以生物法去除苯及二甲苯之研究

Abstract

本研究以生物濾床技術為基礎，將汙泥中分離出的菌株經多次測試篩選後，選擇效能最佳的菌種，植種於濾料上，對苯與二甲苯進行處理。實驗測試氣體進流濃度在0.6至2.0 g m-3的範圍下，調整滯留時間為2分鐘、1分鐘及0.5分鐘，分別觀測其去除效果，結果顯示苯與二甲苯的系統在滯留時間為1分鐘時，最佳可達到逼近90%的去除效率。系統針對苯與二甲苯的移除負荷分別為208 g m-3 h-1與248 g m-3 h-1。本研究亦探討氮源供應或改變及pH值變化對系統的影響，氮源測試方面，在不供應氮源的狀況之下，苯系統之去除效率明顯大符下降，但在二甲苯系統中卻未觀察到明顯的影響。而當系統氮源由原本的硫酸銨改為硝酸鉀，可發現系統對二甲苯的去除率有些微提高。二甲苯系統在pH極端(pH = 3~10)的環境下，去除效率並未因pH值變化而有明顯降低；相較之下，pH變化對苯的系統影響較大，由實驗結果可觀察出苯系統之最佳條件約落在pH值為7.5~10.3的範圍內。隨實驗長期監測溫度變化，可發現二甲苯系統在25 ℃~35 ℃的範圍內，溫度與去除率呈現正相關。

According to previous study, benzene, and xylene are biodegradable in biofilter. In this study, biofiltration of benzene and xylene vapors has been studied in laboratory, with activated packing materials inoculated with appropriate microbial consortium. Various retention time (RT), i.e. 2, 1 and 0.5 min, were tested for xylene and benzene inlet concentration ranging from 0.6 to 2.0 g m-3. Both removal of benzene and xylene achieved the efficiency up to 90% at a retention time of 1 min. The maximum elimination capacity was 208 g m-3 h-1 and 248 g m-3 h-1 for benzene and xylene biofilter, respectively. Nitrogen source and pH effects were also been studied. When nitrogen source was not in benzene system, removal of benzene indeed decreased, where as obvious changed in xylene system. When the nitrogen source changed from (NH4)2SO4 to KNO3, removal of xylene slightly elevated from 79% to 83%. The pH 3 to 10 did not affect removal of xylene. However, reducing sugar increased and accumulation of nitrate when pH was declined. In benzene biofilter, the optimal removal pH was around 7.5~10.3. Removal of xylene was positive related with temperature in the range from 25 ~ 35 ℃。