【作者】 田家宇；

【导师】 李圭白；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2009， 博士

【摘要】 我国的饮用水源普遍受到污染,以有机物和氨氮为主要污染物。另一方面,生活饮用水水质标准不断提高,使得常规处理工艺的局限性越来越明显。为此,水处理工作者不断探索、研发新型高效的水处理技术。其中,膜滤技术表现出诸多的优点,被认为21世纪的水处理技术。而浸没式膜生物反应器(SMBR)将外压膜滤与活性污泥有机组合,已经在污水处理领域得到广泛研究与应用。但是,就其在饮用水处理中的应用而言,由于原水性质显著不同,仍有一些关键问题需要解决。本课题首先就SMBR用于处理受污染水源水的自然启动特性进行研究,结果表明就氨氮的去除而言SMBR的自然启动可在35天左右完成。在长期的稳定运行条件下,SMBR通过生物降解作用始终表现出优良的氨氮去除效能,并且能有效应对饮用水源的氨氮突发污染事件。而SMBR对有机污染物的去除能力较低,主要是因为饮用水源中的有机物可生化性较低的缘故。另一方面,生物活性炭(BAC)是一项成熟的饮用水深度处理技术。现场试验研究表明,进水有机物含量以及滤料粒径对BAC除污染效能影响较大,而滤速、预曝气和反冲洗等因素影响较小。并且,进水中的机物和氨氮等优先通过上部滤料得到去除。研究中在相同的试验条件下对比了BAC和SMBR用于饮用水处理的除污染效能。结果表明,SMBR主要通过生物降解作用去除进水溶解性有机物(DOM),效率较低;BAC通过颗粒炭吸附和生物降解的协同作用,对DOM的去除效率较高,但其出水中仍含有一定量的颗粒性有机物,并且对氨氮的去除能力低于SMBR。为充分发挥BAC去除有机物的能力和SMBR去除氨氮的能力,研究中将两者联用。结果表明,进水首先经BAC处理,水中污染物被部分去除,可以减轻后续SMBR的负荷并延缓膜污染;而其后的SMBR则可进一步强化对BAC出水中有机物和氨氮的去除,并以膜作为最后屏障深度截留颗粒物。但是,将BAC与SMBR联用存在水力停留时间长,占地面积大的缺陷。因此,以粉末活性炭(PAC)代替BAC,将PAC直接投加于SMBR反应器内,构建膜-粉末炭吸附生物反应器(MABR)。在MABR中,膜的物理截留作用、生物降解作用以及PAC的吸附作用协同完成对有机污染物的去除,效率较高,并且显著缩短了水力停留时间。同时,反应器中的PAC还能为微生物生长提供载体,提高对冲击负荷的应对能力。MABR是一项具有广阔应用前景的技术。接下来,研究中尝试在SMBR中直接投加混凝剂,构建膜混凝生物反应器(MCBR)。较之传统SMBR,MCBR不但对有机物的去除率明显提高,还能有效去除溶解性磷酸盐,提高出水生物稳定性。同时,MCBR对氨氮的去除率也达到96%,表明在生物反应器中直接混凝不会对微生物群落造成负面影响。因此,试验中在SMBR中同时投加混凝剂和吸附剂,构建一体化膜混凝吸附生物反应器(MCABR),以期取代现有水处理工艺。在MCABR中,通过膜截留、生物降解、混凝和吸附的作用共同完成对有机物的去除,去除率达70%左右。扫描电镜(SEM)观察表明MCABR中UF膜表面存在一层污泥层,能谱分析表明该污泥层中含有10.4%的Al元素;共聚焦激光显微镜(CLSM)观察发现MCABR中膜表面分布着大量的多糖。推断多糖和Al水解产物在膜表面共同形成网状结构,强化对混合液中有机物的截留,尤其是分子量在300~3000 Da的有机物,同时膜表面富集的PAC层也能强化对有机物的截留。对SMBR组合工艺中的核心单元,即浸没式膜组件处理受污染水源水的运行特性进行了中试研究。结果表明,浸没式中空纤维超滤膜具有优异的除浊效能,但对有机污染物,特别是溶解性有机物去除效果不好。由于膜通量大时膜滤池内污染物的累积程度也增大,通量对膜污染的影响很大。曝气可去除膜表面沉积的泥饼层,因此可在一定程度上延缓膜污染。相同曝气量下连续曝气比间歇曝气更有利于延缓膜污染。曝气量越大,跨膜压增长速度就越低,但需综合考虑对膜污染的延缓作用和能耗,以确定最佳曝气量。对于传统构型的浸没式UF膜而言,气泡尺寸越小越有利于延缓膜污染。而反冲洗则可同时去除膜的孔内污染和表面污染,从而表现出更高的效率。工程应用中需对曝气和反冲洗进行优化组合。另一方面,当膜长期运行时,膜的不可逆污染必然发生。因此,论文中还对NaOH和乙醇联合清洗受污染的中空纤维PVC膜的效能和机理进行了探讨。扫描电镜和原子力显微镜(AFM)分析表明NaOH和乙醇能有效地协同去除中空纤维PVC膜表面和孔内的污染物质,表现出优异的清洗效率。更多还原

