title: Surfactant foam flushing for in situ removal of DNAPLs in shallow soils.
abstract: An innovative process combining surfactant foam and surfactant flushing (SF) for the remediation of a shallow saturated soil contaminated with a dense non-aqueous phase liquid (DNAPL) residual was investigated at bench-scale. First, foam was formed by injecting DHSS surfactant and nitrogen in alternation in soil (SAG process) at constant pressure. The effect of pressure gradients set point (≤90kPam-1) on DNAPL recovery was investigated. Foam front mobilized DNAPL with a piston-like fast propagation (1.8md-1) despite the low pressure gradients. 34-60% of DNAPL residual was extracted with low surfactant consumption (<0.4kgkg-1DNAPL removed). Then, a solubilizing agent (Tergitol) was injected into soil, previously treated with foam, to improve the DNAPL removal. It led a removal up to 95% whereas only 2 porous volume (PV) of solubilizing solution were injected. As a comparison, when the solubilizing agent was injected without foam pre-treatment, 40 PV would have been required to lead the removal up to 90%. Considering the overall treatment, the technology we developed requires 10-times less surfactant than the traditional SF technology. This technology is especially suitable for very shallow soils where injection pressure has to be kept at a low level to avoid soil heaving.
authors.affiliation: Université de Franche-Comté - Besançon, Institut UTINAM - UMR CNRS 6213, 16 route de Gray, F-25030 Besançon cedex, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Maire
authors.affiliation: Université de Franche-Comté - Besançon, Institut UTINAM - UMR CNRS 6213, 16 route de Gray, F-25030 Besançon cedex, France. Electronic address: nicolas.fatin-rouge@univ-fcomte.fr.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Fatin-Rouge
keywords: DNAPL recovery; Foam; Groundwater; Heavy chlorinated compounds; In situ