Self-sustaining treatment for active remediation (STAR) is an emerging, smoldering-based technology for nonaqueous-phase liquid (NAPL) remediation. This work presents the first in situ field evaluation of STAR. Pilot field tests were performed at 3.0 m (shallow test) and 7.9 m (deep test) below ground surface within distinct lithological units contaminated with coal tar at a former industrial facility. Self-sustained smoldering (i.e., after the in-well ignition heater was terminated) was demonstrated below the water table for the first time. The outward propagation of a NAPL smoldering front was mapped, and the NAPL destruction rate was quantified in real time. A total of 3700 kg of coal tar over 12 days in the shallow test and 860 kg over 11 days in the deep test was destroyed; less than 2% of total mass removed was volatilized. Self-sustaining propagation was relatively uniform radially outward in the deep test, achieving a radius of influence of 3.7 m; strong permeability contrasts and installed barriers influenced the front propagation geometry in the shallow test. Reductions in soil hydrocarbon concentrations of 99.3% and 97.3% were achieved in the shallow and deep tests, respectively. Overall, this provides the first field evaluation of STAR and demonstrates that it is effective in situ and under a variety of conditions and provides the information necessary for designing the full-scale site treatment.

An innovative treatment technology has been developed for the treatment of organic wastes. The technology utilizes the waste itself as the primary fuel for treatment via smoldering combustion. The process requires a heat source solely to initiate treatment. Once the process is initiated, treatment is sustained by continuously supplying air. The process may be implemented either ex situ or in situ, with this paper focused on the ex situ application for waste treatment or remediation purposes. This ex situ smoldering combustion treatment technology has been effectively demonstrated at field-scale for the management of oily wastes (e.g. tank bottom sludge, clarifier or pit sludge) and oil-impacted soil. Furthermore, the ex situ application has been demonstrated at pilot scale for domestic and commercial wastes (e.g. biosolids or sanitary sludge, kitchen grease) and ongoing development of the technology indicates other chemicals or wastes may also be effectively treated. If the waste is a combustible organic, or may be mixed with combustible organics, it is possible it may be treated with this technology. The Hottpad configuration is the culmination of collaborative research and technology development between Savron and Chevron. Each Hottpad unit has an engineered and trafficable working surface (or pad) equipped with a heat source to initiate the reaction, and an air distribution system to sustain the smoldering combustion that then propagates upward in the direction of air flow. Each Hottpad system is equipped with an emissions collection and treatment system, as necessary. The technology is cost-effective, robust, and applicable for a broad range of materials. Furthermore, the design is scalable and may be sized to meet project needs (from large centralized facilities, to smaller mobile treatment systems for remote sites). The Hottpad technology is very robust, both in terms of the range of materials that can be treated and from an operations perspective; it is costeffective; it may be implemented on site, reducing off-site transportation, eliminating safety concerns, and reducing the overall remediation carbon footprint; and the treatment will meet stringent treatment or remediation requirements.

Smoldering combustion, commercially available as the Self‐sustaining Treatment for Active Remediation (STAR) technology, is an innovative technique that has shown promise for the remediation of contaminant source zones. Smoldering combustion is an exothermic reaction (net energy producing) converting carbon compounds and an oxidant (e.g., oxygen in air) to carbon dioxide, water, and energy. Thus, following ignition, the smoldering combustion reaction can continue in a self‐sustaining manner (i.e., no external energy or added fuel input following ignition) as the heat generated by the reacting contaminants is used to preheat and initiate combustion of contaminants in adjacent areas, propagating a combustion front through the contaminated zone provided a sufficient flux of air is supplied. The STAR technology has applicability across a wide‐range of hydrocarbons in a variety of hydrogeologic settings; however, there are limitations to its use. Impacted soils must be permeable enough to allow a sufficient flux of air to the combustion front and there exists a minimum required concentration of contaminants such that the soils contain sufficient fuel for the reaction to proceed in a self‐sustaining manner. Further limitations, as well as lessons learned and methods to mitigate these limitations, are presented through a series of case studies. In summary, the successful implementation of STAR will result in >99 percent reduction in contaminant concentrations in treated areas, limited residual contaminant mass, reduced groundwater contaminant mass flux which can be addressed through monitored natural attenuation; and an enhanced site exit strategy, reduced lifecycle costs, and reduced risk. ©2016 Wiley Periodicals, Inc.

