Ability of microorganism along a contaminated plume to degrade chlorinated solvents (ethene, propane, ethane)

Abstract : Our objective was i) to assess the ability of microorganism from a plume to degrade chlorinated solvents to which they are exposed in situ and ii) to determine optimal substrate conditions to stimulate their ability to degrade these products. We monitored chloro-ethene and chloro-ethane, but also chloro-propane for which one little is known on its fate in the environment. Three springs were selected at different distances from the Dense Nonaqueous Phase Liquid source in order to have one monophase water sample (W1) (15 m downstream the DNAPL) with perchloroethene (PCE), trichloroethene (TCE), dichloroethene (DCEcis and DCEtrans) are at the ppm level, a second water sample (W2) (250 m downstream) with these chloro-ethenes at the ppb level and a final diluted site (W3) (1.5 km downstream) with no PCE detected, TCE and DCEtrans at the limit of quantification level (2 ppb), and therefore with DCEcis (30 ppb) as main quantified contaminant. Vinyl chloride (VC) ranged from 0.3 to 0.008 ppm in these waters. Chloro-propanes were also found at the ppm level in the first water, especially the 1,2-dichloropropane (DCPa) (2.5 ppm). Abundance of the total microbial community in these 3 water samples was assessed by qPCR (16S rRNA) and microscopic counting, and abundance of the bacterial community degrading chloro-ethene solvent was assessed by qPCR of reductive dehalogenase genes (pceA, tceA, pdrA, bvcA, vcrA). Water was placed in sacrificial batch units in triplicates with no substrate addition or with lactate (3 mM), acetate (3 mM), soya oil (15 g/L), molasses (0.7 g/L) as carbon substrate to stimulate reductive dechlorination. Degradation of the chlorinated solvent was monitored by GC/FID conditions every 2 weeks for lactate-spiked unit and every month for 4 additional conditions, during 5 months. Preliminary results showed that after one-month incubation, concentrations in PCE, TCE, DCEtrans and VC, significantly decreased to a similar level in presence of lactate or molasses (p < 0.05) in water W1. However in W1, DCEcis and DCPa concentrations did not decreased after one-month incubation. In water W2, PCE, TCE, DCEtrans, VC and DCEcis significantly decreased after one-month incubation with lactate. In the water W3, DCEcis decreased after one-month incubation with lactate. Degradation analyses in the additional substrate conditions are under-going, also additional sampling dates to be performed are meant to generate biodegradation rate. In conclusion, preliminary results suggest that i) bacteria able to degrade chlorinated solvent were present in the three tested water samples, ii) in the water W1, molasses and lactate would have similar potential to stimulate their activity, and iii) DCEcis degradation was not detected within one-month incubation in a sample with high level of PCE and TCE, such as W1, possibly because it is also the product of their degradation; when concentration in PCE and TCE were lower (W2) or not detected (W3), DCEcis degradation was initiated within a month. The present study will provide valuable information for in situ bioremediation, and more specifically regarding choropropanes degradation. The present work will enable to select optimal conditions for further optimization in column units, then in a pilot-scale plant on site.
Type de document :
Poster
Aquaconsoil, Jun 2015, Copenhagen, Denmark. 2015
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https://hal-brgm.archives-ouvertes.fr/hal-01146872
Contributeur : Aourell Mauffret <>
Soumis le : mercredi 29 avril 2015 - 11:59:06
Dernière modification le : vendredi 28 septembre 2018 - 15:10:07

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  • HAL Id : hal-01146872, version 1

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Aourell Mauffret, Louis Hermon, Mickael Charron, Stéfan Colombano, David Cazaux, et al.. Ability of microorganism along a contaminated plume to degrade chlorinated solvents (ethene, propane, ethane). Aquaconsoil, Jun 2015, Copenhagen, Denmark. 2015. 〈hal-01146872〉

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