【作者】 齐鲁；

【导师】 李圭白；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 博士

【摘要】 当前我国的地表水源普遍受到污染,常规给水处理工艺已经无法满足要求日益严格的饮用水水质标准,迫切需要开发新型水处理技术。随着膜技术的进步,人们发现包括微滤和超滤在内的低压操作膜分离过程能满足要求,其中又以超滤出水水质更佳而得到更多的关注。浸没式超滤膜由于其过滤面积较大并且安装操作方便而具有更广泛的应用潜力,但就其在饮用水处理中的实际应用而言,仍存在一些关键问题需要解决。本论文主要针对膜特性、预处理和运行方式等对浸没式超滤膜过滤性能的影响进行研究,从预处理和运行条件两方面来研究膜污染控制技术,提出膜运行优化工艺方案,并分析用浸没式超滤膜来替代常规饮用水生产工艺的可行性,为浸没式超滤膜在水厂的实际应用提供重要技术支撑。首先针对不同截留分子量和材质的超滤膜对原水中有机污染物等的去除效能进行研究,结果表明,随着膜截留分子量的减小,超滤膜对浊度和有机物的去除率逐渐升高,但超滤膜对溶解性有机物的去除率较低。不同材质的超滤膜对有机物的去除率存在差异,表明不同材质的超滤膜与有机物之间存在着不同的相互作用。进而,试验针对膜材质和有机物对膜污染的影响进行研究,结果表明,大于30KDa的亲水性有机物和憎水酸容易引起可逆膜污染,而小于1KDa的亲水性有机物容易引起不可逆膜污染,但有机物引起不同材质超滤膜污染的程度不同,并且引起不同材质超滤膜污染的有机物种类也有所不同。长期膜过滤过程中,聚偏氟乙烯(PVDF)膜对分子量小于1K和1K~3KDa有机物的吸附速度比聚氯乙烯(PVC)膜和聚砜(PS)膜要快,膜污染也较快,聚砜(PS)膜抗有机污染的能力较好。由于浸没式超滤膜对有机物的去除作用有限,并且污染较快,试验考察了预处理对膜出水水质的改善效果及其对膜污染的控制作用。预膜滤试验中,随着预过滤膜孔径或截留分子量的减小,预膜滤对原水浊度和有机物的去除率逐渐升高,而且膜运行过程中的表面饼层阻力逐渐减小,堵孔阻力也有明显降低,但由于吸附阻力主要由小分子有机物引起,试验中采用的预膜滤不能有效降低膜的吸附阻力。其他预处理方式包括混凝、粉末活性炭(PAC)预吸附+混凝、污泥回流、炭泥回流四种,结果发现,膜前预处理对原水浊度和有机物具有较好的去除效能,可显著提高膜出水水质,其中炭泥回流对膜出水水质的改善作用最为明显,在本试验条件下其对原水中浊度、DOC、UV254、CODMn、BDOC和THMFP的去除率分别达到93.8%、37.3%、41.1%、48.7%、83.0%和57.9%。各预处理可对水中颗粒物和膜污染有机物有不同程度的去除作用,因而膜前预处理可以有效降低膜运行的跨膜压力,从而延缓膜污染。对膜运行过程中的膜阻力分析可知,各预处理均能有效降低膜表面饼层阻力和浓差极化阻力,而炭泥回流预处理还可有效降低膜的吸附阻力,且其总阻力值也最低,这主要是由于炭泥回流对原水浊度以及容易引起可逆膜污染和不可逆膜污染的有机物均具有较好的去除效能。研究还发现,运行条件也是影响膜过滤性能的重要因素,试验主要研究了过滤方式对膜出水水质和膜污染的影响以及临界通量的影响因素。结果表明,恒压和恒流两种过滤条件下,膜对颗粒物和有机物的去除作用相差不大。在长期运行过程中,恒压过滤引起的不可逆膜污染比恒流过滤严重,而通过选择合理的膜通量和清洗方式,采用恒流过滤可使膜在较长时间内保持稳定运行。曝气、间歇过滤间歇曝气和混凝均可以提高超滤膜过滤原水时的临界通量,几种操作方式相结合可以在膜长期运行过程中有效缓解膜污染。此外,短期通量阶梯增加试验所得出的临界通量值对浸没式超滤膜的实际应用具有一定的指导意义。在前面实验室研究的基础上,针对国内两处地表水进行了浸没式超滤膜处理地表水的中试研究,在浸没式超滤膜处理苏州内河水的研究中,混凝、PAC预吸附+混凝、污泥回流和炭泥回流四种预处理可以提高超滤膜的出水水质,另外炭泥回流预处理对原水中颗粒物和有机物的去除率比其他三种预处理要高,因而炭泥回流可以更加有效的缓解膜污染。对运行条件的研究结果表明,曝气和间歇过滤相结合可以较好的控制膜污染,但在应用时应选择合理的曝气强度。混凝预处理可降低膜运行的TMP,其与曝气和反洗方式相结合可以更好的缓解膜污染。在浸没式超滤膜处理东江水的研究中,膜出水浊度比水厂同期砂滤出水具有优势,均保持在0.1NTU以下,但膜对有机物的去除率与砂滤相差不大。对膜的运行条件优化研究发现,在东江水水质条件较好的情况下可选取较高的膜通量,运行时膜过滤周期应作适当的缩短,过滤周期之间采用有效的物理清洗并辅助以短时间的在线化学清洗可保证膜过滤的长期稳定运行,另外用NaClO和HCl相结合的清洗方式可使膜比通量有较大程度的恢复。更多还原

