Anaerobic ethylene glycol degradation by microorganisms in poplar and willow rhizospheres |
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Authors: | D Carnegie J A Ramsay |
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Institution: | (1) Chemical Engineering, Queen’s University, Kingston, ON, K7L 3N6, Canada |
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Abstract: | Although aerobic degradation of ethylene glycol is well documented, only anaerobic biodegradation via methanogenesis or fermentation
has been clearly shown. Enhanced ethylene glycol degradation has been demonstrated by microorganisms in the rhizosphere of
shallow-rooted plants such as alfalfa and grasses where conditions may be aerobic, but has not been demonstrated in the deeper
rhizosphere of poplar or willow trees where conditions are more likely to be anaerobic. This study evaluated ethylene glycol
degradation under nitrate-, and sulphate-reducing conditions by microorganisms from the rhizosphere of poplar and willow trees
planted in the path of a groundwater plume containing up to 1.9 mol l−1 (120 g l−1) ethylene glycol and, the effect of fertilizer addition when nitrate or sulphate was provided as a terminal electron acceptor
(TEA). Microorganisms in these rhizosphere soils degraded ethylene glycol using nitrate or sulphate as TEAs at close to the
theoretical stoichiometric amounts required for mineralization. Although the added nitrate or sulphate was primarily used
as TEA, TEAs naturally present in the soil or CO2 produced from ethylene glycol degradation were also used, demonstrating multiple TEA usage. Anaerobic degradation produced
acetaldehyde, less acetic acid, and more ethanol than under aerobic conditions. Although aerobic degradation rates were faster,
close to 100% disappearance was eventually achieved anaerobically. Degradation rates under nitrate-reducing conditions were
enhanced upon fertilizer addition to achieve rates similar to aerobic degradation with up to 19.3 mmol (1.20 g) of ethylene
glycol degradation l−1 day−1 in poplar soils. This is the first study to demonstrate that microorganisms in the rhizosphere of deep rooted trees like
willow and poplar can anaerobically degrade ethylene glycol. Since anaerobic biodegradation may significantly contribute to
the phytoremediation of ethylene glycol in the deeper subsurface, the need for “pump and treat” or an aerobic treatment would
be eliminated, hence reducing the cost of treatment. |
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Keywords: | Ethylene glycol Anaerobic Bioremediation Poplar Willow Nitrate Sulphate |
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