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Open AccessArticle

Microbial Assisted Hexavalent Chromium Removal in Bioelectrochemical Systems

1
Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
2
Department of Earth and Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126 Milano, Italy
3
Department of Agriculture, Food, Environment and Forestry, University of Florence, Piazzale delle Cascine 18, 50144 Firenze, Italy
*
Author to whom correspondence should be addressed.
Water 2020, 12(2), 466; https://doi.org/10.3390/w12020466
Received: 28 November 2019 / Revised: 24 January 2020 / Accepted: 5 February 2020 / Published: 10 February 2020
(This article belongs to the Special Issue Advances in In Situ Biological and Chemical Groundwater Treatment)
Groundwater is the environmental matrix that is most frequently affected by anthropogenic hexavalent chromium contamination. Due to its carcinogenicity, Cr(VI) has to be removed, using environmental-friendly and economically sustainable remediation technologies. BioElectrochemical Systems (BESs), applied to bioremediation, thereby offering a promising alternative to traditional bioremediation techniques, without affecting the natural groundwater conditions. Some bacterial families are capable of oxidizing and/or reducing a solid electrode obtaining an energetic advantage for their own growth. In the present study, we assessed the possibility of stimulating bioelectrochemical reduction of Cr(VI) in a dual-chamber polarized system using an electrode as the sole energy source. To develop an electroactive microbial community three electrodes were, at first, inserted into the anodic compartment of a dual-chamber microbial fuel cell, and inoculated with sludge from an anaerobic digester. After a period of acclimation, one electrode was transferred into a polarized system and it was fixed at −0.3 V (versus standard hydrogen electrode, SHE), to promote the reduction of 1000 µg Cr(VI) L−1. A second electrode, served for the set-up of an open circuit control, operated in parallel. Cr(VI) dissolved concentration was analysed at the initial, during the experiment and final time by spectrophotometric method. Initial and final microbial characterization of the communities enriched in polarized system and open circuit control was performed by 16S rRNA gene sequencing. The bioelectrode set at −0.3 V showed high Cr(VI) removal efficiency (up to 93%) and about 150 µg L−1 day−1 removal rate. Similar efficiency was observed in the open circuit (OC) even at about half rate. Whereas, purely electrochemical reduction, limited to 35%, due to neutral operating conditions. These results suggest that bioelectrochemical Cr(VI) removal by polarized electrode offers a promising new and sustainable approach to the treatment of groundwater Cr(VI) plumes, deserving further research. View Full-Text
Keywords: bioelectrochemical systems (BESs); hexavalent chromium; electrobioremediation; groundwater treatment bioelectrochemical systems (BESs); hexavalent chromium; electrobioremediation; groundwater treatment
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Beretta, G.; Daghio, M.; Espinoza Tofalos, A.; Franzetti, A.; Mastorgio, A.F.; Saponaro, S.; Sezenna, E. Microbial Assisted Hexavalent Chromium Removal in Bioelectrochemical Systems. Water 2020, 12, 466.

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