Restoring groundwater quality on a former chemical site

Project description 

Despite the removal of the Cl-VOCs facilities in the 1990s, mainly Trichloroethylene, other activities remained on site near Dijon (France). Various assessment phases showed the presence of a large Cl-VOCs plume impacting the groundwater quality in private wells as well as the neighbouring surface waters. Thus, the client requested a remediation strategy that will not disturb the site’s on-going activities and which will restore groundwater quality.

TAUW performed a remediation plan for the site aquifer starting with a soil and groundwater sampling phase in order to assess the extent of the plume and to collect matrices to perform lab testing on different remediation alternatives such as chemical oxidation / reduction and biostimulation by the addition of various substrates. TAUW selected the best suited technique, i.e. biostimulation by injection of a complex organic substrate, designed and installed the field pilot, supervised the injection of substrate and performed monitoring and data interpretation. It is TAUW’s aim to propose a final and detailed design for remediation of the overall site.

The remediation technique involves the use of new technologies: 1) the enhancement of anaerobic biodegradation of Cl-VOCs from toxic species, i.e. Trichloroethylene, to the non-toxic daughter specie Ethene, 2) the injection of substrate using a rotating tool, and 3) the use of DNA sequencing technology and qPCR to monitor bacterial community and functional changes with time.

How did the cooperation with the client go? 

INJECTIS performed substrate injection. TERSUS provided the substrate formulation and materials.

HYDREKA performed labs testing, provided insights in the monitoring strategy and the interpretation of biomolecular data, and performed qPCR analysis. ECOLE CENTRALE DE LYON (Metagenomic lab, University of Lyon) performed DNA sequencing and provided insights into the interpretation of biomolecular data.

TAUW was in charge of design, monitoring, supervision of work and project management. TAUW contracted the other work to partners with the client’s agreement. The client appreciated TAUW’s ability for organising the project and cooperation as well as for assembling technical expertise to achieve success. TAUW’s role as project manager was of great importance due to the fact that client contact people were not on site.

The results

The project provided a detailed design for the future remediation works. The field pilot demonstrated the performance of biodegradation processes of Cl-VOCs in the aquifer. It enabled further definition of remediation metrics such as the achievable residual concentrations, the duration and length size of remedial actions, the monitoring program.

This biostimulation remediation technique is a sustainable natural-based solution,making use of soil’s intrinsic function to degrade pollutants. Substrate component injected can be partly derived or recycled from agricultural & food production wastes (molasses, starch, vegetable oil, etc.) and no mobile harmful chemical species are being injected in the aquifer. Both indicators highlight benefits when compared to other solutions such as in-situ oxidation, for example. The technique was also very flexible and had a low footprint on the site since all installations were made of underground injection points and mobile injection systems.