Treatment Of Low-Concentration VOCs Waste Gases By Blotrickling Filter

With the rapid development of science,technology and economic,environmental pollution has become a serious problem that plagues the whole world and threatens all humanity.Especially in China,the air pollution dominated by PM2.5,VOCs,acid rain and ozone pollution is becoming increasingly serious,covering large areas and most cities.Air pollution has gradually become an "invisible killer" that affects human health.Volatile organic compounds(VOCs)are common atmospheric pollutants whose existence can lead to the cause of PM2.5,acid rain,photochemical smog,and greenhouse effect.Thus,for human health,it is very important to efficiently treat VOCs in the atmosphereAt present,the methods for the treatment of VOCs pollutants in the gas phase mainly include physical methods,chemical methods,and biological methods.Physical and chemical methods in VOCs treatment have the advantages of high efficiency and thorough handling.However,the disadvantages of high cost,high energy consumption,and secondary pollution are often occurred.In addition,the VOCs pollutions present in the air are often at low concentration but in large volume,thus,traditional physical-chemical methods are often limited in treating these types of VOCs pollution.Biological methods use bioreactors to treat these VOCs pollutants via microbial metabolism.Therefore,biological methods have the advanage of high efficiency,environment friendly,no secondary pollution,and low cost.Among biological methods,the biotrickling filter(BTF)method has strong regulation and has a wide application prospect in the field of deep-processing low-concentration VOCs,and has been successfully used for the treatment of a variety of VOCs and atmospheric odorous pollutants.However,biological methods are currently recognized as the best available technologies in the treatment of low and moderate concentrations of waste gases containing odors and VOCs because they are cost-effective and environmentally friendly compared to other physical-chemical technologies.However,BTF system also have some limitations in the treatment of VOCs with high hydrophobicity and high toxicity.How to improve the removal performance of hydrophobic VOCs by BTFs is the key problem need to be solved in biological waste gas treatment.In order improve the removal performance of hydrophobic VOCs by BTFs,and optimize the parameters during BTF operation,this review summarizes the recent advances in the design,and mechanism of recent BTFs.In addition,the strategies to improve the removal efficiency of BTFs were discussed from the aspects of the design,operating conditions,mass transfer,packing material,microorganisms.It is purposed in this article that the operation parameters,packing materials,and microorganisms of the BTF are important factors to improve the removal performance of hydrophobic VOCs.The coupling of BTFs methods with other technologies,and utilization of the waste resource by BTFs should be focused in the further studies.Based on this,and in order to treat methyl acrylate waste gas,a three-layer BTF packed with ceramic particles and immobilized with activated sludge was set up.The BTF exhibited excellent removal efficiency that no methyl acrylate could be detected when EBRT was larger than 266 s and inlet concentration was lower than 1879.2 mg/m3 and EBRT was 400 s with the inlet concentration lower than 4291.1 mg/m3.As the inlet concentration continually increased,the RE began to decrease.At the maximum inlet concentration of 7200 mg/m3,the RE can still maintain at over 87,56%and 77.36%.The contribution to remove methyl acrylate of different layer was analyzed,the result indicated that as the EBRT decreased,the total RE first increased then decreased,however the EC increased all the time.The 1st layer performed the best at fixed inlet concentration of 0.42 g/m3.PCR combined with DGGE was performed to detect differences in the different layers of the BTF.The methyl acrylate concentration can significantly affect the bacterial community in BTF.As the inlet concentration increased,the species number decreased and the abundance of the strain who have high acitivity in methyl acrylate biodegradation increased.D.gigas,V.paradoxus,D.koreensis,P.suwonensis,A.caulinodans,H.denitrificans,Hyphomicrobium sp.and C.testosterone formed the bacteria community to treat methyl acrylate waste gas in the BTF.In order to further innovate the BTF system,in this study,BTF were constructed and packed with conductive packing material to treat toluene waste gas.During toluene biodegradation,the output voltage was observed and the voltage decreased with increasing the total air flow.The applied voltage inhibited toluene removal and affected the bacterial community in BTF-E.The results indicated that the elimination capacity reached 120.1 g/m3h corresponding to an inlet concentration of 2.259 g/m3 under 61,5 s of EBRT.Under the acclimatization of applied voltage,autotrophs and strains related to nitrogen cycle become the predominate species,thus,the high abundance only contributed a small part to improving toluene removal.The predominant bacterial genera in BTF-O were Acidovorax,Rhodococcus,Hydrogenophaga,Brevundimonas,Arthrobacter,Pseudoxanthomonas,Devosia,Gemmobacter,Rhizobium,Dokdonella and Pseudomonas.This study showed a first attempt to treat methyl acrylate waste gas by BTF methods,and use conductive packing material in BTFs.This study will procide technical support for the efficient treatment for the biodegradation of methyl acrylate and toluene waste gas.