【作者】 苏晓叶；

【导师】 韩振为；

【作者基本信息】 天津大学 ， 生物化工， 2007， 硕士

【摘要】 甲基叔丁基醚(methyl tert-butyl ether,MTBE)作为一种汽油添加剂被许多国家广泛的应用于无铅汽油中。MTBE是一种溶解性、挥发性有机物,在环境中具有持久性,对生物的毒性很强,并且具有致癌性和致突变性。MTBE的广泛应用,使其成为地下水及地表水中广泛存在的污染物。由于MTBE的自然衰减速度很慢,必须通过物理化学或生物技术修复。近年来随着MTBE降解菌株的发现,MTBE微生物降解技术倍受关注。本文通过考察MTBE的好氧生物降解行为,来研究生物技术修复MTBE污染地下水的可行性。将被石化产品污染土壤中的土著微生物进行培养驯化,分离纯化得到一株降解MTBE的菌株NERC0401,根据菌株形态特征和16S rDNA测序结果,初步鉴定为产酸克雷伯菌(Klebsiella oxytoca)。它的较佳好氧降解条件为:接种量20%,pH 7.0-8.0,温度25-32℃。实验研究了固定化技术对微生物降解性能的影响。以海藻酸钙和聚乙烯醇(PVA)为载体固定微生物,研究表明海藻酸钙固定化细胞活性高于PVA固定化细胞。在海藻酸钠浓度为2%,氯化钙浓度为2%,活性炭浓度为0.5%,粒径为1.50 mm条件下,固定化细胞具有较好的活性、机械强度及传质性能。与游离态菌相比,反应温度、pH值、MTBE初始浓度都有较宽的适应范围,MTBE的去除效率较高。研究还发现乙醇与MTBE共存时,乙醇对MTBE的降解有明显的促进作用。初始溶解氧的增大会增强对MTBE的降解去除效果。采用无泡供氧技术供氧的废水溶解氧高于传统曝气头供氧废水,曝气效率高,促进了生物降解。MTBE浓度约为60 ppm时,利用无泡供氧装置充氧的废水14天的MTBE的去除率为62.9%,而普通曝气头供氧的废水只达到55.4%。将无泡供氧装置与固定床生物反应器组合,建立一套无泡曝气膜生物反应器,考察了这套装置对MTBE的降解效果,建立了固定床生物反应器的拟均相一维模型,得到固定床生物反应器的设计方程,为今后的相关研究提供了一定的依据和参考。更多还原

【Abstract】 Methyl tert-butyl ether (MTBE) has been widely used in many countries as an oxygenated additive to reduce air pollution in unleaded gasoline. MTBE is a water-soluble and volatile organic compound that can persist in environment for a long time. MTBE is toxic and carcinogenic. As a result of its wide use, MTBE has been detected in groundwater and surface waters, and is a cause of concern because of its possible health effects and other undesirable consequences. With the screening of biodegrade strains, removal of MTBE biodegradable technology has become a concern during the last several years. The main object of this paper is to do research on the aerobic biodegradability of MTBE by a MTBE degradate strain, and of the availability bioremediation of the MTBE contaminated groundwater.One stain NERC0401 identified as Klebsiella oxytoca that could degrade MTBE quickly was isolated by enriching, screening and culturing from the soil at Dagang Oil Field, Tianjin, China, and the proper conditions for MTBE aerobic biodegradation were determined by experiments. The pure degraded conditions are under ph7-8, temperature 25-32℃, and inoculated-pathogen quantities 20%.The capabilities of immobilized cells with different carriers have been studied, and find that the sodium alginate (SA) as the carrier has a better effect than polyvinyl alcohol (PVA) as the carrier. The best conditions of immobilization by SA as follows: The results indicated that the immobilized cell had the optimum effect under the conditions of 2% CaClB as cross-linking agent, 2% SA as carrier, 0.3% activated carbon as additive, and 3 mm as the diameter. Compared to free bacteria immobilized cell was able to endure higher temperature and adapt to wide range of pH. The experiment results also indicated that the immobilized cell had the optimum MTBE removal rate. We also found the coexisting of ethanol at some concentrations was helpful for the process.The bioenhancement results showed that the enhancement of dissolved oxygen (DO) could improve the biodegradation of MTBE by strain NERC0401. Bubbleless aeration is a novel aerating technology which could obviously improve the efficiency of oxygen mass transfer than traditional aeration. With the improvement of DO, MTBE removal rate was increased, which improved from 55.4% to 62.9 percent in 14 days. Fixed bed bioreactor augmented with an oxygen-transferring membrane combines a detached bioreactor, viz. membrane-aerated bioreactor. The MTBE removal effect of the bioreactor under continuous operations was studied. An imitated-homogeneous and one dimension model of fixed bed bioreactor with immobilized microbe was developed for forecasting the removal of MTBE. Simulation results fitted well with the experimental data which provided the base for related study.更多还原