respect to hydrological, plant support and runoff quality (removal of heavy metals). A key aspect is to characterise the removal mechanisms in connection with core soil properties to develop generalised knowledge that can be used for choosing appropriate filter substrates for a broad range of applications. A range of substrate amendments will be proposed and tested, with a focus on low carbon footprint (e.g. novel recycled) materials.

If the project is funded we will liaise with University Estates to place trial planter boxes on campus, providing a visual opportunity to promote the TWENTY65 project to a broader audience.


Primary supervisor

Dr Virginia Stovin, Civil and Structural Engineering,


TWENTY65 Theme links

Tailoring treatment using demand-based technologies

The City as a Water Resource