Harnessing Sewage Sludge Microbiota from Wastewater Treatment Plants for Tetrachloroethene Detoxification

Chlorinated solvent contamination in groundwater poses
significant
risks to the ecosystem integrity and public health. Bioremediation
using organohalide-respiring bacteria (OHRB) is a prospective strategy
to address this issue. Identifying accessible and cost-effective bioinoculants
is crucial for the successful application of this approach on the
field scale. In this study, we demonstrate the capability of sewage
sludge microorganisms from wastewater treatment plants (WWTPs) to
reductively dechlorinate tetrachloroethene. Remarkably, 63 of 84 sludge
microbiota samples from WWTPs completely detoxified tetrachloroethene
(PCE) to ethene through various intermediate products. The dechlorination
capacity was attributed to the synergistic activity of diverse OHRB
populations, including Dehalococcoides, Dehalogenimonas, Dehalobacter, Geobacter, and Sulfurospirillum, demonstrating the diversity of OHRB in
this engineered system. Additionally, a range of canonical reductive
dehalogenase genes (e.g., tceA, vcrA, bvcA, pteA, and pceA) were identified, with tceA likely responsible
for the complete dechlorination of vinyl chloride in at least 10 sludge
microcosms. Community-level analysis further revealed a core microbiome
in PCE-dechlorinating microcosms, predominantly composed of fermenters,
methanogens, and syntrophic bacteria, guiding the construction of
tailored dechlorinating consortia for bioremediation applications.
These findings highlight sewage sludge as a valuable and underutilized
microbial resource for application in the remediation of environments
polluted with chlorinated solvents.