Activated persulfate and hydrothermal treatment (HTT) are often employed to treat waste activated sludge, which can improve the efficiency of subsequent sludge treatment and change the distribution of pollutants in the sludge. However, the impact of sludge solid content and temperature on the occurrence and aging of microplastics (MPs) during HTT remains poorly understood. This study investigated the effects of persulfate-HTT (SPS-HTT) co-treatment on the migration, occurrence, and aging of MPs in sludge with different solid contents (2% and 5% solid content). The results indicated that SPS-HTT co-treatment triggers both the disruption of sludge flocs and the melting deformation of MPs at high temperatures, leading to variations in the increasing trend of MP concentration in the solid-liquid phase at different solid contents. 5% solid content sludge showed a weak release of MPs from the solid phase. The proportion of fiber MPs first increased and then decreased with increasing temperature, while no significant changes were observed in the color and type of MPs. Higher temperature and solid content induced the melting deformation of MPs, exacerbated the aging of polypropylene MPs, and resulted in rough surfaces, higher carbonyl index, and variations in crystallinity. Moreover, the correlation between the carbonyl index and aging indicators increased with increasing solid content. The MP-derived dissolved organic matter under HTT primarily comprised soluble microbial by-products and humic acid-like substances. These findings underscore the significance of sludge solid content in affecting the migration and aging of MPs during HTT, and offer novel insights into the application of HTT to MP management in sludge treatment.

中文翻译：

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过硫酸盐与水热协同处理废活性污泥中微塑料的特性及老化：固含量和温度的影响


活性过硫酸盐和水热处理（HTT）常用于处理废活性污泥，可以提高后续污泥处理效率并改变污泥中污染物的分布。然而，污泥固含量和温度对 HTT 过程中微塑料 (MPs) 的产生和老化的影响仍知之甚少。本研究探讨了过硫酸盐-HTT（SPS-HTT）共处理对不同固含量（2%和5%固含量）污泥中MPs迁移、出现和老化的影响。结果表明，SPS-HTT共处理在高温下会引发污泥絮体的破坏和MP的熔融变形，导致不同固相含量下固液相中MP浓度的增加趋势存在差异。 5%固含量污泥显示MPs从固相的微弱释放。随着温度的升高，纤维MPs的比例先增加后减少，而MPs的颜色和类型没有观察到明显的变化。较高的温度和固含量会引起MPs的熔融变形，加剧聚丙烯MPs的老化，导致表面粗糙、羰基指数升高和结晶度变化。而且，羰基指数和老化指标之间的相关性随着固体含量的增加而增加。 HTT下MP衍生的溶解有机物主要包括可溶性微生物副产物和腐殖酸类物质。这些发现强调了污泥固体含量在HTT过程中影响MPs迁移和老化的重要性，并为HTT在污泥处理中MP管理中的应用提供了新的见解。