基于污泥高压脱水的化学预调理反应机制研究
文献类型：学位论文
| 作者 | 张伟军 |
| 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 | 王东升 |
| 关键词 | 活性污泥，深度脱水，胞外聚合物（EPS），化学调理，絮凝，氧化， |
| 其他题名 | Reaction mechanisms of chemical pre-conditioning methods for sludge high-pressure dewatering process |
| 学位专业 | 环境工程 |
| 中文摘要 | 污水生化处理过程中会产生大量的剩余污泥，这些污泥的含水率通常超过99%。开发高效的污泥脱水工艺是缓解污泥快速增长压力的一种重要方式，也是当下中国环境工程领域研究的热点方向。目前，国内污泥深度脱水的主流方式为高压过滤，而化学预调理的选择直接决定了最终的污泥脱水干化效率。 本文研究了不同化学调理方式对污泥脱水性能的改善效率，着重解析了调理反应过程对污泥絮体理化性质的影响机制。研究的主要内容和结果如下： 1. 研究了三种典型无机混凝剂（FeCl3、PAC和HPAC）调理过程中污泥絮体结构和胞外聚合物（Extracellular polymeric substances, EPS）分布的动态变化过程及其与脱水性的关系。结果表明，化学调理后污泥絮体粒径和分形维数均增加，说明调理后的污泥絮体更大且结构强度更高。相比无机聚合物混凝剂，FeCl3 调理后的污泥颗粒小但结构更加紧实。无机混凝剂对活性污泥的调理过程中可以分为两个阶段：电中和效应诱导的污泥胶体颗粒的快速聚集和伴随着混凝剂水解引起的双电层压缩使得絮体致密化过程。此外，化学调理后，污泥比阻（SRF）与溶解性EPS（SEPS）、疏松结合型EPS（LB-EPS）和紧密结合型EPS（TB-EPS）含量表现出显著的相关性，而与动力粘度（KV）、絮体分形维数（DF）和粒径分布无关。说明无机混凝剂对EPS的压缩效应是污泥脱水性改善的主要机理。 2. 采用三维荧光光谱（3D-EEM）和高效体积排阻色谱（HPSEC）研究了两种无机聚合物混凝剂（PACl和HPAC）调理过程中溶解性EPS的变化特征。无机混凝剂对分子量超过2000Da 的EPS具有良好的去除效果，而这些高分子物质是决定污泥脱水性的关键因素。同时，无机高分子混凝剂调理过程中，SRF和不同荧光区域EPS存在极强的相关性。上述结果说明3D-EEM可以作为SRF的替代方法，作为无机混凝剂调理污泥效果的快速评价手段。 3. 评价了Fenton氧化对厌氧消化污泥脱水性的改善效果，同时解析了酸化和Fenton氧化对污泥SEPS特性的影响。Fenton调理可以有效降低污泥的毛细吸水时间（CST）值和离心脱水后泥饼含水率。同时，酸化和Fenton氧化表现出明显协同效应。3D-EEM分析结果显示，酸化过程不仅会溶解EPS组分，同时会破坏蛋白类有机物的分子结构，导致其荧光强度明显降低。最佳的Fenton处理条件为pH=4、过氧化氢=0.3%（v/v）、亚铁和过氧化氢摩尔比=0.1。在调理过程中，污泥EPS的溶解和降解是同步发生的。Fenton氧化对类蛋白物质的降解和去除是脱水性改善的主要机理。 4. 研究了高铁酸钾（K2FeO4）对处理活性污泥脱水性的效果，重点考察了不同pH和剂量条件下，K2FeO4调理对污泥过滤脱水特性和胞外聚合物（EPS）分布和组成的影响，从而深入认识了K2FeO4调理污泥的反应机制。实验发现降低pH值使得污泥脱水性逐渐改善，pH主要通过影响污泥EPS来改变污泥的脱水特性。由于不同pH值条件下质子化和去质子过程，EPS会发生压缩和扩张作用，所以碱性条件下总的可提取EPS含量要高于酸性环境中。K2FeO4调理效果随pH值降低而改善，其不仅有氧化裂解作用导致结合型EPS释放，同时其原位产生的三价铁离子兼具混凝作用，能够通过电中和界面吸附去除部分SEPS，同时压缩EPS，增强污泥絮体结构。此外，当pH值为3，K2FeO4投加量为0.1g/gTSS，污泥过滤脱水速率和效率均达到最佳。过量投加K2FeO4（>0.2g/gTSS）会导致EPS大量释放，增加的污泥过滤阻力，脱水性能随之恶化。 5. 采用过氧乙酸（PAA）预氧化裂解和化学絮凝过程实现污泥减量和强化其过滤脱水性能的双重目标，同时深入解析了组合调理过程中污泥絮体形态特征和EPS性质的变化特征。研究发现PAA处理对污泥可滤性影响不大，但有效提高了过滤脱水泥饼的含固率。PAA能够有效溶解污泥，破坏EPS中的蛋白质类有机物，促使结合水释放。随着pH值的降低，PAA对污泥脱水性的改善效果更佳，酸性环境有效提高了PAA对污泥EPS的氧化效率。投加无机混凝剂后，污泥絮体重新形成，同时污泥过滤性和脱水性也随之改善。另外，由于具有更强的吸附架桥能力，聚合氯化铝（PACl）在改善脱水性方面的效果优于氯化铁。 |
| 英文摘要 | Wastewater treatment processes produce large quantities of sludge commonly containing over 99% water. Development of high-performance dewatering process is the important way to relieve the pressure of rapid increase in waste activated sludge production and also is a hot issue in the field of environmental engineering in China. Currently, the mainstream technology for activated sludge deep dewatering is high-pressure compression filtration process, and the final drying performance is mainly dependent on selection of chemical pre-conditioning technologies. This study investigated the effect of different chemical conditioning technologies on sludge dewatering properties and elucidated conditioning reaction conditions on physicochemical characteristics of sludge floc. Main contents and results of this dissertation are as follows: 1. We investigated the effects of chemical conditioning with three typical inorganic coagulants (FeCl3, PAC and HPAC) on structural characteristics of sludge flocs in relation to sludge dewaterability. It was found that both and fractal dimension and floc size were increased with addition of inorganic coagulants, indicating larger and more rigid floc produced after chemical conditioning. The floc conditioned with FeCl3 was smaller but denser than that of PACl and HPAC. The conditioning process included the rapid aggregation of sludge particles induced by charge neutralization and bridging followed by floc densification caused by double electric layer compression. Furthermore, sludge dewaterability correlated well with the change in concentration of soluble EPS, LB-EPS and TB-EPS, but not with KV, DF, floc size. EPS compression was the major mechanism for improvement of sludge dewatering performance in inorganic coagulants conditioning. 