Abstract
本研究之主要目的在探討以氣舉式生物反應器處理含揮發性有機化合物( VOCs)廢氣之成效，並希望藉由理論模式的建立以瞭解反應器內的動力行 為，以作為反應器設計及操作之參考依據。研究中將個別以甲苯及丙酮為 待處理物質，使用之同心圓氣舉式反應器外管內徑 19 公分，內管內徑 14 公分，總液體體積25升。由實驗分析在不同進口流速及濃度操作條件 下，污染物去除率及氧氣消耗的變化等等。由實驗結果發現，不同進料濃 度(0.16 g/m3~4.05 g/m3)、不同菌體來源(Pseudomonas putida及活性污 泥)等因素對甲苯的去除率影響不大；甲苯的去除率只隨流速(0.35 cm/ s~2.12 cm/s)增加而遞減，去除效率介於80%~90%，整體反應行為主要受 甲苯質傳速率的限制。改以處理另一污染物丙酮時發現，不論濃度及流速 的改變，去除率皆在99.5%以上。再移除反應器之同心圓內管，則變成氣 泡塔式反應器，得到之甲苯去除率略低於氣舉式反應器的去除率。反應器 中液相溶氧值隨進料濃度增加而減少，二氧化碳出口濃度則隨之增加。整 體而言，本氣舉式生物反應器對於污染物進料負荷變動有極佳的適應緩衝 性，且在40多天的操作下，皆能維持良好效能。雖然生物質量會隨操作時 間增長而增加，但並未影響去除率。本研究假設反應器中氣相流動為塞狀 流，液相流動為完全混合，生物分解反應引用Andrews 提出之基質抑制關 係式，推導之動力模式，可印證實驗結果及預測反應趨勢。 A 25-L airlift bioreactor is conducted to treat the waste gases containing toluene or acetone respectively in this study. The source of micro-organisms is activated sludge from the wastewater treatment plant. The system is operated with gas as continuous phase and liquid in batch. Toluene degradation is mainly controlled by mass transfer rate rather than by reaction rate. The removal efficiency of toluene is independent of the inlet toluene concentration which is varied from 0.16 to 4.05 g/ m3 and decreases with an increase in the gas velocity which is varied from 0.35 to 2.12 cm/s. The conversion between 80% and 90% are obtained. In addition, the removal efficiency of toluene in bubble column is slight lower than that in airlift reactor. As for acetone, the removal efficiency is above 99.5% under various conditions. In the reaction, dissolved oxygen concentration decreases to about 30% saturation with an increase in the inlet pollutant concentration. This airlift bioreactor has a good adaptability for pollutant fluctuating loads. Besides, a generalized model is developed to describe the microkinetics, mass transfer, gas and liquid flow patterns in the reaction. This model is experimentally validated and can be used to calculate the reaction volume for a required removal efficiency.