【作者】 蒋波；

【导师】 胡文容；

【作者基本信息】 山东大学 ， 环境工程， 2010， 博士

【摘要】 随着经济发展和城市化进程的加快,城市用水供需矛盾日益加大。进一步开发城市污水,实现污水资源化和中水回用,对于保障城市安全供水和环境资源的可持续利用具有重大的战略意义。近年来,曝气生物滤池(Biological aerated filter,BAF)技术在污水处理领域得到了广泛的应用,但作为三级单元深度处理城市污水,BAF技术仍然存在硝化细菌生长缓慢、脱氮性能不稳定等问题。生物强化技术通过向生物处理系统中引入具有特定功能优势微生物能够起到快速增加细菌数量并提高系统对目标污染物去除效率的作用。研究利用生物强化来改善和提高BAF技术对低浓度污水深度处理的性能具有重大的现实意义和工程应用价值。本文结合我国城市污水处理厂出水的实际水质特征,采用由好氧硝化滤池和缺氧反硝化滤池串联组成的BAF工艺(即倒置反硝化曝气生物滤池工艺,O/ABAF)进行污水深度处理,并从南四湖湿地植物根际和活性污泥中筛选高效氨氧化细菌构建优势菌群对O/A BAF工艺进行强化,重点研究了强化前后O/A BAF工艺运行特性的变化特征以及工况条件的改变对生物强化后O/A BAF工艺性能的影响。在注重工程实际应用的同时,从理论上阐述了采用高效氨氧化细菌强化O/A BAF工艺对低底物浓度废水的脱氮性能的可行性。在此基础上,采用臭氧技术对O/A BAF工艺出水做进一步脱色强化处理,探讨了工艺参数。主要工作如下：1.对生物强化前O/A BAF工艺深度处理城市污水二级出水的运行特征进行了研究,包括工艺的挂膜启动方法和在低曝气量条件下的硝化反硝化特性。(1)在传统闷曝挂膜方法的基础上,增加了单池内循环回流工序,维持硝化滤池在低曝气量条件下(0.3m3/h)进行挂膜培养。25天后,O/A BAF工艺正式启动。此时,硝化滤池最大亚硝酸盐积累率为60%,对应着反硝化滤池13mg/L的甲醇投加量,O/A BAF工艺对总氮的最大去除率为30%。(2)对于进水氨氮负荷为0.04-0.26kgNH4-N/m3.day,有机负荷为0.21-0.65kgCOD/m3·day,控制硝化滤池在低曝气量条件下运行能够维持O/A BAF工艺的短程硝化反硝化特性。当曝气量为0.4m3/h时,硝化滤池实现最大亚硝酸盐积累率(66.9%)。此时硝化滤池中对应的平均溶解氧浓度为1.5mg/L,氨氮去除率为37.2%。(3)硝化滤池在低曝气量条件下(0.3-0.5m3/h)表现出一定的同步硝化反硝化特性。反硝化滤池对总氮的去除与硝化出水中氧化态氮的浓度和甲醇投加量有关。对于曝气量为0.4m3/h的硝化出水,当甲醇投加量为20mg/L时,反硝化滤池出水总氮平均浓度为14.1mg/L,可以满足《城市污水再生利用-景观环境用水水质标准GB/T 18921-2002》的要求,但出水水质不稳定,部分时段出水总氮浓度超标。2.优势氨氧化细菌的分离、筛选及特性研究。(1)从活性污泥和南四湖湿地植物芦竹、三棱草、柳絮等根际土壤中共筛选获得4株高效氨氧化细菌,其中,活性污泥2株(YH-1,YH-2)；芦竹1株(YL-1)；三棱草1株(YS-2)。四株细菌的格兰仕染色结果均呈阴性。通过透射电镜检测确定YL-1为椭球菌、YS-2为短杆菌、YH-1为螺菌、YH-2为长杆菌。(2)四株优势氨氧化细菌在较高的pH值(8.5)和游离氨浓度(18.2mg/L)下均表现出良好的氨氮去除特性,但对高负荷氨氮的去除受氧浓度条件的抑制。3.维持硝化滤池在曝气量为0.4m3/h条件下运行,利用筛选获得的四株高效氨氧化菌株构建优势菌群并投加至硝化滤池,重点研究了优势菌群的投加对O/A BAF工艺短程硝化和脱氮性能的影响。(1)采用人工投加的方式快速提高了硝化滤池中氨氧化化细菌的数量。(2)高效氨氧化细菌的投加提高了硝化滤池对氨氮的去除率和亚硝酸盐积累率,而硝化滤池硝化性能得到改善的同时也提高了O/A BAF工艺整体对总氮的去除效率。(3)在进水流量为2.0m3/h,硝化滤池曝气量为0.4m3/h,反硝化滤池甲醇投加量为20mg/L的条件下,对应着投加前后26.5%的氨氧化细菌增加率,硝化滤池对氨氮的去除率和亚硝酸盐的积累率分别提高了12.1和13.3%,O/A BAF工艺整体对总氮的去除率提高了9.2%。此时,O/A BAF工艺出水总氮平均浓度为11.9mg/L,能够稳定达到《城市污水再生利用-景观环境用水水质标准GB/T18921-2002》的要求。4.研究了曝气强度、甲醇投加量和温度等因素对生物强化后O/A BAF工艺硝化和脱氮性能的影响。(1)生物强化后,O/A BAF工艺对氨氮的去除效率随着硝化滤池曝气量的增加得到明显提高,但短程硝化特性遭到破坏。研究发现,当曝气量为0.6m3/h时,硝化滤池内仍有局部短程硝化现象发生,但当曝气量提高至1.0m3/h时,短程硝化完全消失。曝气量的增加在提高工艺氨氮去除效率的同时,也增强了工艺硝化性能的稳定性。(2)在甲醇投加量受限的条件下,硝化滤池曝气量的提高对反硝化滤池的脱氮性能有明显的抑制。对于进水流量为2.0m3/h,当反硝化滤池甲醇投加量为20mg/L时,控制硝化滤池曝气量在1.0m3/h,O/A BAF工艺可以同时取得较为理想的硝化和脱氮效果。此时,O/A BAF工艺出水氨氮和总氮平均浓度分别为0.79mg/L和13.2mg/L。完全满足《城市污水再生利用-景观环境用水水质标准GB/T18921-2002》的要求。(3)曝气量的增加改变了硝化滤池中氨氧化细菌在固着生物膜和悬浮生物体上的空间分布格局,促使更多的氨氧化细菌集中在具有固定生长优势的生物膜上生长,而固着态生物膜能够凭借其独特的结构特征和庞大的食物链系统,有效地保护氨氧化细菌免予被原生动物捕食和反冲流失,从而维持其高效生长。这也是导致生物强化后,O/A BAF工艺硝化性能稳定性随曝气量的增加而提高的主要原因。(4)生物强化提高了O/A BAF工艺对低温环境的承受力。工艺冬季运行结果表明,在进水流量为2.0m3/h,曝气量为1.0m3/h,甲醇投加量为20mg/L条件下,对于最低温度范围(水温6.4-11.9℃),O/A BAF工艺出水氨氮和总氮平均浓度分别为4.4mg/L和13.8mg/L,能够满足《城市污水再生利用-景观环境用水水质标准GB/T 18921-2002》的要求。5.考察了臭氧对O/A BAF工艺出水的脱色作用(1)在臭氧投加量为2.0mg/L,汽水接触时间为18min的条件下,O/A BAF工艺出水中10-18倍的色度可以降至1倍以下。(2)臭氧在对O/A BAF工艺出水进行脱色的同时,对水中的有机物和氨氮也具有一定的去除作用。本研究的主要创新点：(1)建立的生物强化O/A BAF+O3组合工艺,解决了BAF在三级处理中硝化细菌增长缓慢,脱氮性能不稳定的问题,确保出水稳定达到《城市污水再生利用-景观环境用水水质标准GB/T 18921-2002》,为城市污水深度处理与污水资源化提供了一种新的工艺模式。(2)提出了单池内循环回流+闷曝组合方式进行O/A BAF工艺挂膜启动的新方法,不仅省却了传统循环挂膜方法中单独设立的污泥外流池,而且解决了闷曝挂膜过程中出现的污泥沉积问题,为需要在不同氧条件下运行的滤池工艺的快速启动提供了新的技术途径。(3)筛选并培养了优势氨氧化菌,提高了BAF中生物膜的氨氧化菌的浓度及活性,强化了O/A BAF工艺对总氮的去除效率,阐明了优势氨氧化菌强化短程硝化与脱氮的作用机制。(4)研究了氨氧化细菌在悬浮生物体和固着生物膜上的生长特性和空间分布特征,从微生物学的角度揭示了曝气对生物强化O/A BAF工艺硝化性能的影响机理。更多还原

