Study On Removal Characteristics Of Polycyclic Aromatic Hydrocarbons And Antibiotic By Using Bioelectrochemistry System

The emergence and accumulation of antibiotics and aromatic organic compounds in aquaculture environment not only put forward higher requirements for the purification of aquaculture wastewater,but also brought challenges to the remediation of aquaculture sediment.The research and development of in situ removal of such pollutants in aquaculture sediments is of great significance to the improvement of aquaculture environment and food safety.The microbial electrochemical system can take advantage of the redox characteristics of sediment and water to achieve the removal of refractory organic matter,which is a new application of microbial electrochemical action.In this study,based on the construction of SMFC,the effects of electron intermediaries on the electrical generation characteristics and pollutant degradation of microbial electrochemical system were studied,and the mechanism of action of electron intermediaries was further explained from the perspective of microorganisms.Specific research contents and results are as follows:The construction of bioelectrochemical system and the electric performance of SMFC under different treatment conditions were studied.In the SMFCs polluted by polycyclic aromatic hydrocarbons(PAHs)and polluted by PAHs and antibiotics,the SMFC test equipment can achieve continuous output voltage from the electrode hanging film period to the start-up of the device.The open circuit voltage of each SMFC test group reached 800 m V,and the closed circuit SMFC with Fe(III)and HAs external electron intermediaries obtained higher voltage peak,longer duration of electricity generation period and higher electricity generation efficiency than blank control group.Moreover,different concentrations of electron intermediators showed different electrochemical characteristics in SMFCs contaminated by PAHs and antibiotics.The results showed that an appropriate amount of Fe(III)can significantly reduce the internal resistance of SMFC,but too much Fe(III)can increase the internal resistance of SMFC and reduce the electrical performance.The CV area of the SMFC-Fe(III)test group increased with the increase of Fe(III)concentration,indicating that the oxidation reaction rate of the SMFC-Fe(III)anode region with Fe(III)as the electron shuttles was accelerated,and the current response was more obvious.However,the power density and polarization curves of SMFC-HAs groups have little difference,and the CV area of HAs-0.5g /L group are the largest.The AC impedance spectra showed that the addition of Fe(III)and HAs as electron shuttles could significantly reduce the ohmic resistance,activation resistance and diffusion resistance of SMFC.These results indicated that Fe(III)and HAs can improve the electrical performance of SMFC by promoting the extracellular electron transfer between exoelectrogens and electron acceptor.The effect of bioelectrochemical system on the removal of PAHs and antibiotics in sediments was studied.The results showed that the removal rates of naphthalene,phenanthrene and pyrene were 73.35%,40.72% and 26.53% in the SMFC closed-circuit group,respectively,which were higher than those in the SMFC open-circuit group(67.02%,24.62% and 20.35%,respectively),and SMFC had a better effect on the removal and promotion of phenanthrene in the three-ring structure.SMFCs with Fe(III)and HAs as electron shuttles further promoted the removal of phenanthrene,phenanthrene and pyrene,and the removal rates were 82.79%,54.48%,40.69% and 82.94%,55.57%,41.40%,respectively,and the removal effect of phenanthrene and pyrene which were more difficult to be degraded was more significant than that of naphthalene.In SMFCs contaminated by PAHs and antibiotics,the presence of sulfamethoxazole could inhibit the removal of naphthalene,phenanthrene and pyrene in SMFC-close group.In the first 14 days,the removal rate and degradation efficiency were decreased by 8.93%,2.98%,4.52%,and 0.630mg/kg·d,0.204 mg/kg·d,0.270 mg/kg·d,respectively(P < 0.01).In SMFC-Fe(III)-close and SMFC-HAs-close experimental groups,the removal rates of naphthalene phenanthrene and pyrene were 76.98%,58.42%,51.35% and 78.32%,54.84%,53.00%,respectively,and the degradation rates were all above 0.60mg/kg·d.Sulfamethoxazole can be rapidly degraded in SMFC,especially in SMFC-Fe(III)-close and SMFC-HAs-close groups with 99.17% and99.38% removal rates and degradation efficiencies of 0.220 mg/kg·d and 0.221 mg/kg·d.It was also found that the degradation of naphthalene,phenanthrene,pyrene and sulfamethoxazole in the SMFC system showed a two-phase curve of rapid and slow degradation,and Fe(III)and HAs significantly promoted the simultaneous removal of PAHs and antibiotics from the sediments by SMFC,and the concentrations and properties of PAHs changed at the beginning and end of the experiment.At the end of the experiment,Fe(III)concentration decreased and Fe(II)concentration increased in SMFC,and the structure and transformation rate of HAs components changed significantly.Also,FA decreased and HA increased,and the humic acid humification degree of the soil increased significantly.In SMFC,Fe(III)and HAs could act as electron shuttles to effectively promote the electron transfer efficiency between electron donor and electron acceptor,thus greatly improving the probability of contact between extracellular electrons and pollutants,and greatly promoting the further degradation of toxic and harmful organic compounds that are difficult to biodegrade.The relationship between microbial community structure and electrical performance and pollutant removal in bioelectrochemical system was analyzed by using high-throughput sequencing technology.The results showed that the addition of exogenous electron shuttles in the sediment samples significantly changed the microbial diversity and the community composition at the phylum level.The relative abundance of Actinobacteriota,Firmicutes,Proteobacteria and their typical genera were found to be relatively high.Anode carbon felt samples had screening and enrichment to specific species,particularly in the closed loop electrode landslide is desulfurization coli and bacillus genus,the dominant species was proved to have promote electricity production and degradation of polycyclic aromatic hydrocarbons,and the ability of antibiotics,Fe(III)and HAs also affected the anode carbon felt the strain distribution proportion and the advantages of microbial metabolic pathway.These results indicated that the microorganisms were affected by exogenous electron shuttles and current,and expressed different functional information in each treatment group,thus showing differences in electrochemical performance and pollutant degradation ability.