Response of chlorinated hydrocarbon transformation and microbial community structure in an aquifer to joint H2 and O2.

Hydrogen (H2) and oxygen (O2) are critical electron donors and acceptors to promote the anaerobic and aerobic microbial transformation of chlorinated hydrocarbons (CHCs), respectively. Electrochemical technology can effectively supply H2 and O2 directly to an aquifer. However, the response of CHC transformation and microbial community structure to joint H2 and O2 are still unclear. In this work, microcosms containing different combinations of H2 and O2 were constructed with natural sediments and nine mixed CHCs. The joint H2 and O2 microcosm (H2/O2 microcosm) significantly promoted the biotransformation of trichloroethylene (TCE), trans-dichloroethene (tDCE) and chloroform (CF). Illumina sequencing analyses suggested that a particular microbial community was formed in the H2/O2 microcosm. The specific microbial species included Methyloversatilis, Dechloromonas, Sediminibacterium, Pseudomonas, Acinetobacter, Curvibacter, Comamonas and Acidovorax, and the relative abundance of the tceA, phe and soxB genes synchronously increased. These results suggested that some specific microbes are potential CHC converters using H2 and O2 as energy sources, and aerobic and anaerobic transformations exist simultaneously in the H2/O2 microcosm. It provides a theoretical basis for establishing efficient green remediation technologies for CHC contaminated aquifers.