排泥水絮体“高强度破碎-再絮凝”过程中镉的迁移转化及强化去除

Though the reuse of waste water in drinking water plant can not only save water resource, but also reduce the pollution of water environment, it will result in quality risk of drinking water because of the accumulation of pollutants within drinking water plant during the treatment process of waste water. More attention should be paid to cadmium since its risk has such characteristics as long-term and concealment. Up to date more attentions were paid to the remove of suspended solids from waste water of drinking water plant, however, little is known about the migration, transformation and remove of dissolved pollutants, e. g. cadmium. Based the study of “high strength broken-recoagulation” process of floc during waste water reuse treatment as cut-in point, this project will carry a series of static and dynamic simulation experiments, combined with FTIR, NMR, GC-MS, XRD and TPD. Microcosmic structural features and surface characteristics of flocs during “high strength broken-recoagulation” process are studied; the occurrence mode of cadmium and the distribution of active adsorption points to cadmium on floc surface are discussed; the cadmium’s migration and transformation regular between solid and liquid during “high strength broken-recoagulation” process will be revealed. At last, enhanced remove method of cadmium from waste water will be established and optimal operation conditions of the method will be obtained. The research will provide a theoretical basis on and technical support to cadmium risk control during the reuse of waste water in drinking water plant, and ensure the safety of drinking water quality in cities.

自来水厂排泥水的回用可以节约水资源、减轻水环境污染，但同时也会导致污染物在水处理工艺中的累积，从而引发供水水质风险。其中，镉的风险由于其隐蔽性和长期性，尤为值得关注。当前针对排泥水的研究较多关注悬浮物质，而对于溶解性污染物如重金属镉等的迁移转化和去除认识不足。本项目以排泥水回用处理工艺中絮体的“高强度破碎-再絮凝”过程研究为切入点，通过静态和动态模拟实验，借助傅里叶转化红外光谱、核磁共振、气相色谱-质谱、X射线衍射和程序升温脱附等分析手段，研究“高强度破碎-再絮凝”过程中絮体微观结构特征和表面特性变化；探讨排泥水絮体中重金属镉的赋存形态和表面镉活性吸附位点分布规律；阐明“高强度破碎-再絮凝”过程中镉在固液两相间的迁移转化规律；建立排泥水中镉的强化去除方法，并获得优化运行工艺条件。该研究可为排泥水回用中镉风险控制提供科学的理论指导和直接的技术支持，保障城市供水水质。

自来水厂排泥水的回用可以节约水资源、减轻水环境污染，但同时也会导致污染物在水处理工艺中累积，从而引发供水水质风险。其中，镉风险由于其隐蔽性与长期性，尤其值得关注。当前对排泥水的研究较多关注悬浮物质，而对溶解性污染物如重金属镉等的迁移转化和去除认识不足。本项目以排泥水回用处理工艺中絮体的“高强度破碎-再絮凝”过程研究为切入点，研究排泥水“破碎-再絮凝”过程中镉在上清液与污泥中的迁移转化，主要成果如下：1）探明排泥水絮体中重金属镉的赋存形态规律，主要以铁锰氧化物结合态存在，占总镉量的53.2%~56.7%。2）阐明“高强度破碎-再絮凝”过程中絮体微观结构特征和表面特性变化规律，破碎后絮体颗粒变小，比表面积增大，絮体絮凝核心附近未饱和吸附点位暴露。3）揭示了镉在排泥水固液两相间的迁移转化规律，破碎阶段，主要以铁锰交换态和离子交换态之间的相互转化为主，迁移转化结果为液相向固液迁移；最佳破碎强度包括转速600 rpm，时间小于20 min；浓缩阶段则以铁锰氧化物结合态和离子交换态镉向有机结合态转化为主。4）建立了排泥水中镉的强化去除方法，即“短时高强度破碎-PAM强化再絮凝”技术，优化条件包括高强度破碎2 min，强度600 rpm； PAM投加量4~8 mg/L，再絮凝时间10 min。上述可为排泥水回用中镉风险控制提供科学的理论指导和直接的技术支持，保障城市供水水质。