Feasibility study of in-situ bioremediation for nitrobenzene-contaminated groundwater
Although many studies have simulated in-situ bioremediation of contaminated groundwater, most of them have not considered hydrochemical conditions and indigenous microorganisms, thus potentially rendering results inapplicable to actual in-situ groundwater bioremediation projects. This study focused on a nitrobenzene-contaminated groundwater site located in Jilin City, China. The actual nitrobenzene-contaminated groundwater was taken from Jilin City to simulate in-situ groundwater bioremediation in the laboratory. The feasibility of in-situ bioremediation for nitrobenzene-contaminated groundwater was studied according to actual site conditions and characteristics of nitrobenzene-degrading microorganisms in groundwater. The results showed that nitrobenzene-degrading bacterium strain NB1 was the dominant species that could effectively and rapidly degrade nitrobenzene by a partial reductive pathway. No negative factors on the growth or degrading function of this strain in groundwater could be detected. During a laboratory simulation experiment, combined in-situ bioremediation technologies, namely air sparging and bioaugmentation, could readily remove approximately 89.56% of nitrobenzene from groundwater without adding nutrients; oxygen was found to be the important growth factor for strain NB1. As the substrate of nitroreductase, encoded by the nitrobenzene nitroreductase (nbzA) gene, nitrobenzene was likely to significantly affect the expression of this gene. In conclusion, in-situ bioremediation is a feasible way to solve the problem of nitrobenzene-contaminated groundwater in Jilin City as long as sufficient oxygen and biomass of strain NB1 is ensured.