利用生物反應器分解甲苯和乙苯之研究

Abstract

按照先前文獻的研究已經證實生物處理法可以有效去除揮發性有機物質(volatile organic compounds；VOCs)，本研究室先前也已經做過關於廢氣處理(ex：H2S、1,1,1-trichlorothane、acetone、iso-propyl alcohol等)的實驗。本研究是延伸先前實驗室對toluene和ethylbenzene的初步研究，並探討入流濃度(inlet concentration) 、停留時間(retention time；RT)、pH、營養源饋料頻率(nutrient feeding frequency)、濾料(material)和氮源(Nitrogen source)對生物濾床去除 toluene 和ethylbenzene的影響。 當滯留時間為0.5 min時，在饋料營養源pH範圍為5-7的情況下toluene和ethylbenzene的去除效率會隨著的pH上升而增加。但在pH範圍為7到9之間發現相反的狀況，所以最適pH為7。營養源饋料頻率測試了三種條件：全天、15 min/h 和30 min/day。當NFF為15 min/h的條件下，toluene和ethylbenzene去除效率會明顯高於其他兩項條件，因此最適營養源饋料頻率為15 min/h。在生物濾床中生物質量的生長和積聚關係壓損，並且會導致反應器堵塞和管流現象。由實驗可以觀察到，壓損會隨著氣體流速增加而增加，並且當生物濾床中生物質量積聚後壓損有明顯的增加。實驗結果指出當氮源為(NH4)2SO4時toluene和ethylbenzene可以被有效的去除。此外，當添加KNO3或不提供氮源時菌體的生長和汙染物分解會受到限制的。實驗在不同的toluene和ethylbenzene入流負荷下完成，在toluene負荷為192 gm-3h-1時可以獲得最大的elimination capacity為157 gm-3h-1； ethylbenzene負荷為419 gm-3h-1時可以獲得最大的elimination capacity為302 gm-3h-1。

According to the foregoing investigation, the biotechnologies has been proven to be an effective process for treating volatile organic compounds(VOCs). The goals of this study were to extend the previous study to removal toluene and ethylbenzene. We examined the effects of inlet concentration, retention time(RT), pH of the nutrient feed, nutrient feeding frequency, material and nitrogen source on the biofilter performance for treating toluene and ethylbenzene waste gases. When the retention time was 0.5 min, the toluene and ethylbenzene removal efficiency increased as the pH of the nutrient feed increased in the pH range of 5-7 . However, an opposite trend was observed for pH between 7 and 9. The optimum pH range was 7. Nutrient feeding frequency test was three conditions: all day, 15 min/h and 30 min/day.When the nutrient feeding frequency was 15 min/h, the toluene and ethylbenzene removal efficiency was significantly higher than the other. The development of biomass accumulation is related to the bed pressure drop in the biofilter, and it can cause the bed clogging and channelling. As can be observed, the pressure drop increased as gas flow rate was increased. The pressure drop significantly increased after biomass accumulation in the biofilter. The experimental results indicated that toluene and ethylbenzene could be effectively removed when the nitrogen source was (NH4)2SO4. Moreover, when KNO3 was added or not provid nitrogen source, the bacterial growth and pollution degradation became limited. Experiments at various toluene and ethylbenzene inlet loads were carried out. The toluene maximum elimination capacity was 157gm-3h-1 for an inlet loads 192 gm-3h-1. The ethylbenzene maximum elimination capacity was 302 gm-3h-1 for an inlet loads of 419 gm-3h-1.