Biotic and abiotic reductive dechlorination of chloroethenes in aquitards

Abstract It is generally recognized that reductive processes are more important than oxidative ones in transforming, degrading and mineralizing many environmental contaminants. One process of particular importance is reductive dehalogenation, i.e., the replacement of a halogen atom (most commonly a chlorine atom) by a hydrogen atom. A number of different mechanisms are involved in these reactions. Photochemical reactions probably play a role in some instances. Aliphatic compounds such as chloroethanes, partly aliphatic compounds such as DDT, and alicyclic compounds such as hexachlorocyclohexane are readily dechlorinated in the laboratory by reaction with reduced iron porphyrins such as hematin. Many of these are also dechlorinated by cultures of certain microorganisms, probably by the same mechanism. Such compounds, with a few exceptions, have been found to undergo reductive dechlorination in the environment. Aromatic compounds such as halobenzenes, halophenols and halobenzoic acids appear not to react with reduced iron porphyrins. Some of these however undergo reductive dechlorination both in the environment and in the laboratory. The reaction is generally associated with methanogenic bacteria. There is evidence for the existence of a number of different dechlorinating enzymes specific for different isomers. Recently it has been found that many components of polychlorinated biphenyls (PCBs), long considered to be virtually totally resistant to environmental degradation, may be reductively dechlorinated both in the laboratory and in nature. These findings suggest that many environmental contaminants may prove to be less persistent than was previously feared.

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Reductive dechlorination in recalcitrant sources of chloroethenes in the transition zone between aquifers and aquitards

Environmental Science and Pollution Research ◽

10.1007/s11356-016-7068-4 ◽

2016 ◽

Vol 23 (18) ◽

pp. 18724-18741 ◽

Cited By ~ 6

Author(s):

Diana Puigserver ◽

Jofre Herrero ◽

Mònica Torres ◽

Amparo Cortés ◽

Ivonne Nijenhuis ◽

...

Keyword(s):

Transition Zone ◽

Reductive Dechlorination

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Microbial Chain Elongation and Subsequent Fermentation of Elongated Carboxylates as H2-Producing Processes for Sustained Reductive Dechlorination of Chlorinated Ethenes

Environmental Science & Technology ◽

10.1021/acs.est.1c01319 ◽

2021 ◽

Author(s):

Aide Robles ◽

Theodora L. Yellowman ◽

Sayalee Joshi ◽

Srivatsan Mohana Rangan ◽

Anca G. Delgado

Keyword(s):

Reductive Dechlorination ◽

Chlorinated Ethenes ◽

Chain Elongation

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Biological effects of tourmaline treatment on Dehalococcoides spp. during the reductive dechlorination of trichloroethylene

RSC Advances ◽

10.1039/d0ra10830h ◽

2021 ◽

Vol 11 (20) ◽

pp. 12086-12094

Author(s):

Tielong Li ◽

Jiaxin Wen ◽

Bingjie Li ◽

Shihu Ding ◽

Wei Wang

Keyword(s):

Gene Expression ◽

Cell Proliferation ◽

Community Structure ◽

Reductive Dechlorination ◽

Biological Effects ◽

Dechlorinating Bacteria ◽

Contaminated Aquifers ◽

Tce Degradation ◽

Induced Changes

To explore the application of mineral in bioremediation of contaminated aquifers, this study investigated tourmaline-induced changes in TCE degradation, community structure, cell proliferation and gene expression of dechlorinating bacteria.

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Effects of the Feeding Solution Composition on a Reductive/Oxidative Sequential Bioelectrochemical Process for Perchloroethylene Removal

Processes ◽

10.3390/pr9030405 ◽

2021 ◽

Vol 9 (3) ◽

pp. 405

Author(s):

Edoardo Dell’Armi ◽

Marco Zeppilli ◽

Bruna Matturro ◽

Simona Rossetti ◽

Marco Petrangeli Papini ◽

...

