Study On The Characteristics Of Biological Cathode Microbial Desalination Fuel Cell In The Treatment Of Mustard Wastewater

The production of mustard is one of the important economic industries in Fuling,Chongqing.The"Fuling Mustard"is also known as the world’s three famous pickles with European pickles and Japanese pickles.However,during the production of mustard,a large amount of high-salt,high-nitrogen,and high-organic wastewater with complex composition will be generated.If these wastewaters are directly discharged,it will pose a serious threat to the water environment safety of the Three Gorges reservoir area.Due to the high salinity in mustard wastewater,the general biological treatment method will hinder the degradation of organic matter due to the inhibition of microbial activity;and because the mustard wastewater contains a large amount of suspended matter,it is not conducive to the application of traditional physicochemical treatment technology.Biocathode microbial desalination cell（BMDC）is a type of microbial desalination cell（MDC）.It uses the anode’s electricity-producing microorganisms to oxidize organic pollutants to generate electricity.An electric field is formed between the cathode and anode.Promote the removal of salt ions in the solution of the intermediate desalination chamber,which can achieve multiple functions such as electricity generation,desalination,and pollutant degradation without external energy input.BMDC is characterized by the use of aerobic microorganisms as the cathode electrode catalyst.Compared with the difficulty to recycle potassium ferricyanide solution or the expensive Pt catalyst used in other types of MDC,it has the advantages of safety,environmental protection,and low cost.The cathode can achieve the function of denitrification,which is not possible with the physical-chemical cathode MDC.The mustard wastewater contains not only higher salinity and organic matter but also higher concentrations of ammonia nitrogen and phosphate.Therefore,the use of BMDC in the treatment of mustard wastewater is worthy of discussion and research.In this paper,high-salt,high-nitrogen,and high-organic Fuling mustard wastewater is treated,and the biocathode microbial desalination fuel cell is used as the research subject to construct a classic three-chamber BMDC.From the perspectives of power generation performance,desalination performance,organic degradation performance,and membrane pollution control.Explore the feasibility of BMDC for the treatment of mustard wastewater and provide new ideas for low-cost treatment of mustard wastewater.The main conclusions are as follows.BMDC with aerobic microorganisms as the cathode catalyst has been developed.Compared with PDMC using Pt as the cathode catalyst,the output voltage of BMDC is comparable to PMDC.During multiple power generation cycles,the maximum output voltage of BMDC is 593.85 m V,which is higher than PMDC.531 m V;due to the biofilm growing on the surface of the BMDC cathode electrode,after a period of desalination operation,the internal resistance is only 74.36Ω,while the internal resistance of PMDC reaches 162.5Ωat the same time;lower internal resistance brings higher output power,The maximum output power of BMDC is 6.55 Wm^-3,which is 2.15 times that of PMDC.In terms of desalination,the average desalting rate of BMDC is 20.16 mg/（L·h）,which is slightly faster than PMDC.The salinity of the intermediate salt chamber is reduced from20.3 g/L to 1 g/L.The BMDC takes 980 hours and the desalination rate reaches 95%.the above.The anode organic matter removal rate of both of them exceeds 94%.The highest COD removal rate of BMDC is 97.77%,but its Coulomb efficiency is slightly lower than the PMDC.In order to quickly and efficiently process the mustard wastewater for desalination treatment,the influence of different influent COD concentrations on BMDC was investigated.In the BMDC1#,BMDC2#,and BMDC3#with the COD concentrations of300 mg/L,600 mg/L,and 900 mg/L,the peak voltages were 641 m V,639 m V,and 703m V,respectively.It is 3.46%,12.86%,and 21.29%,which is of great significance to increase the rate of desalination at this point.The BMDC desalination rate under the COD concentration of 900 mg/L feedwater is 15.93%and 8.82%higher than the other two BMDCs.Due to the presence of non-electrolytic bacteria in the anode,increasing the concentration of organic matter in the feedwater increases the degradation efficiency of the organic matter,but reduces the Coulomb efficiency,but the stability of the power generation is still improved.In terms of internal resistance,BMDC1#>BMDC2#>BMDC3#,and the maximum output power BMDC1#<BMDC2#<BMDC3#are 6.42 Wm^-3,7.15 Wm^-3,and 7.88 Wm^-3,respectively.In terms of cathode denitrification,the total nitrogen removal rate of BMDC3#is the highest,reaching 91.19±2.38%,and the ammonia nitrogen removal rate exceeds 97%.Increasing the salinity of the desalination chamber can bring higher output voltage and more stable voltage output to the BMDC,and delay the decline of battery performance to a certain extent.BMDC#1,BMDC#2,and BMDC#3 with initial salinities of 15 g/L,25 g/L,and 35 g/L were installed,and the average peak voltages were 546.75m V,554 m V,and 661 m V,respectively.The activity is affected,and the Coulomb efficiency of BMDC#2 is only 8.03%,which is lower than that of BMDC#1.On the rate of desalination,BMDC#3 achieved the largest TDR of the three,which was 31.21mg/（L·h）,which was 1.72 and 1.62 times the previous two,respectively.At the same time,the higher the salinity of the desalination chamber can reduce the internal resistance of the BMDC at the beginning,but when the salinity of the desalination chamber is reduced to 5 g/L,the internal resistance of BMDC#3 increases the most.This is due to the most serious membrane pollution.In addition to the pollution caused by the precipitation of salt ions,the attachment and growth of microorganisms will also aggravate the degree of membrane pollution,but the pollution can be reduced by cleaning and the service life of the membrane can be extended.Higher salinity will reduce the biodiversity at the level of the cathode and anode biofilm OUT,but it will have little effect on the species composition at the gate level,and the presence of non-electrolytic bacteria will reduce the power generation performance of the battery.