【Abstract】 In recent years surface water has been widely contaminated in China, conventional drinking water treatment processes can no longer meet the requirements of increasingly stringent drinking water quality standards, and the development of new water treatment technology would be urgently needed. With the advances in membrane technology, low-pressure microfiltration and ultrafiltration (UF) were found to meet the requirements, in which ultrafiltration effluent quality is better and get more attention. Immersed UF membrane has a wider range of potential applications because of it has a larger filtration area and relatively easy to operate, but there are still some key issues to be resolved in the practical applications.This research focused on the effect of membrane characteristics, pretreatment and operating conditions on the filtration performance of immersed UF membrane, membrane fouling control technology was developed from the two aspects of pretreatment and operating conditions. The optimized operation programs were proposed, and the feasibility of conventional treatment process to be replaced by submerged UF membranes was analyzed, which could provide important technical support for the practical application of the water plant.In this paper the effect of different materials and molecular weight cutoff on on the organic pollutants removal by membrane in surface water was first to be studied, and the results showed that the removal efficiency of turbidity and organic matters was increased gradually with the decrease of molecular weight cutoff membrane, but the removal of dissolved organic matters was lower. The removal of organic matters by UF membranes of different materials was different, indicating that different membrane materials and organic could interact with each other. Furthermore, tests on the effect of membrane material and organic matter on membrane fouling were studied, the results showed that the hydrophilic and hydrophobic organic acids with the molecular weight cutoff more than 30KDa were the main substance caused reversible membrane fouling, and the hydrophilic organic matter with the molecular weight cutoff less than 1KDa is the main substance caused irreversible fouling. But membrane fouling caused by different materials was varying and the types of organic matter which could cause membrane fouling are also different. In the long-term membrane filtration, the adsorption of organic matter with the molecular weight of less than 1K and 1K~3KDa by PVDF membrane was faster than PVC and PS membrane, membrane fouling is also faster, PS membrane had better resistance to organic pollution. Since the removal of organic matter by submerged membrane was limited and the membrane fouling was faster, pretreatment and pre-filtration were studied to improve water quality and to control fouling. Pretreatment methods included coagulation, powdered active carbon (PAC) adsorption-coagulation, sludge recycling, PAC-sludge recycling. The results showed that the efffcts of pretreatment on raw water turbidity and organic matter were better, which can significantly improve the membrane effluent quality, and PAC-sludge recycling was most effective with the DOC、UV254、CODMn、BDOC and THMFP removal 93.8%、37.3%、41.1%、48.7%、83.0%和57.9%. Four kinds of membrane pretreatment could reduce the TMP since the organic matters and particles could be removed in different degree, and thus the membrane fouling was delayed. The analysis on the membrane resistance during the operation showed that pretreatment could reduce the surface cake layer resistance and concentration polarization resistance, while the PAC-sludge recycling pretreatment could also reduce adsorption resistance, and its total resistance value the lowest, which was mainly due to the turbidity, organic matters with the molecular weight cutoff more than 30KDa and less than 1KDa had been better removed efficiently. In the pre-filtration experiment, the cake layer resistance decreases with the pre-filter membrane pore size or molecular weight cutoff decreases, the pore blocking resistance also decreased significantly, but adsorption resistance mainly caused by the of organic with small molecules could not be effectively reduced.Operating conditions is also an important factor to affect the membrane filtration performance. The effects of operating conditions on membrane effluent quality and membrane fouling were investigated and the influencing factors of critical flux were also studied. The results showed that the removal of particulate matter and organic matter had little difference in the constant pressure and constant flux conditions. In the long run, the constant pressure filtration could caused more serious irreversible fouing than the constant flux condition, and constant flux could make membrane filtration remain stable in a long run by selecting a reasonable flux and cleaning method. Aeration, intermittent filtration and intermittent aeration and coagulation could enhance the critical flux of ultrafiltration membrane, and the combination of these operating modes could effectively alleviated membrane fouling in long-term operation. In addition, critical flux value from the short-term flux-steps tests could have a good guidance to the practical application of immersed UF membrane.Two pilot experiments of immersed membrane in two typical kinds of surface water were researched based on the previous study. In the pilot study in Suzhou, coagulation, PAC-coagulation, sludge recycling, PAC-sludge recycling pretreatment could improve UF effluent quality. The removal of particulates and organic matters by PAC-sludge recycling was better than the other three kinds of pretreatment, and thus PAC-sludge recycling could hae more effective mitigation of membrane fouling. Study on the operating conditions showed that the combination of aeration and intermittent filtration could have better control of fouling, but reasonable aeration intensity should be selected in application. Coagulation pretreatment can reduce the TMP, and the the combination of coagulation, aeration and backwashing could have better mitigation of membrane fouling. In the study of Dongjiang, treating the membrane effluent turbidity had an advantage over the sand filter during the same period, the tubidity of which were maintained less than 0.1NTU, but the removal of organics was the same as sand filter. The test on optimization of operating conditions found that a relatively high flux could be selected in Dongjiang of better water quality, membrane filtration cycle should be shortened appropriately, and effective physical cleaning and auxiliary to short-term Enhanced Flux Maintenance (EFM) cleaning would ensure the long-term stable operation of membrane filtration. The combination with NaClO and HCl cleaning could have a greater degree of recovery on membrane performance.更多还原