Bioreactor Parameters Optimization And Degradation Dynamics For Anaerobic/Aerobic Fluidized Bed Treating Reactive Blue13

Considered as a low cost and practical method for dyeing wastewater treatment, bioremediation has been extensively used. However, further studies of bioreactor optimization, dye degradation mechanism, diffusivity inside biofilm and kinetics of decolorization are required. An anaerobic/aerobic fluidized bed system was built for reactive blue13wastewater degradation in this study. With the help of mathematical models and experiments, the degradation process was improved from the aspect of bioreactor, bacteria, carrier and operational condition. Moreover, the possible degradation pathway, decolorization mechanism and kinetics, as well as diffucion process inside biofim was also studied. Based on the study, a model simulating decolorization inside fluidized bed was created. The main finding and conclusions that drew in this paper are listed below in detail:CFD model is used to simulate the flow pattern inside fluidized bed and the impact of structure parameters of the reactor, such as Din/Dout, H/D and the nozzle size on flow pattern and velocity was also evaluated. The best structure of fluidzed bed was determined with Din/Dout=0.5, H/D=10and nozzle diameter=3mm. PVA beads were chosen as biofilm carrier. Once fluidized, the reactor was considered as completely mixed. The difference on flow pattern in anaerobic and aerobic fluidized bed was also discussed.A Pseudomonas sp. that can effectively decolorize reactive13was isolated. After inoculated, A/O fluidized bed system was able to remove reactive13with a decent removal rate. Under the optimized operational condition(pH=7, Crb13=100mg/L, Cglucose=1000mg/L and HRT=30h), the color removal and COD removal reached83.0%and89.8%, respectively. According to the degradation mechanism, the azo-bond of reactive blue13was cleaved in the anaerobic reactor forming aniline type chemicals, which further broken down into small moleculars and organic acids in aerobic fluidized bed. With the help of microelectrode and diffusion model, a system that can measure the diffusivity coefficient of oxygen inside biofilm was built. The diffusion coeffcient of oxygen biofilm was determined as1.01E-9m/s. A linear relationship between the diffusion coefficient and bifilm density was identified. Based on this finding, the diffusion coefficient of reactive blue13inside the biofilm used in fluidized bed was calculated.Monod equation was found describing the decolorization process well. The Rmax and kr was determined as0.073mg RB13/mg cell/h and135.50mg/L, respectively. The mathematical model simulating diffusion and bioreaction in fluidized bed gave a good prediction about decolorization performance under steady state, as well as transient state.