纳米氧化锌粒径效应对人工湿地运行性能的影响

为考察ZnO NPs粒径效应对人工湿地运行性能的影响，在进水COD约为216.00 mg·L^-1、总氮约为11.10 mg·L⁻¹和总磷约为3.84 mg·L⁻¹的条件下连续运行126 d，对暴露于不同粒径ZnO NPs(10.00 mg·L⁻¹)的人工湿地脱氮除磷性能、填料渗透系数、胞外聚合物(extracellular polymeric substances，EPS)产量和特性以及微生物群落结构和多样性的变化进行了研究。结果表明：与对照组(未投加ZnO NPs)相比，进水中投加15、50和90 nm ZnO NPs后，人工湿地对COD的去除率分别下降了8.73%、7.55%和6.97%；氨氮和总氮的去除率分别下降了21.96%和10.95%、17.75%和10.00%以及15.34%和3.78%。高通量测序结果表明，ZnO NPs粒径越小，对硝化菌属Thauera的抑制作用越明显。投加ZnO NPs后，其释放的Zn²⁺会与水中磷酸盐结合生成磷酸锌等不溶物，同时会增加异养硝化菌Acinetobacter的相对丰度，从而导致总磷的去除率比对照组提高了42.49%~56.38%。此外，与对照组(97.18 mg·g⁻¹)相比，投加15、50和90 nm的ZnO NPs后EPS的产量分别增加到212.97、156.30和128.53 mg·g⁻¹。EPS分泌量的增大，导致填料渗透系数快速降低，在运行83 d后分别下降了71.17%、67.83%和37.50%。

Size-dependent effects of ZnO nanoparticles on operational performance of constructed wetlands

ZnO nanoparticles (ZnO NPs) have catalytic activity, strong oxidability and high stability, which are widely used in semiconductors, dyes, plastic additives, cosmetics and many other fields. The life cycle of the ZnO NPs series of products, will inevitably cause damage to the environment, thus affect the sewage disposal system. laboratory scale horizontal subsurface flow constructed wetlands were operated for 126 days when influent chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were about 216.00 mg·L−1, 11.10 mg·L−1 and 3.84 mg·L−1, respectively. To investigate the size-dependent effects of ZnO NPs on the operational performance of constructed wetlands, the nitrogen, and phosphorus removal performance, the permeability coefficient of fillers, the content and characteristics of extracellular polymeric substances (EPS), as well as the change in microbial community structure and diversity after exposure to different particle sizes of ZnO NPs (10.00 mg·L−1) were studied. The results indicated that compared with the control group, the removal efficiencies of COD in the constructed wetlands exposed to 15 nm, 50 nm, and 90 nm of ZnO NPs decreased by 8.73%, 7.55%, and 6.97%, respectively, meanwhile the removal efficiencies of NH4+-N and TN decreased by 21.96% and 10.95%, 17.75% and 10.00%, and 15.34%, and 3.78%, respectively. High throughput sequencing indicated that the smaller ZnO NPs size, the more significant inhibitory effect on nitrification bacterium (e.g. Thauera). After adding ZnO NPs, the released Zn2+ could combine with phosphate in water to form insoluble substances such as zinc phosphate precipitation, and the relative abundance of the heterotrophic nitrifying bacterium (e.g. Acinetobacter) also increased, which resulted in the increase of TP removal efficiencies by 42.49%~56.38% in comparison with the control group. In addition, compared with the control group (97.18 mg·g−1), the EPS contents when exposing to 15 nm, 50 nm, and 90 nm of ZnO NPs increased to 212.97 mg·g−1, 156.30 mg·g−1, and 128.53 mg·g−1, respectively. The increasing EPS contents led to a rapid decrease of the permeability coefficient of fillers by 71.17%, 67.83%, and 37.50% at 83 days, respectively.