Development Of Chemical Ahsorption-biological Reduction Integrated System For NO_x Removal From Flue Gas:Microbial Communities Feature And Solvent Degradation

Because of the new stringent emission standards and the limit of NOx control technology for boilers, development of novel technologies with low cost is critical for NOx control from industrial boilers. Chemical Absorption-Biological Reduction Integrated System (CABR) under development in our gourp features high efficiency, low cost of investment and non-pollution. It is expected to have a great potential for the application of NOx control from industrial boilers.In our previous work, the CABR system was started up via inoculation of pure culture. In this work, the CABR system was started up via inoculation of mixed culture obatained from a wastewater treatment plant. The performace of this new CABR system was investigated under varous testing conditions with different O2, SO2, and NO concnetrations, as well as different gas and liuquid flow rates. The microbial communities in the new CABR system under different O2 concentrations were analyzed to determine the dominated bacterial using a technology of high-throughput sequencing. Moreover, the degradation of the solvent including iron precipitation and EDTA degradation was also investigated to aid the operation of the CABR system. The main conclusions of this thesis are:(1) CABR sytem started up via inoculation of mixed culture shortened the period of start-up by 25 days compared to that via the inoculation of pure culture reported in our previous work. The new CABR system also featured higher oxygen-tolerance and better performace under the great gas flow rate.(2) The microbial community in this new CABR system was different from that reported in our previous work. The dominant bacteria in the new system were Petrimonas, Enterococcus, Cupriavidu, Chelatococcus, Clostridium sensu stricto, Bacillus. Among those, Petrimonas, Cupriavidus, Chelatococcus, Bacillus and Enterococcus were denitrifying bacteria with a distribution proportion of 63.27%. Clostridium sensu stricto and Bacillus were iron-reducing bacteria with a distribution proportion of 2.42%. The results demonstrated that denitrifying bacteria were in the dominant position of the new CABR system, which was different from that of previous system.(3) In presence of 6%(v/v) oxygen, the dominant baterium was Petrimonas, a strain of anaerobic denitrifying bacterium with a distribution proportion of 51.48%. The results of species richness and diversity analysis showed that the microbial communities in presence of 0% and 10%(v/v) oxgyen were similar. However, they were fairly different from that in presence of 6%(v/v) oxygen.It is believed that O2 concentration determined the variation of the microbial community in the CABR system.(4) Both theoretical calculation and experimental tests revealed that iron loss was mainly in the form of Fe(OH)3 and EDTA degradation occurred during the operation of CARB system.In addition, the solvent loss can be mitigated via the dosage of EDTA.(5) By investigating solvent loss rate and unit solvent loss processing NO load, the influence of inlet gas amount, initial Fe(III)EDTA concentration and O2 concentration on solvent loss were determined. When the initial Fe(III)EDTA concentration was low, the solvent loss moderated with high but fluctuant NO efficiency in long term. At that time, the key factor of high efficiency was EDTA amount.