1、分析重力过滤水厂的污泥沉降试验摘要：在恒压条件下，对市政水厂进行了重力沉降实验和重力过滤实验。理论分析中明确指出，污泥的沉淀对过滤率有明显影响。当地不同的流动阻力决定了不同污泥浓度的沉降速率。固体的沉淀特征和当地的孔隙率与该地区固体抗压压力有关。从沉降速率和沉降平衡的基础数据上评估了重力过滤与过滤率的关系。关键词：压缩特性;重力过滤;渗透特征，沉积;水厂污泥 一 引言重力过滤是固液分离的一个潜在的操作方法，只涉及简单设计和运行。这种方法对悬浮物的过滤尤其有效，在驱动力不大的情况下很容易达到分离效果。例如，在自来水厂污泥分离的过程中，增加重力增稠剂，可大大改善分离效果。以往的研究都集中在一般的加
2、压过滤。因此，没有多少人注重重力过滤的行为。沉积过程中悬浮的粒子，经常导致滤饼的过滤速率发生变化。特别是，在大多数情况下，重力过滤的沉淀颗粒悬浮效果显着。因此，重力过滤行为的分析，必须考虑到颗粒沉淀效果。通过调查了向上和向下加压过滤的沉淀效果和其发展的理论模型来描述通量下降的行为。此外，过滤密切相关的问题是沉积作用中有相似粒子的溶剂和渗透溶剂通过填料床的颗粒越大。在此假设的基础上，根据压缩的压缩饼渗透率，当地的孔隙率和当地固体压缩压力Ps的具体流动阻力，来做重力沉降实验。结果表明，从传统的压缩渗透率数据中得到，在固体压力相对低的地方压缩渗透性能很好。还应该指出，这是相当困难的情况下在压缩细胞通
3、透性较低的条件下取得的结果。通过应用超滤方法，使用压缩渗透与超速离心机分析评估了蛋白质溶液超滤通量衰减行为。最近，用离心机对O/ W乳液油滴的压缩变形渗透特性进行了评价分析，据预计，在相对低压条件下评估重力过滤，得到重力沉降压渗透特性使用方便。在这篇文章中，对市政自来水厂污泥进行批次重力过滤和重力沉降实验，以及关于重力沉降粒子对过滤行为的影响进行了调查，以评估的滤饼平均过滤比阻。其次在压缩渗透的基础上，针对重力沉降用沉降速度发和沉淀平衡法代替传统的重力沉降粒子测量。利用压缩渗透的特点对重力过滤的过滤率下降行为进行评价。二 材料与方法材料在Kasugai水厂，增加污泥增稠剂对悬浮颗粒进行研究。硫
4、酸铝中加入无机混凝剂作为增稠剂，测量用比重瓶，质量分数S的悬浮固体和固体的真密度s，分别是4.6810-3 kg/m3和3.35103 kg/m3。用激光散射粒度分布仪对污泥的固体颗粒粒度分布进行了分析，测量结果如图一所示，直径dp与频率f 为正态分布关系。由于混凝剂的使用，分布明显变广，颗粒的平均比表面积大小是65.8微米。用超纯水稀释过的污泥进行试验。图一： 重力沉降在直径为4.5厘米的垂直有机玻璃圆筒内进行重力沉降批次实验。在实验开始之前开始,将污泥确保混合均匀,然后缓慢倒入一个沉降气缸。测量沉积物与上清液之间的高度，所用时间沉淀时间和悬浮颗粒浓度，一个星期后测量最终平衡高度。测量沉淀速
5、率的方法是，通过对沉淀物的高度变化与时间数据来分析，确定沉淀速率。与此同时，在沉淀平衡方法中，用平衡状态下统一泥沙高度进行分析。重力过滤研究中采用的重力过滤器如图二所示，垂直气缸内径和沉淀试验采用的相同。采用的过滤介质为非织造，平均孔径大小为9m，污泥瞬间被充分搅拌，并倒入汽缸中，开始重力过滤。同样数量的纯水作为排放滤液添加，不断从污泥表面进入气缸。因此，试验过程中重力过滤驱动器始终保持顶部高度不变，如图所示。图 2 重力过滤装置结论市政自来水厂污泥重力沉降过滤实验采用批次实验，以研究有关对重力过滤通量衰减行为的粒子沉淀效果。结果清楚地表明,形成滤饼的平均过滤比阻在中立的条件下可精确的显示离子
6、的沉降水平。压缩渗透的特点，代表了当地的具体流动阻力和当地固体压缩压力函数的孔隙率，这一切都基于从最终的泥沙淤积试验取得的沉积速度数据和综合平衡高度。据重力过滤显示，通量下降的现象是通过对渗透特性所得的沉降数据进行良好的计算所获得的。Analysis of Gravity Filtration Behaviors of Waterworks Sludge Based upon Sedimentation TestsAbstractBoth gravity filtration experiments under constant pressure conditions and gravity
7、sedimentation experiments were conducted using the municipal waterworks sludge. It was clarified from the theoretical analysis that the effect of sedimentation on the filtration rate was noticeable for the sludge used in this study. The local specific flow resistance at various sludge concentrations
8、 was determined by the sedimentation velocity method. The local porosity was related to the local solid compressive pressure by the sedimentation equilibrium method. The decline behaviors in the filtration rate in gravity filtration accompanied by sedimentation were well evaluated only from the sedi
9、mentation data based upon the sedimentation velocity method and the sedimentation equilibrium method.Keywords:Compression characteristics; Gravity filtration; Permeability characteristics; Sedimentation; Waterworks sludgeINTRODUCTION Gravity filtration is one of the potential solid-liquid separation
10、 methods because of the energy-savings involving the simple design and operation. The method is especially efficient for suspension, which is relatively likely to be filtered since the available driving force of separation is not so high. For instance, in the concentration process of waterworks slud
11、ge, the separation efficiency may be significantly improved in the case that the space in the gravity thickener is used for gravity filtration. Previous studies have concentrated on the usual pressurized filtration. Hence, not much is known about the behaviors of gravity filtration.1The process of s
12、edimentation of particles in suspension above the filter cake frequently results in a variation of the filtration rate in filtration. 2-7 Especially, in gravity filtration, the effect of sedimentation of particles in suspension is remarkable in most cases.1 Therefore, the effect of particle sediment
13、ation must be taken into consideration in the analysis of the gravity filtration behaviors. Iritani et al.8 investigated the effect of sedimentation on properties of upward and downward pressurized filtration and developed the theoretical model to describe the flux decline behaviors.In addition, the
14、re is an analogy between sedimentation of particles in a solvent and permeation of a solvent through the packed bed of particles, which is closely related to filtration. On the basis of this hypothesis, the compression-permeability characteristics of the compressed cake, which represent the local po
15、rosity and the local specific flow resistance as functions of the local solid compressive pressure ps, are obtained from batch gravity sedimentation test.9, 10 It was shown that the compression-permeability characteristics in the relatively low solid compressive pressure region obtained from the sed
16、imentation test were well correlated to those obtained from the conventional compression-permeability cell data.11 It should also be noted that it is quite difficult to obtain the compression-permeability characteristics under relatively low pressure conditions by the compression-permeability cell test. By applying the method to ultracentrifugation, Iritani et al. evaluated
