Mechanisms underlying the detrimental impact of micro(nano)plastics on the stability of aerobic granular sludge: Interactions between micro(nano)plastics and extracellular polymeric substances

• Published in: Journal of hazardous materials 2024-10, Vol.478, p.135512, Article 135512
• Main Authors: Huang, Shuchang, Zhang, Bing, Cui, Fuyi, He, Yuankai, Shi, Jinyu, Yang, Xinyu, Lens, Piet N.L., Shi, Wenxin
• Format: Article
• Language: English
• Subjects: Adsorption; Aerobic granular sludge; Aerobiosis; Extracellular Polymeric Substance Matrix - chemistry; Extracellular Polymeric Substance Matrix - metabolism; Extracellular polymeric substances; Interaction behaviors; Micro(nano)plastics; Microplastics - chemistry; Microplastics - toxicity; Nanoparticles - chemistry; Nanoparticles - toxicity; Nitrogen - chemistry; Plastics - chemistry; Sewage - chemistry; Sewage - microbiology; Waste Disposal, Fluid - methods; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - toxicity; XDLVO theory
• ISSN: 0304-3894; 1873-3336; 1873-3336
• DOI: 10.1016/j.jhazmat.2024.135512

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. [Display omitted] •Role of EPS in maintaining the stability of AGS when exposed to MPs/NPs was revealed.•MPs/NPs decreased EPS content, thereby deteriorating the structural stability of AGS.•Tyrosine, tryptophan, and humic acid were more readily bound to NPs than MPs.•Decreased EPS content caused by MPs/NPs elevated the energy barrier of microorganisms.•Electronegativity of MPs increased, while that of NPs decreased upon EPS adsorption.