Removal of nitrate from groundwater by nano-scale zero-valent iron injection pulses in continuous-flow packed soil columns

Injection of zero-valent iron nanoparticles (nZVI) into aquifers has gained increasing attention of researchers for in-situ treatment of NO3--contaminated groundwater. nZVI has proved efficient in chemically reducing NO3- and, according to recent research efforts, in supporting biological denitrification under favoured conditions. Given the scarce research on nZVI pulsed injection in continuous-flow systems, the objective of this study was to evaluate the effect of nZVI pulses on the removal of NO3- from groundwater in packed soil columns and, more particularly, to elucidate whether or not biotic NO3- removal processes were promoted by nZVI. Three identical columns were filled with aquifer soil samples and fed with the same nitrate polluted groundwater but operated under different conditions: (A) with application of nZVI pulses and biocide spiked in groundwater, (B) without application of nZVI pulses and (C) with application of nZVI pulses. Results showed that the application of nZVI (at 30 mg/L and 78 mg/L doses) resulted in an immediate and sharp removal of NO3- (88–94%), accompanied by an increase in pH (from 7.0 to 9.0–10.0), a drop in redox potential (Eh) (from +420 mV to 98%) and the NO3- retention capacity of the nZVI particles (13.2–85.5 mg NO3-/g nZVI).Peer ReviewedPostprint (author's final draft