Pyrogenic carbon modulating TCE dehalogenation through snorkeling electrons under sulfate-reducing conditions

Microbial dehalogenation, using obligate and facultative organohalide-respiring bacteria (OHRB), has been widely used to remediate halohydrocarbon-polluted sites. Owing to the scarcity of OHRB, and poor efficiency in H₂-mediating interspecies electron transfer, microbial dehalogenation relying on OHRB is easily disturbed by Fe(III), sulfate, and nitrate as electron competitors. In the present study, pyrogenic carbon, featuring electron snorkeling, was introduced into the process of microbial dehalogenation, which facilitated the electron transfer from electro-active microbes to halohydrocarbon, then invigorating dehalogenation. As a consequence, fine dehalogenation of trichloroethene (TCE, as representative halohydrocarbon) was obtained, expressed as the nearly complete diminishment of 150 µmol L^-1 TCE and the sequestration of high contents of ethene (72.2-122.3 µmol L^-1 within 80 d). Such fine dehalogenation was ascribed to the synergy between pyrogenic carbon and electro-active microbes. Multiple microbes in mixed cultures, including Clostridium sp., Sporanaerobacter, Sedimentibacter, Paraclostridium, and Tissierella, stimulated TCE dehalogenation by providing electrons to pyrogenic carbon. Redox moieties on pyrogenic carbon enabled it to snorkel electrons, which facilitated the electron transfer from electro-active microbes to TCE, consequently invigorating TCE dehalogenation. Such microbial dehalogenation free of OHRB demonstrates the effectiveness of a novel strategy for remediating halohydrocarbon-polluted environments.