OVERVIEW

Part of the recalcitrance of perchlorate in groundwater may be a result of the lack of suitable conditions for in situ degradation. Therefore, researchers at Penn State investigated methods to stimulate in-situ degradation by determining if perchlorate reduction was limited by one of three factors: insufficient microorganisms in the soil capable of perchlorate degradation; lack of anaerobic conditions; lack of sufficient oxidizable substrate (i.e. insufficient electron donor). The abundance of chlorate and perchlorate reducing microorganisms (CRMs and PRMs) was examined as a part of an ongoing NSF grant. The effect of anaerobic conditions and the importance of sufficient electron acceptors was examined by determining the effect of lactate on perchlorate degradation.

Hydrogen Release Compound (HRC™) was developed by Regnesis Bioremediation Products as a low-cost treatment option for in-situ anaerobic bioremediation of chlorinated aliphatic hydrocarbons (CAHs). According to Regenesis, "HRC is a proprietary, environmentally safe, food quality, polylactate ester specially formulated for slow release of lactic acid upon hydration. Bioremediation with HRC is a multi-step process. Indigenous anaerobic microbes (such as acetogens) metabolize the lactic acid released by HRC, and produce hydrogen. The resulting hydrogen can be used by reductive dehalogenators which are capable of dechlorinating CAHs. Major target compounds in this group include PCE, TCE, and TCA as well as their daughter products. By providing a long-lasting, time-released hydrogen source, HRC can enhance anaerobic reductive dechlorination of chlorinated aliphatic hydrocarbons."

Through a gift by Regenesis to the Logan lab's research on perchlorate, researchers tested whether HRC could be used to support biological perchlorate reduction. Batch tests were conducted with pure and mixed cultures to demonstrate biological perchlorate reduction in comparison to abiotic and non-amended controls. It was found that polylactate could support perchlorate degradation in the laboratory.  Several field tests are now being conducted on in situ perchlorate degradation using HRC.  Results of this work were presented at the Battelle conference by Logan et al. (2000), and have been published by Wu et al. 2001.  For more information on perchlorate degradation, visit the perchlorate webpage.