【作者】 杨国红；

【导师】 郭劲松； 方芳；

【作者基本信息】 重庆大学 ， 市政工程， 2009， 博士

【摘要】 单级自养脱氮工艺是指在一个系统内由自养菌实现NH4+至N2全部转化过程的一类工艺,在处理低C/N比废水方面极具潜力。由于该工艺在控制运行和机理方面有很多难点没有得到很好解决,限制了其在实际工程中的应用。本论文系统地研究了构建单级自养脱氮系统的方法,探讨了运行控制条件对单级自养脱氮工艺的影响机制和单级自养脱氮系统运行的适宜组合工况,并通过对比系统内生物膜和悬浮污泥的单级自养脱氮特性,分析了单级自养脱氮系统内起主导脱氮作用的污泥形式,同时深入研究了单级自养脱氮系统的氮素平衡和NH4+的去除途径。采用4组SBBR(Sequence Batch Biofilm Reactor)反应器构建单级自养脱氮系统,并研究了构建单级自养脱氮系统的适合条件和方法,结果表明:构建单级自养脱氮系统的过程可分为亚硝化启动和单级自养脱氮实现两个阶段。亚硝化启动阶段中系统内的NO2-积累率较高,但系统的脱氮性能较差。单级自养脱氮实现阶段中,系统内的NH4+迅速被转化,NO2-和NO3-基本无积累,单级自养脱氮性能得到提高;间歇曝气和连续曝气两种曝气方式均可构建单级自养脱氮系统,但间歇曝气系统所需的DO(Dissolved Oxygen)浓度高于连续曝气系统;DO过高(连续曝气条件下DO超过1.5mg/L)易导致系统内发生全程硝化反应,不利于构建自养脱氮系统;过低的DO(连续曝气条件下DO低于0.8mg/L)则将延长构建单级自养脱氮系统的时间;单级自养脱氮系统的HRT(Hydraulic Retention Time)应根据一个运行周期内DO和NO3-浓度的突升点来确定,随系统的曝气方式和DO等运行条件进行调节;软性组合填料和弹性立体填料均较多面空心球填料有利于快速挂膜,且软性组合填料较弹性立体填料更有利于微生物的附着,以构建稳定运行的SBBR单级自养脱氮系统;通过T-A克隆的方法,在单级自养脱氮系统中发现2类不同的AOB序列,一类与氨氧化菌标准菌株Nitrosomonas有98%的较高相似性,另一类则与其它一种未得到纯培养的AOB接近,相似性为99%。存在的NOB比较单一,与Nitrospira相似性达到100%。AMAMMOX种类丰富,检测到11种不同ANAMMOX基因序列,与典型的厌氧氨氧化菌具有较高的相似性,相似性分别达到97~99%,主要归属于Candidatus Kuenenia stuttgartiensis及Candidatus Brocadia fulgida两个属。利用已建立的SBBR单级自养脱氮系统,调节其运行控制条件至不同水平,研究了曝气方式、DO、温度和pH值对单级自养脱氮工艺的影响机制及单级自养脱氮系统运行的最适组合工况,结果表明:间歇曝气条件下,单级自养脱氮系统的曝气时间与停曝气时间基本相当时较有利于提高系统的脱氮性能;单级自养脱氮系统的DO浓度应根据曝气方式进行调节。连续曝气和间歇曝气(曝停比为2h:2h)的单级自养脱氮系统的最适DO浓度分别为1.5mg/L和2.0mg/L;DO过低将降低亚硝化反应速率,并导致ANAMMOX(Anaerobic Ammonium Oxidation)反应因缺乏足够的反应物质而无法快速进行,从而降低单级自养脱氮系统的脱氮性能。过高的DO则会破坏生物膜内部的厌氧区,降低ANAMMOX的反应速率,在O2存在的条件下,剩余的NO2-则进一步被氧化为NO3-,不利于NH4+的有效去除;间歇曝气SBBR单级自养脱氮系统的最适温度为30℃。在一定温度范围内(不大于30℃),温度的升高有助于提高系统的NH4+转化速率和脱氮效能。但温度达到35℃时,ANAMMOX反应速率较低而不能把亚硝化反应生成的NO2-全部转化为N2,在系统内DO浓度(2.0mg/L)较高的条件下,部分NH4+将通过全程硝化反应被氧化为NO3-;间歇曝气SBBR单级自养脱氮系统的最适pH值为8。pH值为8左右时,系统内亚硝化和ANAMMOX的反应速率较快,且二者反应速率相当,有利于亚硝化反应和ANAMMOX反应的联合脱氮,单级自养脱氮系统的脱氮性能较好。以单级自养脱氮系统内的生物膜(包括填料上的生物膜和反应器内壁上的生物膜)和悬浮污泥为研究对象,研究了生物膜和悬浮污泥的亚硝化反应、好氧NO2-氧化反应、ANAMMOX反应和单级自养脱氮活性,对比了生物膜和悬浮污泥的自养脱氮特性,并深入分析了造成其自养脱氮性能差别的根本原因及起主导脱氮作用的污泥形式。结果表明:单级自养脱氮系统内填料上生物膜的最大亚硝化反应活性、好氧NO2-氧化活性、ANAMMOX反应活性和单级自养脱氮活性分别为0.153±0.0064 gN·gVSS-1·d-1、0.0087±0.0016 gN·gVSS-1·d-1、0.282±0.0086 gN·gVSS-1·d-1和0.207±0.0045 gN·gVSS-1·d-1;单级自养脱氮系统反应器内壁上生物膜的最大亚硝化反应活性、好氧NO2-氧化活性、ANAMMOX反应活性和单级自养脱氮活性分别为0.167±0.0087 gN·gVSS-1·d-1、0.0045±0.0016 gN·gVSS-1·d-1、0.313±0.014 gN·gVSS-1·d-1和0.298±0.0060 gN·gVSS-1·d-1;单级自养脱氮系统内悬浮污泥的最大亚硝化反应活性、好氧NO2-氧化活性、ANAMMOX反应活性和单级自养脱氮活性分别为0.137±0.0080 gN·gVSS-1·d-1、0.045±0.0038 gN·gVSS-1·d-1、0.095±0.0052 gN·gVSS-1·d-1和0.099±0.011gN·gVSS-1·d-1;填料上生物膜和反应器内壁上生物膜的亚硝化反应活性、ANAMMOX反应活性和单级自养脱氮活性均高于悬浮污泥,好氧NO2-氧化活性则低于悬浮污泥。生物膜比悬浮污泥更有利于形成好氧与厌氧共存的微环境使亚硝化和ANAMMOX反应顺利进行,在单级自养脱氮系统内起主导脱氮作用。利用现代物质分析测试手段,监测了密闭单级自养脱氮系统内,气相和液相中生成的氮化合物的种类及其含量,研究了系统的氮素平衡和NH4+去除的主要形式,结果表明,单级自养脱氮系统内62%的NH4+在微生物的作用下被转化为NO2-、NO3-、NH2OH、N2H4、NO、NO2、N2O和N2等多种氮化合物,其中N2占90.07%,是NH4+转化的主要产物形式。根据单级自养脱氮工艺的几种机理假说及脱氮反应,配制不同的模拟含氮废水,监测不同进水条件下,系统内氮化合物种类及其含量的变化,研究了单级自养脱氮系统内氨氮的去除途径。结果表明:单级自养脱氮系统内6.72%的氨氮是通过吹脱等物化作用去除的,不超过6.02%的氨氮是通过传统硝化反硝化途径去除的,87.26%左右的氨氮是由自养脱氮途径去除的,自养脱氮反应起主要脱氮作用;在足够NO2存在且缺氧的条件下,单级自养脱氮系统内的出水氨氮浓度与空白反应器相当,NH4+并没有被亚硝化单胞菌以NO2为电子受体氧化为NO2-和N2等化合物而得以去除,可能是因为系统内不存在该代谢功能的亚硝化功能菌;单级自养脱氮系统内存在两条ANAMMOX反应途径:其中一条途径即NH4+在好氧条件下被氧化为NH2OH后,生成的NH2OH与系统内的NO2-在缺氧条件下被转化为N2O,N2O则进一步被转化为N2而实现氮的去除;另外一条途径即NO2-首先被还原为NH2OH,生成的NH2OH则与系统内的NH4+反应生成N2H4,N2H4继续被转化为N2而实现氮的去除。更多还原

