Sustainable Zero-Valent Metal (ZVM) Water Treatment Associated with Diffusion, Infiltration, Abstraction, and Recirculation

Abstract

Socio-economic, climate and agricultural stress on water resources have resulted in increased global demand for water while at the same time the proportion of potential water resources which are adversely affected by sodification/salinisation, metals, nitrates, and organic chemicals has increased. Nano-zero-valent metal (n-ZVM) injection or placement in aquifers offers a potential partial solution. However, n-ZVM application results in a substantial reduction in aquifer permeability, which in turn can reduce the amount of water that can be abstracted from the aquifer. This study using static diffusion and continuous flow reactors containing n-ZVM and m-ZVM (ZVM filaments, filings and punchings) has established that the use of m-ZVM does not result in a reduction in aquifer permeability. The experimental results are used to design and model m-ZVM treatment programs for an aquifer (using recirculation or static diffusion). They also provide a predictive model for water quality associated with specific abstraction rates and infiltration/injection into an aquifer. The study demonstrates that m-ZVM treatment requires 1% of the weight required for n-ZVM treatment for a specific flow rate. It is observed that 1 t Fe 0 will process 23,500 m 3 of abstracted or infiltrating water. m-ZVM is able to remove >80% of nitrates from flowing water and adjust the water composition (by reduction) in an aquifer to optimize removal of nitrates, metals and organic compounds. The experiments demonstrate that ZVM treatment of an aquifer can be used to reduce groundwater salinity by 20 -> 45% and that an aquifer remediation program can be designed to desalinate an aquifer. Modeling indicates that widespread application of m-ZVM water treatment may reduce global socio-economic, climate and agricultural stress on water resources. The rate of oxygen formation during water reduction OPEN ACCESSSustainability 2010, 2 2989[by ZVM (Fe 0 , Al 0 and Cu 0 )] controls aquifer permeability, the associated aquifer pH, aquifer Eh and the degree of water treatment that occurs.

Modification of Aquifer Pore-Water by Static Diffusion Using Nano-Zero-Valent Metals

“…They can therefore provide an indication of the modified redox environment and its changes with time. The methodology required to translate the graphical data into modeled aquifer performance results (for an aquifer remediation program) for the design of permeable reactive barriers and aquifer remediation programs is provided elsewhere [1].…”

“…The assumption made (in accordance with standard catalyst theory) is that increasing surface area will increase the availability of active sites and the ability for adsorption/desorption reactions to occur on/in the catalyst. Eh and pH alteration of pore water chemistry is electrochemical [1] and not purely catalytic. The low surface area of the n-ZVM used in this study (Table 1) will result in a domination of fluid, electrochemical (and surface) reactions.…”

“…The n-ZVM powders used are illustrated elsewhere [1] and have a particle size of 44,000-66,000 nm (mesh size: BSS = 240-350; Tyler = 250-325; US = 230-325). The surface area of the n-ZVM used in this study varies from 0.00289-0.01732 m 2 g −1 (Table 1).…”

“…Modification of the aquifer/reservoir redox (Eh, pH) environment and the formation of Fe ions (as active catalytic sites) are essential prerequisites [1] for in situ reservoir (i) decontamination/remediation, (ii) dechlorination of organic contaminants [1][2][3][4][5][6][7][8][9], (iii) desalination, and (iv) catalytic oil restructuring (e.g., as part of an enhanced oil recovery scheme).…”

“…A number of pilot projects have used (i) n-Fe 0 injection (IZVM) [1,[10][11][12][13][14][15][16] and (ii) the placement of permeable reactive barriers (PRB) containing n-Fe 0 within flow paths located in an aquifer to modify …”