Removal of copper and zinc from ground water by granular zero-valent iron: A dynamic freeze–thaw permeable reactive barrier laboratory experiment
Introduction
Zero-valent iron (ZVI) based permeable reactive barriers (PRBs) have been constructed at contaminated sites since the early 1990s (O'Hannesin and Gillham, 1998, Warner et al., 2005). The success of some of these early projects has resulted in the installation of more than 200 PRBs worldwide with 60% of these using ZVI as the reactive media (Henderson and Demond, 2007). As the performance of these barriers continues to be discussed and designs improved, PRBs are becoming an increasingly accepted method for ground water treatment in temperate climates. A major milestone in this process was the publication of the 15-year assessment of the Elizabeth City PRB in North Carolina (Wilkin et al., 2014). This assessment showed that the PRB outlived the chromium plume and continues to treat trichloroethene (TCE) contaminated ground water. However, while these significant investigations have been conducted in temperate climates, research towards the application of PRBs in cold environments has been lacking (Camenzuli et al., 2014).
As operating PRBs consist of water flowing through a permeable material, studies of the impacts of freeze–thaw cycling on PRB media are crucial for the understanding and continued development of this in situ remediation technique for application in areas of freezing ground. The cold-climate PRB longevity concerns of reduced hydraulic conductivity and reactivity are similar to that in temperate climates (see 2.1 Hydraulic conductivity, 2.2 Iron reactivity). Additional challenges due to the climate consist of reduced kinetic rates at low temperatures (Statham et al., under review, Statham et al., in review) and physical particle–solution interactions which can result in particle disintegration and rearrangement during freeze–thaw cycling (see Section 2.3). Previous laboratory freeze–thaw assessments of potential PRB media have consisted of batch testing (Gore et al., 2006b, Li et al., 2002) or measured diesel loaded media permeability (Gore et al., 2006a). If reasonable particle stability during freeze–thaw cycling can be obtained, ZVI may be a favourable additional media for inclusion in PRBs for cold climate applications (Mumford et al., 2013).
This study presents a laboratory based freeze–thaw assessment of contaminant removal using granular ZVI. PRBs are simulated using Darcy boxes and a laboratory incubator. Solution flow changes are monitored at laboratory temperature after 0, 21 and 42 freeze–thaw cycles using both reactive and conservative tracer solutions.
Section snippets
Theory and background
A PRB acts to intercept and treat a migrating contaminant plume. The long term performance and reliability of a PRB is vital in order to provide cost effective treatment. Debate persists concerning the importance of the various mechanisms for the removal of aqueous contaminants by ZVI (Noubactep, 2008, Tratnyek and Salter, 2010). The main contaminant metal removal mechanisms by ZVI are adsorption, precipitation, cementation, co-precipitation and biological processes (Davis et al., 2007, Wilkin
Method
The impact of freeze–thaw cycling on the performance of ZVI mixed with an inert granular media was assessed using duplicated Darcy boxes subjected to 42 freeze–thaw cycles. Measuring static water levels and conducting conservative tracer tests allowed the assessment of bed hydraulics. Reaction kinetics were assessed using step increases in contaminant (copper and zinc) concentrations. All measurements were conducted before, midway and at the end of freeze–thaw cycling. Deconstruction
Heat transfer
Average temperature profiles at different depths during a sample thawing and freezing cycle are presented in Fig. 2. As shown, the seven day cycle was sufficient to ensure the media reached both the high and low temperature set points. The middle of the box was the last region to thaw (supported by individual temperature sensor data), indicating that the thickness of the insulation was insufficient for a comparison with solar induced one dimensional heat transfer. However, there is a greater
Conclusion
As a PRB consists of wet porous media, an understanding of potentially detrimental interactions during freeze–thaw cycling is vital to the design of PRB based remediation systems for application in cold climates. The results for a laboratory based freeze–thaw assessment of granular ZVI media were presented.
Freeze–thaw induced changes to simulated PRBs, contained within Darcy boxes, subjected to 0, 21 and 42 freeze–thaw cycles were assessed using the flow of both reactive and conservative
Acknowledgments
The authors wish to thank Laura Gordon and Damian Gore for XRD analysis and interpretation, Roger Curtain for his assistance to complete the SEM and EDS analyses and Andrew Lee for the photography work. The financial support of the Australian Antarctic Science Grant 4029 is gratefully acknowledged. T.S. also acknowledges the support of an Australian Postgraduate Award. The Particulate Fluid Processing Centre (PFPC) and the Advanced Microscopy Facility at the University of Melbourne are both
References (57)
The modelling of the freezing process in fine-grained porous media: application to the frost heave estimation
Cold Reg. Sci. Technol.
