State Key Laboratory of Pollution Control and Resources Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
College of Environmental Science and Engineering and Key Laboratory of Environmental Biology and Pollution Control (Ministry of Education), Hunan University, Changsha 410082, PR China.
Sci Total Environ. 2023 Apr 15;869:161780. doi: 10.1016/j.scitotenv.2023.161780. Epub 2023 Jan 24.
Microplastics (MPs) and Cd have been proven to inhibit methane production from anaerobic digestion of sewage sludge. However, the published studies mainly focused on their single inhibition. This cannot reflect the real-world situations where MPs and Cd co-exist. This study therefore aims to reveal the combined effect of MPs and Cd on anaerobic digestion of sewage sludge. Experimental results showed that PVC-MPs at environmentally relevant levels (e.g., 1, 10 particles/g total solids (TS)) did not affect methane yield but decrease the toxicity of Cd. When PVC-MPs were 30 particles/g TS, the cumulative methane production recovered from 58.8 % (in the presence of 5 mg Cd/g TS) to 89.7 % of the control. Organic fluxes were significantly increased compared with the control, particularly affecting the content of dissolved substances and short-chain fatty acids during anaerobic digestion. Mechanistic exploration showed that the adsorption of Cd by PVC-MPs was higher than that of sludge-substrate, which reduced the bioavailability of Cd by anaerobes, as evidenced by the increased anaerobes driven carbon flux from solid-phase to bio-methane during anaerobic digestion. Overall, these findings identified important factors in determining the toxicity of pollutants on anaerobic digestion process, providing precise data for toxicity evaluation of MPs and metals in anaerobic environment.
微塑料（MPs）和 Cd 已被证明会抑制污水污泥厌氧消化过程中甲烷的生成。然而，已发表的研究主要集中在它们的单一抑制作用上。这不能反映 MPs 和 Cd 共存的实际情况。因此，本研究旨在揭示 MPs 和 Cd 对污水污泥厌氧消化的联合作用。实验结果表明，在环境相关水平（如 1、10 个/克总固体（TS））下的 PVC-MPs 不会影响甲烷产量，但会降低 Cd 的毒性。当 PVC-MPs 达到 30 个/克 TS 时，累积甲烷产量从存在 5mg Cd/g TS 时的 58.8%恢复到对照的 89.7%。与对照组相比，有机通量显著增加，特别是在厌氧消化过程中影响溶解物质和短链脂肪酸的含量。机理探索表明，PVC-MPs 对 Cd 的吸附高于污泥-基质，这降低了 Cd 对厌氧菌的生物利用度，这可以从厌氧消化过程中固体相向生物甲烷的驱动碳通量增加得到证明。总的来说，这些发现确定了决定污染物对厌氧消化过程毒性的重要因素，为厌氧环境中 MPs 和金属的毒性评估提供了精确的数据。
