【作者】 袁宏林；

【导师】 王晓昌；

【作者基本信息】 西安建筑科技大学 ， 市政工程， 2011， 博士

【摘要】 污水中的污染物按存在形态可以划分为悬浮物和溶解物,按化学性质可以划分为无机物和有机物。常规污水处理的主要目的是去除水中的所有悬浮物和有机物,通常采用以活性污泥法为主的生物处理技术和以沉淀为主的固液分离技术。因此,提高生物降解能力和强化固液分离效率是迄今污水处理技术发展的两个层面。在提高固液分离效率方面,自我造粒流化床技术是近年来发展起来的一项高效固液分离技术,通过混凝剂的合理使用和适宜的机械搅拌在高浓度悬浊液中形成大粒径、高密度的造粒颗粒（Pellets）,能大幅度提高固液分离效率。在提高生物降解能力方面,生物颗粒污泥培养技术的发展受到广泛关注,由于生物颗粒污泥具有生物密度高、生物相丰富、沉降性好等优于一般生物絮体的特点,所以该技术能有效提高生物反应器的降解能力,同时有助于提高后续固液分离效率。但是,生物颗粒污泥培养周期长、控制难度大,从而影响了该技术的实际应用。受以上两项技术的启发,论文提出了将生物处理技术与造粒流化床固液分离技术相结合的“生物造粒流化床”污水处理新工艺,借鉴造粒流化床技术使生物反应器中的松散态活性污泥转变为颗粒污泥,再通过供氧条件的合理控制使造粒颗粒污泥具有与活性污泥同样的生物降解活性,在发挥造粒流化床高效固液分离优势的同时实现有机物的生物降解,使污水中悬浮物分离和有机物生物降解得以同步完成。在国家自然科学基金项目的资助下,论文对生物造粒流化床用于城市污水处理的技术特点和理论原理进行了系统性地研究,主要工作及成果包括:（1）生物造粒流化床污水处理工艺研究建立了生物造粒流化床污水处理中试系统,确立了合理的供氧方式及最佳操作与控制条件,在西安市某污水厂开展了对城市污水直接处理的长期运行实验。研究结果表明,生物造粒流化床用于城市污水处理,可以在一个单元内同时完成生物降解和固液分离。工艺的适宜操作条件为:PAC投量50mg/L、PAM投量5mg/L、上升流速1.32mm/s、搅拌速度10 rmp、回流比50%、排泥周期6h、泥床高度控制范围110cm¹60cm。在上述操作条件下连续运行,生物造粒流化床对城市污水中SS、COD、BOD、NH₃-N、TN、TP、色度、浊度等污染物的平均去除率可分别达到95%、90%、91%、38%、42%、95%、84%、77%。（2）生物造粒流化床中颗粒污泥的物化特性研究研究了生物造粒流化床中颗粒污泥的形成过程和物化特性,结果表明:造粒颗粒污泥的外形多为球状,其粒径分布具有沿流化床纵向自下而上递减的趋势,下、中、上层的粒径范围分别为3mm⁴mm、2mm³mm、1mm²mm。通过粒径和静水沉速分析,得出了造粒颗粒污泥的粒径-密度关系,结果显示,生物造粒流化床中形成的颗粒污泥的有效密度随粒径增大而降低的趋势不明显,表明其具有密实的颗粒构造,有效密度接近于10^-2 g/cm³数量级,比同粒径范围的常规有机絮凝体密度高出一个数量级以上,同时也高于同粒径范围的常规无机絮凝体密度,这是其具有良好固液分离效果的原因所在。（3）生物造粒流化床中颗粒污泥的生物学特性研究通过微生物学和分子生物学分析,可知在造粒颗粒表面及内部均富集有大量的微生物。颗粒污泥的电镜表面观察及切片内部观察结果表明,主要微生物形态为杆状菌和球状菌,前者多分布于流化床下层及颗粒污泥表面,后者多分布于流化床上层及颗粒污泥的内部。细菌计数结果表明,流化床中单位重量污泥中的细菌总数在4000万个/g到9000万个/g之间,且以好氧菌为主,好氧菌占细菌总数的97%以上、厌氧菌数量不到3%;细菌总数和好氧菌数量呈从底部到顶部递减的趋势,而厌氧菌则呈从底部到顶部递增的趋势;厌氧菌主要由反硫化菌和反硝化菌构成,前者占80%左右,后者占20%左右。DGGE分析结果表明,造粒颗粒中微生物种群具有多样性特征,优势种属有20多种,且流化床下层、中层、上层的微生物群落相似性为83.1%,说明沿层高的微生物群落演替不明显、群落结构较为稳定。（4）生物造粒流化床的污染物去除机理探讨结合流化床沿纵向高度的溶解氧分布、微生物群落分布、以及碳、氮、磷等污染物分布特征的分析,探讨了生物造粒流化床的污染物去除机理。总体来说,在混凝造粒和生化降解的协同作用下,床内污染物的去除包括“转移”和“转化”两个过程,前者以混凝和吸附为主,后者以颗粒污泥中的微生物作用为主。污水中属于悬浮物或胶体范畴的污染物在流化床底部通过混凝作用转移到颗粒污泥中,溶解性污染物则通过吸附逐渐转移到颗粒污泥中,然后得以生物降解和转化。生物造粒流化床内以好氧为主的环境条件有助于有机物降解和氨氮的硝化过程,床内存在的局部缺氧大环境（主要在流化床上层）以及颗粒污泥内部存在的缺氧和厌氧微环境则有助于一定程度的反硝化。流化床对磷的去除主要是混凝作用,即化学除磷。（5）生物造粒流化床污水处理工艺的技术评价长期连续中试运行的结果表明,生物造粒流化床用于城市污水处理,处理水的COD、TP、SS指标可达到《城镇污水处理厂污染物排放标准》（GB18918-2002）规定的一级A标准,BOD可达到一级B标准,TN接近一级B标准,NH3-N达到二级标准。但该工艺能在一个处理单元内同时完成混凝造粒、生物处理和固液分离,总水力停留时间在1小时以内,BOD容积负荷可达到4 kgBOD/kgMLSS?d以上,不失为一种根据排水要求可供选用的高效污水处理技术。生物造粒流化床的MLSS浓度可保持在10000¹5000mg/L、MLVSS可保持在5000⁸000mg/L,远高于一般活性污泥法的污泥浓度,这是它实现污染物高效去除的重要原因。更多还原

【Abstract】 Contaminates in wastewater could be classified as particular and soluble components in terms of their size or organic and inorganic components in terms of their chemical property. Therefore, one of the main tasks in wastewater treatment is to remove particular and organic components by means of biological method such as activated sludge and solid/liquid separation such as sedimentation. Researches in wastewater treatment thus focus on improvements of solid/liquid separation and biological degradation efficiencies. A notable technology for improving solid/liquid separation is the fluidized pellet reactor with high performance for particular components removal because