MICROSCALE AND NANOSCALE ZEROVALENT IRON PARTICLES FOR GROUNDWATER REMEDIATION: FROM LABORATORY TESTS TO FIELD APPLICATIONS

Abstract

The use of zerovalent iron micro and nano­particles (MZVI and NZVI) is one of the most promis­ing technologies for groundwater remediation. The par­ticles, ranging is size between few tens of nanomaters (NZVI) up to few microns or tens of microns (MZVI), are dispersed in colloidal solutions and directly inject­ed into the subsurface, thus allowing the treatment of the contaminated plume or source area. In the present work, carried out in the framework of the EU project AQUAREHAB (FP7 - G. A. Nr. 226565), laboratory and field tests for MZVI transport in porous media are presented. The particles were dispersed in guar gum solutions at several polymer concentrations, showing a pseudo-plastic rheological behaviour which guarantees the colloidal stability of the suspensions. Based on the experimental results, a new software was developed for the simulation of coupled particle transport, filtra­tion, and clogging of the porous medium, in 1D and ra­dial geometry (MNMs, freely available at www.polito. it/groundwater/software/MNMs). Finally, two pilot in­jections are presented for guar gum-based dispersions on MZVI delivered under two different flow regimes: one injection was performed using a direct push equip­ment at high pressure, leading to the controlled genera­tion of preferential flow paths, the other one involved a low pressure injection through a screened well, in a flow regime at the threshold between permeation and preferential flow.