INFILTRON package for assessing infiltration & filtration functions of urban soils in stormwater management – INFILTRON

The global methodology of the project relies on four interrelated axes: axis 1) development of INFILTRON-exp device for infiltrating water and injecting nano-tracers, axis 2) development of the nano-tracers for mimicking emerging nano-pollutants and pathogens, axis 3) validation of the engineering nano-tracers under laboratory conditions, and axis 4) development of INFILTRON-mod for modelling and treating the data acquired with INFILTRON-exp.
In more detail, axis 1 aims at the development of an infiltrometer with a large size for activating macropore and fracture networks and for infiltrating water and injecting nano-tracers. This device distinguishes from regular devices by its large size and the concomitant monitoring of water infiltration and nano-tracer transfer. The nano-tracers are designed (axis 2) to behave in the environment as model pollutants and bacteria present in stormwater and to be detectable in the laboratory using Magnetic Resonance Imaging (MRI) and on the field using Ground Penetrating Radar (GPR). These nano-tracers are also tested using laboratory column experiments for several types of porous media. Their transfers are compared to those of the investigated bacteria and model pollutants. The nano-tracers will also be tested in the field. Lastly, the modeling is conducted across scales accounting for several degrees of complexity. The modeling at small scales (column and field devices) is performed to identify and characterize the mechanisms responsible for flow and pollutant transfer. Then parametrization and related simplification of the mechanistic models will lead to a macroscopic model for modeling and treating experimental data acquired with the INFILTRON-exp device.

After two years of the INFILTRON project, all the axes have been addressed with significant progress. The following main results arise:
• Development of INFILTRON-exp large ring infiltrometer for the monitoring of water infiltration and the injection of the tracer in the soils. First tests on the field.
• Development of a set of automated and connected small ring infiltrometers for the simultaneous monitoring of water infiltration into the matrix only
• Design and production of the first set of nanoparticles (nano-tracers of the SPION type - Super Paramagnetic Iron Oxides Nanoparticles).
• Development of a specific in-lab device for the tests of the detectability of nano-tracers with the GPR
• Characterization of mineral nano-pollutants and bacteria in real stormwater samples.
• Design of leaching column experiments with macropored porous media for the investigation of nano-tracer transfer in the laboratory. Validation of the setup with commercial nano-tracers.
• Development of mathematical methods and algorithms for the treatment of the signal for water infiltration data (small and large ring infiltrometers).
• Development of the architecture of INFILTRON-mod for the modeling of the experimental data acquired with INFILTRON-exp device.
Ongoing activities are conducted to provide significant progress for all the tasks.

The following perspectives are envisioned for the completion of the project:
• Improvement of INFILTRON-exp device and optimization of the protocol for the injection of the nano-tracers
• Development of other methods for tracking preferential flows (use of fluids with different rheology properties, including non-newtonian fluids)
• Improvement of the detectability of nano-tracers using GPR
• Validation of the nano-tracers using laboratory columns by comparing their transfer with the targeted nano-pollutants. It is planned to work on the reactivity of nano-tracers and their sizes, given that one sole size has been tested so far.
• Finalize the characterization of stormwater regarding nano-pollutants. The bacteria have already been characterized in stormwater.
• Development of modeling at several scales and the link between complex modeling approaches at small scales and more macroscopic models at larger scales.
• Dissemination and valorization of the results.

1. Lassabatere, L., Di Prima, S., Bouarafa, S., Lovino, M., Bagarello, V., Angulo-Jaramillo, R., 2019. BEST-2K Method for Characterizing Dual-Permeability Unsaturated Soils with Ponded and Tension Infiltrometers. Vadose Zone Journal 18, 180124.
2. Bouarafa, S., Lassabatere, L., Lipeme Kouyi, G., Angulo-Jaramillo, R., 2019. Hydrodynamic Characterization of Sustainable Urban Drainage Systems (SuDS) by Using Beerkan Infiltration Experiments. Water, 11 (4), 660.
3. Colin, Y., L. Marjolet, R. Marti, R. Bouchali, F. Vautrin, V. Rodriguez-Nava, D. Blaha, T. Winiarski, J. Voisin, F. Mermillod-Blondin, B. Cournoyer. 2019. Incidence of bacterial groups originating from urban runoffs and artificial infiltration systems on aquifer microbiome community structures. Submitted to Water Research.
4. Di Prima, S., Castellini, M., Abou Najm, M.R., Stewart, R.D., Angulo-Jaramillo, R., Winiarski, T., Lassabatere, L., 2019. Experimental assessment of a new comprehensive model for single ring infiltration data. Journal of Hydrology 573, 937–951. doi.org/10.1016/j.jhydrol.2019.03.077

Plusieurs articles de conférence et rapports en supplément.

Urbanization completely disturbs the water cycle, through the creation of impervious surfaces which reduce infiltration and massively increase stormwater runoff volumes. With urbanization set to increase, and uncertainty due to climate change impacts, there is a critical and internationally recognized need to increase the permeability of the urban landscape and to restore a more natural water cycle in cities. However, due to the contamination of urban surfaces, runoff water may carry high concentrations of pollutants. Where infiltration is used to mitigate stormwater runoff, this can result in the transfer of pollutants into urban soils and the water table, which poses the question of pollution of groundwater and surface water. Urban soils should be checked regarding their capability to infiltrate water, at the same time as promoting the filtration of pollutants. INFILTRON therefore aims to develop a large ring infiltrometer for evaluating the infiltration & filtration functions of urban soils. The innovative aspects of the project are (i) the development of tracers specifically for emerging pollutants and bacteria, detectable using non-invasive techniques (MRI – magnetic Resonance Imaging for laboratory experiments and GPR – Ground Penetrating radar for field), (ii) the size of the device for addressing the appropriate spatial scales for accounting for preferential flow and mass transfer that often establish in urban soils as the result of their strong heterogeneity, (iii) the development of a methodology and a functional "all-in-one" tool combining the experimental device and a numerical model specifically designed to be user-friendly for use by practitioners and engineers. This tool will allow a quantitative measurement of the infiltration & filtration functions of urban soils, which is of great interest to managers of infiltration systems / bio-retention ponds, but also of polluted sites and soils. To disseminate the results as widely as possible, the consortium will produce an industry-focused guide for the use of the INFILTRON package (with supporting technical reports), build a specific website for online data access, design a commercial strategy for INFILTRON package dissemination and will organize a technical workshop, open to stakeholders, consultant engineers, managers of infiltration systems and polluted sites, and regional and local authorities. The consortium will also ensure an active publication policy in peer-reviewed journals, including high rank open source scientific publications and participation in major international conferences (e.g. EGU, NOVATECH, AGU, WCSS), along with a specific conference on the topic of preferential flow and mass transfer in urban soils to be hosted by EGU and on the management of stormwater and runoff water in the city to be hosted by NOVATECH. In summary, the consortium will deliver knowledge, design guidance and practical tools to support the market for stormwater eco-technologies for the mitigation of urbanization impacts on the water cycle, soil and groundwater quality. The consortium will benefit from committed partnerships with an internationally well-recognized Australian research team in the field of stormwater infiltration systems and with an internationally well recognized Italian team in the field of infiltration measurements.