Study On Simultaneous Removal Of Refractory Organic Matter From Water And Sediment By Bioelectrochemical System

The refractory organic matter with long-term residual,bioaccumulation and high toxicity entered the water environment with the discharge of industrial and agricultural wastewater.The refractory organic matter with different hydrophilicity and hydrophobicity resulted in contamination of both sediment and overlying water.Bio-electrochemical technology has been widely used to remove refractory organics from the environment,but there are still limitations of inefficient energy utilization and the removal of refractory organics from only a single medium.By constructing an“anode-biofilm electrode-cathode”coupled bioelectrochemical system,which can achieve the purpose of simultaneously removing the refractory organic matter in the overlying water and sediment.In addition,modification of the electrode materials in the bio-electrochemical system is an effective way to further improve the removal efficiency of refractory organics.In this study,biofilm electrodes with different carbon-based materials were compared in the biofilm electrode system.Carbon-based material with better physical and chemical properties and pollutant removal performance was used as the biofilm electrode,and the“anode-biofilm electrode-cathode”coupling was successfully constructed.The bioelectrochemical system achieved the in-situ utilization of electrons and simultaneously removed pyrene in the sediment and sulfamethoxazole in the overlying water;To explore different biofilm electrode modification methods to improve the removal performance of the coupled bioelectrochemical system for sulfamethoxazole in overlying water;The biofilm electrode modification method with the best pollutant removal performance was selected to modify the anode in the coupling system,and the optimization effect of the power generation performance and pyrene removal performance in sediments of the modified anode in coupling system was explored.The main research contents and conclusions are as follows:(1)A biofilm electrode system was constructed using carbon-based electrodes of different materials to remove sulfamethoxazole in water.The results showed that the removal efficiencies of carbon brush electrode,activated carbon electrode and graphite rod electrode system for sulfamethoxazole were 98.23%,88.31%and 16.8%,respectively.Compared with activated carbon electrodes and graphite rod electrodes,carbon brush electrodes had better hydrophobicity and larger capacitance.In addition,the surface of the carbon brush electrode was selectively enriched with the high relative abundance of dominant bacteria,such as Pseudomonas(12.1%-15.7%),Brevundimonas(1.8%-2.7%)and Azoarcus(3.8%-14.9%).Therefore,carbon brush is a better choice as the electrode material for the biofilm electrode system.(2)Using carbon brushes as biofilm electrodes,an“anode-biofilm electrode-cathode”coupled bioelectrochemical system was successfully constructed.The current of the system was stabilized at 0.50 m A～0.60 m A,the internal resistance was 2.6 kΩ,and the maximum power density is 19.24 m W/m~2.The removal efficiency of sulfamethoxazole in the overlying water by the closed-circuit system was 76.70%,which was 31.60%and 58.70%higher than that of the open-circuit system and the blank control system,respectively.At the same time,the removal efficiency of pyrene in the closed-circuit system was increased by 26.77%compared with the open-circuit system,and the pyrene in the sediments of the blank control system was hardly degraded.(3)The biofilm electrodes in the coupled bioelectrochemical system were modified with poly(3,4-ethylenedioxythiophene)and reduced graphene oxide,respectively.The modified biofilm electrode increased the specific surface area and formed more active functional groups compared to the unmodified electrode.The coupled system embedded with poly(3,4-ethylenedioxythiophene)modified biofilm electrodes had higher output voltage,larger capacitance and lower charge transfer internal resistance,which were 485 m V,183.50 F and2.50Ω,respectively.The removal efficiency of the poly(3,4-ethylenedioxythiophene)-modified electrode closed-circuit system for sulfamethoxazole in overlying water was 99.28%,which was 10.28%and 21.18%higher than that of reduced graphene oxide modified electrode and unmodified electrode closed-circuit system,respectively.Therefore,the coupled system embedded with poly(3,4-ethylenedioxythiophene)-modified biofilm electrodes had better electrical performance and antibiotic removal performance.(4)The anodes of the coupled systems with embedded biofilm electrodes were modified with poly(3,4-ethylenedioxythiophene).Compared with the unmodified anode system,the maximum output voltage and capacitance of the modified anode system were increased by 264m V and 94.5 F,respectively,while the total internal resistance was decreased by 23.67Ω.The removal rate of pyrene by the modified anode system was 85.04%,which was 18.06%higher than that of the unmodified anode system.The distribution of the microbial community structure on the anode surface was investigated,and the modified anode surface was attached with the PAHs-degrading dominant bacteria,such as Geobacter(2.3%),Azoarcus(1.0%)and Bacillus(0.8%).