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This field study demonstrates bioelectrochemical remediation of real contaminated groundwater containing chlorinated aliphatic hydrocarbons (CAHs) and nitrates using a membrane-less, column-type reactor with a graphite granule biocathode polarized at −650 mV vs. SHE. Laboratory characterization preceded a 75-day field test at a contaminated site near Milan. The reactor achieved effective CAHs degradation through reductive dechlorination, though coulombic efficiency dropped dramatically from 2.43% (synthetic medium) to 0.01% (real groundwater) due to competing microbial processes including methanogenesis, sulfate reduction, and nitrate reduction.

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Abstract

This study uses a membrane‐less reactor to explore the bioelectrochemical remediation of real contaminated groundwater from chlorinated aliphatic hydrocarbons (CAHs) and nitrates. The research focuses on testing a column‐type bioelectrochemical reactor to stimulate in situ degradation of contaminants through the supply of electrons by a graphite granules biocathode. After a preliminary laboratory characterization and operation with a synthetic feeding solution, a field test is conducted in a real contaminated site, where the reactor demonstrates effective degradation of CAHs and inorganic anions. Notably, the cathodic potential promotes the reductive dechlorination of chlorinated species. Simultaneously, nitrate reduction, sulfate reduction, and methanogenesis occurr, influencing the overall coulombic efficiency of the process. The use of real groundwater, compared to the synthetic medium, significantly decreases the coulombic efficiency of reductive dechlorination, dropping from 2.43% to 0.01%. Concentration profiles along the bioelectrochemical reactor allow for a deeper description of the reductive dechlorination rate at different flow rates, as well as increase the knowledge about reduction and oxidation mechanisms. Scaling up the technology presents several challenges, including the optimization of coulombic efficiency and the management of competing microbial metabolisms. The study provides a valuable contribution toward advancing bioelectrochemical technologies for the bioremediation of complex contaminated sites.

Keywords

Reductive dechlorinationEnvironmental remediationEnvironmental chemistryBioremediationGroundwater remediationNitrate

Identifiers

DOI
10.1002/cplu.202400683
Journal
ChemPlusChem
Year
2025