Technology Status Report: In Situ Flushing - CLU-IN

3.1 Flushing Solutions
3.0 ANALYSIS OF IN SITU FLUSHING TECHNOLOGY
Figure 9 is a pie chart illustrating the types of flushing solutions being used in the various case studies of
all scales. For this chart, if more than one type of flushing solution was used in a project, or if a flushing
solution contained more than one type of flushing additive, both were counted (i.e. a project where both
surfactants and co-solvents were used was counted as both a surfactant and a co-solvent project). The
“other” category for this figure encompasses several different potential flushing additives (such as
polymers, electolytes, complexing sugars, etc.), as indicated by the note on the figure, whether or not
these additives are in use alone or combined with surfactant or other solutions. As shown, surfactants,
plain water, other, and then co-solvents (in descending frequency of occurrence) are the top four
categories of the known flushing solutions which have been used. It should be noted that, of the 22 fullscale
studies, where known, the flushing solution used in the majority of the studies was plain water (or
water with addition of nutrients), usually treated site groundwater. Exceptions are six sites located in
Quebec, Canada, and three sites located in the U.S. GWRTAC ID FLSH0011 is the Estrie Region
Machine Shop site in Quebec, Canada, in which a surfactant flushing solution was utilized at a site
contaminated with LNAPL. GWRTAC ID FLSH0037 is a site in Drummondville, Quebec, where
surfactants are used to remediate soil contaminated with benzene, toluene, ethylbenzene, and xylene
(BTEX) and mineral oil and grease (MOG). GWRTAC ID FLSH0042 is the Thouin Sand Quarry Site in
Quebec, Canada, where additives including surfactant were used to remediate DNAPL. GWRTAC ID
FLSH0066 is an aluminum processing facility in Quebec where surfactants were used in the remediation
of polychlorinated biphenyls (PCBs) and MOG. GWRTAC IDs FLSH0067 and FLSH0068 are two
separate projects in Quebec where surfactants were used to treat soils contaminated with BTEX and
MOG at or near petroleum sites. One of the sites in the U.S. thought to be the first to use a flushing
additive other than nutrients at full-scale, is FLSH0050, located in Florida, where an arsenic plume in
groundwater is being remediated using proprietary chemicals in the flushing solution. The remaining two
U.S. projects are in planning stages or are confidential in nature.
Figure 10 is a bar chart depicting the flushing solution type used by project scale. As in Figure 9, more
than one category of flushing solution per project may be included in this figure. As is apparent from this
figure, while surfactants are used in many laboratory-scale studies and are being tested in the field at pilotscale,
only a small number of full-scale applications have occurred to date, and these are outside the U.S.;
six Canadian projects are identified above. However, plans are currently underway to remediate at least
a portion of Operable Unit 2 (OU2) at Hill Air Force Base using a surfactant flood. This is thought to be
the first full-scale (currently funding for 1/5 of the full project is earmarked) application of surfactant
flushing planned in the U.S., and may be underway within the next two years. Still, at least 14 full-scale in
situ flushing case studies have been identified by GWRTAC where water (treated or untreated site
groundwater, or potable water) with no additives other than nutrients is used as the flushing solution.
Considering the laboratory- and pilot-scale studies, which are included in Figure 10, the majority of the
research and demonstration projects have examined the use of surfactants. Only eight of the pilot-scale
projects used co-solvents, compared to 30 which used surfactants. At the laboratory scale, 17 projects
examined surfactants and one examined co-solvents. As mentioned above, the majority of the pilot-scale
projects would have had laboratory work completed prior to the project. Figure 10 shows only
laboratory/bench scale cases in which the given research group is doing laboratory work independently of
a pilot-scale demonstration.
Ground-Water Remediation Technologies Analysis Center © GWRTAC
Operated by Concurrent Technologies Corporation Page 5 Revision 1 11/17/98