Magnetic nanoparticles (NPs) have been widely applied in environmental remediation, biomass immobilization and wastewater treatment, but their potential impact on anaerobic ammonium oxidation (anammox) biomass remains unknown. In this study, the short-term and long-term impacts of maghemite NPs (MHNPs) on the flocculent sludge wasted from a high-rate anammox reactor were investigated. Batch assays showed that the presence of MHNPs up to 200 mg L⁻¹ did not affect anammox activity, reactive oxygen species production, or cell membrane integrity. Moreover, long-term addition of 1–200 mg L⁻¹ MHNPs had no adverse effects on reactor performance. Notably, the specific anammox activity, the abundance of hydrazine synthase structural genes and the content of extracellular polymeric substance were increased with elevated MHNP concentrations. Meanwhile, the community structure was shifted to higher abundance of Candidatus Kuenenia indicated by high-throughput sequencing. Therefore, MHNPs could be applied to enhance anammox flocculent sludge due to their favorable biocompatibility.

磁性纳米颗粒（NPs）已广泛应用于环境修复，生物量固定化和废水处理中，但它们对厌氧铵氧化（anammox）生物量的潜在影响仍然未知。在这项研究中，研究了磁赤铁矿NPs（MHNPs）对从高速厌氧反应器中浪费掉的絮凝污泥的短期和长期影响。批量测定表明，高达200 mg L ^-1的MHNP的存在不影响厌氧氨氧化活性，活性氧的产生或细胞膜的完整性。此外，长期添加1-200 mg L ^-1MHNP对反应堆性能没有不利影响。值得注意的是，特定的厌氧氨氧化活性，肼合酶结构基因的丰度和细胞外聚合物的含量随MHNP浓度的升高而增加。同时，通过高通量测序表明，群落结构向高丰度的念珠菌转移。因此，MHNP由于其良好的生物相容性而可用于增强厌氧氨氧化絮凝污泥。