【Abstract】 One-stage completely autotrophic nitrogen removal process could realize the conversion of ammonium to denitrogen gas by autotrophic bacteria in one reactor, and it has remarkable potential to treat low C/N ratio wastewaters. Many problems of the control method and mechanism of the process have not been well resolved, which restrict its application of the process in engineering. In this paper, the rapid start-up methods of one-stage completely autotrophic nitrogen removal system were studied , the influencing mechanism of control factors and suitable combination work conditions of the process were discussed , in addition, comparing the characteristics of one-stage autotrophic nitrogen removal of biofilm and suspended sludge in the system, the sludge form playing dominant roles in nitrogen removal was analyzed, and the nitrogen balance and the NH4+ conversion pathways were studied in depth.Four SBBRs (Sequence Batch Biofilm Reactors) were employed to start up one-stage completely autotrophic nitrogen removal system and proper conditions and methods of setting up the system were studied, results showed that: (1) The start up process could be divided into two periods. In the first period NO2- accumulation rate was high but nitrogen removal efficiency was low. In the second period, NH4+ was converted quickly and there was little accumulation of NO2- and NO3-, with increasing efficiency of nitrogen removal in the system. (2) Both intermittent aeration mode and continuous aeration mode could be used for starting up one-stage completely autotrophic nitrogen removal system, but higher DO concentration (Dissolved Oxygen) was needed in the intermittently aerated system. (3) Too high DO concentrations (higher than 1.5mg/L in continuous aeration mode) could result in aerobic NO2- oxidation in the whole process, which was not good for the start up of one-stage completely autotrophic nitrogen removal system. However, too low DO concentration (lower than 0.8mg/L in continuous aeration mode) could extend the start-up time. (4) HRT (Hydraulic Retention Time) of one-stage completely autotrophic nitrogen removal system should be determined by“elevation point”of DO and NO3- concentrations in one operation cycle, and adjusted with aeration mode and DO concentration of the system. (5) Both soft combination packing and elastic solid packing were more beneficial for rapid biofilm attachment than globular packing, and soft combination packing was more useful for biofilm adherence and stable operation of one-stage completely autotrophic nitrogen removal system than elastic