基于四氧化三铁的强化混凝/过硫酸盐氧化体系的构建与深度处理垃圾渗滤液的耦合机制研究

Biotechnology has been extensively applied for the treatment of landfill leachate due to its low cost and simple operation. However, its effluent cannot always meet the national discharge permit since it cannot bear the shock loading and breaks down easily. Therefore, the followed advanced treatment is required and needs to be specific concentrated. The related research showed that coagulation and advanced oxidation are economic and effective technologies for treatment of leachate secondary effluent, while both of them are not effective enough to remove the residual contaminants in the leachate secondary effluent when used alone. Developing coupling process base on coagulation and advanced oxidation is the most economic and efficient technology for treatment of leachate secondary effluent at the present stage in China. In this project, ferroferric oxide nanoparticles with even good coagulation-supporting effect and efficient activation to persulfate are prepared by the modified hydrolysis method. Whereafter, it is respectively researched for the treatment of leachate secondary effluent by enhanced coagulation and persulfate catalytic oxidation based on ferroferric oxide. On the study basis of this, the coupling process of enhanced coagulation/ persulfate oxidation will be constructed and introduced into the treatment of leachate secondary effluent, which could couple the advantages of enrichment flocculation-catalysis oxidation-sedimentation removal. Dynamic processes of enhanced coagulation, persulfate oxidation, and enhanced coagulation/persulfate oxidation in the coupling system are systematically researched. Removal performance of the pollutants will be investigated and the coupling mechanism will be derived as well as response relationship. Finally, an economical and efficient advanced treatment technology with our country's characteristics will be developed to handle bottleneck problems like high cost and low efficiency emerging in treatment of leachate secondary effluent, which would provide a new approach for the treatment of leachate secondary effluent.

生物工艺是渗滤液处理的主流工艺，但其出水难以实现达标排放，需后续深度处理，研究表明混凝、高级氧化是渗滤液经济有效的深度处理技术，然而两者单独应用均难以保证污染物的有效去除，开发基于两者的耦合技术是现阶段我国渗滤液深度处理最经济、实效的技术之一。课题拟合成具有良好助凝作用、同时对过硫酸盐具有高效活化作用的纳米四氧化三铁粒子，进而分别开展四氧化三铁强化混凝、四氧化三铁催化过硫酸盐氧化处理渗滤液生化出水的实验研究；在此基础上构建强化混凝/过硫酸盐氧化体系，使之强化混凝和过硫酸盐氧化有机耦合，实现污染物富集絮凝-催化氧化-沉降去除在耦合体系中的优点集成；系统开展耦合体系的强化混凝、过硫酸盐氧化、强化混凝/过硫酸盐氧化动态过程和污染物去除途径的研究，揭示耦合机制及其响应关系；针对目前渗滤液深度处理遇到的处置效率低、运行成本高等瓶颈问题，开发适用于我国国情的深度处理技术，为其有效治理提供一种新途径。

针对垃圾渗滤液生化尾水中存在的残留污染物，项目组制备了纳米四氧化三铁粒子，研究了四氧化三铁强化聚合氯化铝PAC等传统絮凝剂的磁混凝技术处理垃圾渗滤液生化尾水的絮凝效果与絮凝机理，探讨了纳米四氧化三铁等含铁化合物催化过硫酸盐氧化处理渗滤液生化出水的影响因素与相关机制；构建处理渗滤液生化出水的了强化混凝/过硫酸盐氧化耦合体系，探讨了渗滤液中污染物去除途径，分析了耦合工艺中强化混凝与催化氧化的响应关系。本研究为渗滤液尾水的深度处理提供了一种新思路，并为持久性有毒污染物的消减提供了技术借鉴与参考，取得以下主要研究结果。第一，磁性复合絮凝剂MFPAC处理垃圾渗滤液生化出水有着更好的絮凝效果，COD和色度等特征污染物去除率更高；纳米四氧化三铁有效强化了PAC的絮凝效果，磁性纳米颗粒异相成核-絮凝剂絮体聚集是磁混凝的主要机制。第二，纳米四氧化三铁可有效活化过硫酸钠生成硫酸根自由基氧化降解渗滤液生化出水中有机物；氧化效果随着反应时间的延长、氧化剂量的增加而提高，低pH有利于催化氧化过程中硫酸根自由基的生成，进而有利于污染物的降解。第三，采用强化混凝/催化氧化耦合工艺处理垃圾渗滤液尾水，COD去除率可达到70%以上，色度几乎全部去除；对水样处理前后的微观表征分析可知，渗滤液生化出水中的残留污染物得到有效消减，强化混凝/催化氧化耦合工艺，实现了污染物的催化氧化-絮凝富集-沉降去除的优点集成。