Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China.
Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China; Engineering Research Center for Water Pollution Source Control & Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, PR China.
Water Res. 2024 Nov 15;266:122421. doi: 10.1016/j.watres.2024.122421. Epub 2024 Sep 8.
Structural extracellular polymeric substances (SEPS) as valuable biopolymers, can be extracted from waste activated sludge (WAS). However, the extraction yield is typically low, and detailed information on SEPS characterizations, as well as proper treatment of the sludge after SEPS extraction, remains limited. This study aimed to optimize the conditions of heating-NaCO extraction process to increase the yield of SEPS extracted from WAS. Subsequently, SEPS were characterized, and, for the first time, insights into their protein composition were uncovered by using proteomics. A maximum SEPS yield of 209 mg g volatile solid (VS) was obtained under optimal conditions: temperature of 90 °C, heating time of 60 min, Na dosage of 8.0 mmol/g VS, and pH required to precipitation of 4.0, which was comparable to that from the aerobic granular sludge reported in literature. Proteomics analysis unveiled that the proteins in SEPS primarily originated from microorganisms involved in nitrogen fixation and organic matter degradation, including their intracellular and membrane-associated regions. These proteins exhibited various catalytic activities and played crucial roles in aggregation processes. Besides, the process of SEPS extraction significantly enhanced volatile fatty acid (VFA) production during the anaerobic fermentation of residual WAS after SEPS extraction. A maximum VFA yield of 420 ± 14 mg COD/g VS was observed in anaerobic fermentation of 10 d, which was 77.2 ± 0.1 % higher than that from raw sludge. Mechanism analysis revealed that SEPS extraction not only improved WAS disintegration and solubilization but also reduced the relative activity of methanogens during anaerobic fermentation. Moreover, SEPS extraction shifted the microbial population during anaerobic fermentation in the direction towards hydrolysis and acidification such as Fermentimonas sp. and Soehngenia sp. This study proposed a novel strategy based on SEPS extraction and VFA production for sludge treatment, offering potential benefits for resource recovery and improved process efficiency.
结构细胞外聚合物（SEPS）作为有价值的生物聚合物，可以从废活性污泥（WAS）中提取。然而，提取产率通常较低，并且关于 SEPS 特性的详细信息以及 SEPS 提取后污泥的适当处理仍然有限。本研究旨在优化加热-NaCO 提取工艺条件，以提高从 WAS 中提取的 SEPS 的产率。随后，对 SEPS 进行了表征，并首次通过蛋白质组学揭示了其蛋白质组成的见解。在最佳条件下，获得了最大 SEPS 产率 209mg g 挥发性固体（VS）：温度 90°C，加热时间 60min，Na 用量 8.0mmol/g VS，沉淀所需的 pH 值为 4.0，与文献中报道的好氧颗粒污泥相当。蛋白质组学分析表明，SEPS 中的蛋白质主要来源于参与固氮和有机物降解的微生物，包括其细胞内和膜相关区域。这些蛋白质表现出各种催化活性，在聚集过程中发挥着关键作用。此外，SEPS 提取过程显著提高了 SEPS 提取后剩余 WAS 在厌氧发酵过程中的挥发性脂肪酸（VFA）产量。在 10d 的厌氧发酵中，观察到 VFA 产率达到 420±14mg COD/g VS 的最大值，比原污泥高 77.2±0.1%。机理分析表明，SEPS 提取不仅改善了 WAS 的解体和溶解，还降低了厌氧发酵过程中甲烷菌的相对活性。此外，SEPS 提取改变了厌氧发酵过程中的微生物种群，有利于水解和酸化，如 Fermentimonas sp. 和 Soehngenia sp. 本研究提出了一种基于 SEPS 提取和 VFA 生产的新型污泥处理策略，为资源回收和提高工艺效率提供了潜在的好处。