【Abstract】 Many of the drinking water sources in China have been contaminated, with organics and ammonia as the main pollutants. On the other hand, the drinking water standards ever increases, which lead to the development of new water treatment methods with higher capacity than conventional processes. Among these advanced methods, membrane filtration technology exhibits many advantages, and been recognized as the water treatment technology of 21st century. The submerged membrane bioreactor (SMBR), i.e. the combination of membrane separation and activated sludge process, has been widely researched and applied to wastewater treatment on full-scale. However, in drinking water treatment, SMBR is a relatively new technogy, and there still are some key problems remained to be solved due to the difference of raw water qualities between wastewater and drinking water.In this paper, the natural start-up of SMBR for treating contaminated raw water was firstly investigated. Results showed that the natural start-up of the SMBR could be accomplished within about 35 days. During the long-term operation, the SMBR exhibited excellent ammonia removal efficiencies through biological nitrification, and could cope with the sudden high ammonia loads in drinking water source. However, the removal capacity of the SMBR for dissolved organic matter (DOM) is low. The resason might be that natural organic matter in drinking water source is bio-refractory in nature as a whole.Biological activated carbon (BAC) is another advanced technology for drinking water treatment. The field study showed that the influent organic content and carbon size imposed main influence on the BAC for pollutants removal; while the influence of the filtration rate, pre-aeration and backwashing is low. It was also discovered that influent orginics and ammonia were preferentially removed in the upper layer of the BAC. By comparison of SMBR and BAC under the same experimental conditions, it was found that the capacity of SMBR for organics removal is lower than that of BAC, with the main mechanism of biodegradation; while higher removal efficiency of organic matter was achieved by BAC, through the synergetic effect of adsorption and biodegradation. However, particulate organic matter was detected in BAC effluent; and the ammonia removal efficiency by BAC was proved to be lower than that by SMBR.To take the advantages of BAC for organics removal and SMBR for ammonia removal simutaneously, the hybrid process of BAC and SMBR was investigated for the drinking water treatment from polluted surface water. Rsults showed that the pre-treatment by BAC was able to remove a certain amount of pollutans, thus decrease the load of the SMBR and alleviate membrane fouling. On the other hand, the SMBR treatment could further eliminate organics and ammonia in the BAC effluent. Moreover, the membrane in the SMBR served as the final barrier, which could separate the particles almost completely. However, the hydraulic retention time and the corresponding foot-print would be increased when the BAC and SMBR were combined. Therefore, in the study, the BAC was substituted with powdered activated carbon (PAC). PAC was directly dosed into the SMBR, and the membrane adsorption bioreactor (MABR) was constructed. In the MABR, separation by the membrane, biodegradation by the microorganisms, and adsorption by PAC collectively contributed to the removal of organic matter. The MABR was demonstrated to be effective for drinking water treatment; and the HRT was substantially decreased. In the MABR, the PAC could also worked as the surpport for bacterial growth, thus enhance the capacity of the MABR for coping with impact load. MABR might be a promising technology for drinking water treatment.It was attempted to dose inorganic coagulant into the SMBR directly, i.e. the membrane coagulation (MCBR) was constructed. The investigation showed that when compared with conventional SMBR, the MCBR was not only able to reduce much more influent organic matter, but also able to eliminate almost all of influent phosphate, thus improve the biostability of the finished water. On the other hand, the ammonia removal efficiency of the MCBR reached more than 96%, indicating that direct addition of coagulant into SMBR would not adversely affect the microbial community in the bioreactor. Therefore, polyaluminium chloride (PACl) and PAC was dosed into the SMBR simutaneously in the experiments, and the integrative process-membrane coagualtion adsorption bioreactor (MCABR) was established. In the MCABR, four unit effects were identified to contribute to the water purification, i.e. separation by membrane, biodegradation by microorganisms, coagulation by PACl, and adsorption by PAC. As a result, influent organic matter was removed by about 70%. A sludge layer was found on the membrane surface in MACBR through SEM observation; energy diffusive X-ray analysis demonstrated that there was 10.4% of Al element in the sludge layer; CLSM observation showed that polysaccharides was extensively distributed on the membrane surface. Thus, it was inferred that Al hydrolysis product and polysaccharides were combined and form the net structure on the membrane surface, which was able to enhance the membrane for the rejection of DOM in the mixed liquor, especially the organic molecules of 300~3000 Da. Furthermore, the PAC layer with high density formed on the membrane surface during suction could also help to reject the DOM in the mixed liquor. Pilot study was conducted to investigate the operational characteristics of immersed hollow-fiber membrane for ultrafiltraion of polluted surface water. the UF membrane exibited excellent capacity for turbidity separation. However, the UF membrane was not good at removing organics, especially DOM. When the flux increased, the accumulation of pollutants in the membrane tank became more serious correspondingly. Therefore, the flux exerted important influence on the membrane fouling. Air bubbling could remove the sludge layer on the membrane surface, thus mitigate membrane fouling to some extent. Experiments showed that continuous air bubbling was more effective for alleviating membrane fouing under the same air flowrate. On the other hand, the higher the air flowrate was, the slower the TMP development rate would be. However, the energy depletion and operating cost should be taken into account to determine the optimum air flowrate. For the immersed membrane with the conventional configuration, small air bubble was demonstrated to be more effective for alleviating membrane fouling. Bachwashing could remove the surface foulants and in-pore foulants on the membrane simutaneously. Thus, higher cleaning effectiveness could be achieved by bachwashing. Therefore, combination of air bubbling and backwashing should be optimized in practical uses. During the long-term operation of membrane, irreversible fouling would be formed on the membrane inevitably. This paper also investigated effectiveness and mechanism of chemical cleaning of hollow-fiber PVC membrane by the combination of NaOH and ethanol for ultrafiltration surface water was discussed in the paper. SEM and AFM analyses indicated that NaOH and ethanol were able to synergetically remove the surface and in-pore fouing of the PVC membrane, thus exhibited excellent cleaning effectiveness.更多还原