Monday, December 28, 2009

$250 Billion Cost Estimate to Clean 350,000 Toxic Sites in the US, Nano Zero Valent Iron May Be Cheaper Solution


In the U.S. between 2004 to 2033, the cost to remediate  230,000 to 350,000 polluted sites, including many toxic superfund sites,  is estimated to range from $175 billion to $250 billion according to the U.S. Environmental Agency (EPA).

The following table presents an EPA estimate of the number of programs, and the number of sites under their jurisdiction and the price tag to clean up the sites. 




 Nano Zero Valent Iron may play a significant role in the clean up effort.   Currently the material is being tested at 30 sites and is able to treat a variety of toxic chemicals.  It is mixed into a sludge and  pumped into the ground where it forms a permeable barrier that cleanses the water of toxic chemicals as it percolates through the NZVI containing clays, silts and bedrocks.

 Image Credit: EPA

The figure below shows a nanograph of NZVI as well as a drum of NZVI being mixed prior to being pumped into the ground where it disperses and cleans toxins from water as the water flows through a wall of NZVI particles  

Image Credits: EPA   

Zero-valent Nanoscale iron has the potential to degrade many contaminants, including: Volatile Organics, Halogenated aromatics, PCB's, Halogenated herbicides and pesticides, Perchlorate Metals, such as hexavalent chromium and arsenic as well as other contaminants.




 Table Source:  Innovative Research and Products Inc (iRAP)

Although remediation of contaminated groundwater using nanoparticles containing zero-valent iron (nZVI) is one of the most prominent examples of a rapidly emerging  environmental nanotechnologies with considerable potential benefits. There are, however, many uncertainties regarding the fundamental features of this technology, which have made it difficult to engineer applications for optimal performance or to assess the risk to human or ecological health, according to researchers at Oregon Health and Science University Groundwater Research Center.

Oregon Health and Science University's Groundwater Research Center has addressed three of the fundamental features that commonly contribute to misunderstanding of this technology: showing (i) that the nZVI used in groundwater remediation are larger than particles that exhibit "true" nano-size effects, (ii) that the higher reactivity of this nZVI is mainly due to its high specific surface area, and (iii) that the mobility of nZVI will be less than a few meters under almost all relevant conditions.




One implication of its limited mobility is that human exposure due to remediation applications of NZVI is likely to be minimal. There are, however, many characteristics of this technology about which very little is known: e.g., how quickly NZVI will be transformed and to what products, whether this residue will ever be detectable in the environment, and how surface modifications of NZVI will alter its long-term environmental fate and effectiveness for remediation.

An overview of research on contaminant remediation with zero-valent iron led by Drs. Paul Tratnyek and Rick Johnson at OGI's Center for Groundwater Research (CGR) can be found at http://cgr.ebs.ogi.edu/iron/#results

 The NZVI can be pumped into the ground at remote locations as well as the site of contamination.




Image Credits: EPA

The following figure shows the EPA mid-range cost estimate of $209 billion to clean 294,000 contaminated sites.








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