【作者】 宋欣欣；

【导师】 南军；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2009， 硕士

【摘要】 悬浮颗粒物是水处理的主要去除对象,在处理及使用过程中,水中的颗粒物质数量、形态和特征都会发生变化。在水处理工艺中,常采用絮凝除浊的方法进行固液分离,即使水中胶体粒子以及微小悬浮物等杂质在混凝药剂作用下进行聚集,而后通过沉淀去除的过程。从本质上讲,絮凝方法是专门用以改变水中悬浮颗粒粒度分布的,即促使水中悬浮颗粒由粒径较小、数量较多逐渐演变为粒径较大、数量较少的状态,沉淀和过滤工艺也只能去除一定粒径范围的悬浮颗粒。浊度是水中悬浮颗粒浓度、大小、形状、颜色和表面特性等诸因素对光所产生各种影响的一个综合光学性质度量;颗粒计数则是直接测定水中悬浮颗粒数量及大小分布,两者检测原理的差异导致浊度与颗粒总数在一定范围内相关性较差。颗粒计数仪的出现为研究絮体粒度动态分布提供了有效的监测手段。将颗粒计数仪作为浊度仪的有益补充,两者联用,可有效地表征水处理的效果,保证供水安全。本课题采用颗粒计数技术为主要检测手段研究水中含有的悬浮物和胶体杂质颗粒数、大小等分布特征对浊度变化的影响规律。结果表明,水中颗粒物具有不均一性或多分散性,不同粒径的颗粒对浊度的影响不同,在多数情况下水中含有的稳态微颗粒难以由浊度值来生动体现,而颗粒计数仪可直接计数并确定颗粒物的大小,它较全面地提供了有关水中悬浮颗粒物特征的信息,能从细节方面提供水中悬浮颗粒体系的微观特性。分别采用颗粒计数法和图像法对不同水力和水质条件下絮体的大小、数量、离散度等物理性质对絮凝效果的影响进行了试验研究,发现絮体在水处理中的固液分离行为与絮体的分布密切相关。基于絮体分布的脉动现象提出絮凝基线波动值这个新概念,试验结果表明:絮凝基线波动值可以作为反映絮凝过程颗粒聚集(絮凝)状态的有效指标,其在不同水质条件下与剩余浊度之间均具有良好的相关性,能够很好地反映絮凝效果的变化。而通过将分形理论引入到絮体粒度分布规律的研究发现,采用粒度分形维数这一特征指标可以实现不同絮凝反应条件下所形成絮体的粒度分布对絮凝效果影响力的定量描述,其与沉后水小于5μm颗粒数间存在良好的相关性。将絮凝基线波动值与粒度分形维数特征指标联用,不但可以在实际水处理工艺生产运行中优化絮凝条件和改善絮凝效果,还可以针对性地降低处理后水中的稳态微颗粒数量,消除其对城市供水水质安全产生的隐患。更多还原

【Abstract】 In water treatment, suspended particle is one of the major removal targets, the quantity, configuration and characteristics of which all change in application process. Flocculation is usually used for solid/liquid separation process, in which small colloid and suspended particles are aggregated by adding flocculant, and, then, removed via sedimentation process. Essentially, flocculation is adopted to change size distribution of suspended particle, and it can turn a larger number of smaller particles into less amount of larger particles. Obviously, units of sedimentation and filtration can only remove a certain size range of suspended particles.Turbidity is an optical measurement of light scattered by the density, size, shape, color, surface characteristics of suspended particles in water. The particle counting is to calculate the number of suspended particles in water and measure their sizes. Due to their different testing principles, there is poor correlation between the turbidity and the particle population in a certain range. The particle counter has proven to be a useful instrument for studying the dynamic distribution of floc particles. Therefore, the particle counter can be used as a supplement to the turbidimeter. Combined use of the two instruments can effectively demonstrate the effect of water treatment and guarantee water safety.In this paper, particle counting technique was taken as the main detection method to investigate the influence of distribution characteristics of suspended and colloid particles, such as particle amount and size, on water tubidity. The results showed that particulate matter in the water had heterogeneity or dispersion nature, and particle population of various grain size ranges had different effects on turbidity. In most instances, steady-state micro-particles were hardly reflected vividly by turbidity, while particle counter could directly determine particule size. Simultaneously, it could more comprehensively provide information of suspended particle in the water, and reflect microcharacteristic of suspended particle system in detail.In addition, paticle counting and image analysis were respectively used to study the influence of floc physical properties, such as size, amount and dispersion, on flocculation efficiency under different hydrodynamic conditions and different water quality. It was founded that the behavior of flocs was closely related to floc size distribution during solid/liquid separation. Based on pulsation phenomena of floc size distribution, the concept of fluctuation value of flocculation baseline was proposed for the first time. The results showed that the new index could be effective to reflect the aggregation state of particles in flocculation process, and, under different water quality, it had a good correlation with residual turbidity, indicating that the index could reflect flocculation efficiency well. Moreover, fractal theory was introduced into floc size distribution, and fractal dimension of floc size distribution was also proposed. The experimental results showed that this index could quantify the influence force of particle size distribution on flocculation efficiency under different flocculation conditions. The results also displayed that there was a good correlation between fractal dimension of floc size distribution and less than 5μm particle population. Besides, associating application of fluctuation value of flocculation baseline and fractal dimension of floc size distribution could not only optimize flocculation conditions and improve flocculation efficiency, but also appropriately reduce the number of steady-state micro-particles after water treatment, and guarantee water quality in city, then remove hidden danger in time.更多还原