Hydrothermal pretreatment of waste activated sludge (WAS) could eliminate the rate limiting step of anaerobic digestion (AD) -hydrolysis. However, the high organic loading rate may cause acid accumulation, thus leading to an unstable system. This study compared the effect of different hydrochar (HC2–260°C and HC3–320°C) and biochar (BC5–500°C and BC7–700°C) on AD of hydrothermal pretreated WAS (HPS). Results demonstrated that hydrochar was superior to biochar in the methane yield and production rate, especially HC2. HC2 had the highest surface oxygen-containing functional groups that could facilitate direct interspecies electron transfer (DIET). The enhanced methane yield was related with the increased protein utilization, and hydrochar and biochar enriched different microbes related to protein degradation. Metabolomic analysis showed the significantly changed metabolites induced by hydrochar and biochar were involved in fatty acids and amino acids-related metabolism, indicating the rapid conversion of intermediated products, which was consistent with the microbial community structure results. Hydrochar and biochar also induced upregulation of metabolites related to microbial metabolic activity and extracellular electron transfer. Although biochar induced the same metabolic changes, the alterations of these metabolites were weaker than those of hydrochar. The results of this study offered new insights into the molecular mechanisms of enhanced AD of HPS by hydrochar and biochar.

废弃活性污泥（WAS）的水热预处理可以消除厌氧消化（AD）-水解的限速步骤。然而，高有机负载率可能会导致酸积累，从而导致系统不稳定。本研究比较了不同水热炭（HC2–260°C 和 HC3–320°C）和生物炭（BC5–500°C 和 BC7–700°C）对水热预处理 WAS (HPS) 的 AD 的影响。结果表明，氢化炭在甲烷产率和产率方面优于生物炭，尤其是HC2。HC2 具有最高的表面含氧官能团，可以促进直接种间电子转移（DIET）。甲烷产量的增加与蛋白质利用率的增加有关，水炭和生物炭丰富了与蛋白质降解相关的不同微生物。代谢组学分析表明，水炭和生物炭诱导的显着变化的代谢物参与了脂肪酸和氨基酸的相关代谢，表明中间产物的快速转化，这与微生物群落结构结果一致。Hydrochar 和 biochar 还诱导与微生物代谢活动和细胞外电子转移相关的代谢物的上调。尽管 biochar 引起了相同的代谢变化，但这些代谢物的变化比 Hydrochar 弱。这项研究的结果为水炭和生物炭增强 HPS 的 AD 的分子机制提供了新的见解。表明中间产物的快速转化，这与微生物群落结构结果一致。Hydrochar 和 biochar 还诱导与微生物代谢活动和细胞外电子转移相关的代谢物的上调。尽管 biochar 引起了相同的代谢变化，但这些代谢物的变化比 Hydrochar 弱。这项研究的结果为水炭和生物炭增强 HPS 的 AD 的分子机制提供了新的见解。表明中间产物的快速转化，这与微生物群落结构结果一致。Hydrochar 和 biochar 还诱导与微生物代谢活动和细胞外电子转移相关的代谢物的上调。尽管 biochar 引起了相同的代谢变化，但这些代谢物的变化比 Hydrochar 弱。这项研究的结果为水炭和生物炭增强 HPS 的 AD 的分子机制提供了新的见解。这些代谢物的变化比 Hydrochar 弱。这项研究的结果为水炭和生物炭增强 HPS 的 AD 的分子机制提供了新的见解。这些代谢物的变化比 Hydrochar 弱。这项研究的结果为水炭和生物炭增强 HPS 的 AD 的分子机制提供了新的见解。