Biological characteristics of the nitrobenzene-degrading strain NB1 during bioaugmentation of nitrobenzene-contaminated groundwater

Bioaugmentation is a cost-effective and rapid technology for nitrobenzene-contaminated groundwater. However, the biological characteristics of adding the nitrobenzene-degrading strain have not yet been comprehensively investigated. In the present study, a pure culture of the nitrobenzene-degrading strain NB1 was added into nitrobenzene-contaminated groundwater for laboratory-scale bioremediation, and the biological characteristics that include biomass and microbial migration, microbial activities and community structures, and the expression of the nbzA gene were analysed. The removal rate of nitrobenzene could reach 82.98–88.36 % with bioaugmentation, and an approximately 2.0 × 104–3.0 × 104 cfu/mL strain of NB1 could grow better in groundwater, whereas most of the added strain of NB1 would rapidly die. The migration velocity of strain NB1 was approximately 0.08 m/day and groundwater flow was likely to provide the main power of migration. The microbial dehydrogenase activities of groundwater with bioaugmentation were maintained at a higher level compared with those of raw nitrobenzene-contaminated groundwater. Bioaugmentation with strain NB1 did not obviously change the main microbial species. The influence of the introduction of strain NB1 on the microbial community structure was merely that the abundance of strain NB1 was significantly improved, whereas the abundances of other microorganisms were relatively decreased. The relative abundance and expression of the key nitrobenzene-degrading gene nbzA were enhanced by 1.20–1.65 times and by 1.54–8.57 times, respectively, as compared with raw nitrobenzene-contaminated groundwater, which indicated that the addition of strain NB1 showed improved growth and facilitated the degradation of nitrobenzene in groundwater. These research achievements could contribute to the construction of field bioremediation of nitrobenzene-contaminated groundwater with bioaugmentation.