solid packing. (6) Functioning bacteria in the system was identified through T-A cloning. Two sequences of AOB, one sequences of NOB and eleven sequences of AAOB were found in the system.Conditions of the SBBR one-stage completely autotrophic nitrogen removal system were adjusted to study the influence of aeration mode, DO concentration, temperature and pH and the optimal combination work conditions of the system. Results indicated that nitrogen removal efficiency could be improved in intermittent aeration mode when aeration time was equal to non-aeration time in one aeration cycle; Too high DO concentration could reduce the nitrification reaction rate, which led to relatively low ANAMMOX (Anaerobic Ammonium Oxidation) reaction rate and the poor performance of one-stage autotrophic nitrogen removal system. However, too high DO concentration could damage the anaerobic zone in the biofilm, reduce ANAMMOX reaction rate, and the remaining NO2- could be further oxidized to NO3-, which was not conducive to the effective removal of NH4+; DO concentration should be adjusted according to aeration mode of the system. The optimal DO concentrations of the one-stage completely autotrophic nitrogen removal system in intermittent aeration mode (with aeration/non-aeration ratio of 2h: 2h) and continuous aeration mode were 2.0mg/L and 1.5mg/L, respectively. The optimal temperature of intermittent aeration mode SBBR one-stage autotrophic nitrogen removal system was 30℃. The increased temperature (not higher than 30℃) would improve ammonium conversion and nitrogen removal efficiency. But when temperature reached 35℃, reaction rate of ANAMMOX was too low to convert NO2-, which come from nitrification to N2 thoroughly, under the condition of 2.0mg/L of DO concentration, part of NH4+ was oxidized to NO3- through nitrification. With pH=8, the reaction rate of nitrification and ANAMMOX increased, and would be equivalent, which was helpful for combination nitrogen removal of nitrification and ANAMMOX, thus one-stage autotrophic nitrogen removal performed very well.Taking the biofilm (including biofilm on the packing and biofilm on the reactor inner wall) and suspended sludge in one-stage completely autotrophic nitrogen removal system as the research objects, the nitrification of the biofilm and suspended sludge, aerobic NO2- oxidation, AMAMMOX reaction and one-stage completely autotrophic nitrogen removal activity were investigated. And the causes of the denitrification differences and the dominant sludge playing roles in nitrogen removal were in depth analyzed, by comparing the autotrophic denitrification activity of biofilm and suspended sludge. Results showed that nitrification activity, ANAMMOX activity, aerobic NO2- oxidation activity and one-stage completely autotrophic nitrogen removal activity of biofilm on the packing were 0.153±0.0064 gN·gVSS-1·d-1, 0.0087±0.0016 