of the big size and high density pellets formation by means of optimal coagualant dosage and suitable mixing. On the other hand, granules in biological reactors could effectively improve biodegradation efficiency because of its high biomass concentration, rich divergence of species and outstanding settleabliliy that could also improve the solid/liquid separation in the secondary settling tank. However, cultivation of granular sludge is time-comsuming and hard to be well controlled, which limited its practical application.Based on the above-mentioned technological advancement, this study proposed a new technology name as fluidized pellet bioreactor （FPB）, which integrated the granular sludge and pellet solid/liquid separation technologies in one reactor, by using fluidized pellets technology to convert the loose flocs into dense granules quickly and then providing appropriate biological environment such as oxygen to inspire the biological degradation. This study set the scope on the characteristics of fluidized pellet bioreactor for domestic wastewater treatment and its mechanisms for contaminates removal with the support of the National Natural Science Foundataion of China （NSFC）. Results and findings in the study include the following perspectives:（1）Pilot-scale study on the performance of FPBA pilot-scale FPB system was established and a long-term operation was carried out by treatment the domestic wastewater from the inlent of a wastewater treatment plant in Xi’an city, and reasonable oxygen supply approaches and optimized operational conditions were determined. Results demonstrate that the FPB system could simultaneously achiev biodegrading and solid/liquid performances in a single reactor for treating domestic wastewater. The optimized operational conditions were determined as: PAC dosage 50 mg/L, PAM dosage 5 mg/L, upflow velocity 1.32 mm/s, mixing speed 10 rpm, recycle ratio 50%, cycle length of sludge removal 6h and the blanket height 110cm¹60cm. Under the above conditions, the removal efficiency for SS, COD, BOD, NH3-N, TN, TP, color and turbidity was 95%, 90%, 91%, 38%, 42%, 95%, 84%and 77%, respectively.（2）Physical property of pellets in FPBThe formation process of pellets, the morphological characteristics and size distribution of the pellets in the reactor were examined, and the following results could be obtained: The pellets in the reactor were sphere and their size decreased along with the height of reactor, namely, the average size of pellets from the bottom, middle and upper part of the reactor were in the range of 3mm-4mm, 2mm-3mm, and 1mm-2mm, respectively. Additionally, the relationship between diameter and density were determined by floc-settling in static water. It was found that the effective density of pellets slightly decreased with the increased of diameter, suggesting the compact structure. The effective density was in the magnitude of 10^-2 g/cm³, which was one magnitude higher than the inorganic pellets and also higher than the conventional activated sludge. It contributes the high performance of solid/liquid separation.