| Biofiltration technology has become the focus of the research on the treatment of volatile organic compounds（VOCs）.However,studies on the interaction of different kinds of VOCs under thermophilic conditions when treating VOCs mixtures are limited.Therefore,in the current study,the thermophilic biofilter systems were applied for treating different thermophilic（50°C）VOCs gases.On the basis of this,the removal performance of thermophilic VOCs mixtures and the interaction between the compounds were evaluated.In addition,the technologies for stable operation of biofilters were optimized.The differences among thermophilic benzene,hexane and toluene gases when treated using biofilters were compared.The results showed that the removal performance of the three substances by biofilters was: toluene>benzene>hexane.The biomass accumulation of the biofilter treating toluene was the fastest.The specific growth rates were 0.008,0.004,and 0.018 g dry biomass/（g dry filter·day）for benzene,hexane,and toluene,respectively.The pressure drop of the biofilters treating toluene and benzene was much higher than that of hexane.In addition,the CO2 concentration and the leachate TOC of the biofilter treating toluene were the highest,followed by benzene and hexane.The removal performance of biofilters treating the mixtures of benzene and hexane was studied.Comparing with the conclusion in the single phase,the results indicated that when benzene and hexane were mixed with the volume ratio of 1:1,the removal performance of benzene was unaffected while the removal performance of hexane was significantly inhibited with the removal efficiencies dropping from 70%to 35%.The interaction index of benzene with the addition of hexane was only-0.029,indicating that hexane had little effect on the degradation of benzene in the mixing phase.However,benzene inhibited hexane degradation strongly with the interaction index of-0.557.In order to improve the stability of biofilters in the operation,technologies for biomass control were optimized on the basis of the removed dry biomass and the removal efficiencies.The results showed that the technologies of washing with water at 20 °C and 50 °C were more efficient for biomass control of the biofilter in this study.The removed dry biomass obtained by 20 °C and 50 °C water washing wasparallel at 3.1 kg/m3.The average efficiencies of 20 °C and 50 °C water washing were80% and 76%,respectively.The methods of biofilters restarting were also studied.The results showed that raising the concentration gradually could recover the removal performance of the biofilters quickly and the average removal efficiencies reached67%,which indicated that the method was the most effective for biofilters restarting in this study.The biofiltration technology was applied to a chemical enterprise in Tianjin to treat the odours,which included VOCs mixtures and H2S.The results showed that when the inlet concentrations of total VOCs（TVOC）were under 3000mg/m3,the TVOC outlet concentrations maintained below 50 mg/m3;in addition,when the inlet concentrations of H2S were under 3.2mg/m3,the H2S outlet concentrations maintained below 0.015 mg/m3,which indicated that the removal performance of the biofilter in practical engineering was effective.During the startup of the operation（0-30 day）,the pressure drop of the biofilter maintained at 0.35-0.55kPa/m,which indicated that the packing of the biofilter was in good condition. |
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