Self-sustaining Treatment for Active Remediation (STAR)

1. STAR Introduction

Self-sustaining Treatment for Active Remediation (STAR) is a new remediation technology developed for soil contaminated with hazardous organic industrial liquids. STAR was invented via collaboration between a soil/groundwater expert (Gerhard) and a combustion expert (Torero). Their research program was the first to demonstrate that a liquid fuel (coal tar) embedded in inert quartz sand could be smouldered (Pironi et al., 2009). Through a strong partnership with Savron, STAR is now expanding its commercial potential. Here is a Remediapedia article on STAR.

STAR Conceptual Model

What is STAR?

‘Self-sustaining smoldering’ is a highly controlled burning reaction - similar to charcoal in a BBQ. As a remediation technique, it destroys NAPLs embedded in soil while simultaneously generating enough energy to propagate itself through the subsurface. As a result, it avoids the costs and risks of injection/extraction approaches (e.g., surfactant flushing, oxidation) and has the potential to be far less energy intensive (and therefore less costly to operate) than traditional thermal technologies. STAR has the potential to combine technical effectiveness, quick treatment, and substantial savings in operation and maintenance costs relative to currently available techniques.

STAR was introduced this as a remediation approach with proof-of-concept experiments that demonstrated total NAPL destruction with no energy input after initiation (Switzer et al., 2009). The reaction was demonstrated to be robust across a wide range of coal tar and crude oil concentrations and the rate of destruction rate was demonstrated to be a function of the air injection rate (Pironi et al., 2011).

STAR has significant potential for the remediation of NAPL due to a number of key properties of the process:

  1. STAR requires only a short duration energy input (i.e., ignition) at a single location to initiate the reaction,
  2. STAR is then self-sustaining, such that the reaction propagates itself through the NAPL without additional energy input,
  3. STAR is self-targeting, such that the reaction naturally tracks through the subsurface zones occupied by NAPL,
  4. STAR is self-terminating, such that the reaction naturally ceases when no NAPL remains,
  5. STAR avoids injecting costly fluids or conveying NAPL or contaminated groundwater to the surface for treatment

Further benefits include;

  • STAR can be applied in situ or ex situ;
  • STAR is most effective for the most recalcitrant compounds such as coal tars, heavy oils, and petroleum hydrocarbons (as they are the most exothermic);
  • Very rapid clean-up is possible (destructive front propagating on the order of 1 m per day),
  • Unlike many techniques, STAR works better as the contaminant concentration increases (more fuel for the reaction),
  • Essentially non-detect total petroleum hydrocarbons (TPH) are observed in post-treatment soils.

Proof of Concept - Contaminated sediment before STAR treatment (left) and clean sediment after (right).