【作者】 梁炜；

【导师】 黄少斌；

【作者基本信息】 华南理工大学 ， 环境工程， 2012， 博士

【摘要】 酸雨是大气污染物（如硫化物和氮化物）与空气中水和氧之间的化学反应。目前我国酸雨正呈急剧蔓延之势，是继欧洲、北美之后世界第三大重酸雨区。而大气中的氮氧化物（NOx）是酸雨的主要成因之一，我国NOx最大的来源是火力发电厂。生物滴滤法脱除NOx是近年来备受广泛关注的高效低耗气体处理技术。很多燃烧废气首先通过湿洗来减少二氧化硫和灰尘的排放。这种湿洗过程的操作温度一般为50~60℃，所以处理燃烧废气过程中的微生物体系最好能耐受50℃左右的温度。另外，处理燃烧烟气中一般含有3%-8%的氧气，明显降低了生物反硝化脱除NOx效率，制约其工业化应用。因此，驯化筛选能在高温好氧条件下进行高效反硝化的菌株，应用于生物滴滤塔脱除火电厂排放的烟气具有很大的工程应用价值。本论文采用稀释涂平板分离纯化，通过逐步升温方式，从火电厂生物滴滤系统填料的生物膜上筛选分离出在50℃条件能进行高效好氧反硝化的菌种TAD1。该菌株革兰氏染色呈阴性，短杆状，大小为0.78μm×1.27μm。经16S rDNA序列同源性分析，结合生理生化分析，菌种TAD1与螯台球菌属（Chelatococcus）最为相似，命名为Chelatococcus daeguensis TAD1，该菌株是一株新型好氧反硝化菌，现在还未有对此菌株的好氧反硝化性能报导。本论文在50℃下对该菌进行了好氧反硝化性能测定，氮气是反硝化过程的主要终产物。当碳源为丁二酸钠时C. daeguensis TAD1的反硝化效果非常好。然而，TAD1却几乎不利用葡萄糖，24h内几乎没有反硝化效果。最佳pH值为9，24h硝酸盐的去除率达到96.1%，更高的碳源量没有抑制TAD1细胞生长和反硝化能力。TAD1的氧耐受度为5.1mg/L。通过不同氮源测定得知菌株TAD1的亚硝酸盐还原酶只有在硝酸盐还原酶也具有活性的同时才具有较高活性。氨态氮的存在可以提高菌株TAD1的整体脱氮效果，但是提高的幅度不是很大。最后通过改变碳源浓度确定了莫诺方程中菌株TAD1的最大比生长率和半饱和系数。与目前已报道的几种常温好氧反硝化菌相比，菌种TAD1具有更好的反硝化性能。将已筛选出的菌种TAD1接种于高温生物滴滤塔系统，考察该系统对NOx的去除效率。结果表明，当处理NO浓度为133.9-669.6mg/m~3，氧气浓度在8%范围内的模拟烟气时，生物滴滤塔能有效地去除80%以上的NOx。当NO浓度为535.7mg/m~3，氧气浓度在2-20%范围内，生物滴滤塔能有效去除80–93.7%的NO。50℃下生物滴滤塔对NO的生物去除高于25℃，表明TAD1在高温条件下有很好的反硝化性能。通过碳源量的实验得知在本研究中的氮源与碳源的浓度比在理论上是远远过量的，可以很好的保证NO的去除过程。在EBRT相对较短（少于1.5min）的时候，传质成为NO去除过程中的限速步骤。随着EBRT的增加，NO去除效率迅速增加，生物反应成为NO去除过程中的限速步骤。当EBRT继续增大时，微生物反硝化能力达到最大，气相中化学氧化作用随EBRT增大却逐渐增强。生物滴滤塔pH值控制在7.5-8.0左右去除NO效果最佳。生物滴滤塔闲置2、4和8天分别再启动后TAD1在4-16小时后恢复NO去除能力。闲置期越久，所需的恢复时间越久。这些结果表明了该技术对高温下高效长期稳定地脱除火电厂烟气中的NOx有很好的指导意义。为了说明生物滴滤塔内好氧反硝化去除NO的过程，建立了模型。以NO在气液界面浓度分布为基础，模型预测了生物滴滤塔内NO的传质反应过程。此外，通过模型分析了运行参数，如进口NO浓度和空床停留时间，对NO脱除效率的影响。更多还原