(2009)- et al.
The formation of ice from the infiltration of water into a frozen coarse grained soil
Cold Reg. Sci. Technol.
(2007) - et al.
Predictions of long-term performance of granular iron permeable reactive barriers: field-scale evaluation
J. Contam. Hydrol.
(2011) - et al.
Laboratory study on sequenced permeable reactive barrier remediation for landfill leachate-contaminated groundwater
J. Hazard. Mater.
(2009) - et al.
Preferential flow path development and its influence on long-term PRB performance: column study
J. Contam. Hydrol.
(2003) - et al.
Modeling porosity reductions caused by mineral fouling in continuous-wall permeable reactive barriers
J. Contam. Hydrol.
(2006) - et al.
New insights into the role of zero-valent iron surface oxidation layers in persulfate oxidation of dibutyl phthalate solutions
Chem. Eng. J.
(2014) - et al.
Effective removal of AB24 dye by nano/micro-size zero-valent iron
Sep. Purif. Technol.
(2008) - et al.
Mineral precipitation and porosity losses in granular iron columns
J. Hazard. Mater.
(1999) - et al.
Heavy metals removal and hydraulic performance in zero-valent iron/pumice permeable reactive barriers
J. Environ. Manag.
(2010)
Design, installation and preliminary testing of a permeable reactive barrier for diesel fuel remediation at Casey Station, Antarctica
Cold Reg. Sci. Technol.
Hydraulic performance of a permeable reactive barrier at Casey Station, Antarctic
Chemosphere
Reduction of azo dyes with zero-valent iron
Water Res.
An in situ study of the role of surface films on granular iron in the permeable iron wall technology
J. Contam. Hydrol.
Identification, quantification and localization of secondary minerals in mixed Fe0 fixed bed reactors
Chem. Eng. J.
Longevity of granular iron in groundwater treatment processes: changes in solute transport properties over time
J. Contam. Hydrol.
Laboratory evaluation of zero-valent iron to treat water impacted by acid mine drainage
Chemosphere
Fifteen-year assessment of a permeable reactive barrier for treatment of chromate and trichloroethylene in groundwater
Sci. Total Environ.
A natural zeolite permeable reactive barrier to treat heavy-metal contaminated waters in Antarctica: kinetic and fixed-bed studies
Process Saf. Environ. Prot.
Dynamics of fluids in porous media
On-site and in situ remediation technologies applicable to metal-contaminated sites in Antarctica and the Arctic: a review
Polar Res.
Modeling the permeability loss of metallic iron water filtration systems
CLEAN Soil Air Water
Discussion of frost heaving
Frost susceptibility of soil review of index tests
U.S. Dept. of Transportation, Federal Highway Administration
The iron oxides: structure, properties, reactions, occurrences and uses
Effects of increasing acidity on metal(loid) bioprecipitation in groundwater: column studies
Environ. Sci. Technol.
Development of the granular permeable reactive barrier technology (good science or good fortune)
Hydraulics of granular Permeable Reactive Barrier (PRB) materials under freeze–thaw
Cited by (19)
A review on the use of permeable reactive barriers as an effective technique for groundwater remediation
2023, Groundwater for Sustainable DevelopmentSelenium-rich mine effluents treatment using zero-valent iron: Mechanism and removal efficiency in the cold climate of Québec, Canada
2021, Environmental AdvancesCitation Excerpt :This was explained by the control of copper and zinc removal by film transfer and the diffusion process which becomes slower at lower temperatures. However, ZVI in a permeable reactive barrier (PRB) is reported to be efficient for heavy metal treatment in cold climate, although challenges related to longevity, reduced hydraulic conductivity and reactivity, reduced kinetic rates and particle disintegration and rearrangement were reported during freeze–thaw cycling (Statham et al., 2015). Again, PRB enables higher thus effective solid: liquid ratio compared to batch testing.
Performance of passive systems for mine drainage treatment at low temperature and high salinity: A review
2019, Minerals EngineeringCitation Excerpt :In cold-climate conditions, freeze/thaw cycles can modify the hydraulic retention time (HRT) in PRB systems using ZVI. Some studies have shown a HRT decrease of 15–18% after only the first freeze/thaw cycle, remaining constant thereafter (Statham et al., 2015). This decrease of HRT can be associated with a reduction in the porous medium porosity.
Evaluation of applicability of filling materials in permeable reactive barrier (PRB) system to remediate groundwater contaminated with Cd and Pb at open solid waste dump sites
2018, Process Safety and Environmental ProtectionTreatment of soil co-contaminated with inorganics and petroleum hydrocarbons using silica: Implications for remediation in cold regions
2017, Cold Regions Science and Technology