Technology Status Report: In Situ Flushing - CLU-IN

In Situ Flushing Project Summaries
GWRTAC Case Study Database
GWRTAC ID: FLSH0060
Project Name: National Water Res Inst, Env Canada - Humic Acid Flushing
City: Burlington State/Province: ON
Primary GWRTAC Personal
Communication Source
(Name/Organization):
Project Summary:
None
None
Report(s)/Publication(s) (GWRTAC Source):
Lesage, et al., "Use of Humic Acids to Enhance the Removal of Aromatic Hydrocarbons from
Contaminated Aquifers Part II: Pilot Scale"
The following was excerpted from Lesage, et al., "Use of Humic Acides to Enhance the Removal of
Aromatic Hydrocarbons from Contaminated Aquifers Part II: Pilot Scale":
In this project, the aqueous solubility enhancement of aromatic hydrocarbons by humic acids was
studied in laboratory columns (Xu et al, 1994) and in a large scale model aquifer (Lesage, et al.,).
A petroleum source was placed into a constructed model aquifer with a very dense monitoring
network. A humic acid (obtained as the sodium salt and prepared in solution) was used to flush the
model aquifer. The purpose of the study was to determine whether humic acids could be used costeffectively
to enhance dissolution and transport of aromatic hydrocarbons and provide an
environmentally suitable alternative to artificial surfactants.
The model aquifer tank was constructed of 1/4" industrial grade stainless steel (rectangular 2m x
6m x 2m deep) with an external support structure made of steel beams. To induce water flow, a
head tank separated from the aquifer material by a porous plate was used. The plate was
constructed of 1/4" stainless steel, but perforated with 1" holes so as not to impede water flow. The
sand aquifer material was retained by a polyester geotextile. To provide experimental control, the
aquifer model was divided in half longitudinally using a series of stainless steel plates that were
sealed and bolted together. The monitoring well network consisted of 72 bundles of 1/8" stainless
steel tubes. Each bundle consisted of five sampling tubes terminating at 30 cm depth intervals.
The bundles were spaced at 30 cm and 25 cm centres, parallel and perpendicular to the flow
direction, respectively. Two withdrawal wells were installed, one on each side of the tank (5 cm ID,
10 cm OD). A medium to coarse-grained sand (particle size range 75 um to 2.4 mm); hydraulic
conductivity of 0.04 m/s) was used for the aquifer medium. Care was taken to prevent air
entrapment and to remove residual chlorinated compounds during dry sand emplacement and
subsequent tap water saturation, and the sand allowed to settle for a few weeks prior to conducting
tracer experiments.
A conservative tracer test was used to determine optimal placement of the petroleum source. The
source was placed at a depth of 1.2 m, approximately 0.5 m downgradient from the head tank.
Five additional monitoring well bundles were added along the center-line. The residual capacity of
the sand was determined using a column experiment and it was found that approximately 500 mL
of diesel fuel could be retained by 20 kg of sand. To emplace the source, 500 mL of diesel was
Ground-Water Remediation Technologies Analysis Center
Operated by Concurrent Technologies Corporation
Appendix - Page 121 of 164
Copyright GWRTAC 1998
Revision 1
Tuesday, November 17, 1998