Foams for in-situ treatments of vadose zones contaminated by hydrocarbons – MOUSTIC

Measurements in 1 and 2D cells have allowed to forecast the effect of soils’ characteristics over a large range on foam mobility and injectability. A new delivery method has allowed to prevent any nasty interaction between surfactant and amendment : first, foam is injected into the polluted zone. Then, the solution of amendment is slowly injected through the same opening at low pressure; it propagates with a piston-like effect through the foam using the liquid films, pushing away the surfactant solution. This method was set-up carefully from lab to field-scales. Biostimulation and bioaugmentation have been carried out in order to couple chemical oxidation with biodegradation. Tools for the modeling of foam propagation and (bio)chemical reactions have been developed using TMVOC and PHREEQC software.

Prediction of foam rheology on the basis of soil’s characteristics. Selection of the injection method on the basis of soil permeability.
Compared to usual methods, the developed one allows:
- A larger and more isotropic distribution of amendments in anisotropic medium,
- A large increase of the contact time in unsaturated zone,
- A better advanced mineralization of pollutants,
- A better control of exothermic reactions that prevent up-flow of toxic gases.
Innovative methodologies for the selection of micro-organisms for a combination of chemical and biological treatment strategy have been developed and the results are very encouraging.
The monitoring of the treatment using real-time imaging by electric resisitivity tomography is helpful.
New contract (I-SITE BFC) about the monitoring of treatments using geophysical methods.

Besides the development of more robust and more predictable new remediation fluids, the project has shown the interest to be able to monitor in real time actions in the underground through cheap, easily usable but accurate imaging methods.

Method development :
- Bouzid et al. 2017. Compatibility of surfactants with activated-persulfate... JECE, 5, 6098.
- Bouzid et al. 2018. Enhanced remedial reagents delivery... Chemosph., 210, 977.
- Bouzid et al. 2019. Comparative assessment of a foam-based oxidative treatment... Chemosph., 233, 667
- Bouzid et al. 2019. Comparative assessment of a foam-based method for ISCO ... JECE, 7, doi.org/10.1016/j.jece.2019.103346

Prediction of foam transport in soils :
- Maire et al. 2018. Shear-thinning fluids for gravity and anisotropy mitigation... Chemosph., 197, 661.

This project deals with ‘Sustainable Methods and Technologies for Remediation’. It is an inter-sectoral partnership involving environmental biologists, chemists, physico-chemists and field practitioners. It aims at overcoming current limits in terms of efficiency, cost, sustainability and feasibility for the in situ regeneration of unsaturated zones contaminated with petroleum hydrocarbons through the development and the assessment of surfactant foams. It aims at:
- using the promoting properties of these foams to solve problems for contaminants and reactants transport throughout heterogeneous or low accessibility zones (soils with high permeability contrasts or located below building foundations and inside underground buildings) to deliver more homogeneously and within the overall space some active matter (oxidants, micro-organisms, nutrients) in order to ensure an effective contaminant degradation;
- modelling properties for matter transport and transfer of those complex fluids, from soil pore to field scale and the numerical simulation of degradation kinetics;
- testing this technology at the pilot-scale in a contaminated site and to perform a benefits/costs/risks assessment compared to established remediation approaches.