Abstracts

278 - Microbial Subsurface Repopulation Following In Situ STAR
Remediation
Gavin Overbeeke & Jason Gerhard
Department of Civil and Environmental Engineering – University of Western Ontario,
London, Ontario, Canada
Elizabeth Edwards
Department of Chemical Engineering and Applied Chemistry – University of Toronto,
Toronto, Ontario, Canada
Gavin Grant
Savron, Guelph, Ontario, Canada
STAR (Self-sustaining Treatment for Active Remediation) is an emerging remediation
technology that employs a self-sustaining smouldering reaction to destroy nonaqueous
phase liquids (NAPLs) in the subsurface. The reaction is a slow, controlled, flameless exothermic
oxidation reaction that proceeds strictly through NAPL-contaminated soil. The
reaction front travels at rates of 0.5 to 5 m per day and subjects the soil to temperatures
between 400°C and 1000°C. As a result, not only does STAR cause in situ destruction of
NAPL, but it thoroughly dries and likely sterilizes the soil through which it passes. The
objective of this work is to monitor the re-saturation of the soil over time and quantify
the microbial repopulation of the treated source zone. STAR is currently being applied as
a full scale, in situ remedy for coal tar beneath a former creosol manufacturing facility in
New Jersey, USA. STAR is being applied at two depths where significant coal tar contamination
is observed: a shallow fill unit and a deeper fine sand alluvial aquifer, both beneath
the water table. This project includes analysis of soil cores and groundwater samples taken
from both depths immediately after STAR treatment and at regular intervals afterwards,
allowing time for groundwater to reinfiltrate and for microbial populations to reestablish.
Samples were also taken from outside the treatment zones to provide background data.
Both soil and groundwater samples were analyzed for total number of microorganisms
and microbial diversity using Pyrotag analysis. Pyrotag analysis subjects DNA within a soil
sample to quantitative Polymerase Chain Reaction (qPCR), which is used to estimate the
abundance of microorganisms, as well as Amplicon sequencing of 16srRNA genes, which
provides an estimation of microbial composition and diversity. To inform the field research
program, an initial bench top laboratory study using site soil and natural groundwater
is exploring the rate at which STAR-treated soil is repopulated with naturally occurring
microorganisms. The expectation of this research program is to provide insight into the
changes in microbial abundance and diversity as the subsurface transitions from contaminated
to remediated and then repopulated soil. The rate at which the microbial abundance
changes, as well as the variations seen in microbial diversity will be a key factor in determining
the rate at which the subsurface improves towards its natural soil function.
196 - Importance of Groundwater Flow Direction Match in
Groundwater Flow Model Calibration
Hongze Gao & Steve Harris
Conestoga Rovers & Associates, a GHD Company, Waterloo, Ontario, Canada
166 IAH-CNC 2015 WATERLOO CONFERENCE