RCEES OpenIR  > 环境水质学国家重点实验室
强化污泥电脱水过程及同步去除重金属机制的研究
Alternative TitleInvestigation on strengthening sludge electro dewatering process and synchronous removal of heavy metals.
曹秉帝
Subtype博士
Thesis Advisor王东升
2019-05
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name工学博士
Degree Discipline环境工程
Keyword活性污泥, 电 脱水,胞外聚合物, 无机混凝剂 重金属 waste Activated Sludge, Electro-dewatering, Extracellular Polymeric Substance (Eps), Inorganic Coagulants, Heavy Metals.
Abstract

       活性污泥法是20世纪环境工程领域的重大发明之一,在污水处理过程中发挥着不可替代的作用。污水活性污泥法处理过程中伴随着大量的剩余污泥,其含水率高、有机质含量高,同时含有各种微量的污染物和病原体,因而传统的生化工艺已经将污水处理问题转化为固废处理问题。污泥是一种高度亲水且异质化的类胶体体系,通常表面带有高密度的负电荷,在静电斥力的作用下在水中具有相对
的动态稳定性。污泥中的胞外聚合物( EPS)可以形成一种稳定的类凝胶结构通过空间位阻的作用下与水分子相结合,导致污泥具有粘弹性,机械脱水难度大。传统机械脱水方式对污泥脱水效果有限,而在机械脱水的基础上施加电场辅助往往能达到深度脱水效果 。
        本文系统的研究了污泥电脱水过程中阴阳两极EPS和微观形貌的区域化分布特征,明确EPS分布和泥饼孔隙率与污泥电脱水速率的相关性,在此基础上采用无机混凝剂对污泥进行化学预调理,探究不同无机混凝剂对污泥电脱水效果的影响机制;探究了污泥电脱水过程中有害重金属迁移转化的规律,提出了柠檬酸络合耦合电渗透同步实现污泥高效脱水和重金属脱除新工艺,研究的主要 内容和
结果如下:
         1. 研究了不同电压、pH和离子强度下污泥电脱水效果,以及分析阴阳两极滤液中DOM含量确定电脱水过程中污泥EPS的区域化分布特征,同时分析了阴阳两极电脱水速率与DOM含量和污泥泥饼孔隙率的相关性。研究结果发现随着电压的增加和pH的降低污泥的电脱水效果增强,在较低离子强度条件下污泥电脱水效果随着离子强度的增加而增强,当离子强度超过一定范围电脱水效果恶化;阴极的碱化作用会导致EPS大量溶解释放,阳极的酸化氧化作用也会导致EPS溶解释放;阴阳两极的平均电脱水速率与阴阳两极的泥饼空隙率程显著性相关关系;阳极DOM含量和阳极平均电脱水速率没有相关性,而阴极DOM含量与阴极平均电脱水速率呈负相关关系,污泥电脱水过程中阴极是主要的疏水端,在阴极粘性蛋白类物质无法分解成小分子量物质,所以越高的EPS溶解释放会恶化污泥电脱水效果;阳极氧化作用可以将生物质氧化分解成小分子量物质,降低阳极EPS溶解对电脱水效果的影响。
        2. 分析了三种典型的无机混凝剂(FeCl3、PAC和HPAC)预调理对污泥电脱水效果的影响。研究结果随着混凝剂投加量的增加阴极的电脱水速率升高,经FeCl3调理后污泥阴极电脱水速率增加最大, 随着HPAC、PAC和FeCl3投加量的增加污泥Zeta电位上升, 经FeCl3调理形成的污泥絮体较PAC和HPAC更密实,且污泥电渗透强度增加幅度最大,无机混凝剂对污泥EPS结构有压缩作用,使得可溶出的EPS含量降低,缓解滤布堵塞,FeCl3对EPS结构压缩作用最强,相比提升污泥体系离子强度EPS压缩作用对改善污泥电脱水效果有着更重要的影响。
        3. 研究了 不同操作条件下(电压、离子强度、螯合剂)阴阳极滤液重金属含量和泥饼中不同形态重金属迁移转化规律。实验结果表明:随着电压的增加阴极滤液中重金属含量不同程度增加,阳极重金属含量未出现明显变化趋势,Hg含量在增加电压前后均低于检出限;随着离子强度的增加阴阳两极滤液重金属含量均呈现先增加后降低的趋势,在 0.07g/gTSS投加量时,重金属含量达到最大值,这与电脱水速率的变化趋势是一致的,此外可以看到不同离子强度条件下的重金属含量普遍高于电压条件下的重金属含量;随着电压增加,阴极各重金属 PMI指数不同程度增加,重金属活性变高,阴极重金属的 PMI指数随着离子强度的增大先增加后降低,阳极 PMI指数随着离子强度变化趋势未出现明显规 律,适当的增加离子强度可以增加污泥中重金属的活性,过高的离子强度会降低重金属的活性;当的增加离子强度可以增加污泥电脱水过程中的重金属去除率,但是过高的离子强度会影响其对污泥中重金属的去除效果 ; 柠檬酸的加入可以缓解蛋白质对重金属的吸附作用,进一步提高污泥中重金属的去除率,柠檬酸可以达到强化污泥电脱水同步去除重金属的效果。