Keyword(s):

Reductive Dechlorination ◽

Nitrate Reduction ◽

Coulombic Efficiency ◽

Reducing Power ◽

Mineral Medium ◽

Process Conditions ◽

Microbial Electrolysis Cells ◽

Dehalococcoides Mccartyi ◽

In Series ◽

Synthetic Groundwater

Chlorinated aliphatic hydrocarbons (CAHs) are common groundwater contaminants due to their improper use in several industrial activities. Specialized microorganisms are able to perform the reductive dechlorination (RD) of high-chlorinated CAHs such as perchloroethylene (PCE), while the low-chlorinated ethenes such as vinyl chloride (VC) are more susceptible to oxidative mechanisms performed by aerobic dechlorinating microorganisms. Bioelectrochemical systems can be used as an effective strategy for the stimulation of both anaerobic and aerobic microbial dechlorination, i.e., a biocathode can be used as an electron donor to perform the RD, while a bioanode can provide the oxygen necessary for the aerobic dechlorination reaction. In this study, a sequential bioelectrochemical process constituted by two membrane-less microbial electrolysis cells connected in series has been, for the first time, operated with synthetic groundwater, also containing sulphate and nitrate, to simulate more realistic process conditions due to the possible establishment of competitive processes for the reducing power, with respect to previous research made with a PCE-contaminated mineral medium (with neither sulphate nor nitrate). The shift from mineral medium to synthetic groundwater showed the establishment of sulphate and nitrate reduction and caused the temporary decrease of the PCE removal efficiency from 100% to 85%. The analysis of the RD biomarkers (i.e., Dehalococcoides mccartyi 16S rRNA and tceA, bvcA, vcrA genes) confirmed the decrement of reductive dechlorination performances after the introduction of the synthetic groundwater, also characterized by a lower ionic strength and nutrients content. On the other hand, the system self-adapted the flowing current to the increased demand for the sulphate and nitrate reduction, so that reducing power was not in defect for the RD, although RD coulombic efficiency was less.

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A Microcosm Treatability Study for Evaluating Wood Mulch-Based Amendments as Electron Donors for Trichloroethene (TCE) Reductive Dechlorination

Water ◽

10.3390/w13141949 ◽

2021 ◽

Vol 13 (14) ◽

pp. 1949

Author(s):

Edoardo Masut ◽

Alessandro Battaglia ◽

Luca Ferioli ◽

Anna Legnani ◽

Carolina Cruz Viggi ◽

...

Keyword(s):

Electron Donor ◽

Environmental Sustainability ◽

Reductive Dechlorination ◽

Environmental Remediation ◽

Low Cost ◽

Chlorinated Solvents ◽

Electron Donors ◽

Chlorinated Ethenes ◽

Dehalococcoides Mccartyi ◽

Wood Mulch

In this study, wood mulch-based amendments were tested in a bench-scale microcosm experiment in order to assess the treatability of saturated soils and groundwater from an industrial site contaminated by chlorinated ethenes. Wood mulch was tested alone as the only electron donor in order to assess its potential for stimulating the biological reductive dechlorination. It was also tested in combination with millimetric iron filings in order to assess the ability of the additive to accelerate/improve the bioremediation process. The efficacy of the selected amendments was compared with that of unamended control microcosms. The results demonstrated that wood mulch is an effective natural and low-cost electron donor to stimulate the complete reductive dechlorination of chlorinated solvents to ethene. Being a side-product of the wood industry, mulch can be used in environmental remediation, an approach which perfectly fits the principles of circular economy and addresses the compelling needs of a sustainable and low environmental impact remediation. The efficacy of mulch was further improved by the co-presence of iron filings, which accelerated the conversion of vinyl chloride into the ethene by increasing the H2 availability rather than by catalyzing the direct abiotic dechlorination of contaminants. Chemical analyses were corroborated by biomolecular assays, which confirmed the stimulatory effect of the selected amendments on the abundance of Dehalococcoides mccartyi and related reductive dehalogenase genes. Overall, this paper further highlights the application potential and environmental sustainability of wood mulch-based amendments as low-cost electron donors for the biological treatment of chlorinated ethenes.

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