1. Bioremediation of Chlorinated Solvent-Contaminated Groundwater
Chlorinated solvents, such as tetrachloroethene (PCE)
and trichloroethene (TCE), are prevalent groundwater contaminants. Anaerobic
microorganisms such as Dehalococcoides ethenogenes and related species
can reductively dechlorinate PCE and TCE completely to the non-chlorinated,
non-toxic end product, ethene. Because Dehalococcoides sp.
requires hydrogen (H2), as electron donor, or energy source, to degrade
PCE and TCE and many other groundwater organisms may compete with Dehalococcoides
for hydrogen, how to deliver hydrogen specifically to Dehalococcoides
is an challenging issue in groundwater bioremediation. It is important
to understand the microbial ecology (i.e., how the different microorganisms
interact) in order to devise sound bioremediation strategies.
2. Chemical reduction of chlorinated solvents catalyzed by vitamin B12
Studies have shown that vitamin
B12, a cobalt cofactor found in Dehalococcoides and many other
microorganisms, is the reactive component of the enzymes that catalyze
the reductive transformation of chlorinated pollutants including PCE and
TCE. Understanding how B12 reacts with PCE and TCE will help us understand
how microbial and enzymatic dechlorination reactions occur and what factors
control these reactions.
3. Microbial transformation of chlorinated solvents coupled with anaerobic Fe(0) corrosion
One of the emerging technologies for the remediation solvent-contaminated
groundwater is permeable reactive barriers
(PRBs), which involves use of reactive materials, such as elemental
iron, to remove or degrade contaminants in groundwater in situ.
While the chemistry of solvent degradation with Fe(0) has been studied
by many, the role of microorganisms in these Fe(0) barriers is not well-understood.
A study conducted in our laboratory has shown that anaerobic iron corrosion
can support biological transformation of chlorinated ethenes. Here
of the Fe(0) surface with microbial colonies, taken from a culture-amended
sample in which TCE was reduced both chemically by Fe(0) and biologically
by the organisms. Since the abiotic and the biological reduction of TCE
occur through different routes in the pathway,
different products (i.e., non-toxic ethene and ethane vs. toxic vinyl chloride)
may form. Such iron-microbe interactions may have many important
implications and applications for site remediateion.
4. Using elemental iron to enhance the degradability of refractory compounds in wastewaters
Elemental iron has been used for groundwater remediation
since the mid-1990s. Although iron has also been shown to transform
many compounds commonly found in wastewaters, to date, it has not been
applied to wastewater treatment. Dr.
Daniel Cha and I are in the process of developing new wastewater treatment
technologies using elemental iron.
5. Graphite-mediate reduction of nitroaromatic pollutants with elemental iron
Cast iron has been used in dozens
of permeable reactive barriers (PRBs) to treat groundwater contaminated
with chlorinated solvents, heavy metals, radionuclides, and nutrients.
Cast iron contains mostly (~90%) elemental iron and some non-iron components
(graphite and other metals). Most of the studies to date have focused
on the transformation of pollutants by elemental iron, whereas the role
of the impurities such as graphite remains largely uninvestigated.
We recently found that graphite inclusions in cast iron may control the
reaction pathway and products of nitroaromatic pollutants. This process
is critical for designing and modeling groundwater and wastewater treatment
processes involving cast iron. It is also important for accurate
prediction of the fate of pollutants.
General chemistry, physics, and calculus
Recommended: organic chemistry and microbiology (or biochemistry)
Students may work for credit, work-study, stipend,
or as a volunteer.
Contact Prof. Pei Chiu, Department of Civil & Environmental Engineering, 356C DuPont Hall