Ormeci Banu
Department of Civil and Environmental Engineering, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Water Sci Technol. 2008;58(7):1379-84. doi: 10.2166/wst.2008.724.
Shear intensity, shear time, and polymer dose are the main parameters that determine the dewaterability of wastewater sludge. Polymer dose required to condition the sludge increases with the increase of shear intensity (G) and shear time (t). Therefore, in order to minimize the polymer demand during conditioning and dewatering, shear should be optimized. Optimization of shear can be achieved if the total shear that the sludge network is exposed to during conditioning and dewatering can be measured and quantified. This is quite a challenge since total shear includes unintended shear introduced during piping and pumping, and currently there is no direct or indirect technique that can measure this unintended shear. Unintended shear increases the polymer demand and shifts the optimum polymer dose to a higher dose, which in turn decreases the cake solids concentration and the efficiency of the dewatering process. Thus, quantification of the unintended shear and adjustment of the polymer dose accordingly are essential for the optimization of dewatering processes. The main objective of this study was to develop a method for sludge shear measurement based on the rheological characteristics of sludge and illustrate its possible applications at treatment plants. The results of this study indicate that the rheological characteristics of sludge can be used to estimate an unknown amount of shear that sludge network is exposed to, and to match the jar-test mixing conditions to that of the full-scale mixers employed at treatment plants.
剪切强度、剪切时间和聚合物剂量是决定废水污泥脱水性能的主要参数。调理污泥所需的聚合物剂量随着剪切强度（G）和剪切时间（t）的增加而增加。因此，为了在调理和脱水过程中尽量减少聚合物用量，应优化剪切。如果能够测量和量化污泥网络在调理和脱水过程中所承受的总剪切力，就可以实现剪切的优化。这颇具挑战性，因为总剪切力包括管道输送和泵送过程中产生的意外剪切力，目前尚无直接或间接的技术能够测量这种意外剪切力。意外剪切力会增加聚合物用量，并将最佳聚合物剂量转移到更高的剂量，进而降低滤饼固体浓度和脱水过程的效率。因此，量化意外剪切力并相应调整聚合物剂量对于优化脱水过程至关重要。本研究的主要目的是基于污泥的流变特性开发一种污泥剪切测量方法，并说明其在处理厂的可能应用。本研究结果表明，污泥的流变特性可用于估计污泥网络所承受的未知剪切力，并使烧杯试验混合条件与处理厂使用的全尺寸混合器的条件相匹配。
