Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Engineering Science


Civil and Environmental Engineering


Gerhard, Jason I.

2nd Supervisor

Grant, Gavin P.



Growing environmental concern and regulations around petroleum producing and refining facilities, along with the divesting of legacy properties, have necessitated the need for rapid, high capacity, and cost-effective treatment technologies for remediating these sites and their produced wastes. Self-sustained liquid smouldering – known as STAR technology - has been studied extensively at small scales and has been proven as an effective in situ remediation technique for heavy hydrocarbons. However, STAR as a large-scale ex situ waste disposal method (STARx) has yet to be demonstrated. Here STARx is evaluated for the first time in soil pile configurations, using an engineered base concept called HottpadTM, at both the prototype (0.35 – 1.3m3) and field (80 – 160m3) scales. The treatment was applied to oily sludge from crude oil tank bottoms and oil water separation processes mixed with sand or soils at concentrations from 4 020 – 115 000mg/kg total petroleum hydrocarbons (TPH). The relationships between initial soil concentrations, off-gas production, mass destruction rates, cycle times, and peak temperatures provide important insights into the performance and costs of applying the technology at field scale. STARx was shown to successfully destroy the wastes to below laboratory detection limits, with contaminant mass removal efficiencies of greater than 98% being observed. Overall, this work demonstrates for the first time that STARx is a viable large-scale option for hydrocarbon sludge treatment.

Summary for Lay Audience

Waste products from the oil & gas industry can cause serious environmental impacts in the forms of soil, groundwater, and surface water contamination. The majority of these wastes are unusable by-products from the oil refining processes (sludges), which have historically been kept in lagoons. Forced by regulatory agencies or by property transactions, these wastes must eventually be disposed of. Current technologies are expensive and energy intensive. Here, smouldering combustion is proposed as alternative disposal method by mixing the sludges with soil and piling that mixture onto an engineered platform called a HottpadTM. The Hottpad ignites the sludges and waste is destroyed and removed from the soil as off-gases, which are captured and treated. This research explores the Hottpad design and the behaviour of the smouldering reaction, at both a small prototype scale and a large field-scale and establishes various relationships between factors that influence treatment performance, such as sludge loading (contaminate concentration) and pile height. The Hottpad was shown to successfully remove sludge from the soil piles using less energy than current methods. Overall, this work demonstrates for the first time that Hottpad is a viable large-scale option for the treatment of oil wastes.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.