重金属废水化学沉淀颗粒污泥结构与深度脱水的关系

Hazardous sludge generated from heavy metal wastewater treatment possesses properties such as high water content, slow sedimentation, and poor dewaterability, presenting a significant risk of secondary pollution. With much more stringent environmental protection policies, the hazardous sludge problem has risen to a serious threat to the development of this industry. In our previous studies, a novel method for granular sludge formation during heavy metal wastewater treatment (HM-GS for short) was developed. Such HM-GS has excellent settling performance, but the water content of sludge cake after filtration is still high and its deep dewatering performance needs to be improved. Herein, this project includes the following three aspects: (i) study on the solid surface-scale behaviors of bound water adhesion in HM-GS in order to provide evidence for transforming bound water into free water effectively, (ii) investigation of pore-scale behaviors of water flow in HM-GS in order to guide the fast flow of free water, and (iii) establishing structural models for HM-GS deep dewaterability to ascertain the optimum of solid-liquid separation. All the studies are dedicated to clarify the influencing mechanism of HM-GS structure on dewaterability, providing groundwork for the advanced solid-liquid separation technology of HM-GS.

重金属废水国际上普遍采用化学沉淀法处理，形成絮状污泥危废沉降性差、含水率高，直接影响污泥安全处置，成为行业亟待解决的重大难题。申请人前期研究率先提出了沉淀污泥颗粒化技术，可大幅提高污泥沉降性能，但固液分离后污泥的含水率却居高不下。本项目以重金属废水化学沉淀颗粒污泥为研究对象，拟研究：①污泥固液界面结合水粘附作用机制，阐明结合水转化为自由水的固相介质表面及固液界面行为；②污泥孔隙(道)中自由水渗流迁移规律，揭示孔隙分布对自由水迁移与扩散的影响机制；③污泥深度脱水的结构模型，探究污泥含水率和脱水性能的可能极限。旨在阐明重金属废水化学沉淀颗粒污泥中水分粘附、转化、渗流的行为特征及其影响机制，形成污泥深度脱水新技术原型。

含重金属废水污水/废水处理会产生大量的污泥，包括生物污泥和无机污泥，深度脱水是制约其高效处理与处置的前提与关键环节。本项目制备和获取了5种具有不同宏观、微观及组成特征的典型重金属污泥作为研究对象，比较分析了其脱水性能差异。阐明了典型污泥颗粒表面特征及水分子粘附结合形态，为结合水的转化和脱除提供了理论依据。借助先进的Nano-CT技术，率先建立了污泥微观孔隙结构无损、原位分析方法，可真实呈现污泥中孔隙结构和水分渗流迁移规律，研究表明污泥孔隙度对流体渗透性的影响包括两个方面：一是大孔带来的高孔隙度拓宽了流通空间，激发水流流速；二是多孔带来的高孔隙度可增加渗流路径，促进水分的流通效率，这为指导实际污泥的孔隙分布调控提供了重要依据。基于Nano-CT对污泥孔隙结构的重构结果，结合微流体技术和COMSOL仿真模拟技术，建立了污泥孔隙水分迁移的可视化研究方法，国际上率先发现了无效连通孔对污泥深度脱水的决定性作用，分类阐明了盲端孔、收缩区域孔、细颗粒堆积孔对污泥中水分迁移流通的影响机制，为污泥深度脱水提供了新的发现和理论依据。项目按计划完成了相关研究，执行期内共发表SCI论文6篇（第一标注2篇），申请国家发明专利2项，培养博士研究生1人、硕士研究生1人，项目负责人入选中国科协第六届“青年人才托举工程”项目，圆满完成项目考核指标。