Long-Term Performance Assessment at a Highly Characterized and Instrumented DNAPL Source Area following Bioaugmentation
Abstract
The long-term behavior in chlorinated ethene DNAPL source areas following in situ bioaugmentation in heterogeneous media was investigated in this study. Monitoring was performed up to 3.7 years following active bioremediation using a high-density monitoring network. Soil sampling, passive flux meters, and push-pull tracer testing was performed. Results showed that, despite the absence of lactate, lactate fermentation transformation products, or hydrogen, biogeochemical conditions remained favorable for the reductive dechlorination of chlorinated ethenes. While ethene levels suggested relatively low dechlorination of the parent TCE and daughter products, CSIA showed that the extent of complete dechlorination was much greater than indicated by ethene generation. Results of the push-pull tracer testing confirmed that DNAPL remained in a portion of the source area, consistent with soil and groundwater data. Overall, study results suggest biological processes may persist to treat TCE years after cessation of active bioremediation, thereby serving as an important component of remedial design and long-term attenuation. Reliance on ethene generation alone as an indicator of complete dechlorination significantly underestimated the extent of complete dechlorination, as CSIA analysis provided a more reliable estimate; highlighting the importance of utilizing isotopic data to determine dechlorination rates in complex systems. Results also emphasize the need for high-resolution characterization and monitoring to facilitate improved design and performance monitoring to optimize resources to achieve remedial goals.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 22, 2017
- Accession Number
- AD1055290
Entities
People
- Alexander Haluska
- Charles E Schaefer
- Graig M. Lavorgna
- Michael D. Annable