Dewatering is an indispensable link in sludge treatment, but its effect on the microplastics (MPs) remains inadequately understood. This study investigated the physicochemical changes and leaching behavior of MPs during the mechanical dewatering of sludge, as well as the impact of MP leachates on activated sludge (AS). After sludge dewatering, MPs exhibit rougher surfaces, decreased sizes and altered functional groups due to the addition of dewatering agents and the application of mechanical force. Meanwhile, plastic additives, depolymerization products, and derivatives of their interactions are leached from MPs during sludge dewatering process. The concentration of MP-based leachates in sludge is 2–25 times higher than that in water. The enhancement of pH and ionic strength caused by dewatering agents induces the release of MP leachates enriched with protein-like, fulvic acid-like, and soluble microbial by-product-like substances. The reflux of MP leachates in sludge dewatering liquor to the wastewater treatment system negatively impacts AS, leading to a decrease in COD removal rate and inhibition of the extracellular polymeric substances secretion. More importantly, MP leachates cause oxidative stress to microbial cells and alter the microbial community structure of AS at the phylum and genus levels. These findings confirm that MPs undergo aging and leaching during sludge dewatering process, and MP leachates may negatively affect the wastewater treatment system.

中文翻译：

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污泥机械脱水过程中微塑料的浸出行为及其对活性污泥的影响


脱水是污泥处理中不可或缺的环节，但其对微塑料（MPs）的影响仍知之甚少。本研究研究了污泥机械脱水过程中 MP 的物理化学变化和浸出行为，以及 MP 浸出液对活性污泥（AS）的影响。污泥脱水后，由于脱水剂的添加和机械力的应用，MPs 表现出更粗糙的表面、减小的尺寸和改变的官能团。同时，塑料添加剂、解聚产物及其相互作用的衍生物在污泥脱水过程中从MP中浸出。污泥中MP基渗滤液的浓度比水中高2-25倍。脱水剂引起的 pH 值和离子强度的增强导致富含蛋白质类、黄腐酸类和可溶性微生物副产品类物质的 MP 渗滤液的释放。污泥脱水液中的MP渗滤液回流至废水处理系统会对AS产生负面影响，导致COD去除率下降并抑制细胞外聚合物的分泌。更重要的是，MP渗滤液会对微生物细胞造成氧化应激，并改变AS在门和属水平上的微生物群落结构。这些研究结果证实，MP在污泥脱水过程中会发生老化和浸出，MP渗滤液可能会对废水处理系统产生负面影响。