【Abstract】 With the rapid development of economy and urbanization, the contradiction between water supply and demand becomes more serious. Therefore, further exploit municipal sewage and realize resources recycling are of great important to the security of water supply and the sustainable utilization of environment resources. Recently, the technology of biological aerated filter (BAF) has been wildly applied in wastewater treatment. However, as the tertiary treatment unit of municipal sewage, BAF shows the characteristics of slow growth rate of nitrifying bacteria, and unstable performance of nitrogen removal. Since biological enhancement technology could achieve the goals including to rapid increase bacteria amount and improve the removal efficiency of the target pollutants by introducing the dominant microbe with special functions to systems, it is of great significance and application value to study and adopt biological enhancement technology to improve the performance of BAF for treating municipal sewage with low substrate concentration.According to the actual characteristics of the effluent of Jinan wastewater treatment plant, this paper adopted oxic/anoxic BAF process (O/A BAF) to conduct tertiary treatment of municipal sewage. The dominant ammonia oxidizing bacteria (AOB) isolated from activated sludge and the rizhosphere of Nansi lake wetland plant were employed to enhance the performance of O/A BAF. The variation characteristic of O/A BAF performance before and after enhancement, as well as the effects of operation conditions on the enhanced O/A BAF performance was studied. On the basis of paying attention to the actual engineering application, the feasibility of adopting dominant AOB to enhance the performance of nitrification and denitrification of O/A BAF was elaborated theoretically. Finally, the effluent of O/A BAF was further decolorized by ozone, and the operation parameters of ozone process were discussed. The main works of this study were as follows:1. The operation character of O/A BAF before biological enhancement was studied, which includes the method of culture and startup, and the nitrification and denitrificaiton performance of O/A BAF under the conditions of low aeration rate.(1) On the basis of aeration, liquid recirculation was added to each filter. Nitrifying biofilter was cultivated at low aeration rate condition (0.3m3/h). After 25 days, O/A BAF achieved startup. This time, the maximum nitrite accumulation rate of nitrifying biofilter reached 60%, the highest removal rate of total nitrogen of denitrifying biofilter at the dosage of 20mg/L for methanol was 30%.(2) For the influent ammonia loadings of 0.04-0.26kgNH4-N/m3·-day and organic loadings of 0.21-0.65kgCOD/m3·day, it’s possible to maintain the performance of partial nitrification and denitrification of O/A BAF by operating nitrifying bio-filter at low aeration rate level. When the aeration rate was 0.4m3/h, nitrifying biofilter achieved the maximum nitrite accumulation rate of 66.9%. In this case, the corresponding dissolved oxygen concentration and ammonia removal efficiency of nitrifying biofilter was 1.5 mg/L and 37.2%, respectively.