Colloidal particles such as microorganisms, minerals and engineered nanoparticles are ubiquitous in subsurface environment. The knowledge about transport behavior of colloidal particles would be critical for prediction of groundwater contamination in managed aquifer recharge (MAR) sites. The main objective of this study was understanding the effect of MS2 on graphene oxide nanoparticle (GONP) transport and retention in porous media.
Design and methodology
The GONPs transport experiments were conducted in saturated limestone aquifer columns in either the presence or absence of MS2 at low (10 mM NaCl) or high (5 mM CaCl2) ionic strength. Furthermore, some other experiments were conducted in biofilm-conditioned columns with treated wastewater to determine the effect of biofilm on retention of GONPs. The breakthrough curves and retention profiles of GONPs were also obtained to identify the dominant mechanisms effecting GONP retention.
Original data and results
The results showed there was no difference in the transport and retention behavior of GONPs in the presence of MS2 at high ionic strength. At 5 mM CaCl2, the retention of GONPs in the presence and absence of MS2 were 7.09 and 5.96 %, respectively. However, in low ionic strength conditions, enhanced transport and decreased retention of GONPs was observed. The co-presence of MS2 led to an increasing percentage of the eluted mass of GONPs from 45.0% in the absence of MS2 to 60.08 % when MS2 was present. Moreover, the pre-conditioning of limestone with biofilm enhanced GONPs retention, while no significant changes in GONPs transport were observed affected by MS2 co-presence.
Ultimately, it is obvious that at low ionic strength which is similar to that of typical aquifers, the risk of groundwater contamination by engineered nanoparticles co-transported with virus is higher than at high ionic strength. Furthermore, biofilm acts as a bio-filter against discharging engineered nanoparticles into the groundwater.