污泥电渗透压滤脱水过程中EPS溶解的区域化特征及其对有害污染物迁移转化的影响

Sludge treatment and disposal has become is one of hot environmental issues in China. Highly effectively dewatering process is an important way to reduce the sludge amount to be disposed and relieve the rapid growth pressure of waste sludge, it is also a crucial and common technical demand for overcoming the obstacles in sludge recycle. In comparison to traditional sludge dewatering processes, pressure electro-dewatering has many advantages on high sludge dewatering efficiency, low conditioners dosage, and cake is beneficial to further recycling of waste sludge. In general, complex electrochemical effects (eg. ohmic heating, electrochemical oxidation and reduction and pH gradient effect) are accompanied by electro-dewatering process. These electrochemical effects will inevitably affect the key constituents-chemical characteristics of extracellular polymeric substances (EPS) and consequently migration and transformation behavior of harmful pollutants in waste sludge. This project will take the horizontal electric field assisted pressure dewatering as research object, aims to: (1) investigate the compartmentalization characteristics of EPS solubilisation-release characteristics under various electro-dewatering conditions (operating conditions of electric field and sludge solution chemistry); (2) explore the forms transformation and migration behavior of harmful heavy metals; (3) get insights into solubization, oxidative degradation and transferring process of typical emerging organic contaminants (EOCs) based on the understanding of their physicochemical properties, finally unravel the effects and mechanisms of EPS variation on transformation and migration process of harmful pollutants in sludge. Project achievements are expected to accelerating technical progress of electro-dewatering and promote sludge recycle level in China.

污泥处理处置已成为我国当前的热点环境问题之一。开发污泥高效脱水工艺不仅是实现污泥减量、缓解污泥快速增长压力的重要方式，也是打破我国污泥资源化瓶颈的关键共性技术。相比传统脱水工艺，电渗透辅助-压滤技术具有脱水效率高、调理剂投加量低和有利于污泥资源化利用等优势。电渗透脱水过程伴随着一系列复杂的电化学效应（如欧姆热效应、氧化还原和pH梯度效应等），这必然影响剩余污泥的关键组分—胞外聚合物（EPS）的化学性质和有害污染物的迁移转化行为。本申请课题以水平电场辅助-压滤污泥脱水过程为研究对象，拟深入解析不同电场运行参数和污泥溶液化学条件下EPS溶解释放的区域化特征，探究农用控制重金属的形态转化和迁移行为，同时结合典型新兴污染物（EOCs）的理化性质，明确其溶解、氧化和转移过程，在此基础上揭示EPS变化对有害污染物迁移转化的影响作用机制。项目成果有望推动电渗透脱水技术的进步，提升我国污泥资源化利用水平。

污泥是由微生物细胞、胞外聚合物（Extracellular Polymeric Substances, EPS）、无机矿物等组成的高度异质化聚集体，其含水率一般在90%以上，具有触变性、高度可压缩、难脱水等特点。本项目探究了电渗透脱水条件（电场运行条件、污泥性质和化学预调理）对EPS溶解释放区域化特征的影响机制，考察了混凝剂、炭基材料助滤对污泥电渗透脱水效能的影响，探究了揭示了电渗透脱水过程中不同重金属形态转化和迁移规律。项目主要取得了以下进展：基于电辅助污泥脱水的微界面调控原理，揭示了电压、pH值和离子强度对电化学效应和污泥电脱水性能的影响作用机制，发现污泥电渗透脱水过程中两极的EPS转化具有显著的差异性，阳极氧化导致EPS降解作用可以促进电渗透脱水过程，而阴极碱化作用导致EPS溶解，污泥过滤性能恶化。电脱水运行参数(电压、pH值和离子强度)主要通过调控电化学反应来影响电渗透设备不同区域的EPS溶解和降解过程，进而对污泥电渗透脱水行为和重金属迁移转化产生影响。在此基础上，提出了污泥电渗透脱水耦合重金属去除/燃料化处理的工艺技术：第一，针对较高浓度重金属污染的污泥，通过调节污泥溶液化学性质和投加有机酸络合剂，实现电化学效应与络合作用的协同耦合，达到污泥中重金属强化分离的目的；第二，通过引入石墨化炭基材料以强化电脱水过程中电子传递，提高泥饼的导电性能，协同炭基材料的骨架助滤作用和EPS吸附作用改善污泥脱水性能。项目总计发表SCI论文34 篇；申请专利6 项，授权3 项；完成学术专著1部（正在出版中）。