Research On Effects Of COD/N And Substitution Of Banana Peel Carbon Source On The Nitrogen Removal Performance Of Single-chamber Microbial Fuel Cells

Microbial fuel cell（MFC）is a new microbial system which can convert the chemical energy of organics in water body into electric energy directly.In recent years,it has been studied and discussed widely for the good application potential in the field of wastewater nitrogen removal treatment.Among all kinds of MFCs,single-chamber MFC has the advantages of material cost and operation cost saving,high output power,so it has an excellent prospect for simultaneous N removal from wastewater and power generation.However,this application of MFC still lacks sufficient theoretical basises and practice tests,aimed at this situation,a single-chamber air cathode MFC simultaneous nitrification and denitrification system was established to remove COD,NH₄⁺-N and total nitrogen（TN）from wastewater containing NH₄⁺in this research,and the power generation of the MFC was also monitored.The treatment performance of different COD/N wastewater in this system and the difference of the microbial community structure in the system were compared comprehensively.Moreover,in view of the COD deficiency of wastewater containing N in the biological treatment process,in this study,banana peel,a cheap agricultural waste carbon source,was used as an alternative carbon source for this system to investigate its effect on pollutants removal and power generation,and to compare it with the effect of the traditional carbon source MFC system.The main conclusions of this study are listed as follows:（1）The COD/N of the wastewater containing N has little effect on the output voltage of this system,which basically maintains at around 0.57V in the stable electricity generation stage;The MFC system treating low COD/N wastewater has better electrochemical performance due to the low H⁺mass transfer resistance in the cathode biofilm and other reasons.（2）The lower the COD/N of the wastewater,the higher the removal amount of NH₄⁺-N and TN in MFC,but the removal effect was relatively unstable,and the COD residue was more,all of these were caused by the competition between the denitrifiers and anode respiratory bacteria for the substrate;The formation of the cathode biofilm will make the OH^-generating from the cathode O₂ reduction reaction accumulate below the depth of 200μm of the biofilm,which will reduce the p H in the system gradually.（3）The anodic bacteria community structure of the MFC treating different COD/N wastewater has little differences,and Geobacter is always the dominant bacteria（64.24-67.43%）,however,the cathode community is easily affected by COD/N,and most nitrifiers and denitrifiers grow in the cathode biofilm;Furthermore,the abundance of denitrifiers in the cathode biofilm decreases with the depth of the biofilm.（4）Replacing banana peel as the alternative carbon source will make the power generation of the system slightly lower than that of the MFCs using acetate and glucose as the substrate,and the electrochemical performance of the system after the replacement depends on the substrate using in the pre-adaptation stage;The replacement of alternative carbon sources can improve the NH₄⁺-N removal efficiency,although this will slow down the COD removal rate,because banana peel is a kind of slow-release carbon source.（5）The type of substrate has a decisive influence on the functional community in the system,which significantly affects the main anode respiratory bacteria in MFC;The influence of substrate on the anode community structure is more significant than that on cathode community structure,and the more complex the substrate is,the worse the anode community diversity is;In addition,nitrifiers,denitrifiers,organic fermentation and hydrolysis bacteria mostly grow within the cathode biofilm in the MFC with complex organic substrate.