【作者】 张艳；

【导师】 李圭白；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2011， 博士

【摘要】 由于工业的迅速发展,饮用水水源污染日益严重,尤其是富营养化现象频繁发生,使得目前水厂普遍采用的常规饮用水处理工艺面临严峻的挑战。如何有效的去除富营养化水体中的藻细胞及其分泌物已成为保障供水安全的关键性问题之一。采用超滤膜技术去除藻细胞及其分泌物是富营养化水体处理技术研究的新方向。深刻理解藻细胞及其胞外分泌物生长代谢的基本规律和特征是寻找实用性水处理技术和正确应用超滤膜技术的基础。论文以实验室培养的铜绿微囊藻（Microcystis aeruginosa,M. aeruginosa）作为研究对象,从以下5个方面论证超滤膜处理含藻水的可行性:1.通过定性和定量分析揭示了铜绿微囊藻细胞及其分泌物随时间变化的基本规律和特点;2.对比研究了超滤（UF）和粉末炭超滤（PAC/UF）生物反应器对含藻水的处理效果和跨膜压差（Trans-membrane Pressure,TMP）变化及其机理;3.探讨了膜反应器的主要运行参数以及原水水质对聚氯乙烯（Polyvinylchloride,PVC）超滤膜处理含藻水的影响;4.通过中试试验研究了浸没式超滤膜处理受污染水源水的效果;5.研究了不同清洗剂对受污染膜的清洗效能与机理。通过对实验室培养的铜绿微囊藻及其胞外分泌物进行研究证实,铜绿微囊藻细胞浓度随生长时间的增加逐渐增大,在稳定期达到最高值后又逐渐降低。在生长对数期和稳定期时,铜绿微囊藻细胞的等电点在pH4⁵之间,随着pH值的增大电负性不断加强。研究还发现,在不同生长阶段胞外分泌物的主要成分均为亲水性的大分子物质（大于30kDa）。在对分泌物的重要组成物质（碳水化合物、蛋白质和藻毒素）进行分析后发现,其浓度均随藻细胞的生长繁殖逐渐增加。随着时间的变化,碳水化合物与溶解性有机碳（Dissolve Organic Carbon,DOC）比值逐渐降低,而蛋白质与DOC的比值以及蛋白质与碳水化合物的比值均呈增加的趋势。通过对比UF和PAC/UF生物反应器处理含藻水的效果发现,UF能够去除全部的藻细胞,但对胞外有机物的去除效果不明显,从而造成严重膜污染;相比UF工艺,PAC/UF生物反应器可明显减缓TMP的上升速率,同时提高DOC、UV₂₅₄和MC-LR_eq的去除率（分别为10.9±1.7%、27.1±1.7%和40.8±4.2%）。但是,PAC对膜处理碳水化合物和蛋白质等大分子有机物的效果几乎没有改变。UF反应器中对有机物的去除机理主要包括膜截留、生物降解和污染层强化截留作用,PAC/UF反应器中的生物作用优于UF工艺。实验还发现,由于PAC降低了反应器内的光照强度,从而导致PAC/UF反应器中碳水化合物和蛋白质的生成量下降;虽然光照强度对反应器中MC-LR_eq影响不明显,但PAC的吸附作用使其浓度大幅降低。通过改变PVC超滤膜反应器处理含藻水的运行参数（通量、曝气量和反洗条件等）,研究了TMP随时间变化的规律。通量对膜污染的影响随藻细胞浓度的增加而增大;虽然膜污染程度随气液比的增加不断降低,但综合考虑其它因素认为在本实验条件下最适宜的气液比为12:1。随着pH值的提高,污染物与膜表面的负电性逐渐增强,同时高分子量物质所占比例不断增加,使得TMP上升速度不断下降。实验同时证实,相比K⁺和Al³⁺,Ca²⁺对膜污染的缓解效果更加明显。推断认为,Ca²⁺能更有效地促使水中有机物络合生成大分子物质。藻细胞和腐殖酸间的协同作用,造成了更加严重的膜污染。从实际工程改造角度出发,通过中试实验研究了浸没式超滤膜以混凝沉淀作为预处理工艺过滤受污染水的效果。不受原水水质影响,超滤膜出水中浊度始终低于0.1NTU,且完全去除原水中的藻细胞。由于混凝预处理作用,超滤出水中有机物指标基本达到国家饮用水标准。在长期（40天）运行时,膜反应器始终保持高通量运行（不低于40L/m²/h）。实验结束后采用300mg/L NaClO溶液对膜进行清洗,通量恢复率达到93.6%。为了进一步了解藻及其胞外分泌物对膜污染的影响,系统地研究了不同化学药剂（NaOH溶液,NaClO溶液,HCl溶液,EDTA溶液）对被含藻水污染后的超滤膜清洗效果。结果表明,100mg/L NaClO溶液对不可逆污染的清洗效果最佳（88.4±1.1%）。衰减全反射傅里叶转换红外光谱（ATR-FTIR）也证实NaClO溶液能够几乎去除全部的污染物质（如碳水化合物类和蛋白质类物质）。然而,虽然证实500mg/L NaOH溶液能够去除PVC膜表面的部分污染物,但是其对不可逆污染的去除率仅为1.5±1.0%。通过扫描电子显微镜（Scanning Electron Microscope,SEM）和原子力显微镜（ Atomic Force Microscope,AFM）分析,发现NaOH可能改变了膜表面残余污染物的化学结构,使它们更紧密的粘附在膜表面;或改变了膜表面性质,从而导致NaOH溶液对通量恢复效果不明显。更多还原

