Treatment Of Waste Gas Containing Toluene And Dichloromethane Using Double Dielectric Barrier Discharge Combined The Airlift Biofilm Packing Reactor

Volatile organic compounds(VOCs)are one of the main precursors of PM2.5 and O3 pollution.VOCs emission reduction is an urgent problem to be solved in China's atmospheric environment protection.In comparison to other different physico-chemical techniques,the single biological process for gas-phase VOCs which are water soluble and biodegradable is an effective and economical method.However,the use of the bioreactor system to treat industrial VOCs emissions containing several poorly soluble and recalcitrant pollutants like substances containing chlorine and benzene series is not satisfactory.In this study,highly efficient bacterial strains were isolated and biological purification process was strengthened,to solve the problem that single biological process is hard to remove multi-component recalcitrant VOC emission from pharmaceutical industries.The results are as follows:The double dielectric barrier discharge(DDBD)reactor was investigated to remove DCM and toluene.Results showed that the DDBD reactor without catalysts has barely promotion on DCM and toluene removal.The removal efficiency(RE)of DCM is close to 0.When the DDBD reactor loaded with Ti-Mn/alumina pellets catalyst,the RE of toluene at the concentration of 500 mg m-3 and 100 mg m-3 reached 58%and 69%,respectively.Compared with no catalysts,the maximum RE of toluene increased by 42%and 33%respectively.The RE of DCM at the concentration of 500 mg m-3 and 100 mg m-3 reached 34%and 45%,respectively.The addition of Ti-Mn/alumina pellets catalyst can greatly enhance the DDBD removal efficiency of DCM and toluene,which can be used as a biological pretreatment process.A novel airlift biofilm packing reactor was developed to remove mixed gas with DCM and toluene.The RE of toluene and DCM are 58%?65%and 71%?79%,respectively,at the empty bed residence time(EBRT)of 19.3 s.Over 95%of toluene RE was obtained when the EBRT was increased to 38.7 s,while the DCM removal didn't increase significantly with the EBRT.Results showed that the removal of DCM was limited by biodegradation rate,while the removal of toluene was limited by mass transfer rate.It showed that the reactor has good resistance to starvation.In this study,DDBD coupled the airlift bioreactor was established to strengthen the degradation of toluene and dichloromethane.10 g alumina pellet loaded with 1%mass fraction Ti-Mn catalyst was added to the DDBD part.During the total residence time of 20.0 s,the RE of DCM and toluene was over 90%in the inlet concentration of 100 mg m-3 to 1000 mg m-3.Unsteady experiments show that the DDBD combined the airlift bioreactor has good stability against inlet load fluctuations.Furthermore,the microbial community structure changed greatly after the DDBD was added.Hyphomicrobium and Pseudomonas replace Rhodococcus as the dominant genus.Coupling system was proved to have richer microbial diversity than tranditional biological methods.On the theoretical basis of the results in the study,a project was carried on a medicine enterprise in Anhui.A DDBD coupled with the airlift bioreactor was added behind the existing exhaust gas treatment system to strengthen removal efficiency of toluene and methanol.The overall removal performance of toluene and methanol has been greatly improved.The system has significant environmental benefits and can reach up-to-standard discharge stably?...