IN SITU MICROCOSM ARRAY (ISMA) VS. STANDARD LABORATORY ASSESSMENT OF CANDIDATE REMEDIATION TECHNOLOGIES – A PERCHLORATE CASE STUDY

Treatability studies for bioremediation projects are typically performed in a laboratory setting either as simple batch experiments or as more advanced column studies employing continuous-flow regimes. While this allows for testing of site-specific microorganisms or microbial communities to degrade specific contaminants, the applicability of laboratory-generated results to the actual remediation site is limited.

To address these issues, we relocate the proven concept of continuous-flow, sediment column studies to an in situ setting with a device called the “in situ microcosm array” (ISMA). The ISMA contains all the components of a conventional laboratory column study in a shell that can be deployed in a groundwater well. A slim design enables its use in standard groundwater monitoring wells measuring 4 inches in inner diameter. During field deployment, the ISMA device draws groundwater directly from the formation in real time for in situ feasibility testing of candidate treatment technologies under consideration for site cleanup.

We have applied the ISMA technology to a perchlorate-contaminated site in Phoenix, AZ. The in situ treatment strategies tested included monitored natural attenuation, biostimulation and bioaugmentation. In addition to ISMA tests, we also have conducted laboratory batch bottle tests and laboratory flow-through tests using site sediment and groundwater. Results from these three datasets will be presented and the distinct advantages and disadvantages of each testing approach will be discussed.