【Abstract】 With the quick development of industry, the pollution of the drinking water sources has been getting more and more serious. Especially the eutrophication phenomenon which frequently happens makes the waterworks with conventional processes facing austere challenges. It is a key problem to remove the algal cells and their extracellular organic matter （EOM） in eutrophic water to insure the safety of drinking water.It is a new technical approach to remove the algal cells and their EOM by ultrafiltration （UF） membrane. To find out intrinsic rules and characteristics of the growth and secretion of the algal cells and the EOM will contribute to find out the practicable water treatment technology and the rational UF membrane application. Microcystis aeruginosa （M. aeruginosa） cultured in the lab was used as the main object in this research. This dissertation consisted of the following contents: 1. To find out the rules and characteristics of the algal cell concentration and the EOM with the time development by qualitative and quantitative analyses; 2. To find out the efficiencies and mechanisms of algal-rich water treatment by UF and PAC/UF bioreactor; 3. To find out the effect of running parameters of the membrane reactor and influent properties on the algal-rich water treatment by polyvinylchloride （PVC） UF membrane; 4. To study the efficiency of polluted source water treatment by immersed UF membrane; 5. To investigate the cleaning efficiencies and mechanisms of different chemical reagents on the fouled membrane by algal-rich water.By investigating M. aeruginosa cells cultured in the lab and their extracellular organic matter （EOM）, it was found that the cell concentration increased with time and reached maximum at stationary phase, then decreased. The isoelectric point of the algal cells was at pH4⁵ during both exponential and stationary phases. With pH increase, the electronegativity of algal cells strengthened. Meanwhile, the EOM in the different phases showed high hydrophilicity and high molecular weight （MW, more than 30 kDa）. By analyzing the important components of EOM (carbohydrates, proteins and MC-LR_eq), it was found that their concentrations were gradually increasing with the growth of algal cells. The ratio of carbohydrates to dissolve organic carbon （DOC） decreased with the time development, while both the ratios of proteins to DOC and that of proteins to carbohydrates increased.By comparing the efficiency of algal-rich water treatment by UF and PAC/UF bioreactor, it was found that UF achieved an absolute removal of M. aeruginosa cells, but a poor removal of algogenic organic matter （AOM） released into water, with severe membrane fouling. Compared with UF process, PAC/UF bioreactor significantly reduced the development velocity of TMP and enhanced the removal of DOC （by 10.9±1.7%）, UV₂₅₄ （by 27.1±1.7%）, and MC-LR_eq （by 40.8±4.2%）. However, PAC had little effect on the rejection of high MW AOM such as carbohydrates and proteins. The mechanisms of organic matter removal in UF reactor included membrane sieving, biological oxidation and strengthening sieving by cake layer. The biological oxidation effect in PAC/UF reactor was much more obvious than that in UF reactor. It was also identified that PAC reduced the concentrations of carbohydrates and proteins in the reactor due to decreased light intensity; as well as the MC-LR_eq concentration by PAC adsorption when there was little effect of lower light intensity on MC-LR_eq secretion.The influences of the running parameters （including flux, aeration, backwashing） on the trans-membrane pressure （TMP） development were also investigated. The influence of flux on membrane fouling enhanced with the algal cell concentration increasing. Increasing the ratio of air to liquid could alleviate membrane fouling phenomenon. However, it was considered that the best ratio of air to liquid was 12:1 under the test condition in this dissertation . It was also found that increasing pH value enhanced the electronegativity of the pollutant and membrane surface, and promoted the increasing of the ratio of high MW EOM, which led to the reduction of the TMP increasing velocity. Meanwhile, it was revealed that with the comparison of K⁺ and Al³⁺, Ca²⁺ was more efficient to alleviate membrane fouling. It was deduced that Ca²⁺ contributed to the formation of high MW materials. The algal cells and humic acid had synthetic effect on the membrane fouling, which could cause more serious membrane fouling.The efficiency of polluted source water treatment by immersed UF membrane with the pretreatment of coagulation and sedimentation was studied in pilot experiment for practical reconstruction. Without being influenced by raw water quality, turbidity in UF effluent was absolutely lower than 0.1NTU. The algal cells could not be found in UF effluent. Due to the pretreatment of coagulation and sedimentation, the contents of organic matters in UF effluent basically reached Chinese sanitary standard for drinking water. During running phase （for 40 days）, membrane flux always kept a high value （not less than 40 L/（m²·h））. The recovery of membrane flux could reach up to 93.6% after cleaning by 300 mg/L NaClO at the end of the experiment.To further understand the membrane fouling caused by algal cells and their EOM, the cleaning efficiencies of hollow-fibre PVC membrane with different chemical reagents （NaOH, HCl, EDTA, and NaClO） after ultrafiltration of algal-rich water were also investigated. The result showed that 100 mg/L NaClO exhibited the best performance in terms of removing the irreversible fouling resistance （88.4±1.1%）. This might be attributed to the fact that NaClO could eliminate almost all the major foulants such as carbohydrate-like and protein-like materials on the membrane surface, as suggested by attenuated total reflection fourier transform infrared spectroscopy analysis. However, negligible irreversible resistance （1.5±1.0%） was obtained when the membrane was cleaning by 500 mg/L NaOH, although the NaOH solution could also desorb a portion of the major foulants from the fouled PVC membrane. Scanning electron microscope and atomic force microscope analyses demonstrated that NaOH could change the structure of the residual foulants on the membrane, making them more tightly attached to the membrane surface or change the characteristics of membrane surface. This phenomenon might be responsible for the negligible membrane permeability restoration after NaOH cleaning.更多还原