Gao Jun, Li Lei, Yuan Shijie, Chen Sisi, Dong Bin
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
Water Res. 2022 Nov 1;226:119249. doi: 10.1016/j.watres.2022.119249. Epub 2022 Oct 14.
Humus accumulation during sludge stabilization is attracting increasing attention because of its land use potential. This study investigated the effects of thermal hydrolysis pretreatment (THP) on sludge humification and the related regulatory mechanisms during anaerobic digestion (AD). The sludge subjected to AD with THP at 160 °C (AnD-160) exhibited 7.3% and 8.5% higher total extractable carbon (TEC) and humic acid carbon (HAC) concentrations than the unpretreated sludge, respectively, while the sludge subjected to AD with THP at 180 °C (AnD-180) exhibited 1.4% and 7.0% lower concentrations. Humification of AnD-160 and AnD-180 were enhanced and inhibited, respectively. THP influenced sludge humification during AD through both intracellular polyphenol synthesis and extracellular humus condensation pathways related to polysaccharide metabolism. The 160 °C-pretreated sludge exhibited higher polysaccharide availability (more soluble polysaccharides and reducing sugars) than the other samples and thus had more active intracellular polyphenol metabolism during AD. The polyphenol accumulation stimulated the synthesis of related condensation enzymes (polyphenol oxidase and quinone oxidoreductases), facilitating extracellular HA production during AD. However, THP at 180 °C resulted in the highest production of melanoidins with CO-C heterocycles through C = O and CH sites of polysaccharides (778.46 vs. 193.87 R.U. nm-mL/g for the unpretreated sample). This heterocyclization decreased the polysaccharide availability and inhibited intracellular polyphenol synthesis, consequently inhibiting condensation enzymes supply and extracellular HA production during AD. Overall, this study highlights the crucial but neglected role of polysaccharides in sludge humification during AD: the availability of polysaccharides affected by their occurrence state and molecular structure could determine the humification, which can be regulated by THP at different temperature.
由于污泥稳定化过程中腐殖质积累具有土地利用潜力，因此受到越来越多的关注。本研究调查了热水解预处理（THP）对厌氧消化（AD）过程中污泥腐殖化的影响及其相关调控机制。在160℃进行THP预处理后进行AD的污泥（AnD-160），其总可提取碳（TEC）和腐殖酸碳（HAC）浓度分别比未预处理污泥高7.3%和8.5%，而在180℃进行THP预处理后进行AD的污泥（AnD-180），其浓度分别低1.4%和7.0%。AnD-160和AnD-180的腐殖化分别得到增强和抑制。THP通过与多糖代谢相关的细胞内多酚合成和细胞外腐殖质缩合途径影响AD过程中的污泥腐殖化。160℃预处理的污泥比其他样品表现出更高的多糖可用性（更多的可溶性多糖和还原糖），因此在AD过程中具有更活跃的细胞内多酚代谢。多酚积累刺激了相关缩合酶（多酚氧化酶和醌氧化还原酶）的合成，促进了AD过程中细胞外腐殖酸的产生。然而，180℃的THP通过多糖的C=O和CH位点产生了最多的含C-O-C杂环的类黑素（未预处理样品为778.46 vs. 193.87 R.U. nm-mL/g）。这种杂环化降低了多糖可用性并抑制了细胞内多酚合成，从而抑制了AD过程中缩合酶的供应和细胞外腐殖酸的产生。总体而言，本研究突出了多糖在AD过程中污泥腐殖化中关键但被忽视的作用：受其存在状态和分子结构影响的多糖可用性可以决定腐殖化，而这可以通过不同温度的THP来调控。
