絮体与超滤膜协同作用下的净水效能与机制
文献类型：学位论文
| 作者 | 马百文 |
| 学位类别 | 博士 |
| 答辩日期 | 2015-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 曲久辉 |
| 关键词 | 超滤膜 表面预沉积 腐殖质 蛋白质 膜污染控制,Ultrafiltration membrane Surface pre-deposition Humic substances Protein Membrane fouling control |
| 其他题名 | Ultrafiltration membrane purification efficiency and mechanism with the synergistic effect of flocs |
| 学位专业 | 环境工程 |
| 中文摘要 | 超滤膜技术以其自身的优点，在水处理中的应用越来越广泛，但膜污染不可避免，一定程度上制约了膜效能发挥和膜技术的推广应用。因而，探索通过膜表面预处理和絮凝过程，调控膜-颗粒物作用行为的机制，以改进膜的运行周期和净水效果是本研究的核心问题。 首先通过平板超滤膜，将不同种类铝盐或铁盐絮体以自然沉降方式预先沉积在超滤膜表面，考察了污染物的去除情况及膜的净水行为。结果表明与单独铁盐絮体相比，单独铝盐絮体能更好的去除腐殖质（HA）和蛋白质（BSA），较大程度地减缓膜污染，氯化铝效果尤为明显。当氯化铁和氯化铝以不同摩尔比复合后，随着其中铝盐摩尔比的增加，对 HA和BSA的去除率提高，并可有效地保护超 滤膜。与任一摩尔比复合的混合絮体相比，单独氯化铝絮体能更好地去除污染物，减缓膜污染。对氯化铝而言，絮体性质受 pH影响较大。较低pH时，氯化铝絮体的分形维数较小，但其絮体粒径更小，导致形成的沉积层相对致密，且此时超滤膜表面粗糙度较大。Zeta电位分析结果表明，低pH时氯化铝絮体的正电性更强，较容易吸附负电性的 HA和BSA分子，使低pH条件下去除HA和BSA效果更好，提高膜通量程度更大。 预沉积铁盐絮体不能有效减缓膜污染，但纳米铁具有较大的比表面积，能大量吸附有机物。实验结果表明将纳米铁预先沉积在超滤膜表面后，HA能被大量去除，膜通量得以提高，预先沉积乙醇改性（增大纳米铁比表面积）的纳米铁后效果更好，但超滤膜表面预沉积纳米铁或改性纳米铁后容易导致出水铁浓度超出生活饮用水水质标准（0.3 mg/L，GB5749-2006）。 以中空纤维膜为研究对象，以 HA为目标污染物，通过在膜池内曝气使氯化铝絮体预先悬浮于膜表面，进一步考察了该方法对超滤膜的保护作用。结果表明此时氯化铝絮体仍能有效吸附/截留 HA，跨膜压差增长缓慢。膜污染控制效果受絮体注入量、曝气位置、曝气方式和絮体注入方式等影响。注入絮体总量越大，吸附/截留 HA的效果越明显，保护超滤膜作用越显著。在远离膜池底部间歇曝气，即靠近中空纤维超滤膜组件底部时，尽管能有效缓解超滤膜表面滤饼层的累积，但是容易导致大量氯化铝絮体沉降在膜池底部而不发挥作用。在膜池底部连续曝气，即远离中空纤维超滤膜组件底部时，氯化铝絮体可充分悬浮于膜表面，膜污染程度降低。此外，将氯化铝絮体一次性注入膜池内，在运行过程中会出现絮体“老化”现象，并不能充分发挥作用，降低了氯化铝絮体保护膜的有效性。但如果将氯化铝絮体分批次注入时，则能保持絮体的活性，较大程度地发挥絮体的作用。同时整个运行期间，中空纤维超滤膜处理系统未排泥。 |
| 英文摘要 | Ultrafiltration (UF) membrane processes have been increasingly used in water treatment, mainly due to the superior and stable effluent quality. However, membrane fouling is inevitable and is still a major impediment to broader application of membrane technology. Thus, new technology should be explored to improve membrane performance after regulating and controlling the effect between membrane surface and flocs/particles. Different kinds of alum flocs or iron flocs were pre-deposited onto the flat sheet UF membrane surface to test their anti-fouling properties. The results showed that alum flocs alone performed better on removing humic substances (humic acids, HA) or protein (bovine serum albumin, BSA) in comparison to that of iron flocs alone,especially AlCl3 flocs. When different mole ratios of the mixed FeCl3/AlCl3 flocs were pre-deposited onto the membrane surface, membrane performed better in the presence of higher mole ratio of alum. For AlCl3 flocs, the characteristics were significantly influenced by solution pH. Although the fractal dimension of alum flocs was smaller under lower pH conditions, their particle sizes were much smaller,resulting in a denser cake layer on the membrane surface, of which the roughness was larger. In addition, the positive charge of alum flocs under lower pH values was higher, and negatively charged HA or BSA molecules were easily to be adsorbed. Thus, the pre-deposited membrane performed much better under lower pH conditions. The adsorption ability of nanozero valent iron (NZVI) was better due to its large specific surface area. Although the pre-deposited iron flocs alone performed worse,NZVI was pre-deposited onto the membrane surface followed by filtering HA. It was presented that HA was largely removed by the pre-deposited NZVI membrane, and the membrane flux was also significantly increased, especially when NZVI was modified by ethanol. However, Fe concentration in the effluent could be exceeded the drinking water quality standards (0.3 mg/L, GB5749-2006). Further research was focused on the hollow fiber UF membrane, of which AlCl3 flocs were pre-injected by air sparging in membrane tank. HA could also be largely removed and the corresponding membrane fouling was alleviated. Membrane performance was easy to be influenced by the concentration of alum flocs, air sparging position, air sparging mode and injection mode of flocs, etc. The more alum flocs were injected, the better the removal efficiency was and the membrane performed. When the position of air sparging was far away from the bottom of the membrane tank and intermittent aeration was used, plenty of alum flocs could be settled, and could not be made full use. When the position of air sparging was on the bottom of the membrane tank and continuous aeration was used, alum flocs could be well suspended in the membrane tank and membrane fouling was less serious. In addition, membrane performed worse once alum flocs were injected only one time,owing to more alum flocs “aged”. Transmembrane pressure increased slowly when alum flocs were pre-injected in batches. Furthermore, no sludge was discharged during the whole operation time. |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/34353]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 马百文. 絮体与超滤膜协同作用下的净水效能与机制[D]. 北京. 中国科学院研究生院. 2015. |
入库方式： OAI收割
来源：生态环境研究中心
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