Higher thermal remediation temperature facilitates the sequential bioaugmented reductive dechlorination

The coupling of thermal remediation with microbial reductive dechlorination (MRD) has shown promising potential for the cleanup of chlorinated solvent contaminated sites. In this study, thermal treatment and bioaugmentation were applied in series, where prior higher thermal remediation temperature led to improved TCE dechlorination performance with both better organohalide-respiring bacteria (OHRB) colonization and electron donor availability. The 60 °C was found to be a key temperature point where the promotion effect became obvious. Amplicon sequencing and co-occurrence network analysis demonstrated that temperature was a more dominating factor than bioaugmentation that impacted microbial community structure. Higher temperature of prior thermal treatment resulted in the decrease of richness, diversity of indigenous microbial communities, and simplified the network structure, which benefited the build-up of newcoming microorganisms during bioaugmentation . Thus, the abundance of Desulfitobacterium increased from 0.11 % (25 °C) to 3.10 % (90 °C). Meanwhile, released volatile fatty acids (VFAs) during thermal remediation functioned as electron donors and boosted MRD. Our results provided temperature-specific information on synergistic effect of sequential thermal remediation and bioaugmentation, which contributed to better implementation of the coupled technologies in chloroethene-impacted sites.