State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, No.7 Donghu South Road, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing, China.
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, No.7 Donghu South Road, Wuhan 430072, China.
Water Res. 2022 Sep 1;223:119017. doi: 10.1016/j.watres.2022.119017. Epub 2022 Aug 23.
Contamination by nanoplastics in urban water has aroused increasing concern. The impact of nanoplastic exposure on the wastewater treatment process in the long term is still unclear. This study investigated the effect of continuous nanoplastic exposure (R1:0, R2:10, R3:100, and R4:1000 μg/L) on the nitrification and denitrification processes for over 200 days in a sequencing batch reactor (SBR). The results revealed that nanoplastic exposure does not demonstrate significant inhibition of total nitrogen removal. The ammonia oxidation rate (19.24 ± 0.01 mgN/gMLVSS/h, p < 0.05) and denitrification rate (11.78 ± 0.11 mgN/ gMLVSS/h, p < 0.05) in R4 was significantly lower than the control (R1: 0 μg/L). The maximal reaction velocities of NO reduction (Vmax) were improved after long-term exposure to nanoplastics in high concentrations. The R3 demonstrated the highest Vmax value-six times higher than R4 and approximately 20 times higher than R1 and R2. The microbial structure largely varied with the exposure to nanoplastics, where the exposure to a high concentration largely suppressed the nitrifier and selectively enriched the denitrifier. The percentage of the top 20 genera of denitrifiers increased from 31.76% to 63.42%, and the nitrifiers decreased from an initial 12.40% to 2.83% for R4. The predominant genera were found to be Thauera, Azoarcus, and Defluviicoccus in R4 and R3 which indicated their tolerance to nanoplastics. The function prediction results indicated that the membrane transport function was significantly enhanced and the lipid metabolism function was significantly reduced in R4 as compared with the control (R1, p<0.05). This may be attributed to the adsorption of nanoplastics on bacteria. Observation under a scan electronic microscope demonstrated that the nanoplastics were firmly attached to the microbe surface and aggregated in activated sludge at high nanoplastics dosed reactor. These results deepen the understanding of the effect of nanoplastics on the urban wastewater treatment process and provide valuable information for the management of nanoplastic contamination in urban wastewater.
纳米塑料在城市水中的污染引起了越来越多的关注。纳米塑料暴露对废水处理过程的长期影响仍不清楚。本研究在序批式反应器（SBR）中考察了连续纳米塑料暴露（R1：0、R2：10、R3：100 和 R4：1000μg/L）对硝化和反硝化过程的影响，超过 200 天。结果表明，纳米塑料暴露对总氮去除没有显著的抑制作用。R4 的氨氧化速率（19.24±0.01 mgN/gMLVSS/h，p<0.05）和反硝化速率（11.78±0.11 mgN/gMLVSS/h，p<0.05）明显低于对照（R1：0μg/L）。在高浓度纳米塑料长期暴露后，NO 还原的最大反应速度（Vmax）得到提高。R3 表现出最高的 Vmax 值，是 R4 的六倍，约为 R1 和 R2 的 20 倍。微生物结构随纳米塑料的暴露而发生很大变化，高浓度暴露大大抑制了硝化菌，并选择性地富集了反硝化菌。反硝化菌的前 20 个优势属的比例从 31.76%增加到 63.42%，硝化菌从初始的 12.40%减少到 2.83%，对于 R4。R4 和 R3 中主要的属被发现是 Thauera、Azoarcus 和 Defluviicoccus，这表明它们对纳米塑料具有耐受性。功能预测结果表明，与对照（R1，p<0.05）相比，R4 中的膜转运功能显著增强，脂质代谢功能显著降低。这可能归因于纳米塑料在细菌上的吸附。扫描电子显微镜观察表明，纳米塑料牢固地附着在微生物表面，并在高纳米塑料剂量反应器中的活性污泥中聚集。这些结果加深了对纳米塑料对城市废水处理过程影响的认识，为城市废水中纳米塑料污染的管理提供了有价值的信息。
