Study On The Efficiency And Mechanism Of Advanced Treatment Of Antibiotic-Containing Livestock Wastewater By Three-Dimensional Electrocatalytic Biological Filter

Three-dimensional electrocatalytic biofilter reactor was a good choice for the problem of difficult biodegradation of antibiotic macromolecular organic compounds represented by tetracycline in livestock and poultry breeding wastewater,but problems in the application of the reaction system were unsolved.In order to solve the present situation of few active components,high resistance and high cost of conventional biological filter media,the flotation tailings with rich catalytic components were selected as the main raw materials,accompanied by certain pore-forming agent and binder.Granular bioelectrode was prepared and its performance and mechanism were explored.The three-dimensional electrocatalytic filter reactor was constructed to analyze its degradation efficiency and mechanism of simulated livestock and poultry breeding wastewater.According to the experimental phenomenon,the reactor was optimized for deep treatment of duck factory wastewater.In order to ensure the possibility of practical implementation of the project,a further optimization scheme for the reactor was proposed,thus providing a new theoretical basis and technical support for the degradation of antibiotics in livestock wastewater.The flotation tailings with rich catalytic components were selected as the main raw materials,and the granular bioelectrode was prepared by the method of high temperature and short temperature.The characterization results showed that the granular bioelectrode possesses high proportion of skeleton and liquid phase,good degree of oil spill,strong mechanical strength and reasonable pore structure.Through adsorption experiments and three-dimensional electrochemical experiments,it was found that there was the ability of"adsorption-electrocatalysis"in situ regeneration on the granular biological electrode.the synergistic mechanism of"adsorption-electrocatalysis"on granular biological electrode was inferred by exploring adsorption performance（adsorption influencing factors,adsorption kinetics,adsorption isotherm and adsorption thermodynamics analysis）and three-dimensional electrocatalysis performance（electrochemical performance,electrocatalysis influencing factors and kinetic analysis）.A dynamic experimental study was carried out on the treatment of simulated livestock and poultry breeding wastewater,and the typical antibiotic-tetracycline-was selected as the target pollutant.The degradation efficiency,electrochemical characteristics,intracellular electron transfer mechanism of microorganisms and the effects of electric field and electric field polarity on microbial morphology and community structure of three-dimensional electrocatalytic biological aerated filter were analyzed.The results showed that the removal of ammonia nitrogen,COD and total phosphorus in livestock and poultry breeding wastewater was mainly concentrated in the middle area of three-dimensional electrocatalytic biofilter,while total nitrogen was more easily removed near the cathode（TN:cathode>anode>middle>BAF）.It was worth noting that tetracycline was more easily degraded near the cathode and anode（tetracycline:anode>cathode>middle>BAF）.The reduction ability of the granular electrode was larger than that of the granular biological electrode,but there was no much difference between the oxidation ability and the granular biological electrode.The electron density near the cathode was high,which provides a large number of electrons to the microorganisms near the cathode through the reduction or electron transfer between bacteria.The microorganisms near the cathode transfer these electrons to the respiratory chain through the electron transport chain,which increases the ATPase activity.The microorganisms near the anode absorb electrons in the system while oxidizing the degraded pollutants by enzyme catalysis.The electrocatalysis process can provide electrons for the respiration process,participate in the electron transfer process of the intracellular respiratory chain,and act on the synthesis of catalase and peroxidase in the biochemical reaction process,which can effectively enhance the respiration of microorganisms.It was beneficial to the increase of biomass.The microorganisms near the cathode and anode were large in size and less in EPS,so the"huge"microorganisms were more likely to come into direct contact with the biodegradable products in the sewage.Among them,tetracycline was the most harmful to the microorganisms in BAF;in the three-dimensional electrocatalytic biofilter,the degradation ability of electroactive microorganisms to tetracycline at different locations was as follows:intermediate>anode>cathode.In addition,the dominant bacteria of three-dimensional electrocatalytic biofilter are:Paracoccus(paratococcus,Truepera（Tauerella）,Microcella（microcellular bacteria）and Actinotalea（actinomycetes）.It was worth noting that there were obvious differences between the species in the three-dimensional electrocatalytic biofilter and the BAF.Among them,the similarity of the microorganisms near the cathode and anode in the three-dimensional electrocatalytic biofilter was higher,and the middle area was slightly different from that near the cathode and anode,which indicates that the short-term exchange of cathode and anode has little effect on microorganisms.In order to degrade antibiotics more effectively,the relative area of cathode and anode of three-dimensional electrocatalytic biofilter was optimized,and the expanded anode three-dimensional electrocatalytic biofilter was constructed,and compared with the traditional aerated biofilter.The wastewater from duck factory was deeply treated.The results show that because the start-up time of organic matter was longer,in order to more accurately determine whether the three-dimensional electrocatalytic biofilter was started successfully or not.It was suggested that organic matter should be used as the evaluation standard.It was found that the three-dimensional electrocatalytic biofilter increased ammonia nitrogen（8.005%）,total nitrogen（35.920%）,total phosphorus（11.201%）,COD（22.196%）,organic matter（18.976%）,Cr⁶⁺（25.641%）,Ni⁺（23.809%）,turbidity（14.852%）and chromaticity（37.111%）.The difference was that the removal capacity of Cu²⁺in the three-dimensional electrocatalytic biofilter was lower than that of BAF（-21.739%）.It was worth noting that compared with electrochemical removal of Cu²⁺,Cu²⁺was more suitable for microbial adsorption.At the same time,further optimization schemes and suggestions were put forward for the problems of three-dimensional electrocatalytic biological aerated filter,such as cathode scaling,sidewall flow and low current efficiency.