Harnessing Sewage Sludge Microbiota from Wastewater Treatment Plants for Tetrachloroethene Detoxification

Abstract

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.