Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Dr. Jason I. Gerhard

Abstract

Growing stockpiles of industrial liquid waste stored in lagoons are an outstanding problem worldwide. Self-sustaining Treatment for Active Remediation (STAR) is an emerging technology based on smouldering combustion that has been successfully deployed for in situ remediation of field sites (Grant et al., 2016). STAR is currently being developed as an ex situ treatment system (STARx) for industrial wastes by intentionally mixing them with sand. One engineering concept for STARx is the “hotpad”, for which some initial experiments have been conducted. However, a thorough experimental investigation is challenging due to the cost and time associated with each experiment. This work employed a two-dimensional (vertical cross-section) numerical model to systematically explore sensitivity of STARx hotpad performance to system design, operational parameters, and environmental factors. The phenomenological model that was used uniquely combines a multiphase flow code and a front expansion routine (MacPhee et al., 2012; Hasan et al., 2015). First, the model was calibrated and validated against pilot-scale (~ 2 m width) hotpad experiments, providing confidence that the rate and extent of treatment were correctly predicted. Pilot-scale simulations then investigated the sensitivity of system performance to: injected airflow rate, organic liquid concentration, hotpad configuration, system dimensions, heterogeneity of intrinsic permeability, and heterogeneity of organic liquid concentration. The expected performance of two field-scale configurations (~ 10 m width) was also explored. Hotpad performance is predicted to be most sensitive to the injected air flux, with higher air fluxes achieving higher rates of organic liquid destruction and treating larger fractions of the initial mass. The uniformity of the advancing smouldering front was predicted to be highly dependent on the effective permeability ratio between untreated and treated materials. As a result, increased heterogeneity – of intrinsic permeability in particular – is predicted to degrade remedial performance. Full-scale systems were predicted to achieve treatment rates an order of magnitude higher than the pilot-scale for a similar organic liquid concentration and injected air flux. It is anticipated that this work will increase understanding of several key processes that impact STARx performance and help optimize hotpad design and operation.

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