【作者】 肖景霓；

【导师】 杨凤林； 张捍民；

【作者基本信息】 大连理工大学 ， 环境工程， 2007， 博士

【摘要】 氮、磷是导致水体富营养化的优势污染物。反硝化除磷技术具有节省有机碳源、减少温室气体排放、剩余污泥产量小等优点，符合可持续发展理念，具有广阔的发展前景。本研究采用序批式膜生物反应器（SBMBR）周期性运行，通过对其运行模式及操作参数的优化调整，强化其除磷脱氮能力，同时对不同工艺模式下SBMBR对氮磷的去除性能、污泥特性及膜污染等进行了考察。首先通过将AO模式运行的SBMBR和传统膜生物反应器（CMBR）运行模式进行对比，考察二者在不同进水碳氮比（COD／TN=28.2～3.4）条件下对氮磷的去除能力。结果表明：CMBR中TP的去除率在14％～96％之间波动；在进水COD／TN降至6.3时，对TN基本无去除效果。以AO方式运行的SBMBR具有很好的污染物去除能力，即使在进水COD／IN降到6.3时，TN和NH₄⁺-N的去除率仍可达到65％和90％以上；TP去除率保持在90％左右，在此COD／TN范围内，基本不受进水COD／TN变化影响；而且验证序批式的运行方式有助于减缓膜污染。为强化SBMBR的反硝化除磷能力，在AO MBR中引入缺氧段，并通过对工艺运行模式的调整，逐步强化其反硝化除磷效果。依次考察单反应器形式的AOA、A²O MBR及双反应器MUCT-MBR对污染物的去除性能，比较各工艺模式的反硝化除磷能力。结果表明：在AO MBR好氧末引入缺氧段而形成的AOA MBR工艺，具有一定的反硝化除磷性能；但PHB因好氧吸磷而被大量氧化，使缺氧段中聚磷菌（PAOs）的内碳源不足，而无法最大限度的提高系统反硝化除磷能力，因此缺氧段的除磷量占总除磷量的比例仅为28％。为解决上述不足，将缺氧段提前到厌氧阶段末，形成了A²O MBR系统，通过外加硝酸盐为反硝化吸磷提供电子受体。其缺氧段反硝化除磷量占总除磷量的比例提高到50％以上，但外加硝酸盐形成缺氧环境造成工艺操控复杂。因此，进一步改进工艺为双反应器的MUCT-MBR，两反应器中均有明显的缺氧吸磷现象，整个系统由缺氧段所去除的磷约占总除磷量的60％。系统以好氧产生的NO₃^-作为缺氧吸磷的电子受体，实现了无外加NO₃^-的条件下强化系统的反硝化除磷性能。采用FISH技术对PAOs占全菌的比例进行检测，得出AO、AOA及A²O MBR中PAOs所占比例依次增大；污泥磷元素分析结果显示，三系统中污泥含磷率依次增大，即吸磷能力逐渐提高。对污泥产率的计算结果为，SBMBRs中的污泥产率均明显低于传统活性污泥（CAS）工艺，且随反硝化除磷能力的增强，污泥产率减少，A²O MBR中污泥产率仅为0.29 kgVSS.kgCOD^-1。但由于其具有较高的污泥含磷率，从而保证了良好的除磷效果。研究发现：在AO、AOA、A²O MBR至MUCT-MBR的改进过程中，随着反硝化除磷能力的逐步提高，污泥的比好氧吸磷速率下降。表明对缺氧环境的强化更有利于具有反硝化能力的聚磷菌的生长，相应的对好氧聚磷菌的生长及活性产生抑制。O₂与NO₃^-同时存在时的比吸磷速率大于仅有O₂存在时的速率，且伴有NO₃^-的消耗。表明混合电子受体条件下，存在好氧反硝化吸磷。除磷工艺中磷的去除包括好氧吸磷、缺氧反硝化吸磷和好氧反硝化吸磷三种机制。更多还原

