微塑料 (MP) 是尺寸小于 5 毫米的塑料颗粒:它们在市政污水处理厂中的去除主要导致较粗的部分积累到污泥中。处理过的污泥作为土壤改良剂的普遍应用引发了 MPs 不受控制地释放到环境中的问题,这表明需要确定合适的对抗策略。本工作简要回顾了在常规污泥处理过程中关注 MPs 归宿的最新研究,并根据该分析结果提出了废活性污泥 (WAS) 的热预处理(120 °C,30 分钟)。不同种类的 MPs,以研究其对厌氧生物降解能力以及 MPs 的丰度和物理特性的影响。实验结果表明,高温不会改变聚对苯二甲酸乙二醇酯 (PET) MPs,而是改变可生物降解的可堆肥 (BIO-MPs),符合 UNI EN 13432 标准。含有 PET-MP 的热预处理样品的甲烷生成曲线并未表明厌氧过程受到任何抑制,这受到 WAS 中 BIO-MP 的积极影响:在对照样品中观察到 100% 和 25% 的甲烷增加和没有热预处理,分别。需要进一步研究以更好地了解可生物降解 MPs 行为的机制,并研究高温处理对厌氧过程中较小尺寸 MPs 的影响。符合 UNI EN 13432 标准。含有 PET-MP 的热预处理样品的甲烷生成曲线并未表明厌氧过程受到任何抑制,这受到 WAS 中 BIO-MP 的积极影响:在对照样品中观察到 100% 和 25% 的甲烷增加和没有热预处理,分别。需要进一步研究以更好地了解可生物降解 MPs 行为的机制,并研究高温处理对厌氧过程中较小尺寸 MPs 的影响。符合 UNI EN 13432 标准。含有 PET-MP 的热预处理样品的甲烷生成曲线并未表明厌氧过程受到任何抑制,这受到 WAS 中 BIO-MP 的积极影响:在对照样品中观察到 100% 和 25% 的甲烷增加和没有热预处理,分别。需要进一步研究以更好地了解可生物降解 MPs 行为的机制,并研究高温处理对厌氧过程中较小尺寸 MPs 的影响。在有和没有热预处理的对照样品上,分别观察到 100% 和 25% 的甲烷增加。需要进一步研究以更好地了解可生物降解 MPs 行为的机制,并研究高温处理对厌氧过程中较小尺寸 MPs 的影响。在有和没有热预处理的对照样品上,分别观察到 100% 和 25% 的甲烷增加。需要进一步研究以更好地了解可生物降解 MPs 行为的机制,并研究高温处理对厌氧过程中较小尺寸 MPs 的影响。
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Microplastics in sewage sludge destined to anaerobic digestion: The potential role of thermal pretreatment
Microplastics (MPs) are plastic particles with size smaller than 5 mm: their removal in municipal wastewater treatment plants mostly results in the accumulation of the coarser fraction into the sludge. The common application of the treated sludge as soil amendment raises the issue of the uncontrolled release of MPs into the environment, which depicts the need to identify suitable counteraction strategies. This work briefly reviews the most recent studies that focus on the fate of MPs during conventional sludge treatments, and, based on the results of this analysis, proposes the thermal pretreatment (120 °C, 30 min) of waste activated sludge (WAS) containing different kinds of MPs, in order to investigate its effect on the anaerobic biodegradability as well as on the abundance and physical features of MPs. Experimental results show that high temperatures did not alter polyethylene terephthalate (PET) MPs but the biodegradable-compostable ones (BIO-MPs), complying with the UNI EN 13432 standards. The profile of methane generation from thermally pretreated samples containing PET-MPs do not indicate any inhibition of the anaerobic process, which was positively influenced by the BIO-MPs in WAS: a 100% and 25% methane increase was observed over the control samples with and without the thermal pretreatment, respectively. Further studies are needed to better understand the mechanisms underlying biodegradable MPs behavior as well as to investigate the influence of high temperature treatments on smaller size MPs during anaerobic processes.