Evaluation of the Bioelectrochemical Approach and Different Electron Donors for Biological Trichloroethylene Reductive Dechlorination.

Edoardo Dell'Armi,Marco Petrangeli Papini,Marta Maria Rossi,Lucia Taverna,Marco Zeppilli

doi:10.3390/toxics10010037

Edoardo Dell'Armi, Marco Petrangeli Papini + Show 3 more

Open Access

https://doi.org/10.3390/toxics10010037

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Journal: Toxics	Publication Date: Jan 13, 2022
Citations: 6	License type: CC BY 4.0

Affiliation: Sapienza University of Rome

Abstract

Trichloroethylene (TCE) and more in general chlorinated aliphatic hydrocarbons (CAHs) can be removed from a contaminated matrix thanks to microorganisms able to perform the reductive dechlorination reaction (RD). Due to the lack of electron donors in the contaminated matrix, CAHs’ reductive dechlorination can be stimulated by fermentable organic substrates, which slowly release molecular hydrogen through their fermentation. In this paper, three different electron donors constituted by lactate, hydrogen, and a biocathode of a bioelectrochemical cell have been studied in TCE dechlorination batch experiments. The batch reactors evaluated in terms of reductive dechlorination rate and utilization efficiency of the electron donor reported that the bio-electrochemical system (BES) showed a lower RD rate with respect of lactate reactor (51 ± 9 µeq/d compared to 98 ± 4 µeq/d), while the direct utilization of molecular hydrogen gave a significantly lower RD rate (19 ± 8 µeq/d), due to hydrogen low solubility in liquid media. The study also gives a comparative evaluation of the different electron donors showing the capability of the bioelectrochemical system to reach comparable efficiencies with a fermentable substrate without the use of other chemicals, 10.7 ± 3.3% for BES with respect of 3.5 ± 0.2% for the lactate-fed batch reactor. This study shows the BES capability of being an alternative at classic remediation approaches.

Highlights

Chlorinated aliphatic hydrocarbons (CAHs) are common soil and groundwater contaminants due to their large-scale use and inadequate disposal or storage [1,2,3,4,5]
The most important microorganism involved in the degradation of chlorinated compounds is Dehalococcoides mccarty (Dhc), which can eliminate chlorine atoms (by the reductive dechlorination (RD) pathway) from the carbon skeleton of perchloroethylene (PCE), trichloroethylene (TCE) up to the formation of ethylene, a completely harmless molecule [12]
Since the inoculum comes from biomass acclimatized to lactate, the experimental data confirmed the effectiveness of lactate as a hydrogen slow-release source through its fermentation

Summary

Introduction

Chlorinated aliphatic hydrocarbons (CAHs) are common soil and groundwater contaminants due to their large-scale use and inadequate disposal or storage [1,2,3,4,5]. In Italy, regarding the CAHs of our interest, the threshold concentration limits of perchloroethylene (PCE), trichloroethylene (TCE), 1,1-dichloroethylene (1,1-DCE), and vinyl chloride (VC) are 1.1, 1.5, 0.05 and 0.5 μg/L respectively. As new sustainable and eco-friendly strategies are gaining attention [7], bioremediation technologies have been of increasing interest to the science community [8,9,10]. These technologies are based on the activity of specific microorganisms, whose metabolism can transform the contaminant into less toxic and hazardous compounds [11]. The most important microorganism involved in the degradation of chlorinated compounds is Dehalococcoides mccarty (Dhc), which can eliminate chlorine atoms (by the reductive dechlorination (RD) pathway) from the carbon skeleton of perchloroethylene (PCE), trichloroethylene (TCE) up to the formation of ethylene, a completely harmless

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Conclusion