Abstract
ABSTRACT
The feasibility of sustained removal of carbon tetrachloride (CT) by Pseudomonas stutzeri KC was evaluated in two 2 meter-long columns packed with aquifer material from a CT-contaminated aquifer at Schoolcraft, MI. CT-contaminated groundwater was pumped continuously through both columns until the aqueous and adsorbed CT had equilibrated. CT transformation was initiated by inoculating an 8 cm-wide alkaline-adjusted zone near the upstream end of both columns with groundwater containing strain KC and acetate. CT-contaminated groundwater was then pumped continuously through the columns. Both columns received weekly acetate additions in the bioaugmentation zone. Base and phosphate additions were performed weekly in one column and twice weekly in the second column. A CT-transforming zone developed in the bioaugmentation zone of both columns, with 97% removal of CT in the column receiving weekly base additions and 93% removal in the column receiving twice-weekly base additions. Strain KC was detected on the solids of both columns. When acetate and base additions were discontinued, CT transformation decreased, and chloroform (CF) production was observed in the column that had received twice-weekly base additions (no CF was detected in the other column). The results indicate that efficient CT removal without CF production is possible over extended periods. The results also suggest that microbial populations indigenous to the Schoolcraft aquifer can convert CT to CF, and that such populations were selected by twice-weekly base additions. Weekly base additions evidently failed to select such populations.
Key words:
Bioaugmentation; biocurtain; bioremediation; carbon tetrachloride; Pseudomonas stutzeri KC; sand column
Get full access to this article
View all access options for this article.