Experimental Study On The Treatment Of Refractory Organic Wastewater By Three-Dimensional Biofilm Electrode Reactors(3D-BERs)

In this thesis,a three-dimensional biofilm electrode reactors(3D-BERs)were experimentalized to degrade refractory organics of Tetrabromobisphenol A(TBBPA)and Rhodamine B(Rh B)which were constructed using particle activated carbon(GAC)and granular zeolite(GZ)as particle electrodes and microbial carriers.The effects and mechanism were discussed about different particle electrode materials and electric field conditions on the operation effect of the reactor,as well as biofilm formation.The research conclusions are as follows:1.Under the domestication of different particle electrode materials and electric fields,different biofilms are formed,and the diversity and dominant population of microorganisms are greatly different.The removal efficiency of TBBPA was better in GZ reactor,and the removal rate was over 90%.The debromination effect of GAC reactor was better,and the concentration of bromide ion in effluent exceeded 4mg/L.The longer the hydraulic residence time(HRT),the higher the voltage,and the better the treatment effect of Rh B simulated wastewater in the reactor;on the contrary,the treatment effect is poor.When HRT was 24 h and the voltage was 9V,the average removal rates of Rh B,TOC and TN were 71.9%,73.3% and 74.4%,respectively.2.GAC and GZ have different characteristics in morphology,distribution,structure and metabolic activity due to differences in morphological structure,elemental composition,functional group and conductivity.Compared with GZ,the biofilm generated on GAC has higher diversity and biological activity,which forms a good synergistic effect with electrochemical oxidation.Electrochemical oxidation produces abundant intermediate products,which provide abundant carbon sources for microorganisms and enhance the degradation of TBBPA.3.The enhancement of the electric field effect can improve the treatment effect of the reactor,but it reduces the diversity and biomass of the biofilm,weakens or even loses the biological metabolism,and the degradation mechanism changes from synergistic effect to electrochemical effect.Appropriate electric field can select microorganisms with strong tolerance and strong degradation,enhance the metabolic activity,maximize the biological metabolism,and form a good synergistic effect with electrochemistry,and enhance the degradation of Rh B.4.The degradation of pollutants is the result of synergistic effects such as particle electrode adsorption,electrochemical redox and microbial metabolism.Adsorption is the precondition of degradation,and electrochemical oxidation and microbial metabolism are the main degradation mechanisms.The contaminants are first adsorbed on the particle electrode,then it is converted into small molecular intermediates by redox and metabolism.This process is repeated until the final contaminant is mineralized,which simultaneously regenerates the particle electrode.