Microplastics (MPs) and nanoplastics (NPs) present in wastewater can pose a negative impact to aerobic granular sludge (AGS). Herein, this study found that MPs and NPs (20 mg/L) deteriorated the sludge settleability and granule integrity, resulting in a 15.7 % and 21.9 % decrease in the total nitrogen removal efficiency of the AGS system, respectively. This was possibly due to the reduction of the extracellular polymeric substances (EPS) content. The subsequent analysis revealed that tyrosine, tryptophan, and humic acid-like substances in EPS exhibited a higher propensity for chemisorption and inhomogeneous multilayer adsorption onto NPs compared to MPs. The binding of EPS onto the surface of plastic particles increased the electronegativity of the MPs, but facilitated the aggregation of NPs through reducing the electrostatic repulsion, thereby mitigating the adverse effects of MPs/NPs on the AGS stability. Additionally, comprehensive analysis of the extended Derjaguin-Landau-Verwey-Overbeek theory indicated that the suppressed aggregation of microorganisms was the internal mechanisms contributing to the inadequate stability of AGS induced by MPs/NPs. This study provides novel insights into the detrimental mechanisms of MPs/NPs on the AGS stability, highlighting the key role of EPS in maintaining the structural stability of AGS when exposed to MPs/NPs.

中文翻译：

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微（纳米）塑料对好氧颗粒污泥稳定性产生不利影响的机制：微（纳米）塑料与胞外聚合物的相互作用


废水中存在的微塑料 (MP) 和纳米塑料 (NP) 会对好氧颗粒污泥 (AGS) 造成负面影响。研究发现，MPs 和 NPs (20 mg/L) 会恶化污泥沉降性和颗粒完整性，导致 AGS 系统的总脱氮效率分别降低 15.7% 和 21.9%。这可能是由于细胞外聚合物（EPS）含量减少所致。随后的分析表明，与 MP 相比，EPS 中的酪氨酸、色氨酸和腐殖酸类物质在 NP 上表现出更高的化学吸附和不均匀多层吸附倾向。 EPS与塑料颗粒表面的结合增加了MPs的电负性，但通过减少静电斥力促进了NPs的聚集，从而减轻了MPs/NPs对AGS稳定性的不利影响。此外，对扩展Derjaguin-Landau-Verwey-Overbeek理论的综合分析表明，微生物聚集的抑制是MPs/NPs诱导AGS稳定性不足的内部机制。这项研究为 MPs/NPs 对 AGS 稳定性的有害机制提供了新的见解，强调了 EPS 在暴露于 MPs/NPs 时维持 AGS 结构稳定性的关键作用。