Particulate Fluids Processing Centre, Department of Chemical and Biomolecular Engineering, The University of Melbourne, 3010, Australia.
Water Res. 2015 Oct 1;82:37-46. doi: 10.1016/j.watres.2015.04.004.
Water and wastewater treatment sludges exhibit compressible behaviour due to flocculation and aggregation. At a critical solids concentration called the gel point, which is as low as 1-2 v/v%, a continuous interconnected network of particles is formed that can resist an applied load. The applied load (mechanical filtration pressure or buoyancy in settling for example) must exceed the network strength in order to consolidate the network. The network strength increases with solids concentration such that the equilibrium extent of consolidation is a function of the applied load. Improved understanding of the nature of compressible suspensions can have a significant impact through optimising design and operation of sludge handling and dewatering processes. This work gives an overview of compressional rheology, which has proven to be a useful tool for describing the solid-liquid separation of compressible systems. This is followed by three examples where compressibility effects must be taken into account, namely the extraction of material properties for extremely compressible materials, consolidation and crust formation during constant rate evaporation, and the effect of bed height in thickening.
污水处理厂的污泥由于絮凝和聚集而表现出可压缩性。在一个称为凝胶点的临界固体浓度下，固体浓度低至 1-2v/v%，形成了连续的颗粒相互连接的网络，能够抵抗施加的负荷。为了使网络固结，施加的负荷（例如机械过滤压力或沉降中的浮力）必须超过网络强度。网络强度随固体浓度的增加而增加，因此固结的平衡程度是施加负荷的函数。通过优化污泥处理和脱水过程的设计和操作，更好地了解可压缩悬浮液的性质可以产生重大影响。这项工作概述了压缩流变学，它已被证明是描述可压缩系统固液分离的有用工具。接下来是三个必须考虑可压缩性影响的示例，即极其可压缩材料的材料特性提取、恒速蒸发过程中的固结和结壳形成，以及增稠过程中床层高度的影响。