（3）Biological property of pellets in FPBThe characteristics of microbial community and predominated bacteria species as well as their metabolic features were investigated.A large amount of bacteria could be observed in the entire pellet, using microbial and molecular biological technologies. SEM photo shows that bacteria were predominated by bacillus and coccilus. The former were mainly on the surface of pellets especially for those pellets near the bottom, and latter were mainly inside the pellets or on the surface for those granules from the upper side. The number of bacteria was in the of 40⁹0 milion/g and the aerobic bacteria accounted for more than 97% and the anaerobic was less than 3%. Along with height of the reactor, aerobic bacteria decreased due the oxygen deficiency, anaerobic bacteria however increased. The DGGE results show that the diversity of microbe in pellets was rich, and there were more than 20 strips predominated, indicating that the environmental in the reactor was suitable for the proliferation of microbes. From bottom to top, there were a large number of common strips, and the comparability of the microbial communities from bottom to top was 83.1%, indicating a very stable structure of the microbial communities.（4）Mechanisms of contaminate removal in FPBThe distribution of oxygen, organic matters, nitrogen and phosphorus were analyzed along the height of the reactor to identify how contaminates were removed. Two processes, transfer and degradation, were happened in the reactor for contaminate removal. Contaminates were firstly transferred on the surface of pellets by coagulation, flocculation and adsorption and then be biodegraded by microbes in the pellets which was similar with that happened in conventional sludge systems. However, the removal efficiency of soluble contaminates was very low indicating the biodegradation was slight, therefore transferring of contaminates was the main mechanisms.The aerobic and anaerobic zones in the pellets could provide the condition for nitrification and denitrification. However, the phosphorus was removed mainly by chemical precipitation.（5）Evaluation of FPB in wastewater treatmentThe long-term pilot operation shows that, the COD, TP and SS in the effluent of FPB system treating domestic wastewater could meet the standard GB18918 level I class A and BOD could meet that standard GB181918 level I class B, and TN was close to GB18918 level I class A. NH3-N could only meet the standard GB181918 level II. However the system could achieve pellet formation, biodegradatia and solid\liquid separation in a single unit and the total hydraulic retention time（HRT） was less than 1 hour, and the sludge loading rate was 4 kgBOD/kgMLSS·d. Therefore the FPB reactor was a high performance reactor. The MLSS and MLVSS remained in the range of 10000¹5000 mg/L and 5000⁸000 mg/L, even in the upper side of the reactor, It was much higher than the conventional sludge system, which was the main reason of high performance of FPB.更多还原