2 research outputs found
Biodegradation of <i>cis</i>-1,2-Dichloroethene in Simulated Underground Thermal Energy Storage Systems
Underground
thermal energy storage (UTES) use has showed a sharp
rise in numbers in the last decades, with aquifer thermal energy storage
(ATES) and borehole thermal energy storage (BTES) most widely used.
In many urban areas with contaminated aquifers, there exists a desire
for sustainable heating and cooling with UTES and a need for remediation.
We investigated the potential synergy between UTES and bioremediation
with batch experiments to simulate the effects of changing temperature
and liquid exchange that occur in ATES systems, and of only temperature
change occurring in BTES systems on <i>cis</i>-DCE reductive
dechlorination. Compared to the natural situation (NS) at a constant
temperature of 10 °C, both UTES systems with 25/5 °C for
warm and cold well performed significantly better in <i>cis</i>-DCE (<i>cis</i>-1,2-dichloroethene) removal. The overall
removal efficiency under
mimicked ATES and BTES conditions were respectively 13 and 8.6 times
higher than in NS. Inoculation with <i>Dehalococcoides</i> revealed that their initial presence is a determining factor for
the dechlorination process. Temperature was the dominating factor
when <i>Dehalococcoides</i> abundance was sufficient. Stimulated
biodegradation was shown to be most effective in the mimicked ATES
warm well because of the combined effect of suitable temperature,
sustaining biomass growth, and regular <i>cis</i>-DCE supply
Geochemical and Microbiological Characteristics during in Situ Chemical Oxidation and in Situ Bioremediation at a Diesel Contaminated Site
While
in situ chemical oxidation with persulfate has seen wide
commercial application, investigations into the impacts on groundwater
characteristics, microbial communities and soil structure are limited.
To better understand the interactions of persulfate with the subsurface
and to determine the compatibility with further bioremediation, a
pilot scale treatment at a diesel-contaminated location was performed
consisting of two persulfate injection events followed by a single
nutrient amendment. Groundwater parameters measured throughout the
225 day experiment showed a significant decrease in pH and an increase
in dissolved diesel and organic carbon within the treatment area.
Molecular analysis of the microbial community size (16S rRNA gene)
and alkane degradation capacity (<i>alkB</i> gene) by qPCR
indicated a significant, yet temporary impact; while gene copy numbers
initially decreased 1–2 orders of magnitude, they returned
to baseline levels within 3 months of the first injection for both
targets. Analysis of soil samples with sequential extraction showed
irreversible oxidation of metal sulfides, thereby changing subsurface
mineralogy and potentially mobilizing Fe, Cu, Pb, and Zn. Together,
these results give insight into persulfate application in terms of
risks and effective coupling with bioremediation