Time-Release Electron Donor Technology: Results of Forty-Two Field Applications (PDF)
Hydrogen Release Compound (HRC) is a food grade, polylactate ester that, upon being deposited into the aquifer, is slowly hydrolyzed to release lactic acid and other organic acid derivatives. The organic acids are fermented to hydrogen, which in turn donates electrons that drive reductive bioattenuation processes. HRC delivers electrons in a time-release fashion for about one year. The material is applied to the aquifer by push-point injection or backfill-auguring and is normally indicated for treatment dissolved phase plumes and hydrophobically sorbed contaminant. It has long been known that enhancing bioremediation can facilitate desorbtion of the residual, sorbed phase; now this has been specifically established in an HRC-mediated environment. HRC has now been used on over 120 sites, which we believe make it the most widely used electron donor for accelerating bioattenuation. Of these applications, forty-two are in a position to be evaluated. From among these there were nine sites that displayed exceptional results, defined as demonstrating very rapid and complete dechlorination. At twenty-two sites results are very positive, displaying accelerated degradation rates with varying degrees of daughter product formation depending on the age of the data set. Finally, nine sites are showing moderately accelerated rates of dechlorination with varying degrees of daughter product formation depending on the age of the data set, and two sites were unresponsive to a single treatment.