【作者】 董亚梅；

【导师】 张振家；

【作者基本信息】 上海交通大学 ， 环境工程， 2012， 博士

【摘要】 微生物固定化技术具有处理效率高、稳定性强、生物浓度高和固液分离效果好等优点,最近几十年逐渐引入水处理领域并得到了广泛的关注和应用,但是目前大多处于实验室试验阶段,实现大规模工业化应用的较少,主要原因是常用的固定化载体性能不稳定、价格较高、使用寿命较短、难以适应水处理系统中的长期连续运行。本文根据聚氨酯水凝胶的特点,合成了一种新型聚氨酯丙烯酸酯大分子单体作为包埋载体,以硝化细菌作为被包埋微生物,对聚氨酯包埋硝化菌颗粒的制备和应用进行了系统地研究。采用大单体合成技术,以异佛尔酮二异氰酸酯(IPDI)、甲基丙烯酸羟乙酯(HEMA)和聚醚多元醇(PMPO)为原料分步合成了一种新型聚氨酯丙烯酸酯大分子单体,并利用元素分析、红外光谱和核磁共振图谱对聚氨酯预聚体进行了表征,确定所得预聚体为结构规整分子量均一的大分子单体。对影响该大分子单体合成的各因素进行了分析,确定以二月桂酸二丁基锡催化剂,适宜的反应温度和反应时间分别是65℃和4 h。重点对IPDI/PEG/HEMA大分子单体分步合成反应的动力学进行了探讨,确定了反应级数和反应基团的顺序,表明IPDI与PMPO和IPDI聚氨酯中间体与HEMA的反应均为二级反应,对应的反应速率常数分别0.0165mol/L·min和0.0264 mol/L·min,并计算出其对应的反应活化能分别为55.02 kJ/mol和101.52 kJ/mol。根据实验室的小试结果和反应动力学的理论分析,通过中试放大,建立了一套规模为200吨／年的生产装置。在聚氨酯丙烯酸酯大分子单体乳液经自由基聚合形成水凝胶的反应中,选取过硫酸钾(KPS)/四甲基乙二胺(TEMED)作为双组分的氧化还原引发体系,并采用正交试验优化了聚氨酯水凝胶的制备方法,确定最优配比为：大分子单体10%,催化剂TEMED 0.5%,引发剂KPS 1.0%,添加剂粉末活性炭3%。利用红外光谱和扫描电镜对聚氨酯凝胶颗粒的结构进行了分析,表明聚氨酯水凝胶网络结构稳定且形成孔洞并具有较大的比表面积。根据Arrhenius公式估算了聚氨酯凝胶颗粒的使用寿命,在25℃,pH 6-8的环境,凝胶颗粒可以稳定运行长达20年。在水凝胶制备的基础上,考察了固定化试剂和操作条件对硝化菌活性的影响,确定聚氨酯包埋硝化菌颗粒的工业化生产流程为：在特制模具中将10%聚氨酯乳液、3%粉末活性炭和MLSS 2.0×104 mg/L硝化菌浓缩液混合均匀,加入催化剂TEMED 0.5%,引发剂KPS 1.0%,在25℃下反应10 min,并将得到规整凝胶体放入专业切粒机中切成3×3×3 mm的立方体,清洗,即得到聚氨酯包埋硝化菌颗粒的成品。分别采取了间歇和连续两种驯化方式恢复包埋硝化菌颗粒的活性,结果说明连续提高进水氨氮浓度的驯化方式较为理想,氨氧化速率可较快达到350mg-N/L-pellet·h。利用扫描电子显微镜(SEM)对驯化前后的包埋颗粒内的微生物进行分析,并对聚氨酯载体的经济性进行了评价,聚氨酯包埋颗粒的运行成本较低,适合工业化应用。包埋硝化菌颗粒应用于模拟废水中氨氮的去除,分别研究了包埋硝化菌颗粒在不同初始氨氮浓度中的硝化动力学,在高浓度条件下,为零级反应,反应动力学常数为329.7mg-N/L-pellet·h；而在低浓度条件下,则为一级反应,反应动力学常数为24.72/L-pellet·h.并引入灵敏度分析法,分别考察了高、低氨氮浓度条件下,各个环境因素对包埋硝化菌颗粒硝化特性的影响,确定了最佳操作点分别为：pH=9,DO=4 mg/L,温度为30℃(低浓度)；pH=8,DO=6 mg/L,温度为30℃(高浓度)。与游离态硝化菌相比较,表明包埋硝化菌颗粒在更宽的pH和温度范围内都具有明显的优势。连续去除模拟废水中氨氮运行结果说明包埋硝化菌颗粒在不同浓度的模拟废水处理中均具有较高的氨氮去除效率。最后将包埋硝化菌颗粒应用于各种实际废水处理中以去除氨氮,运行结果表明氨氮去除效果良好,在多数情况下氨氮去除率都能达到80%,实验结果表明本文中提出的聚氨酯包埋硝化菌颗粒具有良好的应用前景。更多还原

