School of Environment Science and Spatial Informatics, China University of Mining and Technology, 1 Daxue Road, Xuzhou 221116, China.
Jiangsu Key Laboratory of Resources and Environmental Information Engineering, China University of Mining and Technology, Xuzhou 221116, China.
Int J Environ Res Public Health. 2022 Aug 2;19(15):9502. doi: 10.3390/ijerph19159502.
Silver nanoparticles (AgNPs) are released into the sewage pipes and ultimately wastewater treatment plants during manufacturing, use, and end-life disposal. AgNPs in wastewater treatment plants aggregate or dissolve, and may affect the microbial community and subsequent pollutant removal efficiency. This study aims to quantitatively investigate the fate of AgNPs in synthetic high ammonia nitrogen wastewater (SW) and sludge from an up-flow anaerobic sludge blanket (UASB) anammox reactor using a nanoparticle tracking analysis (NTA), dynamic light scattering (DLS), transmission electron microscope (TEM), and atomic absorption spectroscopy (AAS). Results showed that 18.1 mM NH, 2.11 mM Mg in SW caused less negative zeta potential (ζ-potential, -18.4 vs. -37.4 mV), aggregation (388.8 vs. 21.5 nm), and settlement (80%) of citrate-coated AgNPs (cit-AgNPs) in 220 min. The presence of 18.5 mM Cl in SW formed AgCl, AgCl and eventually promoted the dissolution (9.3%) of cit-AgNPs. Further exposure of SW-diluted AgNPs to sludge (42 mg L humic acid) and induced a more negative ζ-potential (-22.2 vs. -18.4 mV) and smaller aggregates (313.4 vs. 388.8 nm) due to the steric and hindrance effect. The promoted Ag dissolution (34.4% vs. 9.3%) was also observed after the addition of sludge and the possible reason may be the production of Ag(NH) by the coexistence of HA from sludge and NH from SW. These findings on the fate of AgNPs can be used to explain why AgNPs had limited effects on the sludge-retained bacteria which are responsible for the anammox process.
银纳米粒子（AgNPs）在制造、使用和最终处置过程中会释放到污水管道中，并最终进入废水处理厂。废水中的 AgNPs 会聚集或溶解，并可能影响微生物群落及其后续的污染物去除效率。本研究旨在使用纳米颗粒跟踪分析（NTA）、动态光散射（DLS）、透射电子显微镜（TEM）和原子吸收光谱（AAS）定量研究 AgNPs 在合成高氨氮废水（SW）和上流式厌氧污泥床（UASB）厌氧氨氧化反应器污泥中的归宿。结果表明，SW 中 18.1mM NH₄+和 2.11mM Mg²⁺会导致带负电荷的柠檬酸包覆的 AgNPs（cit-AgNPs）的zeta 电位（ζ-电位，-18.4 对-37.4mV）更低、聚集（388.8 对 21.5nm）和沉降（80%）能力降低。SW 中 18.5mM Cl 的存在形成了 AgCl，AgCl 最终促进了 cit-AgNPs 的溶解（9.3%）。进一步将 SW 稀释的 AgNPs 暴露于污泥（42mg LHAs）中，并由于空间位阻和阻碍效应，导致更负的 ζ-电位（-22.2 对-18.4mV）和更小的聚集（313.4 对 388.8nm）。加入污泥后也观察到 Ag 溶解的促进（34.4% 对 9.3%），这可能是由于污泥中的 HA 与 SW 中的 NH₄⁺共同存在生成了 Ag(NH₃)₅⁺。这些关于 AgNPs 归宿的发现可以用来解释为什么 AgNPs 对负责厌氧氨氧化过程的污泥保留细菌的影响有限。