【Abstract】 Acid rain is the chemical reaction between atmospheric pollutants (such as sulfides andnitrides) and water and oxygen in the air. Amount of acid rain in China have undergone analmost exponential increase over the past decade and become the world’s third largest acidrain area after Europe and North America.Anthropogenic emissions of nitrogen oxides (NOx),which are mainly produced during the burning of fossil fuels, have negative effects onecosystems and contribute to the formation of acid rain. In China NOx are mainly emittedfrom coal-fred power plants. The biological removal of NOx from contaminated gas streamsby biofilters is efficient low-cost NOx abatement technologies with no second-pollution. Gasexiting the scrubbers typically exhibit temperatures between50and60℃. The bioreactorpacking materials must contain suitable concentrations of denitrifying bacteria within thistemperature range. Additionally, While the flue gas discharged from coal-fired power plantsis estimated to contain typically3%-8%(v/v) O2, which had negative effect on traditionaldenitrifying process. In order to eliminate these drawbacks in biofilters, the technology ofnovel aerobic denitrifying bacterial, which were cultured and inoculated in biotrickling filterto ascertain oxygen effects on NOx removal under thermophilic condition, is meaningful.In the present study, an aerobic denitrifier was isolated from the biofilm of an fieldbiotrickling filter and its aerobic denitrification activity was evaluated under variousconditions in batch reactor experiments at50℃. This bacterium was Gram negative, shortrod, with the size of0.78μm×1.27μm. Based on biochemical studies and16S rRNAsequencing analysis, the isolate was identified as Chelatococcus daeguensis strain TAD1. Atpresent, no C. daeguensis strain has been reported to be an aerobic denitrifier. The C.daeguensis TAD1was examined to determine the effects of different carbon sources, C/Nratios and dissolved oxygen concentration on aerobic denitrification activity at50℃. C.daeguensis TAD1efficiently removed nitrate using disodium succinate as the sole carbonsource. Nitrate was hardly reduced when glucose was used at50℃. The optimal C/N ratiowas9, giving a denitrification efficiency of96.1%and higher carbon concentrations did notinhibit cell growth and denitrification activity. C. daeguensis TAD1tolerated oxygen levelsabout5.1mg/L. By change of different nitrogen sources activity of nitrite reductase was determined that its high activity was only high in the appearance of nitrate reductase activity.The presence of ammonia nitrogen could improve the overall nitrogen removal efficiency ofstrain TAD1, but the level of increase is not large. The maximum specific growth rate μmaxand the saturation constant Ks in the Monod equation were further determined by changingcarbon concentration. The denitrification efficiency of C. daeguensis TAD1was higher thanthat of mesophilic bacterium.The development of a thermophilic biotrickling flter (BTF) system to inoculate a newlyisolated strain of Chelatococcus daeguensis TAD1for the effective treatment of nitric oxide(NO) is described. A bench-scale BTF was run under high concentrations of NO and8%O2in thermophilic aerobic environment. The inlet NO concentration fluctuated betweenapproximately133.9and669.6mg/m~3and kept on a steady NOx removal rate above80%inan oxygen stream of8%at50℃. The BTF system was able to consistently remove80–93.7%NO when the inlet NO was535.7mg/m~3in an oxygen stream of2–20%. The biologicalremoval efficiency of NO at50°C is higher than that at25°C, suggesting that the aerobicdenitrifer TAD1display well denitrification performance under thermophilic condition. Inthe first phase, relatively shorter EBRT (less than1.5min), the removal was a masstransfer-limited process. However, at a phase with longer EBRT bacteria, the reaction becamethe limiting step of the removal process. When EBRT continue to increase, capacity ofmicrobial denitrification reached largest, and chemical oxidation in the gas phase increaseswith EBRT has gradually increased. The optimal pH value of biotrickling filterwas wascontrolled at about7.5-8.0. Starvation for2,4and8days resulted in the re-acclimation timesof Chelatococcus daeguensis TAD1ranging between4and16hours. A longer recovery timethan that for weekend shutdown will be required when a longer starvation occurs. The resultspresented here demonstrate the feasibility of biotrickling flter for the thermophilic removal ofNOx from gas streams.To illustrate the process of NO aerobic denitrifying removal by biotrickling filter, adynamic model has been developed. Based on the mass component profile of NO at thegas–liquid interface, the model was used to depict the mass transfer reaction process of NO inbiotrickling filter, focusing on the concentration distribution of NO in the gas, liquid phases.Additionally, effects of operating parameters such as inlet NO concentration and empty-bed residence time on NO removal efficiency were evaluated through a sensitivity analysis of themodel.更多还原