2. The effects of chemical conditioning with inorganic coagulants on SEPS were investigated with three-dimensional fluorescence spectroscopy (3DEEM) and high performance size exclusion chromatography (HPSEC). The organic matters with larger molecular weights (>2000Da) might play a more important role in sludge dewatering, which could be easier to be removed from aqueous phase. Strong correlation was found between fluorescent intensity of protein-like peaks and SRF during chemical conditioning. Thus, monitoring these physicochemical parameters of sludge liquor might be an alternative way to evaluate sludge dewatering performance and optimize the dosage of inorganic coagulants in sludge conditioning process. 3. The sludge conditioning efficiency of Fenton process for improving anaerobic digested sludge dewaterability was evaluated. Conversion of SEPS composition was analyzed in detail under acidification and Fenton treatment. Fenton oxidation can effectively reduce sludge CST values and the moisture content of centrifuged cake. Meanwhile, acidification and Fenton oxidation showed significant synergies. EEM analysis showed that the acidification process will not only lead to dissolve EPS will also destroy the molecular structure of the protein, resulting in decreased fluorescence intensity. Optimum conditions of Fenton process is pH = 4, the hydrogen peroxide = 0.3% (v / v), and molar ratio of hydrogen peroxide and iron = 0.1. During oxidation process, sludge EPS dissolution and degradation occur synchronously. Fenton oxidation is the main mechanism to improve dewaterability, because degradation and removal of protein-like substances in EPS. 4. We focused on activated sludge conditioning efficiency with potassium ferrate (K2FeO4), emphasizing on investigating pH effect and the dosage of potassium ferrate on sludge filtration dewatering characteristics with the aim to get insights into the sludge conditioning reaction mechanism. The result indicated that sludge conditioning efficiency with ferrate was improved with decrease in pH. Ferrate can solubilize EPS through oxidation process and also remove a portion of soluble EPS (SEPS) by charge neutralization and interfacial adsorption of hydrolyzed ferric ions, consequently compressing EPS and decreasing total extractable EPS content. In addition, when pH and potassium ferrate were 3 and 0.1g/gTSS, both sludge filtration dewatering rate and drying performance reached the maximum. Overdosed potassium ferrate (>0.2g/gTSS) resulted in release of large amount of bound EPS, consequently increase in filtration resistance and deterioration of dewatering property. 5. The peracetic acid lysis and chemical re-flocculation was used to achieve reduction and dewaterability enhancement of waste activated sludge. The dynamic variation in sludge floc morphology and distribution and composition of EPS was investigated in depth. The results indicated that PAA treatment had very limited effect on sludge filterability, while filtration drying performance was effectively improved. PAA could effectively solubilize the sludge particle and destroy the protein-like substances, resulting in release of bound water. Sludge dewatering property was enhanced with decrease in pH level after PAA oxidation, this is because oxidative ability of PAA was higher under acid conditions. No integral sludge floc could be observed after treatment with PAA at high dosages. Floc reformed after addition of inorganic coagulants; meanwhile both filterability and dewaterability were improved. Furthermore, PACl performed better in improving sludge dewatering performance due to high adsorption and bridging abilities. |
| 源URL | [http://localhost/handle//34473]  |
| 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 | 张伟军. 基于污泥高压脱水的化学预调理反应机制研究[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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