| The purpose of this dissertation is to investigate the degradation charcteristics of 3 strains which could grow on nitrobenzene as its sole carbon source. A defined microbial consortium was constructed through orthogonal experiments by using 1#, 2# and 3#. The degradability and immobilization by adsorbed in polyurethane foam was studied. As far as the characteristics of the real nitrobenzene wastewater are concerned, the degradation of nitrobenzene under high shock-loadings and hydraulic loadings and in high salinity or in the presence of other organic compounds (phenol, aniline or phenol and aniline) was carried out to evaluate the perspectives of applications. It provided the theoretical evidence for the degradation of nitrobenzene.The polyurethane foam of DW-22 was selected as the immobilized material. The optimal conditons for nitrobenzene degradation by polyurethane-foam-immobilized cells are as followed: amounts of carrier: 5.1 mg/ml; temperature:30℃, 30℃and 25℃; pH 7.0; shaking velocity 150 r/min, innocula 6 mg/L, 10 mg/L and 6 mg/L, respectively. The heat-resistant, toleerance of high toxicity and pH of the immobilized cells were enhanced compared to freely susupended cells. The results also indicated that SDS could remove partially the plasmid. The antibiotic capability of the strain decreased after the plasmid curing, and so did the degrading capability also decreased, conjecturing that the plasmid was related definitely to the growth characters of the bacteria strain, with possibly the relative glue of organism degradation.A defined microbial consortium was constructed through orthogonal experiments by using of strain 1#, 2# and 3#. The optimal ratio of 1# to 2# to 3# was 1:3:3. The optimal conditons for the nitrobenzene degradation by the consortium were as followed: temperature 30℃, pH7.0, shaking velocity 150 r/min, innocula 10 mg/L. Compared to 3 pure strains, the consortium degraded nitrobenzene under severe conditions and had a wider substrates range. The consortium degraded nitrobenzene effectively in high salinity of 3% (NaCl). The degradation of nitrobenzene (200 mg/L) by the consortium was not influenced in the presence of 100 mg/L phenol or 50 mg/L aniline. The optimal conditons for the nitrobenzene degradation by the immobilized consortium were as followed: temperature 30℃, pH7.0, shaking velocity 130 r/min, innocula 8 mg/L. The nitrobenzene degradation process showed that the degradation efficiency of immobilized consortium was apparently superior to that of free suspended cells. The degradation of nitrobenzene followed the model of first order reaction kinetics when the initial nitrobenzene concerntions were lower than 112.18 mg/L. Under the optimal conditions, the degradation kinetics of immobilized cells was fit well with Andrews model with qmax=11.8451/h, Ks=254.6464 mg/L, Ki=129.1570 mg/L, respectively. During semi-continuous degradation in the shaken culture, the immobilized cells could degrade nitrobenzene over long periods of 100 and 57 days without losing the degrading-activity at the initial concentrations 200 mg/L and 400 mg/L, respectively. The immobilized cells could tolerant higher nitrobenzene shock-loadings by contrast with freely suspended cells, and could degradation nitrobenzene (200 mg/L) in 5% salinity without inhibition. Furthermore, decreased performance on the degradation of nitrobenzene by the immobilized cells in the presence of phenol, aniline or phenol and aniline was achieved. It can be concluded that the presence of phenol, aniline or phenol plus aniline inhibited the decomposition of nitrobenzene in the sequence: phenol plus aniline > aniline > phenol. Thus, more efficient degradation of nitrobenzene could be achieved by immobilized cells and the immobilized cells might be superiority to remove nitrobenzene in practical wastewater treatment system. The results demonstrate that the system with 9.32% inoculums has the strongest removal efficiency. During 34 days operation, the degradation efficiency maintains more than 85%.
|
PDF Full Text Request