Enhanced Removal Of Organic Waste Gases In Biotrickling Filters By Surfactants And Zn(Ⅱ)

The emission of volatile organic compounds (VOC) has already been regardedone of the most important environmental problems. Though biotrickling filter (BTF)has already been recognized as an extremely effectively alternative for control ofVOC, this technology can not provide a commendable performance when treatinghydrophobic compounds. Additives-enhanced biotrickling filter technology, whichmay reduce the mass transfer resistance between the gas phase and the biofilm phaseor enhance the microbial activity, thereby improving the subsequent biodegradationrate, is turning into a promising technique to break this limitation.Ethylbenzene was used as model VOC in this study, and Tween-20, a non-ionicsurfactant, along with Zn(II), was used as the additives. At the start-up period,microorganisms accumulated within the packing materials were subject to a lowethylbenzene concentration of350mg m-3and an empty bed retention time of40suntil the highest removal efficiency reached97%. Turbidity experiments wereconducted subsequently. Results indicated that Tween-20was beneficial to microbialactivity at0.0-737mg L-1and the higher the concentration, the more obvious thefacilitating role, while Zn(II) affected adversely when the concentration overpassed5.0mg L-1. Additive was added into the BTF to examine their enhanc ed effects.When the concentration of surfactant was increased from3.684to7.368,36.84,73.68mg L-1, the RE firstly increased to maximum at7.368mg L-1and then it graduallydecreased. To find out a more accurate optimum value, we tested other threeconcentrations around7.368mg L-1and the result indicated that11.79mg L-1wasthe optimum concentration. On that basis, the optimum additive concentration of1.0mg L-1of Zn(II) was found out. And the final removal efficiency was90%. Thephenomenon of excessive biomass accumulation occurred two times throughout theentire process.After two identical BTFs were successfully started up, comparative experimentswere carried out with BTF1fed with optimum concentrations of Tween-20and Zn(II)while BTF2(the control BTF) without them. When the inlet ethylbenzeneconcentration was increased from720to1450and2100mg m-3, corresponding toorganic loading rates of64.8,130.5and189g ethylbenzene m-3h-1, the average REof BTF1could reach94%,84%and69%accordingly, while for BTF2, the final REof it was just74%,63%and54%. When subjecting both the BTFs to constantorganic loading rate of248.4g ethylbenzene m-3h-1and different EBRT values of30,20and10s, the RE for BTF1kept going up (64%,65%,68%) while the RE forBTF2gradually declined (53%,48%,41%). The RE for both BTFs decreased (91%,78%,61%for BTF1and73%,59%,37%for BTF2) with the decreased EBRT of60, 30and15s when inlet concentration was fixed at1650mg m-3. Removal rates o fBTF1were higher than that of BTF2under this three operation conditions andexcessive biomass accumulation of BTF1was relatively infrequent compared withthat of BTF2throughout the entire operation process of170days, indicating thatapplication of surfactant and Zn(II) could enhance the BTF performance forethylbenzene removal.