Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Dr. Jason Gerhard

2nd Supervisor

Dr. Elizabeth Edwards

Joint Supervisor

Abstract

In situ STAR (Self-sustaining Treatment for Active Remediation) is an emerging remediation technology which uses smouldering combustion to destroy nonaqueous phase liquid (NAPL) contamination in the subsurface. Since STAR smouldering travels through contaminated soils slowly (~0.5 to 5 m/day) and subjects them to high temperatures (400–1000°C), it is expected that this technology will thoroughly dry and sterilize the zones which it treats. Further, soils surrounding the treatment zone which are not smouldered will be heated, although not smouldered, by virtue of their proximity to STAR, impacting microbial communities within them. Therefore, the objectives of this work are to quantify the microbial repopulation of the STAR treated zone, and observe heating effects on microorganisms living in surrounding soils. 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. This study analyzed soil cores taken at regular intervals following STAR treatment, allowing time for groundwater to re-infiltrate and for microbial populations to potentially reestablish. Treated soil, as well as untreated soil above the treatment zone and groundwater were analyzed for bacteria abundance and microbial diversity. Results demonstrate rapid bacterial repopulation over a 2-month period to ~107 gene copies/g of soil in the treated zone, and variable impacts within untreated soils. In general, long term microbial abundance was largely dependent on the amount of organic matter present in the soil following STAR. In order to examine microbial transport and repopulation of STAR treated soils in more detail, and to consider the effects of bio-stimulating amendments, a bench top column study using site soil and artificial groundwater explored the rate at which STAR-treated soil is repopulated with naturally occurring microorganisms in the presence and absence of lactate and elevated sulfate concentrations. Results demonstrated that this amendment scheme increased the carrying capacity of the STAR treated soil and shifted the microbial community to promote sulfate reducing bacteria. Overall, the work illustrates that microbial populations in STAR treated soil do recover via groundwater infiltration but robust communities will take time to naturally establish.

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