Exploration Of The Effective Nitrobenzene-degrading Bacterial Consortium And Its Application Capability

Nitrobenzene is a highly toxic organic compound and widely used in the manufacture of organic products, nitrobenzene-containing wastewater can cause great harm to the environment and human. Currently, bacterial strains capable of degrading nitrobenzene were described by many researchers. However, because of the high toxicity and complexity of nitrobenzene-containing wastewater, bacterial strain can not survive in nitrobenzene-containing wastewater with high toxicity, and the nitrobenzene-degrading bacterial strain can only studied in the laboratory level. Therefore, we exploration of the effective nitrobenzene-degrading bacterial consortiums and immobilized them to deal with industrial wastewater contained nitrobenzene. This study demonstrates the application potential of the immobilized bacterial consortiums to nitrobenzene industrial wastewater.In this study, bacterial strains capable of degrading nitrobenzene were isolated and identified, and constructed effective bacterial consortiums combined with nitrobenzene-degrading genetical engineered strain. The degrading properties of these bacterial consortiums were intensively studied. These bacterial consortiums were immobilized with macro-pore carrier, and then added into hybrid biological treatment system, to deal with industrial wastewater contained nitrobenzene. The nitrobenzene biodegradation characteristics, kinetics of immobilized cells and the reactor process parameters were investigated. The main results are reported as follows:(1) Isolation and identification of nitrobenzene-degrading bacterial. Five bacterial strains (EJB11, EJB10,4B, BG-1and TOLU1) capable of degrading nitrobenzene were isolated and identified, the nitrobenzene consumption rate were about20%after cultured for70hours at nitrobenzene concentration of200mg/L. On the basis of phylogenetic analysis of16SrDNA gene sequence, five strains were respectively belonging to Pseudomonas spp., Bacillus spp. and Flavobacterium sp.(2) The effective bacterial consortiums were constructed and its nitrobenzene degradation properties were studied. Effective bacterial consortiums were constructed by the five strains and nitrobenzene-degrading genetical engineered strain. Rate of nitrobenzene degradation for the most effective bacterial consortium is83.13%, while is25.41%for the most effective strain, when the400mg/L initial nitrobenzene concentration. The degrading properties of these bacterial consortiums were intensively studied, including effect of initial nitrobenzene concentration (The different initial concentration of nitrobenzene can be completely degraded by bacterial consortium CF and ACDE), SOD activity (The maximum SOD activity of bacterial consortium CF was542.30NU mg"1prot at140h, while247.53NU mg-1prot at70h for bacterial consortium ACDE), the cell-surface hydrophobicity (The bacterial consortium ACDE’s cell-surface hydrophobicity was larger than the ACDE’s) and degradation products analysis (The metabolite2-aminophenol was detected by GC/MS)(3) Nitrobenzene degradation kinetics of immobilized bacterial consortium. The bacterial consortiums were immobilized by macro-pore carrier, and nitrobenzene biodegradation characteristics and kinetics of immobilized cells were investigated. The results showed that:At a concentration range of100-500mg/L, the kinetics of nitrobenzene degradation by immobilized bacterial consortium was well expressed by the zero-order reaction model.(4) The best process parameters for hybrid biological treatment system used to degredation simulated wastewater contain nitrobenzene. The reactor process parameters were tested:amount of aeration:2～4mL/min*L, flow rate:0.1～0.5mL/s, HRT (hydraulic retention time):20～25h, pH:6～8, temperature:25～30℃. The nitrobenzene and COD removal efficiencies cultured for24hours is100%and60%at nitrobenzene concentration of300～400mg/L,respectively.