Crawling ciliates play important role in activated sludge as they improve flocculation and remove loosely attached bacteria from the flocs. However, there are discrepancies concerning their influence on nitrifying bacteria and nitrification efficiency. We conducted a five weeks experiment in six bioreactors simulating the Sequencing Batch Reactor (SBR) process using activated sludge from a plant in start‐up phase. Half of bioreactors were inoculated with dense Aspidisca cicada culture and the remaining bioreactors served as control. The density of protozoa was regularly evaluated. Artificially increased density of A. cicada did not impair nitrifying bacteria abundance nor flocs structure. On the contrary, when A. cicada abundance was the highest, the total nitrogen in effluent was significantly lower in treatment in comparison to control. Most probably nitrifying bacteria occurring in form of dense colonies or hidden inside the flocs were inaccessible for ciliates.

中文翻译：

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蝉粉虱对硝化细菌和活性污泥絮凝形态的影响

爬行的纤毛虫在活性污泥中起着重要的作用，因为它们改善了絮凝作用并从絮凝物中清除了松散附着的细菌。但是，它们对硝化细菌和硝化效率的影响存在差异。我们在六个生物反应器中进行了为期五周的实验，在启动阶段使用来自工厂的活性污泥模拟了序列间歇反应器（SBR）过程。一半的生物反应器接种了密集的Aspidisca cicada培养物，其余的生物反应器用作对照。定期评估原生动物的密度。人工增加的蝉密度不会损害硝化细菌的丰度或絮凝物结构。相反，当蝉与对照相比，处理中的丰度最高，废水中的总氮显着降低。纤毛虫难以接近以密集菌落的形式存在或隐藏在絮状物内部的硝化细菌。