(3) Nitrifying biofilter showed the characteristics of simultaneous nitrification and denitrification (SND) at the low aeration rates (0.3-0.5m3/h). The performance of denitrifying filter on the removal of total nitrogen (TN) was mainly related with the concentration of nitrogen oxide (NOx) and the dosage of methanol. For the effluent of nitrifying biofilter at aeration rate of 0.4m3/h, as the dosage of methanol was 20mg/L, the average concentration of TN in the effluent of denitrifying biofilter was 14.1 mg/L This could meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002). Despite of it, the concentration of TN in the effluent of denitrifying biofilter was unstable, it was out of limits sometimes.2. The isolation, selection, and performance study of dominant AOB(1) Four strains of dominant AOB were isolated from activated sludge and the rizhosphere of Nansi lake wetland plants, which including one strains of Arundo donax (YL-1), one strains of Herb of rice galingale (YS-2),and 2 strains of activated sludge (YH-1, YH-2). The results of Glanz staining of four dominant AOB strains all show negative. By the observation of transmission electron microscopy (TEM), it can be determined that, the strains of YL-1, YS-2, YH-1 and YH-2 was coccoid, brevibacterium, spirillum and bacillus, respectively. (2) Four dominant AOB strains all showed excellent ammonia removal performance under the conditions of high pH value (8.5) and free ammonia concentrations (18.2 mg/L). Despite of it, their performance on the removal of high ammonia loading was limited by the concentration of oxygen.3. Micro-flora constituted by the four dominant AOB strains was added to the nitrifying filter which operated at aeration rate of 0.4m3/h,, and the effects of micro-flora on the nitrification and de-nitrification of O/A BAF was studied emphasizely(1) The amount of AOB in nitrifying filter increased rapidly after the micro-flora being added.(2) The introduction of micro-flora improved ammonia removal efficiencies and nitrite accumulation rate of nitrifying biofilter at the low aeration rate of 0.4m3/h. The improvement of nitrification performance of nitrifying filter enhanced the denitrifying efficiency of O/A BAF simultaneously.(3) As the inflow rate was 2.0 m3/h, aeration rate was 0.4m3/h, and the dosage of methanol to denitrifying biofilter was 20 mg/L, corresponding to the 26.5% increase of AOB amount in nitrifying biofilter, the ammonia remove efficiency and nitrite accumulation rate of nitrifying biofilter increased by 12.1% and 13.3%, respectively, and the TN removal efficiency of the O/A BAF increased by 9.2%. The concentration of TN in the effluent of O/A BAF process was 11.9 mg/L, which could meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002).4. The effects of aeration rate, methanol dosage and temperature on the nitrification and denitrification performance of enhanced O/A BAF.(1) After the biological enhancement, the ammonia remove efficiency of nitrifying biofilter improved significantly with the rise of aeration rate, while its partial nitrification performance was undermined. As aeration rate was 0.6m3/h, there was local partial nitrification occurred in nitrifying biofilter, nevertheless, as aeration rate being raised to 1.0m3/h, the accumulation of nitrite disappeared in nitrifying biofilter. The increase of aeration rate could improve not only the efficiency but also the stability of ammonia removal of nitrifying biofilter.(2) As the dosage of methanol was limit, the increase of aeration rate in nitrifying biofilter inhibit the TN removal performance of denitrifying biofilter. For the inflow rate of 2,0m3/h, as the dosage of methanol was 20 mg/L, satisfactory removal efficiencies of both ammonia and TN could be achieved by O/A BAF simultaneously when the aeration rate of nitrifying biofilter was controlled at 1.0m3/h. In this case, the concentrations of ammonia and TN in the final effluent of O/A BAF were 0.79 mg/L and 13.2 mg/L, respectively. This could meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002) completely.