Effect Of Anode Biofilm Characteristics On The Toxicity Sensing Performance Of Microbial Fuel Cells

Water toxicity sensing&early warning based on microbial fuel cell?MFC?is a cutting-edge research hotspot in recent years.It has the advantages of low cost,simple operation,rapid response and self-sustainment.It is of great interest in both theoretical research and practical application in the field of toxicity sensing of municipal&industrial water sources.Electroactive biofilm of microbial fuel cell,as the only signal recognition element of the sensor system,is the most critical factor affecting the applicability of the technology.The living cell content,biofilm thickness and the evolution of community structure in toxic environment and the establishment of toxic resistance will directly affect the sensing performance of MFC toxicity sensors.However,few studies have involved with the correlation of the MFC sensing performance and biofilm characteristics.This work mainly focuses on the characteristics of MFC biofilm.To improve the sensing performance,the electroactive biofilm morphology,living cell content and microbial community distribution were analyzed for investigating the relationship between MFC toxicity sensing performance and biofilm property.The main contents and results are summarized as follows:?1?The biofilm structure could be tailored by selecting different microstructure anodes.With Pb²⁺as the target poison,Carbon felt anode based MFC?CF-MFC?exhibited a linear relationship of Pb²⁺concentration(C_pb²⁺)vs.voltage inhibition ratio?IR?at C_pb²⁺range of 0.1mg L^-1 to 1.2 mg L^-1,and the highest IR was only 38%.ITO anode based MFC?ITO-MFC?also revealed a linear relationship of C_pb²⁺and IR at C_pb²⁺of 0.1 mg L^-1 to 1.5 mg L^-1,and the IR gradually approached to 100%as C_pb²⁺futher increased.The uniform distribution of thin layer biofilm on the surface of ITO-MFC had low mass transfer resistance,and could be completely exposed to the toxic environment at the same time.As compared with ITO-MFC,the CF-MFC biofilm showed unevenly distribution,large porosity and higher mass transfer resistance of the poiso.Therefore,ITO-MFC exhibited an excellent sensing sensitivity.?2?The accumulation time of dead cells in the biofilm can be mediated via the alternation of the MFC running time,thus thus obtaining the anode biofilm with different contents of living cells.The proportion of MFC live bacteria running for 10 cycles was as high as 83.57%,while the proportion of MFC live bacteria running for 20 cycles was only 18.86%.By using high current density,the proportion of MFC live bacteria could be increased to 41.91%after20 cycles.The results of Pb²⁺toxicity sensing indicated that MFCs toxicity sensing performance could be improved by increasing the proportion of live bacteria.The Pb²⁺resistance of microbial community was established in MFCs that subjected to toxic stimuli for a long time.The negligible improvement?about 4%?of MFC sensing performance was observed by the increase of the proportion of viable bacteria?3?The different microbial community structures of anode biofilms can be obtained changing the acclimation temperature of MFC.Microbial communities show different adaptability to environmental factors?such as temperature?,and different anode microbial community structures will be formed at different ambient temperatures.The microbial community structure was analyzed by high-throughput sequencing.It was found that the MFC anode electrogenerated bacteria were mainly Geobacter,which accounted for 57.2%and 90.1%of the MFC acclimated at room temperature?25°C?and low temperature?10°C?,respectively.And the cold-tolerant strain Janthinobacterium appeared in the low temperature acclimated MFC.Electrochemical analysis showed that the low temperature acclimated MFC has higher electrochemical activity and low electron transfer resistance.The Pb²⁺toxicity sensing test results indicated that the low temperature acclimated MFC sensor exhibited a relatively higher sensing sensitivity under low temperature conditions.In addintion,no obvious difference of sensing performance can be detected for the MFCs under normal temperature conditions.