Iron-Enhanced Sediment Microbial Fuel Cell For Excess Sludge Decrement And Pollutants Degradation

The technology of microbial fuel cell(MFC)converts chemical energy of organic matters into electric energy directly by exoelectrogens,and has attracted wide attention.As a type of single-chamber MFC,sediment microbial fuel cell(SMFC)has the advantages of simple structure,convenient maintenance,and low cost,which has great potential for application.However,SMFC has two issues of low utilization rate of organic matters in the sediment and the difficulty of storing the generated electricity,which limit the practical application of SMFC.In response to the issue of low utilization rate of organic matters in the sediment,zero-valent iron(ZVI)and iron carbon(Fe-C)package were added to the anode of SMFC,respectively.The strong reducibility of ZVI and the Fe-C micro-electrolysis were used to enhance the utilization rate of organic matters and the sludge decrement.In response to the issue of the difficulty of storing the generated electricity,the electricity of SMFC was used to drive the electro-Fenton in-situ by modifying y-FeOOH on the SMFC cathode,which could make make full use of the electricity generated by SMFC to degrade the herbicides in the mariculture wastewater.While solving two issues of SMFC,the practical applications of SMFC were expanded in the treatment of excess sludge and the degradation of pollutants.The main contents and results of the research are as follows:Firstly,ZVI was added to the the anode of SMFC(FeSMFC)to strengthen the anaerobic atmosphere of anode,reduce the anodic oxidation-reduction potential(ORP),and adjust the pH of the system.The results showed that the ORP in FeSMFC was stable below-200 mV.The removal efficiencies of total chemical oxygen demand(TCOD),soluble chemical oxygen demand(SCOD),volatile suspended solids(VSS),and extracellular polymeric substances in FeSMFC were increased by 177.6%?15.5%?24.4%and 16.8%,respectively,compared with SMFC without ZVI(NSMFC).The addition of ZVI improved the sludge decrement of SMFC.The ohmic resistance of FeSMFC was reduced by 37.0%,and the stable output voltage and maximum power density(Pmax)were 0.39 V and 11.93 W/m3,respectively,which were significantly higher than NSMFC(the stable output voltage and Pmax were 0.14 V and 2.93 W/m3,respectively).In the study of ZVI improving the sludge decrement of SMFC,Fe-C micro-electrolysis may also play a role in improving the performance of SMFC when iron and carbon were in contact in the solution.The influences of Fe-C micro-electrolysis at neutral pH on the sludge decrement and electricity generation performance of SMFC are worthy of further study.Fe-C package was added to the anode in the following research.One experimental group and four control group were set up to investigate the influence of Fe-C micro-electrolysis on the sludge decrement and electricity generation of SMFC at neutral pH.The results showed that the Fe-C package significantly promoted the degradation of organic matters in the sludge.The removal efficiencies of VSS and TCOD in the open-circuit reactor with Fe-C package were increased by 51.5%and 104.8%,respectively.In the closed-circuit reactors,compared with the SMFC without the Fe-C package(NSMFC),the removal efficiencies of VSS in the reactor with the Fe-C package separated from the circuit(FeC-SMFC)and in the reactor with Fe-C package connected to the circuit(FeCSMFC)were increased by 15.3%and 27.6%,respectively.The removal efficiencies of TCOD in FeC-SMFC and FeCSMFC were increased by 67.8%and 92.7%than that in NSMFC,respectively.The Pmax of FeCSMFC was 37.28 W/m3,which was 6.06 and 1.76 times higher than that of NSMFC and FeC-SMFC,respectively.Through the technology of high-throughput sequencing,it was found that the Fe-C package promoted the enrichment of exoelectrogens,especially the enrichment of typical exoelectrogens belonging to Proteobacteria.To solve the second issue of SMFC,SMFC with marine sediment as the substrate was used to drive the electro-Fenton reaction in-situ to degrade the herbicides in the mariculture wastewater.The cathode of SMFC was modified with ?-FeOOH to realize the electro-Fenton driven by SMFC reacting at neutral pH.In addition,?-FeOOH is a semiconductor material.Under the conditions of simulated sunlight,we studied the effect of ametryn(AMT)degraded by SMFC-driven electro-Fenton combined with photocatalysis.The degradation pathway of AMT in this multi-reaction system was analysed.The results showed that the removal efficiency of AMT in SMFC with ?-FeOOH modified carbon felt as the cathode(?-FeOOH-SMFC)reached 98.7%,which was 5.54 times higher than that in the naturally degraded reactor.The Pmax of ?-FeOOH-SMFC was 44.60 W/m3,which was 3.38 times higher than that of SMFC with bare cathode,and it was also higher than that of SMFC with?-FeOOH modified cathode in the dark(34.49 W/m3).In addition to the effects of sludge digestion and SMFC in ?-FeOOH-SMFC,the combined effect of electro-Fenton and photocatalysis increased the amount of active free radicals generated at the cathode,which greatly enhanced the removal efficiency of AMT.In summary,the cost-saving materials of iron and carbon were used to enhance the decrement effect of SMFC on excess sludge,and SMFC was used to drive the electro-Fenton in-situ combined with the photocatalysis of ?-FeOOH,achieving the degradation of herbicides in seawater.To a certain extent,the two issues of low utilization rate of organic matters in the sediment and the difficulty of storing the generated electricity were solved in the research,and the practical application range of SMFC was expanded.