Large quantities of sludge is generated from different sections of a wastewater treatment plant operation. Sludge can be a solid, semisolid or liquid muddy residual material. Understanding the flow behaviour and rheological properties of sewage sludge at different sections of a wastewater treatment plant (WWTP) is important for the design of pumping system, mixing, hydrodynamics and mass transfer rates of various sludge treatment units, optimization of conditioning dose and for sustainable sludge management. The current article provides a comprehensive review on up to date literature information on rheological behaviour of raw primary sludge, excess activated sludge, thickened excess activated sludge, mixture of raw primary and thickened excess activated sludge (mixed sludge), digested sludge, and biosolid under the influence of different operating parameters and their impacts on process performance. The influences of various process parameters such as solid concentration, temperature, pH, floc particle size, primary to secondary sludge mixing ratio, aging and conditioning agent doses on the rheological behaviour of sludge from different treatment units of WWTPs are critically analysed here. Yield stress was reported to increase with increasing solid concentration for all types of sludge whereas viscosity showed a decreasing trend with decreasing total solid concentration and percentage of thickened excess activated sludge in the mixture. Temperature showed an inverse relationship with yield stress and viscosity. Viscosity was reported to be decreased with decrease in pH. The effect of various conditioning agents on the rheological behaviour of sludge are also discussed here. The applicability and practical significance of various rheological models such as Bingham, Power Law (Ostwald), Herschel-Bulkley, Casson, Sisko, Careau, and Cross models to experimental rheological characteristics of various sludges were presented here. The reported results on various rheological parameters such as shear stress, yield stress, flow index, infinite, zero-rate viscosity, and flow consistency index of different sludge types obtained from the best fitted model were also compiled here. Conclusions have been drawn from the literature reviewed and few suggestions for future research direction are proposed.

废水处理厂运营的不同部分会产生大量污泥。污泥可以是固体，半固体或液体的泥状残留物。了解污水处理厂（WWTP）不同区段的污水污泥的流动行为和流变特性对于泵送系统的设计，各种污泥处理单元的混合，流体动力学和传质速率，优化调节剂量以及实现可持续发展非常重要。污泥管理。当前文章全面回顾了有关原始初级污泥，过量活性污泥，稠化过量活性污泥，原始初级污泥和稠化过量活性污泥（混合污泥），消化污泥的流变行为的最新文献资料。和生物固体在不同操作参数的影响及其对工艺性能的影响。本文重点分析了各种工艺参数，如固体浓度，温度，pH，絮凝物粒度，一次污泥与次要污泥的混合比，老化和调节剂的用量对不同污水处理厂污泥流变行为的影响。据报道，对于所有类型的污泥，屈服应力都随着固形物浓度的增加而增加，而粘度却随着总固形物浓度的降低和混合物中过量活性污泥的增稠百分比的降低而呈现下降趋势。温度与屈服应力和粘度呈反比关系。据报道粘度随pH降低而降低。本文还讨论了各种调节剂对污泥流变行为的影响。本文介绍了各种流变模型的适用性和实际意义，例如宾厄姆，幂律（Ostwald），Herschel-Bulkley，Casson，Sisko，Careau和Cross模型对各种污泥的实验流变特性。此处还汇总了从最佳拟合模型获得的各种流变参数（例如剪切应力，屈服应力，流动指数，无限，零速率粘度和不同污泥类型的流动一致性指数）的报告结果。从回顾的文献中得出了结论，并为未来的研究方向提出了一些建议。本文介绍了各种流变模型的适用性和实际意义，例如宾厄姆，幂律（Ostwald），Herschel-Bulkley，Casson，Sisko，Careau和Cross模型对各种污泥的实验流变特性。此处还汇总了从最佳拟合模型获得的各种流变参数（例如剪切应力，屈服应力，流动指数，无限，零速率粘度和不同污泥类型的流动一致性指数）的报告结果。从回顾的文献中得出了结论，并为未来的研究方向提出了一些建议。本文介绍了各种流变模型的适用性和实际意义，例如宾厄姆，幂律（Ostwald），Herschel-Bulkley，Casson，Sisko，Careau和Cross模型对各种污泥的实验流变特性。此处还汇总了从最佳拟合模型获得的各种流变参数（例如剪切应力，屈服应力，流动指数，无限，零速率粘度和不同污泥类型的流动一致性指数）的报告结果。从回顾的文献中得出了结论，并为未来的研究方向提出了一些建议。此处还汇总了从最佳拟合模型获得的各种流变参数（例如剪切应力，屈服应力，流动指数，无限，零速率粘度和不同污泥类型的流动一致性指数）的报告结果。从回顾的文献中得出了结论，并为未来的研究方向提出了一些建议。此处还汇总了从最佳拟合模型获得的各种流变参数（例如剪切应力，屈服应力，流动指数，无限，零速率粘度和不同污泥类型的流动一致性指数）的报告结果。从回顾的文献中得出了结论，并为未来的研究方向提出了一些建议。