Research On Chlorobenzene Purification Performance And Anti-Interference Mechanism Of Fungal-Bacterial Trickling Filter

Volatile organic compounds,as precursors of ozone and secondary organic aerosols,have strong carcinogenicity,teratogenicity,and mutagenicity,are strictly controlled by the government.Biotrickling technology is environmentally friendly and has low operating costs.The construction of a fungal-bacterial system in a biotrickling filters is conducive to the synergy between microorganisms,improving the purification performance and anti-interference ability.In this essay,chlorobenzene degrading fungus was isolated from previously domesticated mixed sources,determined the optimal inoculation ratio of the fungal-bacterial system,and explores the degradation ability under factors such as temperature,p H,and chlorobenzene concentration.A fungal-bacterial trickling filter（BTF2）was constructed while the bacterial trickling filter（BTF1）was as a control to investigate the purification performance during the start-up stage and under different operating conditions.The recovery of performance after shutdown and the performance at different moisture contents was explored.The degradation mechanism and anti-interference ability was clarifoed through changes in biofilm characteristics,enzyme activity and degradation pathway analysis and metagenomic analysis.The main research results are as follows:（1）Two strains of chlorobenzene degrading fungi,named as MY-1 Aspergillus niger and MY-3 Aspergillus flavus,were isolated from a mixed source.The degradation rates of chlorobenzene were 44.21%and 44.78%,respectively.The optimal inoculation ratio for fungal MY-1,MY-3,and bacterial GZ-7 chlorobenzene degradation systems was 1:1:2.The composite system showed stronger tolerance,and the degradation efficiency of chlorobenzene in the composite system was higher than that of bacterial GZ-7 at temperatures ranging from 15℃to 35℃and p H ranging from 3.5 to 7.5.The difference between the two was more significant at low temperatures and low p H.The kinetic fitting experiment results showed that the degradation rate constant of the composite system,k=0.34 d^-1,was 1.25 times that of the bacterial system.The key degrading enzymes of fungus bacteria system are 1,2-dioxygenase and Lignin peroxidase.The GC-MS results showed that the intermediate products of fungal bacterial degradation of chlorobenzene were mainly succinic acid,malonic acid,and 3-chloro-1,2-propanediol.Therefore,it can be inferred that the degradation pathway of chlorobenzene is as follows:under the action of degrading enzymes,3-chlorocatechol is first generated,followed by substances such as 2-chloro-2,4-diaphthalic acid,3-chloro-1,2-propanediol,etc.The chlorine atoms are removed to generate small molecule acids such as succinic acid and malonic acid,Finally,it enters the TCA cycle and is converted into CO₂ and biomass.（2）The removal rate of BTF2 can stabilize at over 85%on the 20th day,with a removal load of 7.57 g/（m³·h）.At this point,BTF2 started and the startup time was shortened by 3 days compared to BTF1.During long-term operation,the overall removal load in both BTFs shows an upward trend.After stabilization,the removal load in BTF2 is almost always higher than that in BTF1 and closer to the 100%removal line.The purification performance of BTF2 for chlorobenzene is better than that of BTF1.When the residence time was 45 seconds,the maximum removal load of BTF2 was35.62 g/（m³·h）,which is 5.31 g/（m³·h）higher than that of BTF1.The SEM of the biofilm showed that the distribution of BTF2 microorganisms was more separated and uniform;After long-term operation,the protein content in BTF1 and BTF2 biofilms was 20.81 and 26.72 mg/g,with relative hydrophobicity of 62.17%and 72.83%,and Zeta potentials of-8.85 mv and-7.72 mv.Compared with BTF1,BTF2 had higher protein content and relative hydrophobicity,lower Zeta potential,stronger neutralization and adsorption capacity for negative charges,causing stronger adhesion and stability on the surface of biofilm（3）15-day short-term and 40-day long-term shutdown recovery experiment and drought resistance tests was carried out.The results showed that after 15-day short-term shutdown,both BTF1 and BTF2 could recover to the performance before shutdown,and the removal load of BTF2 was 26.21%higher than that of BTF1.After 40 days of long-term shutdown,the removal load of BTF2 could recover to 21.74 g/（m³·h）,and the biomass and enzyme activity decreased by 10.36 mg/g and 0.13 U/m L,respectively,with little difference compared to before shutdown.The most suitable filler moisture content for the fungal bacterial system was 33.4%to 38.2%.The removal load in BTF2under low filler moisture content is 21.30 g/（m³·h）,which is 15.51%higher than that in BTF1.This indicated that the fungal-bacterial system had good purification performance and strong drought resistance.The number of functional genes related to metabolism,energy conversion,and biofilm formation in BTF2 increased by 9.09%.The expression of genes related to degradation enzymes,EPS synthesis,and chemotaxis in BTF2 was more abundant than that in BTF1.The activity of degradation enzymes and the stability of biofilms in the system was strong,and microorganisms can tend to capture pollutants,improving the purification performance and anti-interference ability of BTF2.There are 36 figures,16 tables,and 118 references in this thesis.