Growing stockpiles of waste oil sludge (WOS) are an outstanding problem worldwide. Self-sustaining Treatment for Active Remediation applied ex situ (STARx) is a treatment technology based on smoldering combustion. Pilot-scale experiments for the STARx Hottpad prove this new concept for the mobile treatment of WOS mixed intentionally with sand or contaminated soil. The experiments also allowed for the calibration and validation of a smoldering propagation numerical model. The model was used to systematically explore the sensitivity of Hottpad performance to system design, operational parameters, and environmental factors. Pilot-scale (~1.5 m width) simulations investigated sensitivity to injected air flux, WOS saturation, heterogeneity of intrinsic permeability, and heterogeneity of WOS saturation. Results reveal that Hottpad design is predicted to be successful for WOS treatment across a wide range of scenarios. The operator can control the rate of WOS destruction and extent of treatment by increasing the air flux injected into the bed. The potential for smoldering channeling to develop was demonstrated for the first time. Under certain conditions, such as WOS saturations of 80%, high heterogeneity of WOS saturations, or moderate to high heterogeneity of soil permeability, smoldering channeling was predicted to accelerate to the point that remedial performance was degraded. Field-scale simulations (~10 m width) predicted successful treatment, with WOS destruction rates an order of magnitude higher than the pilot-scale and treatment times increasing only linearly with bed height. This work is a key step toward the design and effective operation of field STARx Hottpad systems for eliminating WOS.

Treatment of oil-impacted soil and management of oily waste are often significant challenges of environmental stewardship at E&P facilities. Both oil-impacted soil and oily waste (e.g. tank bottoms, clarifier or pit sludge) result from E&P activities at sites that are distant from waste disposal or treatment facilities, or may not have such facilities available. A technology to effectively treat these materials onsite has been developed and field demonstrated at two different sites. One field demonstration project was specific to sludge treatment, while the other project assessed the treatment of oil-impacted soil from active remediation sites. The treatment technology that has been developed is an ex situ method for treating oil containing materials on a flat working surface, referred to here as Hottpad. The process utilizes the oil content in the material to be treated as the primary fuel for treatment via smoldering combustion. Hottpad is an innovative technology to initiate and sustain the treatment process. Each Hottpad unit is equipped with a heat source to initiate the reaction, and an air distribution system to keep the smoldering reaction active and propagating upward in the direction of air flow. The heat source is only required for a short duration, after which time it is turned off and the supply of air is sufficient for the treatment to continue to completion without the need of additional external energy (i.e. self-sustaining). The current Hottpad configuration is the culmination of more than 5 years of collaborative research and technology development. The resulting technology is cost-effective and robust, applicable to a broad range of materials. The initial scale-up of the technology was performed in 2016, when a full-size unit was operated for the treatment of large volumes of sludge (> 45 m3 per batch). The initial project was to demonstrate the viability of the technology at large scale. The favorable results prompted additional modifications of the test system, essentially converting the system to a more practical configuration representative of an actual remediation unit. The modifications included the addition of vertical walls around the perimeter and testing of different emissions treatment methods. The second demonstration project focused on assessing the treatability of high clay, oil, and moisture content oil-impacted soil from an active remediation site. Leveraging learnings from the first field demonstration project, most notably that a small prototype unit can be used to scale up to large systems, a cost-effective small scale Hottpad system was used to run the treatability tests. The small-scale units were also equipped with vertical walls. The smaller units allowed for more runs in a shorter time, using less material, yielding more information. The additional field tests have improved our understanding of the technology and provided results that will help improve its application in the future. Of significance, the results confirm the technology is very robust, both in terms of the range of materials that can be treated and from an operations perspective; the technology is very cost-effective; the technology may be implemented on site, reducing off-site transportation and eliminating safety concerns, while simultaneously reducing the overall remediation carbon footprint; and the treatment will meet even the most stringent remediation requirements. In addition, these projects confirm that small-scale treatability testing, when necessary for potentially difficult to treat materials, will provide the necessary information to assess site-specific technology applicability.