| At present,the treatment of nitrogen containing heterocyclic compounds has been paid much attention,and quinoline and indole as typical nitrogenous heterocyclic compounds have also attracted the attention of researchers.With the rapid development of industry,quinoline has gradually become the main pollutant in soil and water.Quinoline can cause malformations,canceration and mutation.Such pollutants are harmful to the environment and also harmful to organisms.Indole is widely distributed in coking wastewater,pharmaceutical wastewater,dyestuff wastewater and other refractory industrial wastewater.Indole has weak alkalinity and low toxicity.There are three traditional methods for the treatment of nitrogenous heterocyclic compounds:physical,chemical and biological methods,but they have their own limitations.The physical method can not completely transform them into non-toxic and harmLess substances.The chemical degradation rate is high,but the cost is high,and the operation is complex.While the biodegradation efficiency is slow,the degradation efficiency is slow.The problem of high energy consumption.Therefore,it is very important to study the process of highly efficient degradation of such compounds.Microbial fuel cell（MFC）is a new kind of wastewater treatment process.It combines with microorganism on the basis of traditional fuel cell.With the continuous oxidation of the anode organic matter and the continuous cathodic reaction,it can not only achieve wastewater treatment,but also can recover electrical energy and reduce energy.The effect of consumption.Therefore,using MFC technology to degrade organic matter and generate electricity has gradually become a new research hotspot.People began to explore whether nitrogen heterocyclic compounds can be degraded and utilized by MFC under suitable conditions.With the extensive application of MFC technology in sewage treatment,the advantages of its economy and no two pollution have been recognized by the public,but there are some problems to be solved urgently,such as the unstable biological treatment efficiency,the long cycle and the longer start-up time of the reactor.Many harmful compounds,such as nitrogen heterocyclic compounds,are difficult to remove in MFC because of their toxicity,tolerance and inhibition.Therefore,improving the anaerobic reduction performance of MFC is very important for the degradation of quinoline.Zero valent iron（ZVI）,as a reductant,is widely used in the fields of wastewater treatment,groundwater remediation and soil remediation because of its cheap,reliable and medium reduction.In recent years,ZVI has become a toxic and degrading pollutant with its unique reducibility,enhanced enzyme activity and flocculation and adsorption properties.One of the important means.ZVI was added to the anaerobic microorganism system.Under anaerobic conditions,ZVI and H2O were corroded to produce OH-,which could maintain a stable pH environment for the cooperative system and provide electron for anaerobic microorganism.Therefore,ZVI enhanced anaerobic-MFC（ZVI-MFC）coupling technology has been widely concerned at home and abroad.In this paper,a single matrix of quinoline and indole was used as fuel to construct a bipolar chamber MFC and to study the effect of MFC on the treatment of typical nitrogen heterocyclic compounds and the effect of zero valentiron anaerobic microorganism-MFC（ZVI-MFC）coupling technology on the degradation effect.It will lay a theoretical foundation for whether MFC can be applied to actual wastewater treatment.In this paper,the following studies were carried out to study the degradation of MFC and the effect of ZVI on typical nitrogen containing heterocyclic aromatic hydrocarbons:First,a bipolar chamber MFC was built to cultivate sludge from the domesticated coking plant.Then,quinoline and indole of 250mg?L-11 were cultured in the anode chamber.At the same time,two 400mLanaerobic sludge bottles were selected to start and domesticate according to the start-up mode of MFC.This experiment mainly analyzed and compared the efficiency of traditional anaerobic treatment of typical nitrogen containing heterocyclic compounds and the closed loop degradation effect of microbial fuel cells.On this basis,the dosage of ZVI in the quinoline system and the indole system was optimized separately,and the dosage of ZVI was determined.Then,in order to better explore the coupling of ZVI strengthening anaerobic-MFC,the time of ZVI intensifying anaerobic was optimized,and the optimal strengthening time was determined.Thereafter,ZVI was used to intensify the anaerobic MFC coupling system,so as to achieve the improvement of degradation efficiency.Through the experimental process,we get the following experimental conclusions.（1）An open-circuit bioanode(ie,simple anaerobic microbial oxidation,250mg?L-1quinoline or indole as an electron donor)was used as a control,the degradation rates of quinoline and indole in the bioanode(250mg?L-1quinoline or indoleand electrode as an electron donor)increased 7%and 6%than opened bioanode（pure anaerobic microbial reduction）,respectively.It showed that the bioanode can enhanced reduction of quinoline or indole to the corresponding products.（2）In the experiment of optimizing the dosage of ZVI,0g?L-1,2g?L-1,4g?L-1,6 g?L-11 and 8 g?L-11 were added to the pure anaerobic system of indole and quinoline respectively through the experiment of parallel contrast experiments.The multi cycle experiment was carried out.Finally,it is found that 4 g?L-11 is the best cast iron.The optimal time of the ZVI fortified quinoline and indole system was determined by the experiment.After anaerobic 24h,the most obvious effect was to promote the anaerobic-MFC coupling system,and the effect was best.（3）Finally,the anaerobic-MFC coupling system was strengthened with ZVI for 24h,It is concluded that under this condition,the effect of iron and closed circuit is the best.The degradation rate of quinoline in iron closed circuit can reach 95%when the reaction is carried out for 4 days,and the degradation rate is9%,11%and 20%higher than that of iron open road,iron free closed circuit and iron free open road.When the reaction lasted for 5 days,the iron was completely degraded by closed circuit.The degradation rate of indole in iron closed circuit was 95%when the reaction was carried out for 4 days.The degradation rate was8%,12%and 20%higher than that of iron open road,iron free closed circuit and iron free open path.When the reaction lasted for 5 days,the iron was completely degraded by closed circuit.It indicated that the addition of ZVIcouldstrengthened the degradation of quinoline and indole.（4）Under the optimal condition of 24h,quinoline was used as a single matrix operating reactor with the highest voltage of about 500mV,and the current decreased gradually,the voltage reached the lowest value within 4d and remained stable,and the operation time of the electric cycle was about 4d.（5）Under the optimal condition of 24h,indole was used as a single matrix operating reactor with the highest voltage of about 500mV,and the current decreased gradually,the voltage reached the lowest value within 4d and remained stable,and the operation time of the electric cycle was about 4d.（6）High-throughput sequencing techniques were used to analyze the microbial community composition of four different systems（ZVI closed circuit,ZVI open circuit,ZVI filled closed circuit,ZVI filled open circuit,and raw sludge）and showed that the big difference existed in ZVI and ZVI systems.The microbial community structure is quite different,and the content of microbial species related to the degradation of quinoline in the ZVI-added synergistic system is obviously increased.This explains that the adding ZVI to promote MFC degradation of quinoline is reasonable.（7）In the high-throughput sequencing experiments of quinoline and indole,the addition of iron in the reaction system is beneficial to the enrichment of Firmicutes.Protebacteria is more abundant in iron-free systems and is more suitable for survival in iron-free MFC.（8）In the quinoline degradation experiment,the iron-enclosed pathway can promote the enrichment of Acinetobacter and Brevibacillus,both of which contribute to the degradation of quinoline.In the decomposing experiment of thorium,the addition of iron closed circuit promotes the enrichment of Streptomyces sp.,which is beneficial to the degradation of thorium. |
