An Anaerobic Fluidized Bed Microbial Fuel Cell System For Coal Industry Wastewater Treatment

Energy conservation and wastewater treatment have become the common challenge today for many industries.As a typical bio-refractory and high strength industrial organic wastewater,coking wastewater contains complicated contaminants such as cyanide,ammonia,phenols,polycyclic aromatic hydrocarbons and heterocyclic compounds.According to the latest official statistics,coking wastewater discharged by most coking factories can’t get well treatment,and the COD and priority control pollutants concentration of the effluent can’t achieve the discharge standard.Microbial fuel cells（MFCs）have been received extensive attention as a novel biotechnology for wastewater treatment with concomitant electricity generation by microorganisms.In this work,an integrated system termed single chambered air cathode anaerobic fluidized bed microbial fuel cell（AFB-MFC）was constructed for treating coking wastewater and producing electricity.The effects of COD concentrations and three microorganism acclimatization ways（direct acclimatization,gradient acclimatization and enrichment culture）on electricity generation and wastewater treatment of the AFB-MFC utilizing coal pyrolysis wastewater were investigated.The results showed that electricity can be generated by AFB-MFC with the diffierent coking wastewater influent concentrations（952,1528,2238,3419 mg/L）,the output voltage and electricity generation increased with increasing COD loading rates.When the COD of the influent was 2238 mg/L,the maximum output voltage and maximum power density of MFC were 284.5 mV and 14.69 mW/m²,respectively.The properties of electricity generation and wastewater treatment in AFB-MFC were best under gradient acclimatization with the maximum power density（10.95 mW/m²）and COD removal efficiency（86.28%）.Nanometer Fe₃O₄ was prepared by the chemical co-precipitation method and used for modifying the graphite rod anode of an AFB-MFC.The electrochemical properties were described by cyclic voltammetry and electrochemical impedance spectroscopy,the results showed that Fe₃O₄ promoted the electron transfer and electrochemical activity on the surface of anode.When the modified anode was used in MFC,the maximum power density and output voltage were up to 9.81 mW/m² and 243 mV,respectively,which were 114% and 23.4% higher than those of the unmodified anode.Besides,the composition of organic compounds and degradation characteristic of phenols were analyzed by GC/MS internal standard method.According to GC/MS results,phenols,benzenes,alcohol,heterocyclic compound and polycyclic aromatic hydrocarbon were degraded fully,their removal efficiency were 99.63%,97.6%,98.3%,97.5% and 92.87%,respectively.The mass concentrations of main five phenol pollutants were measured.The detection limits of phenol pollutants were 2.48 5.50 μg/L,and the linear correlation coefficients（R²）were higher than 0.993 and the average recoveries values ranged from 72.6% to 115.8%.According to the methyl benzoic acid intermediate metabolites,the preliminary conclusion was that benzoic acid derivative was formed by the carboxylation and further oxidized to open the ring.When the initial concentration of phenol,o-Cresol and 2,4-Dimethylphenol were 274.7,231.8,76.7 mg/L,the biodegradation of phenols from coking wastewater followed the first-order kinetics in AFB-MFC,and the rate constant of reaction were 0.06989,0.07641 and 0.08783 h^-1,respectively.