【Abstract】 The microorganisms, after being immobilized, can be kept in the reactor more effectively for an unlimited period time so that they can be used continuously and repeatedly. Cell immobilizing processes have been receiving the increasing attention in the field of water treatment in the recent decades. Although the immobilized microorganism technology was carried out over a wide range of research area, it was still in the laboratory tests and was difficult for large-scale industrial applications. The key point was that the current carrier materials were not stability. Therefore, a novel cell entrapment method that involves mild gelation and strong gel structure is desired.Based on the characteristics of polyurethane hydrogel and previous research, a novel microorganism immobilization method involving synthesis, gelation of polyurethane prepolymer has been developed. The feasibility of the proposed immobilization method was tested by nitrifying bacteria. Using macro monomer technology, IPDI/PMPO/HEMA prepolymer was synthesized by two-step reaction. The molecular weight and structure of polyurethane prepolymer were characterized by elemental analysis, IR and NMR spectra. Factors affecting prepolymer synthesis reaction were studied respectively to determine the order of group response, the appropriate reaction temperature, reaction time and the category of catalysts. Focus on the IPDI/PEG/HEMA macromonomer reaction kinetics; the reaction order and the order of groups were discussed. The reactions of PMPO and IPDI and IPDI polyurethane were confirmed to be the second-order reaction. The optimum reaction temperature was 65℃and reaction time was 4 h. And the reaction rate constants were 0.0165 mol/L·min and 0.0264 mol/L·min, and the corresponding activation energy were 55.02 kJ/mol and 101.52 kJ/mol, respectively. According to the laboratory test results and the theoretical analysis of reaction kinetics, through the scale-up response, a plant with the production scale of 200 tons/year was established.Radical polymerization was triggered by the KPS/TEMED as a two-component redox initiation system. The orthogonal test method was used to determine the best formula of preparation of polyurethane gel. The optimized polyurethane hydrogel contained:polyurethane monomer 10%, a promoter TEMED 1.0%, an initiator KPS 0.5%, an additive powdered activated carbon 3%. The structure of polyurethane hydrogels was characterized by IR spectra and scanning electron microscopy. According to Arrhenius equation, the lifespan of polyurethane gel pellets was up to 20 years at 25℃, pH 6～8 of the environment.According to effects of the immobilized reagents and operating conditions on the activity of nitrifying bacteria, we have established the following optimal preparation processes. Nitrifying bacteria concentrate (MLSS 2.0×104 mg/L) was mixed with 10% prepolymer emulsion, a promoter TEMED 1.0%, an initiator KPS 0.5% and an additive powdered activated carbon 3% in a special mold. The mixture was allowed to stand for about 10 min at a temperature of 25℃. The resulting polymerized gel carrier was cut into 3×3×3 mm cubes and then washed thoroughly with distilled water. Thus polyurethane immobilized nitrifying bacteria pellets were obtained. The intermittent and continuous domestication ways were adopted to restore the activity of immobilized nitrifying bacteria pellets, and the results confirmed that the method of continuously improving ammonia concentration was better for pellets domestication and ammonia oxidation rate could reach 350 mg-N/L-pellet·h rapidly. The SEM pictures showed the quantity of the ammonia oxidation bacteria increased substantially during the acclimation. Nitrification kinetics of immobilized nitrifying bacteria pellets in different initial ammonia concentration was studied. Nitrification reaction of immobilized pellets was followed zero-order reaction at the high concentration and first-order reaction at low concentration. Based on the sensitivity analysis, effects of different environmental factors for free and immobilized nitrifying bacteria were investigated under high and low ammonia concentration. The immobilized nitrifying bacteria showed advantage nitrification performance than the free nitrifying bacteria. The optimal operating point were:pH=9, DO=4 mg/L, temperature 30℃(low concentration); pH=8, DO=6 mg/L, temperature 30℃(High concentrations). The results of continuous operation to remove ammonia by immobilized nitrifying bacteria pellets confirmed that immobilized pellets had high ammonia removal efficiency in wastewater treatment system.The immobilized nitrifying bacteria pellets were used for nitrogen removal in various actual wastewaters, and the operation results showed ideal ammonia removal efficiency. The result verified that the polyurethane immobilized-cell method developed in this study has great potential for a variety of applications.更多还原