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| Titel |
Simulation of the injection of colloidal suspensions for the remediation of contaminated aquifer systems |
| VerfasserIn |
Tiziana Tosco, Francesca Gastone, Rajandrea Sethi |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094824
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| Publikation (Nr.) |
 EGU/EGU2014-10256.pdf |
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| Zusammenfassung |
| Concentrated suspensions of microscale and nanoscale zerovalent iron particles (MZVI and
NZVI) have been studied in recent years for the remediation of contaminated aquifers. The
suspensions are injected into the subsurface to generate a reactive zone, and consequently the
prediction of the particles distribution during the injection is a key aspect in the design of a
field-scale injection.
Colloidal dispersions of MZVI and NZVI are not stable in pure water, and shear thinning,
environmentally friendly fluids (guar gum and xanthan gum solutions) were found to be
effective in improving colloidal stability, thus greatly improving handling and injectability
(1 - 3). Shear thinning fluids exhibit high viscosity in static conditions, improving the
colloidal stability, and lower viscosity at high flow rates enabling the injection at limited
pressures.
Shear thinning fluids exhibit high viscosity in static conditions, improving the
colloidal stability, and lower viscosity at high flow rates enabling the injection at
limited pressures. In this work, co-funded by European Union project AQUAREHAB
(FP7 - Grant Agreement Nr. 226565), laboratory and pilot field tests for MZVI
injection in saturated porous media are reported. MZVI was dispersed in guar gum
solutions, and the transport behaviour under several polymer concentrations and
injection rates was assessed in column tests (4). Based on the experimental results, a
modelling approach is proposed to simulate the transport in porous media of nanoscale
iron slurries, implemented in E-MNM1D (www.polito.it/groundwater/software).
Colloid transport mechanisms are controlled by particle-collector and particle-particle
interactions, usually modelled by a non equilibrium kinetic model accounting for
deposition and release processes. The key aspects included in the E-MNM1D are
clogging phenomena (i.e. reduction of porosity and permeability due to particles
deposition), and the rheological properties of the carrier fluid (in this project, guar gum
solution). The influence of colloid transport on porosity, permeability, and fluid
viscosity is explicitly lumped into the model and the shear-thinning nature of the
iron slurries is described by a modified Darcy law generalized for non Newtonian
fluids.
Since during the injection in wells the velocity field is not constant over the distance,
E-MNM1D was modified in order to account for variable colloidal transport coefficients on
flow rate thus allowing the estimation of the radius of influence during a full scale
intervention. The flow and transport of MZVI slurries is solved in a radial domain for the
simulation of field-scale injection, incorporating the abovementioned relevant mechanisms.
The governing equations and model implementation are presented and discussed, along with
examples of injection simulations.
References
1. Tiraferri, A.; Sethi, R. Enhanced transport of zerovalent iron nanoparticles in saturated
porous media by guar gum. J Nanopart Res 2009, 11(3), 635-645.
2. Tiraferri, A.; Chen, K.L.; Sethi, R.; Elimelech, M. Reduced aggregation and
sedimentation of zero-valent iron nanoparticles in the presence of guar gum. Journal of
Colloid and Interface Science 2008, 324(1-2), 71-79.
3. Dalla Vecchia, E.; Luna, M.; Sethi, R. Transport in Porous Media of Highly
Concentrated Iron Micro- and Nanoparticles in the Presence of Xanthan Gum. Environmental
Science & Technology 2009, 43(23), 8942-8947.
4. Tosco, T.; Gastone, F.; Sethi, R. Guar gum solutions for improved delivery of iron
particles in porous media (Part 2): iron transport tests and modelling in radial geometry.
Journal of Contaminant Hydrology (submitted). |
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