The rapid growth of the use of nanomaterials in different modern industrial branches makes the study of the impact of nanoparticles on the human health and environment an urgent matter. For instance, it has been reported that titanium dioxide nanoparticles (TiO₂ NPs) can be found in wastewater treatment plants. Previous studies have found contrasting effects of these nanoparticles over the activated sludge process, including negative effects on the oxygen uptake. The non-utilization of oxygen reflects that aerobic bacteria were inhibited or decayed. The aim of this work was to study how TiO₂ NPs affect the bacterial diversity and metabolic processes on an activated sludge. First, respirometry assays of 8 h were carried out at different concentrations of TiO₂ NPs (0.5–2.0 mg/mL) to measure the oxygen uptake by the activated sludge. The bacterial diversity of these assays was determined by sequencing the amplified V3–V4 region of the 16S rRNA gene using Illumina MiSeq. According to the respirometry assays, the aerobic processes were inhibited in a range from 18.5 ± 4.8% to 37.5 ± 2.0% for concentrations of 0.5–2.0 mg/mL TiO₂ NPs. The oxygen uptake rate was affected mainly after 4.5 h for concentrations higher than 1.0 mg/mL of these nanoparticles. Results indicated that, in the presence of TiO₂ NPs, the bacterial community of activated sludge was altered mainly in the genera related to nitrogen removal (nitrogen assimilation, nitrification and denitrification). The metabolic pathways prediction suggested that genes related to biofilm formation were more sensitive than genes directly related to nitrification–denitrification and N-assimilation processes. These results indicated that TiO₂ NPs might modify the bacteria diversity in the activated sludge according to their concentration and time of exposition, which in turn impact in the performance of the wastewater treatment processes.

在不同的现代工业分支中，纳米材料的使用迅速增长，使得研究纳米颗粒对人类健康和环境的影响成为当务之急。例如，据报道在废水处理厂中可以发现二氧化钛纳米颗粒（TiO ₂ NPs）。先前的研究已经发现这些纳米颗粒在活性污泥过程中的对比作用，包括对氧气吸收的负面影响。氧气的不利用反映出好氧细菌被抑制或腐烂。这项工作的目的是研究TiO ₂ NPs如何影响活性污泥上的细菌多样性和代谢过程。首先，在不同浓度的TiO _2上进行8 h的呼吸测定NPs（0.5–2.0 mg / mL）用于测量活性污泥对氧气的吸收。这些测定的细菌多样性是通过使用Illumina MiSeq对16S rRNA基因的扩增V3-V4区域进行测序来确定的。根据呼吸测定法，对于浓度为0.5–2.0 mg / mL的TiO ₂ NP ，有氧过程的抑制范围为18.5±4.8％至37.5±2.0％。对于浓度高于1.0 mg / mL的这些纳米颗粒，吸氧速率主要在4.5 h后受到影响。结果表明，在TiO ₂存在下NPs，即活性污泥的细菌群落，主要在与除氮（同化，硝化和反硝化）有关的属中发生了变化。代谢途径的预测表明，与生物膜形成相关的基因比与硝化-反硝化和氮同化过程直接相关的基因更敏感。这些结果表明，TiO ₂ NPs可能会根据其浓度和暴露时间改变活性污泥中的细菌多样性，进而影响废水处理过程的性能。