A Study On The Pollutant Degradation Mechanisms By Microbial Fuel Cells With River Sediment

River pollution control is one of the mostly concerned and most challenging issues in the field of environmental science and engineering.In this paper,sediment microbial fuel cell(SMFC)was used to study the degradation process of typical pollutants such as TOC,sulfide and polycyclic aromatic hydrocarbons in the black and smelly river sediments.In this paper,the contaminant degradation processes and microbial communities varaitions in the sediments with a distance of 0-5 cm to anode surface was periodicaly analyzed during the 60-day experiment.The main findings are as follows:(1)SMFC could accelerate the degradation of anode organic matter,and the TOC concentration gradually decreased at the anode.The concentration of small molecular organic acids(including formic acid,acetic acid,lactic acid)in the interstitial water gradually decreased,indicating that the higher metabolic activity of microbial catalytic oxidation of organic acids in the vicinity of the anode.The concentration of polycyclic aromatic hydrocarbons(PAHs)in the sediments decreased overtime.The degradation rate is increased,indicating SMFC which can promote the degradation of PAHs and small molecular organic substances.After 60 days of SMFC operation,the SMFC anode sediments increased from-185 mV to 23.8 mV,which could sitmulate the oxidzation of sulfides and organic matters.The concentration of formic acid and lactic acid decreased slowly,and the concentration of acetic acid decreased more rapidly,probably because electrogenic microorganisms prefer to use acetic acid as an electron donor.(2)The SMFC electricity production accelerated the oxidation of sulfides to sulfate.At the anode,HS~-was oxidized to sulfate;at the same time,the black odor component,acidic volatile sulfur(AVS),was also oxidized,and the concentration was gradually decreased.(3)The effects of different current densities on the remediation of contaminated sediments were studied by using different external resistances.When the current density was increased,the ORP increased in the sediment;the pH decreased,the HS~-concentration also decreased the AVS decreased,the sulfate concentration increased,and the PAHs concentration is positively correlated with the current density.(4)Analysis of microbial community structure showed that SMFC had a significant effect on the microbial community structure of the sediment,and the influence was more significant near the electrode.Sulfur oxidation and sulfate-reducing bacteria(Desulfobulbus,Desulfurivibrio,etc.)were enriched on the electrode surface,and the abundances of typical electrogenic microorganisms such as Geobacter and Pseudomonas were also gradually increased toward the electrode.Predictive function analysis by FAPROTAX showed that sulfur,sulfate,iron,and aromatic degradation are enhanced toward the anode,.The above functions on the electrode surfacewere significantly higher than the sediment near the electrode,indicating the presence of a hot zone of carbon,sulfur and iron on the surface of the anode,The metabolic activity gradually reduced along with the distance to anode increased.In summary,this paper studies the co-removal effect of SMFC on pollutants such as sulfides and PAHs in contaminated sediments,and systematically reveals their spatiotemporal coupling mechanism for the first time.The results provide necessary information for the optimization and application of SMFC technology to strengthen black odor river remediation Moreover,the results are important to the filed application of large-scale integrated SMFC in riversediments.