An in-situ bio-remediation of nitrobenzene in stimulated aquifer using emulsified vegetable oil

Widespread nitrobenzene (NB) contamination in groundwater requires an economical and effective remediation technology. In situ microbial reactive zone enhanced by injecting emulsified vegetable oil (EVO) is an effective method for remediating NB-contaminated groundwater, which can be reduced to aniline (AN) effectively in the reactive zone. However, the bio-mechanism of NB remediation in a real contaminated site is still unclear. Thus, a 3-D tank was established to conduct a pilot-scale experiment and the bacterial communities in the tank were analyzed by 16S rDNA high-throughput sequencing. The results suggested that the injection of EVO can stimulate some certain microorganisms to grow, and reduce NB though biological and biochemical processes. There were three degradation pathways of NB: (1) direct oxidation by Pseudomonas; (2) direct mineralization by Clostridium sensu stricto; and (3) coupled reduction of NB through microbial dissimilatory iron reduction by Geobacter and Arthrobacter. Among these pathways, the coupled reduction process is the main degradation pathway.

Automated summary

The in situ microbial reactive zone enhanced by injecting emulsified vegetable oil is an effective method for remediating nitrobenzene-contaminated groundwater, as it can stimulate the growth of certain microorganisms to reduce nitrobenzene through biological and biochemical processes. Analysis through 16S rDNA high-throughput sequencing revealed three degradation pathways for nitrobenzene, with the coupled reduction process identified as the main pathway.