(3) The buildup of aeration intensity changed the space distribution of AOB between attached biofilm and suspended biosolids in nitrifying biofilter, and induced much more AOB to grow on attached biofilm. The special structure and complicated food chain of attached bio-film could protect AOB from being washout by backwash or predated by predator, and ensure their stable growth rate. This is also the main reason why the stability of nitrification performance of nitrifying biofilter improved with the rise of aeration rate.(4) Biological enhancement improved the shock resistance capacity of O/A BAF to the low temperature. The operation results of winter showed that, as the inflow rate was 2.0m3/h, aeration rate was 1.0m3/h and methanol dosage was 20mg/L, for the lowest temperature conditions (water temperature 6.4-11.9℃), the concentration of ammonia and TN in the effluent of O/A BAF was 4.4 mg/L and 13.8 mg/L, respectively. These concentrations could meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002).5. The decolorization effects of ozone on the effluent of O/A BAF(1) As the dosage of ozone was 2.0mg/L, and the contact time between gas and liquid was 18 min, about 10-18 folds of chroma in the final effluent of O/A BAF could be reduced to smaller than one fold. This could meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002).( chroma<30 folds).(2) Ozone also showed a certain removal performance of organic substance and ammonia to the effluent of O/A BAF when carried out the decolorization.The main innovation of the study was as follows:1. Aimed at the characteristics of poor organic substrate and low C/N ratio to the secondary effluent of municipal sewage, biological enhancement technology was introduced to O/A BAF for tertiary treatment of municipal sewage. This technology resolved the problems of O/A BAF about slow growth rate of nitrifying bacteria and unstable performance of TN removal aroused from the poor substrate conditions, and ensure the final effluent of O/A BAFs meet the requirement of landscape and environmental water quality standards (GB/T 18921-2002).This work provided a new process pattern for the application of BAF technology in wastewater treatment.2. Proposed a new culture method that aeration and liquid recirculation carried out simultaneously in a single reactor. This method could not only save the extra-designed sludge tank in traditional recalculating culture method, but also resolved the problem of sludge deposition in the aeration culture method. This method provided a new technical approach to the anoxic and facultative aerobic biofiltration process for achieve rapid culture and start.3. Selected and cultivated dominant AOB to increase the activity and quantity of AOB on attached biofilm, and thus enhance the removal of total nitrogen, Elucidated the mechanism of dominant AOB to the nitrification and denitrification performance of O/A BAF.4. By compared the growth properties and space distribution character of AOB on attached bio-film and suspended bio-solids, the affecting mechanism of aeration on nitrification performance of enhanced O/A BAF was revealed from the perspective of microbiology.更多还原