Self-sustaining Treatment for Active Remediation (STAR) is a new remediation approach with the potential to combine technical effectiveness, quick treatment, and substantial savings in operation and maintenance costs relatively to currently available techniques.
What is STAR?
STAR is a new and innovative technology to remediate Non-Aqueous Phase Liquids (NAPLs). It uses smoldering combustion – the type of combustion that turns charcoal into ash in your barbeque grill – to quickly and efficiently destroy contaminants.
STAR requires a one-time, short-duration, highly localized energy input to start the process where NAPL is intersected in the subsurface. After that, only air injection is required because all the energy for the combustion process comes from the NAPL itself, making STAR a self-sustaining technology!
As smoldering requires the presence of NAPL, STAR is also self-tracking (i.e., the smoldering front follows the distribution of NAPL) and self-terminating (i.e., smoldering stops when all the NAPL is destroyed).
What can it treat?
STAR is an effective treatment for a variety of different NAPLs including coal tar, creosote, petroleum, hydrocarbons, diesel range organics, oils and greases, mineral oil, and solvents/oil mixtures.
How does it work?
The STAR process starts by inserting a heating element into the target treatment zone. A short duration input of energy is then applied to heat the NAPL adjacent to the heating element to the target ignition temperature. Once this temperature is attained (typically between 200 and 400 °C), air is injected to ignite the NAPL. The NAPL combusts, releasing heat energy which is retained by the porous medium and used to pre-heat NAPL farther away from the ignition point. At this stage, the heating element can be turned off, and as long as sufficient air is supplied, the combustion process will continue, propagating away from the air injection point.