Simultaneous Nitrogen Removal And Electricity Generation Performance Of Mfc With A Novel Slow-release Carbon Source As Co-substrate

Microbial fuel cells（MFC）are devices that use microbes to convert chemical energy into electricity directly.The denitrification of MFC anode is suitable for the treatment of sewage with both organic matter and nitrate,and the widely used external carbon sources are liquid ones as methanol,etc.,which have the disadvantages of high cost and difficult dosage control.The cost-effective poly caprolactone（PCL）artificial polymer and typical agricultural waste corncob（CC）were crushed into powder,and then evenly mixed in poly vinyl alcohol-sodium alginate（PVA-SA）to form a novel slow-release carbon source filler（CPSP）by crosslink action.The denitrification performance of CPSP was extensively investigated,and the combination of solid denitrification and anode denitrification was realized by CPSP addition in the anode pool of MFC.The main research results were as follows:（1）Compared with PCL,CC and PVA-SA,the surface structure of CPSP is more suitable for microbial adhesion,which has more uniform carbon distribution and more hydrophilic surface functional groups;the leachate of CPSP has higher acetic acid to the short chain fatty acids ratio（56.48±3.71%）,smaller organic molecule and lower humification degree.In the denitrification experiment,CPSP has shorter start-up period than other carbon sources.The COD release from CPSP accounts for only 75%of that from CC in the initial stage,and 173%at the stable period.The average NO₃^--N removal rate（43.03±2.05%）of CPSP group is similar to that（42.35±3.08%）of CC group.（2）CPSP-added MFC group（MFC-C）has slightly longer start-up period than that of the control group（MFC-0）,but the maximum output voltage and power density（2738 m W/m³）of the former are increased by 5%and 15%respectively.The substrate degradation process of MFC-C and MFC-0 in a cycle can be divided into two stages:the first stage is 0-8 h,during which the degradation COD and NO₃^--N follows the rule of zero-order kinetic characteristics;the second stage is 9-48h,and the COD degradation follows the rule of first-order kinetic characteristics.The COD and NO₃^--N degradation and kinetic processes of electricity generation of both MFC-0 and MFC-C conforms to the Han-Levenspiel model.（3）Microbial morphology of the anode biofilm and the suspended sludge in MFC anode chamber has some difference.Intermediates are generated in the MFC anodic solution after CPSP addition.Reduction and oxidation peaks are observed in the denitrification stage by cyclic voltammetry of the anodic biofilm,and the electron transfer mode of the anodic biofilm is cell-surface contact.High-throughput sequencing results indicate that CPSP addition in the anode chamber of MFC can affect the distribution of microbial communities in both of the anode biofilm and suspended sludge.Meanwhile,CPSP can improve the synthesis of denitrification functional genes in the suspended sludge,promote the expression of synthetic-related catalytic enzymes,and enhance the cellular activity of denitrification microorganisms in MFC.