WRF: Experimental observation and modeling of coagulant mediated contaminant removal: flocculation, floc blankets, and sedimentation

PI名称：Monroe L.Weber-ShirkProposal编号：1704472絮凝是用于将河流、溪流和水库的水转化为安全饮用水的核心过程。在絮凝过程中，颗粒和一些溶解的污染物粘在一起，形成大的聚集体，可以通过沉淀去除。虽然絮凝是地表水处理的主力，但人们对它的了解并不充分，因此无法优化国家饮用水处理基础设施的设计。PIS计划详细调查在减少混合条件下运行的颗粒聚集机制(锥形絮凝)，以此作为一种通过去除饮用水处理中的颗粒来提高性能的技术。初步研究表明，建议的锥形絮凝设计有可能将过滤器的污染物负荷降低10倍，这将显著降低饮用水处理的运行和维护成本。PI产生的模型表明，以沉淀水浊度衡量的絮凝性能是当前处理工艺序列的最重要限制因素。在絮凝过程中，随着絮凝过程的进行，絮凝颗粒之间不断增加的分离距离限制了高速絮凝/沉淀产生颗粒浓度小于几mg/L的水。本研究的主要目的是通过逐步降低混合强度来降低碰撞时刻颗粒的相对速度，从而增加絮凝颗粒的数量。速度梯度的减小使以前达到最大尺寸的聚集体能够成功地与较小的粒子发生碰撞。因此，每减小一次流体变形率，生长颗粒之间的距离就减小一次，并且不可沉降颗粒有额外的机会转变为可沉降颗粒。实验将在不同流速和成像能力的中试处理厂进行。这些实验装置具有改变速度梯度和成像絮体的组合能力，以确定进水和出水中的粒度分布。该实验设计能够研究水力絮凝器和絮凝毯絮凝器中不同停留时间、速度梯度和能量耗散率的渐变絮凝，以确定最佳的絮凝设计。在该项目下进行的研究将被整合到康奈尔？S·阿瓜克拉拉计划中，该计划于十多年前启动，旨在开发低成本的水处理技术，使社区能够自筹资金并可持续地运营市政水处理厂。锥形絮凝技术有可能显著降低高质量水处理的成本，并使低成本处理厂的发展成为可能，以保护尚无法获得安全饮用水的约20亿人的健康。

PI Name: Monroe L. Weber-ShirkProposal Number: 1704472Flocculation is a core process used to convert water from rivers, streams, and reservoirs into safe drinking water. In the flocculation process, particles and some dissolved contaminants stick together and form large aggregates that can be removed by sedimentation. Although flocculation is the workhorse of surface water treatment, it is not well understood, and thus it has not been possible to optimize the design of the nation's drinking water treatment infrastructure. The PIs plan a detailed investigation of particle aggregation mechanisms that operate under decreasing mixing conditions (tapered flocculation) as a technique to enhance performance as measured by particle removal in drinking water treatment. Preliminary studies indicate that the proposed tapered flocculation design has the potential to decrease contaminant loading to filters by a factor of 10, which would significantly reduce operation and maintenance costs for drinking water treatment.Models produced by the PIs indicate that flocculation performance as measured by settled water turbidity is the most significant limiting factor for current treatment process sequences. In flocculation the increasing separation distance between flocculating particles, as the flocculation process proceeds, limits high rate flocculation/sedimentation from producing water with particle concentrations less than a few mg/L. The primary goal of this investigation is to increase the number of particles flocculating by lowering the relative velocity of particles at the moment of collision through a stepwise decrease in mixing intensity. A decrease in velocity gradient enables aggregates that had previously reached maximum size to have successful collisions with smaller particles. Thus, each time the fluid deformation rate is decreased, the distance between growing particles is decreased, and non-settleable particles have an additional opportunity to be transformed into settleable particles. Experiments will be carried out on pilot treatment plants with differing flow rates and imaging capacities. These experimental units have the combined capacity to vary velocity gradients and image flocs to determine size distribution in both influent and effluent. This experimental design has the capability to investigate tapered flocculation in hydraulic and floc blanket flocculators with varying residence time, velocity gradients, and energy dissipation rates to determine optimal flocculation design. The research performed under this project will be integrated into Cornell?s AguaClara program, which was initiated over a decade ago for developing low-cost water treatment technologies so that communities can self-finance and sustainably operate municipal water treatment plants. The tapered flocculation technology has the potential to significantly lower the cost of high quality water treatment and enable the development of lower cost treatment plants to protect the health of the approximately two billion people who do not yet have access to safe drinking water.