Self-sustaining Treatment for Active Remediation (STAR)

2. Field Trials & Prototypes

In Situ Pilot Test of Coal Tar Destruction

Gerhard, in collaboration with SiREM/Geosyntec and an industrual site owner, is conducting a phased pilot test of in situ NAPL smouldering at the Pitt Consul site in New Jersey, USA. This cresol manufacturing site from the late 1800s, and acquired by the owner in 1998, exhibits extensive coal tar contamination between 1.5m and 3m below ground surface. In September 2009, a single well test demonstrated that, after a short ignition of several hours, self-sustained smouldering was continued for 9 days below the water table. Carbon balance on the emissions indicates that approximately 240 kg of coal tar was destroyed during the test. Phase II targeted a 7m wide by 18m long pilot test area (PTA) enclosed by sheet piling that exhibited high saturation coal tar below the water table. 9 ignition/air injection wells were installed and a complete gas capture/treatment system employed.

New Jersey in-situ pilot test site

During the 12 days of self-sustaining treatment, more than 4500 kg of coal tar was destroyed, with destruction rates as high at 800 kg/day. The front propagating up to 12m laterally from an ignition well and treated coal tar over the full 1.5 m target depth interval. An average reduction in TPH concentration of 99.7% was observed in post-treatment soil cores. Phase III of this trial demonstrated that in situ STAR is feasible at more than 7m depth below the water table and achieved a radius of influence of 3.5m, destroying more than 800 kg of coal tar in 6 days. In Situ STAR is now being evaluated for full treatment of the site and as well field trials are proceeding at other sites in North America and Europe.

Soil core before STAR in-situ treatment

Soil core after STAR in-situ treatment

Ex Situ Reactor

STAR ex-situ reactor

There is significant potential for treating crude oil sludge in an ex situ, on-site reactor. The academics are collaborating SiREM/Geosyntec and Chevron on a pilot ex situ reactor to demonstrate and optimize STAR for this purpose. A 1m diameter x 3 m high STAR reactor has been constructed in collaboration with Gudgeon Thermofire Inc. (London). A suite of experiments are exploring how to optimize the process and material handling to facilitate construction of a full scale reactor. Initial results have been very promising; for example, destroying more than 350 lb of contaminant in approximately 24 hr. This work suggests that the above-ground treatment of excavated contaminated soil and also the intentional mixing of sludges and other liquid contaminants with sand for contaminant destruction with STAR is expected to be energy efficient manner and allow complete recycling of the sand.