海水作为汲取液的正渗透浓缩污水效能研究

发布时间：2018-06-26 23:18

本文选题：正渗透 + 城市污水　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：正渗透工艺作为膜处理中的新型技术,具有节能环保、高效的耐污染性能、出水水质优良等优点。由于无需外加压力,减弱了滤饼层的形成和运行成本,使正渗透工艺在污水处理中备受关注。传统工艺处理后污水排放入自然水体造成的水环境中污染物,对淡水资源和近海环境造成极大的威胁。使用来源广泛的海水作为汲取液稀释后直接排放,可满足高渗透压及安全无毒的汲取液需求,在进一步降低能耗的同时,提升了工艺的简易性,也由于正渗透对污染物的高截留率优化了出水水质,对水环境的保护和利用具有重要意义。本课题主要对海水汲取液进行正渗透污水处理的效能进行考察。考察了海水汲取液的运行特性,如错流速率与温度对通量和溶质反渗的影响,以及海水汲取液的浓缩能力。通过分析得出高温高错流速率对通量和溶质反渗都有大幅提升,PRO模式中增加幅度大于FO模式。污水实验测定反应前后污染物浓度如COD、总磷、氨氮等含量,以考察正渗透膜对污染物截留性能。观测长期运行对通量带来的影响,以及溶质反渗随膜污染情况增加的变化,考察膜污染对正渗透膜性能的影响。测量主要金属离子的反渗程度,分析金属离子在膜表面沉积吸附,或穿过膜渗透入原料液程度。实验得出物理清洗可以去除活性层表面污染层获得一定程度的通量恢复,但支撑层内部污染很难除去。正渗透工艺在长时间运行时对污染物的截留率能够达到90%以上,二价离子钙镁离子大多附着于膜表面,反渗程度可以忽略。膜通量随着膜孔堵塞程度增加而降低,而PRO运行模式下随着支撑层内部污染的加剧,溶质反渗逐渐降低,但FO模式中盐离子反渗程度随着活性层表面污染加剧而升高。正渗透过程中的浓差极化现象由于不可逆的特性成为降低正渗透性能的主要因素。本研究对污水中主要成分进行模拟,探讨不同运行模式与不同污染物对浓差极化程度的影响。实验得出有机物是影响浓差极化的污染成分,尤其是支撑层内部的浓差极化现象,而混合污染中无机盐的影响可以忽略。对于相同浓度的原料液,高浓度的汲取液引起的浓差极化程度较小。对于相同浓度的汲取液,低浓度的原料液引起的浓差极化程度较低。在正渗透过程中由于静电斥力对蛋白质的浓缩效果较好,但对于蛋白质与其他污染物质的混合溶液,蛋白质的凝聚强化了浓差极化层的形成。
[Abstract]:As a new technology in membrane treatment, normal osmosis process has the advantages of energy saving, environmental protection, high efficiency pollution resistance and good effluent quality. The formation and operation cost of the filter cake layer is weakened without external pressure, which makes the normal osmotic process become more and more important in wastewater treatment. The pollutants in the water environment caused by the sewage discharged into the natural water body after the treatment of the traditional process pose a great threat to the freshwater resources and the offshore environment. The direct discharge of seawater from a wide range of sources after dilution can meet the requirements of high osmotic pressure and safety and non-toxic solution, while further reducing energy consumption and improving the simplicity of the process. Because the high rejection rate of positive osmosis to pollutants optimizes the effluent quality, it is of great significance for the protection and utilization of water environment. The purpose of this paper is to investigate the efficiency of seawater-water sewerage treatment. The effects of cross-flow rate and temperature on flux and solute reverse osmosis as well as the concentration capacity of seawater extract were investigated. It is found that the high temperature and high cross-flow rate has a significant increase in flux and solute reverse osmosis in the pro model, which is larger than that in the FO model. The concentration of pollutants such as COD, total phosphorus and ammonia nitrogen were measured before and after the reaction in order to investigate the retention of pollutants by osmotic membrane. The effects of long-term operation on flux and the change of solute reverse osmosis with membrane fouling were observed and the effects of membrane fouling on the performance of normal osmotic membrane were investigated. The degree of reverse osmosis of main metal ions was measured, and the degree of metal ion deposition and adsorption on the membrane surface or permeating through the membrane into the raw material solution was analyzed. The results show that physical cleaning can remove the surface fouling layer of the active layer to a certain extent, but it is difficult to remove the internal pollution of the supporting layer. The rejection rate of pollutants can reach more than 90% when the process of normal osmosis is running for a long time, and the bivalent ion calcium and magnesium ions are mostly attached to the membrane surface, and the degree of reverse osmosis can be neglected. The membrane flux decreases with the increase of membrane pore plugging degree, while the solute reverse osmosis decreases with the increase of the pollution inside the supporting layer in pro mode, but the salt ion reverse osmosis degree in FO mode increases with the increase of the surface pollution of the active layer. The concentration polarization phenomenon in the normal osmotic process is the main factor of decreasing the normal osmotic performance due to the irreversible characteristics. In this study, the main components of sewage were simulated, and the effects of different operating modes and pollutants on the concentration polarization were discussed. The results show that organic matter is the pollutant that affects the concentration polarization, especially the concentration polarization phenomenon in the supporting layer, but the influence of inorganic salts in the mixed pollution can be neglected. For the same concentration of the raw liquid, the concentration polarization caused by the high concentration extraction solution is small. For the same concentration of absorbent, the concentration polarization caused by low concentration of feedstock solution is lower. In the normal osmotic process, the electrostatic repulsive force has a good effect on the concentration of protein, but for the mixed solution of protein and other pollutants, the condensation of protein strengthens the formation of the concentration polarization layer.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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