Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Gerhard, Jason I.

2nd Supervisor

Grant, Gavin P.

Affiliation

Savron, a subdivision of Geosyntec Consultants

Co-Supervisor

Abstract

Smouldering remediation is a promising technique for destroying organic contaminants in soil. Forced airflow is vital to supporting the smouldering reaction and to propagate it through the contaminated zone. This research focuses on investigating the effects of permeability heterogeneity on smouldering. A series of unique column experiments, combined with numerical model simulations, were conducted. The results suggest that smouldering can successfully propagate through layers in series despite more than a 1000:1 permeability contrast. However, extinction can occur in the finer layer when smouldering propagates through layers in parallel with a permeability ratio above 3:1. Extinction may occur due to insufficient airflow in the fine layer or due to conductive heat losses from the fine to coarse layers. However, for more complex heterogeneity, smouldering extinction can be eliminated. Overall, this research provides unique insights into managing heterogeneous soils to ensure the successful application of smouldering remediation.

Summary for Lay Audience

Industrial processes have led to pollution of the environment, including soils and groundwater near former factories. Hydrocarbons, such as tars and petroleum products, are among the most significant challenges in the field of subsurface cleanup. Smouldering combustion, like glowing red charcoal in a barbeque, is a new approach for the destruction of these pollutants. Injecting air into the soil is needed to support this cleanup technique and most soils occur in layers. Therefore, understanding the factors that affect airflow and smouldering patterns in layered soils will help improve the smouldering cleanup of these sites.

A series of smouldering column experiments, combined with computer modelling, were conducted to study the impact of soil layering. The results show how most air flows through the more conductive soil layer, and this can make treatment of the finer layers difficult in certain cases. Besides, loss of heat between layers can cause the treatment to fail in some cases. However, in other cases, smouldering can be successful in all layers, despite large differences in soil types. By explaining the key differences between these cases and how they affect smouldering treatment, it is expected that more polluted sites will be successfully cleaned up in the future.

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