Evaluation of a bioelectrochemical reductive/oxidative sequential process for chlorinated aliphatic hydrocarbons (CAHs) removal from a real contaminated groundwater
Edoardo Dell’Armi, Marco Zeppilli, Maria Letizia Di Franca, Bruna Matturro +8
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82% confidenceThis study demonstrates a sequential bioelectrochemical process using two membrane-less microbial electrolysis cells (MECs) for complete mineralization of chlorinated aliphatic hydrocarbons (CAHs) from real contaminated groundwater. The reductive MEC (−450 mV vs SHE) achieved complete PCE-to-VC conversion, while the oxidative MEC (15 mA galvanostatic) removed 92% of VC at 1.7 d HRT. Biomarker analysis confirmed Dehalococcoides mccartyi and functional genes for both pathways, with ecotoxicity tests demonstrating significant toxicity reduction in treated effluent.
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Abstract
In the present study, the sequential reductive/oxidative bioelectrochemical process has been tested with real groundwater from a contaminated site in Northern Italy for chlorinated aliphatic hydrocarbons (CAHs) removal. The sequential system was developed by connecting in series two membrane-less microbial electrolysis cells (MECs) equipped with an internal graphite counter electrode. The first MEC aimed at the CAHs reductive dechlorination (RD) and was constituted of a granular graphite working electrode. In the second MEC, a mixed metal oxide working electrode stimulated the oxidative dechlorination of the low chlorinated RD's by-products through oxygen production. The sequential process allowed complete mineralization of the CAHs contained in the real groundwater. A complete reduction of the perchloroethylene into vinyl chloride (VC) was observed in the first MEC polarized at −450 mV vs SHE, while the resulting VC was oxidized with a 92 ± 2 % efficiency in the second MEC due to the HRT increment from 0.7 to 1.7 days. Biomarkers of the reductive (Dehalococcoides mccartyi 16S rRNA and reductive dehalogenase genes) and oxidative (etnE, etnC genes) dechlorination have been monitored in the two MECs along with the ecotoxicity tests. Overall, they provide information on the efficiency of the applied technology and allow to assess the potential adverse effects. According to the Tetrahymena pyriformis reproduction inhibition test and Panagrellus redivivus mortality tests, showed a significant ecotoxicity reduction with respect its initial inhibitory effect at the tested concentrations.
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- Journal
- Journal of Water Process Engineering
- Year
- 2022