gN·gVSS-1·d-1, 0.282±0.0086 gN·gVSS-1·d-1 and 0.207±0.0045 gN·gVSS-1·d-1, respectively, and that of biofilm on the reactor inner wall were 0.167±0.0087 gN·gVSS-1·d-1, 0.0045±0.0016 gN·gVSS-1·d-1, 0.313±0.014 gN·gVSS-1·d-1 and 0.298±0.0060 gN·gVSS-1·d-1, respectively, and that of suspended sludge were 0.137±0.0080 gN·gVSS-1·d-1, 0.045±0.0038 gN·gVSS-1·d-1, 0.095±0.0052 gN·gVSS-1·d-1 and 0.099±0.011gN·gVSS-1·d-1, respectively. Nitrification activity, ANAMMOX activity and one-stage completely autotrophic nitrogen removal activity of two kinds of biofilm were higher than that of suspended sludge, but aerobic NO2- oxidation activity of biofilm were lower than that of suspended sludge, which indicate that biofilm is more beneficial for the formation of aerobic-anaerobic micro-environment to make nitrification and ANAMMOX reaction perform well, and biofilm played dominant parts in one-stage completely autotrophic nitrogen removal system.The varieties and contents of the intermediate products in the gas phase and fluid phase in the airtight one-stage completely autotrophic nitrogen removal system were determined by modern matter analysis measurement method, the nitrogen balance and the NH4+ removal ways of the system were studied. Results showed that 62% of NH4+ was converted to NO2-, NO3-, NH2OH, N2H4, NO, NO2, N2O and N2 under the microbial performance, N2 accounted for 90.07%, which was the main form of NH4+ removal.According to several mechanism hypothesis and denitrification reaction of one-stage autotrophic nitrogen removal process, different artificial nitrogen wastewaters were prepared, types and contents variations of compounds under different water conditions were monitored, and NH4+ removal pathways in one-stage autotrophic denitrification system were studied.Results showed that 6.72% of ammonia nitrogen was removed in the physical-chemical way, no more than 6.02% of ammonia nitrogen was converted by the conventional nitrification denitrification process, and about 87.26% of ammonia nitrogen was removed by the completely autotrophic nitrogen removal in one reactor process. But the effluent ammonium in the anoxic reactor, where enough NO2 were present, was equal to the blank system, and no ammonium was converted to such nitrogen compounds as NO2- and N2 by Nitrosomonas eutropha using NO2 as electron acceptor, which maybe caused by lack of the function bacteria. There were two ANAMMOX reaction pathways in the one-stage autotrophic nitrogen removal system. One way was that after part of NH4+ was oxidized to NH2OH under aerobic conditions, NH2OH and NO2- were converted to N2O under anaerobic conditions, at last N2O was further converted to N2 which realized the nitrogen removal; Another way was that at first NO2- was reduced to NH2OH, NH2OH reacted with NH4+ to form N2H4, which was further converted to N2 subsequently, realizing the nitrogen removal.更多还原