Research On Process And Mechanism Of Nonthermal Plasma Coupled With Bio-trickling Filter For Chlorobenzene Treatment

In recent years,the threat of volatile organic pollutants?VOCs?to the environment and human has attracted more and more attention.As anewtechnology,Non-thermal plasma coupled with Bio-trickling filter process?NTP+BTF?has good potential for application to treat non-biodegradable VOCs and high concentrations of VOCs.In this paper,the performance of chlorobenzene degradation by Non-thermal plasma technology was investigated,as well as the combination of this technology and Bio-trickling filter treatment process.In the experimental study of Non-thermal plasma degradation of chlorobenzene,effects of various technologic parameters like discharge voltage,EBRT,relative humidity and initial concentration of chlorobenzene were studied respectively.the chlorobenzene removal efficiency was increased with the increase of EBRT and voltage for different inlet concentration.And the chlorobenzene removal efficiency was best when RH is 35%-65%.the removal efficiency decreased with the increase of inlet concentration when the EBRT and voltage was fixed at certain value.At the same time,the intermediate products and O₃,CO₂were examined and analyzed in the process of discharge.The experimental results showed that the amount of CO₂ had a linear relationship with mixed gas removal loading?y=1.5603x?.Chlorobenzene was not fully degraded to CO₂ and H₂O,Only 66%degraded chlorobenzene was transformed to CO_2,and the amount of CO₂ was reduced with the decrease of EBRT.Meanwhile the by-products O₃ was analyzed and the results show that both the inlet concentration and RH have an effect on the amount of CO₂.The amounts of O₃ generation could reach the maximum in a suitable humidity range between 35%and 65%,The amount of O₃ was reduced with the decrease of inlet concertration.And the amount of CO₂ and O₃ increased with the rise of voltage and then keep stability.The analyzed result of degradation of chlorobenzene showed that the main products were molecules which have good water soluble that could be degraded easily by microorganisms.There are two BTFs which was setted up with chlorobenzene as sole carbon source,directional domesticated activated sludge and high efficient degradation bacteria as inoculation fluid.Experimental results showed that Two BTFs biofilm were able to finish cultivate within 19 d.After start-up period,the NTP was accessed to the system as pretreatment compared with single BTF system.The operation condition and performance of NTP+BTF and single BTF system were analyzed.The removal efficiency of two systems had a trend of decline with the increase of inlet concentration and inlet loading.The removal rate of single BTF system changed significantly compared with NTP+BTF coupling system,Coupling process showed better removal performance,and it mainly owe to some small molecules produced by NTP pretreatment which had good water solubility and can be degraded easily by microorganism.The remove loading of two systems were increased with the increase of inlet loading,The highest removal loading of single BTF was 53.41 mg/m³·h.and highest removal loading of NTP+BTF coupling system was 85.24 g/m³·h.The amount of CO₂ was increased with the increase of chlorobenzene removal loading,the mineralization rate of NTP+BTF coupling system was 92%which was higher than single BTF.BTF was operated without carbon source provided.The result showed that after starvation period of 21 days,the coupling system could restore stability in 7 days,while single BTF system needed 13 days.The result of Scanning Electron Microscope?SEM?show that the NTP pretreatment had an effect on microbial morphology and distribution.The NTP not only influenced the growth of biofilm,also affectd the growth of different kinds of microorganism.High-throughput sequencing was used to research biofilm microbial population structure and diversity,The results showed that the dominant bacterial community still existence along with the running of the reactor,such as Alphaproteobacteria?Gammaproteobacteria?Sphingobacteria?Betaproteobacteria.The dominant bacteria Planctomycetacia which was existenced in two BTFs now less than 1%.The NTP pretreatment had a certain influence on microbial community structure,For example,Subdivision3 bacteria accounted for only 1.03%in a single BTF system,but accounted for7.21%in the coupling system.Through OTU cluster analysis showed that the microbial diversity and abundance of the coupling system were lower than that of single BTF system,may be due to the O₃ produced by NTP pretreatment,which has inhibitive effect on microorganisms in BTFs.