Objective:

Extensive documentation indicates that perchlorate is biodegradable under anaerobic conditions and can be expected to naturally attenuate in some aquifers. However, there are essentially no data showing that perchlorate does naturally attenuate, and the conditions under which this attenuation is most likely to occur have not been studied. Without clear, convincing evidence for the natural attenuation of perchlorate, there may be a tendency to push for aggressive remediation approaches whenever perchlorate is detected. While aggressive remediation is warranted at some sites, there are likely other sites where monitored natural attenuation (MNA) is appropriate. The overall objective of this project is to provide the Department of Defense (DoD) and other site managers with the tools needed to: (1) identify sites where MNA may be appropriate for management of perchlorate releases; and (2) demonstrate that perchlorate MNA is effective for controlling adverse impacts to the environment.

Technology Description:

The project team will first identify a variety of DoD sites that have known perchlorate releases and where it is suspected that natural attenuation is occurring. A subset of these sites will be selected, and the rate and extent of perchlorate biodegradation will be evaluated in bench-scale microcosm studies. The use of enzymatic activity assays and isotopic ratio measurements as indicators of perchlorate biodegradation then will be evaluated in laboratory incubations. Further, the rate and extent of MNA at two field sites will be assessed. From these studies, a protocol for monitoring the natural attenuation of perchlorate will be developed. Knowledge gained about perchlorate MNA will be transferred to the regulatory community.

Expected Benefits:

There is convincing evidence that petroleum hydrocarbons and chlorinated solvents naturally attenuate at some sites. This study will determine whether MNA is also appropriate for perchlorate plumes. The information gained from this project on perchlorate MNA will be useful under a variety of scenarios. For example, in higher organic carbon sites, MNA may be sufficient to completely contain the perchlorate, preventing significant down-gradient migration and eliminating the need for active remediation. In lower organic carbon sites, MNA of perchlorate may be occurring but at a slow rate. Under these conditions, a large perchlorate plume may have already developed requiring active remediation. However, once the most highly concentrated areas are treated, it may be possible to manage the more dilute plume fringes through MNA. At many sites, the down-gradient extent of the groundwater plume is limited by discharge to surface water. Extensive research has shown that some riparian buffers can remove a large fraction of the nitrate in groundwater prior to surface discharge. If perchlorate is also removed during flow through riparian buffers, this could significantly reduce the total mass discharged to surface water and the impact on drinking and irrigation water supplies. Information on the fate of perchlorate in the environment also will be useful in prioritizing sites for assessment. (Anticipated Project Completion - 2008)

Principal Investigator:
Mr. M. Tony Lieberman
Solutions Industrial & Environmental Services, Inc.
3722 Benson Drive
Raleigh, NC 27609
Telephone: (919) 873-1060
Fax: (919) 873-1074
E-mail: tlieberman@solutions-ies.com

DoD Liaison:
Ms. Erica S.K. Becvar
HQ AFCEE/TDE
3300 Sidney Brooks, Building 532
Brooks City-Base, TX 78235-5112
Telephone: (210) 536-4314
Fax: (210) 536-5989
E-mail: erica.becvar@brooks.af.mil