Removal Of Mixed Waste Gas By A PH Independent Multi-layers Biotrickling Filter

Hydrogen sulphide(H2S),Tetrahydrofuran(THF)and Dichloromethane(DCM),as one of the more common pollutants of industrial waste gas,is entering environments increasingly day by day for its great wide usage,inevitably increasing the possible adverse health effects,the risk of ecological and environmental damage and related complaints.A pH independent multi-layers biotrickling filter(MLBTF)was employed to remove H2S,THF and DCM mixed waste gas,while ordinary biotrickling filter(BTF)as a reference to do comparative experiments.The start-up procedures of MLBTF and BTF were finished by pure bacteria inoculation within 22d and 28d,respectively.Scanning electron microscopy(SEM)revealed that bacterial communities grew well on the carriers,and the upper layer of MLBTF were mostly coccus and bacillus,the middle was mostly bacillus,and the lower layer were mostly bacillus and filamentous bacteria,however,BTF were mostly bacillus,but also part of coccus and filamentous bacteria.Each component in the mixed waste gas inlet concentration of H2S 200mg·m-3 of THF 100mg·m-3,and DCM 100mg·m-3,under conditions,when longer empty bed residence time(EBRT 50s),the tower had good removal efficiency;in shorter the EBRT(20s),The total removal efficiency of the mixed waste gas in MLBTF was much higher than BTF.Layers of MLBTF have mixed waste components corresponding advantages of micro-organisms,which mixed waste gas of H2S component removal in the lower layer,and the THF components and DCM component were removed in the middle and upper layers.According to Michaelis-Menten kinetics model fitting,MLBTF and BTF for all components of the mixed waste gases by gas saturation constant Ks and maximum degradation rate of unit volume rmax were H2S:0.719g·m-3、312.5g·(m3·h)-1,THF:0.174g·m-3、54.3g·(m·h)-1,DCM:0.116g·m-3、18.9g·(m3·h)-1;H2S:0.133g·m-3、120.Sg·(m3·h)-1,THF:0.071g·m-3、28.3g·(m3·h)-1,DCM:0.042g·m-3、9.4g·(m3·h)-1,respectively.After short-term starvation period(30d),the mixed waste gas removal performance under normal operating conditions gradually restored,but in the long-term starvation period(90d),the mixed waste gas removal performance cannot reach the state of the original removal performance,the need to re-add the efficient high activity degrading bacteria to gradually recover.Through PCR-DGGE analysis,the microbial populationin the carriers differed obviously during the start-up period,and changed into relatively stable during the steady operation period.The MLBTF stable operation of the layers of the main strains as follows:In the upper layer are Pseudomonas DT4,M.rhodesianumH13,Pseudomonas fluorescens,the middle layer are Pseudomonas DT4,M.rhodesianumH13,Pseudomonas veronii,the lower layer are Amorphus sp.YIM DIO,Acidithiobacillus thiooxidans,Methylosinus sp.LW3;in the BTF are mainly Pseudomonas DT4,M.rhodesianumH13,Achromobacter piechaudii,Acidithiobacillus thiooxidans.