Field test of a scaled-up bioelectrochemical sequential reductive/oxidative process for chlorinated aliphatic hydrocarbons (CAHs) remediation from contaminated groundwater

Chlorinated Aliphatic Hydrocarbons (CAHs) such as Perchloroethylene (PCE) and Trichloroethylene (TCE) are widespread groundwater contaminants due to their persistence and low solubility. Bioelectrochemical systems (BES) can create favorable redox conditions to stimulate the activity of dechlorinating microorganisms by providing reducing power directly or via hydrogen mediation in microbial electrolysis cells. This study presents the performance of a scaled-up sequential anaerobic/aerobic BES applied to a CAH-contaminated site in Northern Italy, integrated with a Groundwater Circulation Well system. The pilot system, consisting of four 105 L modules, operated under three different hydraulic retention times (HRTs) and potentiostatic conditions. Maximum tetrachloroethane (TeCA) removal was 1.23 mg/L·d, with a coulombic efficiency of 0.83 %. The study includes aquifer geological characterization, essential for assessing the long-term behaviour of the dense non aqueous phase liquid (DNAPL) source, and microbial analysis of the inoculum used to prime the system. Ecotoxicity tests were conducted on both influent and effluent to evaluate environmental risks. Results showed slight initial toxicity for Aliivibrio fischeri but no adverse effects on protozoa, plants, or Daphnids. This study presents the development of a pilot plant, representing the largest effort to scale up a bioelectrochemical process for the remediation of chlorinated aliphatic hydrocarbons, and one of the largest bioelectrochemical pilot installations overall in terms of the electrode active area. The findings highlight both the potential and the challenges of scaling up BES for CAH remediation. • The largest scaled-up BES pilot for CAH groundwater remediation was tested in a real site. • Pilot BES performances have been affected by TeCA remobilization and groundwater scarcity issues. • Energy consumption resulted below 1 kWh/m 3 , showing potential benefits vs. conventional methods. • TeCA removal was 1.36 mg/L·d with 0.83 % coulombic efficiency in reductive stage. • Multidisciplinary approach allowed for a comprehensive remediation process characterization