Other Abstract

        Wastewater treatment processes produce large quantities of sludge commonly containing over 99% water, the sludge transportation is difficult and cost is high because the high sludge moisture content is often accompanied by a large sludge volume. Therefore, the development of sludge dewatering technology has become one of the important topics for the research of environmental protection workers in China. The traditional mechanical dewatering method has limited effect on sludge dewatering, and the application of electric field assist on the basis of mechanical dewatering can often achieve deep dewatering effect.
In this paper, the EPS composition and distribution characteristics at both electrodes in sludge electro-dewatering process were studied under different operating conditions ( voltage, pH and ionic strength). Meanwhile, the sludge cake porosity at both electrodes were analyzed, the correlation between EPS distribution and sludge cake porosity and sludge electro-dewatering rate was clarified. On this basis, the inorganic chemical conditioning agent was used to pre-condition the sludge, and the influence mechanism of different chemical agents on the sludge electro-dewatering effect was investigated. The migration and transformation of harmful heavy metals in the process of electro-dewatering process was studied, and use the complexing agent citric acid to simultaneously enhance the electro-dewatering effect and remove heavy metal content. Main contents and results of this dissertation are as follows:
        1. In this study, the effects of voltage, pH and ionic strength on sludge electro-osmotic dewatering performance and electrochemical effects were investigated. The solubilization and degradation of EPS were analyzed by examining the variation of dissolved organic matter (DOM) in the filtrate, and the relationships between microstructural properties of sludge cake and DOM and electro-osmosis dewatering performance in electro-dewatering process was examined. It was found that electro-dewatering properties were improved by raising the operating voltage or decreasing the pH value, while dewatering rate initially increased at low ionic strength it decreases with increased ionic strength. In addition, the porous structure of cathodic cake was more plentiful than that at the anode. At the cathode, the EPS dissolution was mainly related to alkalization, while the oxidation and acidification were responsible for release of EPS at the anode. Meanwhile, electrophoresis effect was able to promote migration of EPS toward the anode. The average electro-osmotic dewatering rate at the anode and at the cathode strongly correlated with the volume of pore of sludge cake. There was no correlation between the total content of anodic DOM and electro-osmotic dewatering rate at the anode, however, the content of cathodic DOM negatively correlated with average electro-osmosis dewatering rate of cathode. Since cathode is the main water-permeable side in sludge electro-dewatering, and the sticky biopolymers (proteins and humic subtances) could not be converted into small molecules, higher EPS release was associated with worse sludge filterability. As for the anode, the biopolymers were degraded into small molecules due to electrochemical oxidation, which greatly reduced the impact of DOM on dewatering effect.
       2. The effects of pretreatment of three typical inorganic coagulants (FeCl3, PAC and HPAC) in the process of electro-dewatering were analyzed. The results showed that the electro-dewatering rate at cathode were increased with the raised of the coagulants dosage, and the rate of electro-dewatering increased the most after conditioning by FeCl3. As the dosage of HPAC, PAC and FeCl3 increased, the zeta potential of the sludge raised. Sludge flocs formed by FeCl3 conditioning are denser than PAC and HPAC, and the increase of sludge electroosmotic strength is the largest. The inorganic coagulant compresses the EPS structure of sludge, which reduces the soluble EPS content and relieves the filter cloth blockage. FeCl3 has the strongest compression effect on EPS structure, and it has a more important effect on improving the sludge dehydration effect than improving the ionic strength EPS compression of sludge system
       3. The present study investigated the sludge electro-dewatering behavior and the heavy metal migration and transformation at varying operation conditions (voltage, ionic strength and chelating agent) during waste activated sludge electro-dewatering. Results indicated that increasing voltage improved the mobility of heavy metals, and electro-dewatering performance was improved by raising the ionic strength, The alkalization was enhanced at cathode and promoted the dissolution of EPS, which intensify the mobility of heavy metals bound with biopolymers, and the transformation ability of heavy metals in sludge cake from stable state to active state was enhanced. The addition of inorganic salts and chelating agents (citrate acid) promoted electro-dewatering of sludge, and changed the existing states of heavy metals in sludge and facilitate harmful heavy metal removal in sludge electro-dewatering. In addition, the content of heavy metals in cathodic filtrate is higher than that in anodic filtrate under different operating conditions due to the free heavy metals ions and positively charged complex heavy metals moved to the cathode chamber due to electro-migration.

Pages108
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42273
Collection环境水质学国家重点实验室
Recommended Citation
GB/T 7714
曹秉帝. 强化污泥电脱水过程及同步去除重金属机制的研究[D]. 北京. 中国科学院生态环境研究中心,2019.
Files in This Item:
File Name/Size DocType Version Access License
曹秉帝-强化污泥电脱水过程及同步去除重金(2502KB)学位论文 开放获取CC BY-NC-SAApplication Full Text
Related Services
Recommend this item
Bookmark
Usage statistics
Export to Endnote
Google Scholar
Similar articles in Google Scholar
[曹秉帝]'s Articles
Baidu academic
Similar articles in Baidu academic
[曹秉帝]'s Articles
Bing Scholar
Similar articles in Bing Scholar
[曹秉帝]'s Articles
Terms of Use
No data!
Social Bookmark/Share
All comments (0)
No comment.
 

Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.