Study On Denitrification Performance Of High-salt Dual-chamber MFC Bioelectrode

The bioelectrode denitrification process based on bioelectrochemical theory can directly use cathode current electrons as electron donors in the denitrification process,which can get rid of dependence on organics to a certain extent.In the process of wastewater treatment,the biological electrode denitrification process can not only recover energy,but also prevent secondary pollution while controlling pollution.This study aims to find the best way to cultivate electrode denitrification biofilm in high-salt state through different sludge inoculums,to obtain electrophilic denitrification bacteria group(electric energy nutrition denitrification bacteria group)that can directly use cathode electrons On this basis,the effects of current intensity and pH of the cathode solution on the electricity generation performance and electrode denitrification performance of the high-salt dual-chamber microbial fuel cell(MFC)were investigated.At the same time,16S rRNA gene sequencing technology was applied to the anode cathode The biofilm structure and the types and abundance of dominant bacteria were analyzed.Thus,the denitrification mechanism of high-salt double-chamber biocathode electrode denitrification MFC was proved,and the reactor operating conditions were optimized.This study mainly draws the following conclusions:(1)By comparing the cathode,first inoculate ordinary anaerobic sludge and then inoculate ordinary aerobic sludge,inoculate high-salt anaerobic sludge first and then inoculate high-salt aerobic sludge,inoculate high-salt aerobic sludge and then inoculate high-salt anaerobic sludge With these three different inoculation methods,it was found that inoculation of high-salt activated sludge can quickly cultivate a high-salt dual-chamber biological cathode electrode denitrification MFC reactor.It was also found that the inoculation method of inoculating high-salt aerobic sludge first and then inoculating high-salt anaerobic sludge is more in line with the nitrification and denitrification process of ammonia nitrogen removal.Oxygen sludge is more conducive to shorten the reactor cultivation time.The average removal rate of cathode nitrate is2.95mg/L*d,the highest rate is 5.18mg/L*d,and 100%removal of total cathode nitrogen is achieved on the 31st day of the reaction.The maximum power density is1.080W/m~3,the open circuit voltage is 796mV,the internal resistance is 209Ω,and the Coulomb efficiency is 9.39.(2)The three kinds of inoculation methods of anode biofilm and electricity-producing bacteria include Xanthobacter,Methanosaeta,and norank＿f＿＿norank＿o＿＿SBR1031,with relative abundances of 39.72%,32.36%,and41.58%,respectively.Inoculate high-salt aerobic sludge first and then inoculate high-salt anemia Oxygen sludge inoculation method group has the highest content,and the electricity generation performance is also the best among the three groups.The genus of cathode related to nitrification includes SM1A02(19.62%,23.65%,24.12%)and unclassified＿f＿＿Nitrosococcaceae(0.02%,0.04%,1.02%).Bacteria of cathode and electrode denitrification accounted for 1.84%,9.32%and 11.76%respectively.The group with high-salt aerobic sludge first and then high-salt anaerobic sludge had the highest content.The main denitrifying bacteria were the electrophilic electrode denitrifying denitrification microorganisms Pseudomonas stutzeri(2.41%)and Acholeplasma(9.35%).The blank cathode control group had almost no two kinds of bacteria,indicating that the electrophilic denitrifying microbial bacteria could not be enriched on the cathode that was not conditioned by current.After long-term operation,the bacterial community in the biofilm becomes more diverse compared to inoculation with activated sludge.(3)When the circuit strength changes from 0.35mA to 1.76mA,the denitrification rate of the cathode nitrate electrode is positively correlated with the current strength.The greater the current intensity,the faster the electron donor and the faster the electrode denitrification.When the maximum current intensity of the reactor is 1.76 mA,the current density is 7.52A/m~3.The removal rate of nitrate is the largest,the average removal rate of nitrate is 5.72 mg/L*d,the maximum removal rate is 8.45 mg/L*d,and 100%of total nitrogen is removed in 20 days.When the reactor current intensity is 0.51mA,the power generation performance is the best.At this time,the Coulomb efficiency is 17.19,the maximum power density is1.12W/m~3,and the internal resistance is 252Ω.When MFC is run in a high-salt matrix,the migration speed of ions is accelerated,resulting in a significant decrease in the internal resistance of MFC and a significant increase in power density.(4)The electrode denitrification reaction requires a pH-neutral environment,and denitrification produces alkalinity,so the environment cannot be alkaline,and microorganisms have the highest activity in a neutral environment.When the cathode solution pH=7,the removal rate of nitrate is the best.The average removal rate of nitrate was 8.59 mg/L*d,and the maximum removal rate was 12.01 mg/L*d.However,the average removal rate of nitrate was only 6.45 mg/L*d at the cathode solution pH=6,and the average removal rate of nitrate was only 5.73 mg/L*d at the cathode solution pH=8 and pH=9.When the cathode solution pH=7,the electricity generation performance is also the best.The current intensity and current density are 1.17 mA and 5.00A/m~3respectively,the voltage output value reaches 117mV,the Coulomb efficiency is 14.39,and the maximum output power is 0.93W/m~3,open circuit voltage is 920mV,internal resistance is 775Ω.