【Abstract】 Nitrogen and phosphorus are key nutrients that result in water eutrophication. Denitrifying phosphorus removal has many advantages, such as saving of organics, decrease in greenhouse gas emission and less sludge production, in accord with the concept of sustainable development. So this technique has broad development prospects.In this research, sequencing batch membrane bioreactor（SBMBR） was operated in a periodic way to improve the denitrifying phosphorus removal ability by optimizing the operation modes and adjusting operation parameters. The performance of SBMBRs on nitrogen and phosphorous removal, the sludge characteristics and membrane fouling were examined in different operation modes at the same time.Firstly, the nitrogen and phosphorous removal abilities were investigated by comparing the AO mode of SBMBR with conventional membrane bioreactor（CMBR） under different nitrogen loads（COD/TN=28.2～3.4）. The results indicated that the TP removal rate fluctuated between 14% and 96% in CMBR system. When the COD/TN of influent reduced to 6.3, there was almost no effect of TN removal. However, SBMBR system had a better performance on nitrogen and phosphorus removal at different COD/TN ratios. Even though the COD/TN of influent reduced to 6.3, the TN and NH₄⁺-N removals of SBMBR could be maintained over 65% and 90%, respectively. TP removal rate of SBMBR was approximately 90% during most of the experiment time, which were almost not affected by the COD/TN of influent. Furthermore, the sequencing batch operation mode can reduce membrane fouling.Anoxic phase was introduced into AO MBR to enhance its denitrifying phosphorus removal ability by adjusting the operation modes step by step. The nutrients removal performances of AOA, A²O MBR and double reactors MUCT-MBR were examined respectively and the capacities of denitrifying phosphorus removal of different processes were compared. The results showed that AOA MBR formed by introducing an anoxic phase at the end of the aerobic phase of AO MBR had definite denitrifying phosphorus removal ability without NO₃^-added externally. PHB was depleted by aerobic phosphorus uptake which resulted in the deficiency of inner carbon source in phosphorus-accumulation organisms（PAOs） during anoxic stage. So it cannot maximize improvement of the denitrifying phosphorus removal ability of the system. The ratio of phosphorus removal in anoxic phase to that in the whole cycle was only 28%. In order to solve the insufficiency mentioned above, anoxic phase was moved up to the end of the anaerobic stage of AO MBR with external nitrate addition, A²O MBR system was formed and the ratio was increased to over 50%, but the operation process synchronously became more complex. So the process was modified and then MUCT-MBR was tested. It was evident that denitrifying phosphorus removal phenomena occurred in both reactors of MUCT-MBR and the percentage was about 60%. In this system, NO₃^-produced in aerobic phase was utilized as the electron acceptor for denitrifying phosphorus uptake, which enhanced the denitrifying phosphorus removal ability without NO₃^-external addition.FISH technology was adopted to examine the ratio of PAOs in total bacteria. The results indicated that the ratios increased from AO, AOA to A²O MBR. Analysis results of phosphorus content of sludge showed that the phosphorus uptake ability improved too. The sludge yield of SBMBRs was distinctly lower than that of conventional activated sludge process（CAS）, reduced with the improvement of denitrifying phosphorus removal ability. In A²O MBR, the yield was only 0.29 kgVSS·kgCOD^-1. The higher phosphorus content of sludge ensured its phosphorus removal performance.It was found that the aerobic specific phosphorus uptake rate of sludge was decreased with the increase of denitrifying phosphorus removal ability in the processes of AO, AOA, A²O MBR and MUCT-MBR. This indicated that the enhancement of anoxic phase was benefit for the growth of denitrifying PAOs rather than aerobic PAOs. The specific phosphorus uptake rate in the condition that both O₂ and NO₃^-existed was bigger than that in the condition that only O₂ existed. Aerobic denitrifying phosphorus uptake existed in the mixed electron acceptors environment. Three mechanisms might be included in the phosphorus removal process, that is, aerobic phosphorus uptake, denitrifying phosphorus uptake under anoxic condition and that under aerobic condition.更多还原