The objectives of this study were to investigate the influence of chromium nanoparticles (Cr NPs) on the nitrogen and phosphorus removal performance and the bacterial structures of an activated sludge (AS) system. Also, we through molecular ecological networks (MENs) discussed the bacterial interactions. At last we researched the change of the functional genes and their expression patterns related to nitrogen and phosphorus removal in an AS system. The results showed that long-term exposure to 1 mg/L Cr NPs significantly promoted the denitrifying process and phosphorus removal in the AS system. The relative abundance of denitrifying and phosphorus removal microorganisms, such as Denitratisoma, Thauera, Dechloromonas, and Defluviicoccus, increased significantly. Candidatus Accumulibacter, well-known as polyphosphate-accumulating organisms (PAOs), increased significantly; the relative abundance of Candidatus Competibacter, known as glycogen-accumulating organisms (GAOs), decreased significantly. Furthermore, metagenomic and metatranscriptomic analysis revealed that most of the genera related to denitrifying and phosphorus removal had greatly increased, according to the quantities of denitrifying and phosphorus genes, and the corresponding transcription likewise greatly increased. Lastly, MENs analysis showed that although the overall network became smaller and looser in the presence of Cr NPs, the microbial connections among members related to nitrogen and phosphorus removal were enhanced. The abundance increases of denitrifiers and PAOs, and their increased transcription of functional genes, together with the enhanced interactions may be associated with the promotion of the denitrifying process and phosphorus removal.

这项研究的目的是研究铬纳米颗粒（Cr NPs）对活性污泥（AS）系统的脱氮和除磷性能以及细菌结构的影响。另外，我们通过分子生态网络（MENs）讨论了细菌的相互作用。最后，研究了AS系统中功能基因的变化及其与脱氮除磷相关的表达方式。结果表明，长期暴露于1 mg / L Cr NPs显着促进了AS系统中的反硝化过程和磷的去除。反硝化和除磷微生物（如Denistratisoma，Thauera，Dechloromonas和Defluviicoccus）的相对丰度显着增加。众所周知的聚乳酸假丝酵母菌（PAOs）显着增加。竞争念珠菌的相对丰度被称为糖原累积生物（GAOs）的显着下降。此外，宏基因组和元转录组分析表明，根据反硝化和除磷基因的数量，与反硝化和除磷有关的大多数属都大大增加了，相应的转录也大大增加了。最后，MENs分析表明，尽管在Cr NPs的存在下整个网络变得越来越小和松散，但与氮和磷去除相关的成员之间的微生物连接却得到了增强。反硝化剂和PAO的大量增加，以及功能基因转录的增加，以及相互作用的增强，可能与反硝化过程的促进和磷的去除有关。