![](media/image1.jpeg){width="3.513888888888889in"
height="2.2777777777777777in"}

Abstract Submission Form

Desert Remedial Action Technologies

Please complete and e-mail this form to:

<Aycock.Mary@epa.gov>

**Title:** In Situ and Ex Situ Perchlorate Bioremediation in Vadose Zone
Contaminated Soil

**Name of First Author:** Laurie LaPat-Polasko

**Email of Author:** llapat@geomatrix.com **Author Phone Number:**
480-348-1283

**Organization to Which Author(s) belong** Geomatrix Consultants

**Conference Theme Considered Appropriate for Contents of
Presentation:** In situ and ex situ perchlorate soil bioremediation

**Other Authors (name and e-mail):** Stephanie Koehne;
<skoehne@geomatrix.com>; Andrew MacHugh; amachugh@geomatrix.com

**Author Biography:**      

Dr. LaPat-Polasko has more than 20 years of experience as a technical
consultant and project manager for efforts involving groundwater and
soil remediation and wastewater treatment. Combining her knowledge of
microbiology with a background in civil engineering, Dr. LaPat-Polasko
has focused on remediation and natural attenuation of groundwater and
soil impacted by organic and inorganic compounds. She has dealt with
contaminants ranging from fluoride and arsenic to chlorinated solvents
and explosives. Dr. LaPat-Polasko has been actively involved in numerous
Water Quality Assurance Revolving Fund (WQARF) and Superfund (CERCLA)
sites.

Dr. LaPat-Polasko has developed, designed, and implemented remediation
plans for water and soil systems. She has field- and laboratory-tested
aerobic and anaerobic methods for treating contaminated groundwater and
soil and has studied the treatment role of various microbial
communities. She has identified and evaluated a wide variety of
pathogens in surface water and groundwater. She has taught several
graduate courses in water and soil remediation at Arizona State
University. Dr. LaPat-Polasko has extensive experience interacting with
the U.S. Environmental Protection Agency (EPA), the Arizona Department
of Environmental Quality (ADEQ), and various county and city regulatory
agencies in Arizona and California.

**Text of the Abstract:**

A series of bench-scale studies were performed to evaluate the potential
benefit of using biostimulation and bioaugmentation for the complete
anaerobic biodegradation of perchlorate in vadose zone contaminated
soil. The first phase of the bench-scale study evaluated the
effectiveness of the indigenous microbial population to biodegrade
perchlorate when amended with various electron donor sources in both
in-situ and ex-situ microcosms.

The in-situ microcosm set-up involved placing approximately 1,200 grams
of soil, spiked with approximately 1,000 milligrams per kilogram
perchlorate, in six 1,000 milliliter polyethylene columns. During the
first seven months, periodic additions of hexene, a semi-gaseous carbon
substrate, and minimal moisture were injected into the soil columns. A
second set of in-situ soil columns was amended with yeast and sodium
acetate to evaluate the potential of an established carbon substrate to
promote biodegradation of perchlorate. The ex-situ microcosm set-up
included placing perchlorate-contaminated soil in sealed glass
containers within a glove bag under nitrogen conditions. This soil was
amended with periodic additions of corn syrup, sodium acetate, moisture,
and/or yeast.

Native control microcosms were not treated with any amendments to assess
the potential for natural attenuation in the in-situ and ex-situ
microcosms. The microcosms were monitored for pH, total organic carbon,
moisture, total phosphorus, total Kjeldahl nitrogen, anaerobic and
aerobic heterotrophs and perchlorate reducing bacteria using the
chlorite dismutase gene polymerase chain reaction (PCR) assay.

The results of the first bench-scale study indicated that there was an
extremely low concentration of indigenous heterotrophic microbes in the
vadose zone soil. Likewise, the PCR assay showed that the native soil
contained non-detectable concentrations of the chlorite dismutase gene.
The addition of amendments eventually increased the anaerobic
heterotrophic microbial population after a three month amendment period.
Likewise, the soil that had been amended with corn syrup and sodium
acetate showed positive results for the chlorite dismutase gene.
However, even though the amended soil contained perchlorate reducing
bacteria, perchlorate removal was not significant in the in-situ columns

The second phase of the study involved setting up four microcosms
amended with sodium acetate at two different moisture contents. Two of
the microcosms were bioaugmented with commercial microbes and microbes
from wastewater treatment plant (WWTP). The results of the second phase
indicated that the commercial microbial population did not significantly
increase the perchlorate biodegradation rate. However, when the ex-situ
microcosms were amended with waste activated sludge from a WWTP and the
moisture conditions were above 37%, greater than 99.98% perchlorate
degradation occurred within about two weeks.

A field-scale study was performed using site soil and activated sludge
from a local wastewater treatment plant. Perchlorate-contaminated soil
was amended with activated sludge and water to promote a moisture
content level of at least 20%. After approximately four weeks the
perchlorate concentration had decreased by about 47 to 87 percent in the
wastewater amended containers and after about 2.5 months, some of the
soil containers showed as high as 95% perchlorate reduction.