ASU Researcher Rolf Halden (left) and his research team prepare to deploy the In Situ Sampler or IS2 — a device capable of sensitive monitoring of groundwater, at lower cost and with less environmental damage. Credit: The Biodesign Institute at Arizona State University |
The
U.S. spends around 2 billion dollars a year on remediation at hazardous
waste sites, with a large portion of this used for groundwater
monitoring. Yet, according to Rolf Halden, a researcher at Arizona State
Univ.’s Biodesign Institute, the information gathered is often of
limited value.
Under
a new three-year, $1.15 million grant from the U.S. Department of
Defense, Halden, assistant director at the Institute’s Swette Center for
Environmental Biotechnology, is pursuing a novel method to conduct
these vital tests. His team’s efforts are part of a quest to provide
more accurate results at lower cost and produce fewer harmful byproducts
during the monitoring process.
When
considering techniques suitable for groundwater monitoring, three
components are key: the quality of data provided, the cost of the
procedure, and the environmental impact. Conventional monitoring
typically accounts for at least 20% of the total cleanup costs
incurred during site remediation. From a project management standpoint,
however, the analyses and acquired data can often be misleading and
unsatisfactory, as well as environmentally damaging.
Normally,
groundwater is extracted from the earth for testing and then sent to a
lab for detailed analysis. The method is financially and environmentally
costly, because the water must be transported and the process can
generate significant amounts of hazardous waste at the surface.
Halden’s
technique involves monitoring groundwater while it is still in place in
the subsurface, using a device known as the in situ sampler or IS2,
which may be custom fit into groundwater monitoring wells. The IS2 is
deployed downhole, where its integrated pumps draw up ambient
groundwater at milliliter per day rates. Analytes of interest are
concentrated onto solid adsorption media for analysis. One of the
advantages of this in situ approach is that effluent from the device
remains in the subsurface. Only the device itself with the extracted
analytes is removed from the well. In this way, monitoring can be
conducted without the use of purge water or the liberation of wastewater
at the surface.
Once
the device has completed its work and is removed from the well, the
contaminant-charged media are shipped to the laboratory, where they
undergo automated analysis assisted by robotics, as well as standard
methods including mass spectrometry and ion chromatography. The new
technology boasts extremely low detection limits—in the ng/L to pg/L
range. Further, it produces no wastewater and may be carried out at a
low cost per sample, thanks to the use of automation.
The
IS2 sentinel will be applied on a pilot basis at DoD sites and used in
multiple deployments to examine a range of groundwater contaminants,
including volatile organic compounds like tetrachloroethene,
trichloroethene, and vinyl chloride; water-soluble fuel components
(benzene and toluene); explosives (RDX and TNT); semi-volatile compounds
(phenol); polycyclic aromatic hydrocarbons (naphthalene and
phenanthrene); inorganic water contaminants (perchlorate); and heavy
metals (arsenic and lead). Each of these analytes will be captured in
situ, using a pair of customized IS2 devices. Results will be compared
to those obtained with conventional water monitoring approaches.
The
project seeks to demonstrate improved detection limits, 10 to 100-times
lower than those achieved through current EPA methods. The accuracy,
reproducibility and precision of results should also exceed EPA methods,
providing detailed analyses of a broad spectrum of compounds at
considerably lower costs. While initial efforts focus on monitoring at
DoD hazardous waste sites, ultimately, the technology should find broad
applicability for groundwater oversight.
