Fluctuations in influent concentrations and variations in waste air composition challenge the application of biofiltration technology in the chemical industry. An integrated system of a cyclic 2-bed adsorption/desorption unit and a trickle bed air biofilter (TBAB) is proposed and applied in this study. The primary goal of the study was to maintain long-term, stable consistent high performance of volatile organic compounds (VOCs) degradation in the TBAB. Five specific studies were conducted to accomplish the primary objective. Investigations were conducted on independent TBABs under single VOC interchange with periodic backwashing as biomass control. The VOCs considered were common solvents used in paint booth industries. Two aromatic compounds (styrene and toluene) and two aliphatic compounds (Methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK)) were studied. This study simulated VOC emission rotation as the process of production rotated in certain chemical industries. Experimental findings indicated that the biofilter required apparent re-acclimation period when the VOC was interchanged to aromatic ones. The second phase investigated two mixtures of these VOCs in two independent parallel trains of TBAB under step change in influent concentration. Critical loadings were determined under backwashing and starvation operating strategies. In the third phase, the buffering capacity of a cyclic 2-bed adsorption unit under a square wave of fluctuating condition was evaluated for a feeding composition based on EPA industrial emission report. The cyclic 2-bed adsorption unit succeeded in attenuating load fluctuations as compared to non-cyclic operations. Furthermore, the time to breakthrough of contaminants encountered in non-cyclic operations could lead to a starvation period to the followed biofilter and eventually long period of acclimation after breakthrough of VOCs from the adsorber. In the fourth phase, the integrated system of 2 cyclic adsorption/desorption beds and TBAB was applied to the VOC mixture. Four square wave feeding conditions were applied on the system. A parallel control system with an independent TBAB only was run to compare its performance to the integrated system. Experimental findings revealed that the integrated system was able to achieve high stable performance as compared to the control unit. Finally, microbial communities were investigated for the biofilters utilized in VOC interchange and VOCs mixture experiments. Microbial diversity showed consistent transition for the interchange of VOCs. Community structure for VOC mixtures showed high independency to the component content in the mixture.
|School:||University of Cincinnati|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/10(E), Dissertation Abstracts International|
|Keywords:||Adsorption, Biofiltration, Cyclic, Integration, Tbab, Waste gas|
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