Protozoa are significant components of activated sludge which purify the effluent of free swimming bacteria as well as trigger floc formation. In addition, their presence is often used as an indicator of process quality. In classical models, the impact of protozoa on biomass is implicitly included in the bacteria decay rates, which in most cases gives a sufficient level of detail. However, modeling of certain processes, such as bioaugmentation, would greatly benefit from a functional model including protozoa grazing explicitly. To further establish the approach for protozoa grazing modeling, the authors have summarized the current state of knowledge in this area, as well as pointed out crucial elements that have to be considered. Aspects of the endogenous oxygen uptake rate (OUR), the preference of protozoa towards particular bacteria groups, and alternative sources of nutrient are presented and discussed. Based on the drawn conclusions, the authors have proposed a modeling concept towards protozoa grazing that will maintain both stability and accordance with generally accepted activated sludge models (ASM). The presented approach includes a division of each bacteria group into dispersed and flocculated bacteria that emerge from newly formed flocculation and deflocculation processes, with a different level of grazing on both components.

原生动物是活性污泥的重要组成部分，可净化游离游泳细菌的出水并触发絮凝物的形成。此外，它们的存在通常被用作过程质量的指标。在经典模型中，原生动物对生物量的影响隐含在细菌的腐烂率中，这在大多数情况下可提供足够的详细程度。但是，某些过程的建模（例如生物强化）将极大地受益于包括原生动物放牧的功能模型。为了进一步建立原生动物放牧建模的方法，作者总结了该领域的当前知识水平，并指出了必须考虑的关键要素。内源性氧气吸收率（OUR）方面，原生动物对特定细菌群的偏好，提出并讨论了营养的替代来源。基于得出的结论，作者提出了一种原生动物放牧的建模概念，该概念既要保持稳定性，又要符合公认的活性污泥模型（ASM）。提出的方法包括将每个细菌组划分为分散的和絮凝的细菌，这些细菌从新形成的絮凝和反絮凝过程中出现，两种成分的放牧水平不同。