Soluble organic compounds released by alkaline (ALK), ultrasonic (ULS) and combined alkaline-ultrasonic (ALK-ULS) pretreatment as well as their transformation in the anaerobic digestion systems were investigated. The maximum methane production of 197.1 ± 3.0 mL CH₄/g tCOD_feed was observed with ALK-ULS pretreated sludge (pH 12 and specific energy input of 24 kJ/g TS). The combined treatment likely enhanced the sludge solubilization and produced more low molecular weight (LMW) substances, which were beneficial to improve the biogas generation rate. However, such pretreatment released not only easily biodegradable substances but also more recalcitrants, such as humic substances (HS) and complex high molecular weight (HMW) proteins. Thus, more residual dissolved organic matters (DOMs) were detected after digestion, which may pose adverse effects on the downstream water treatment. Refractory HS and hydrophobic dissolved organic carbon (HO DOC) were the main components of the residual DOMs, which accounted up to 35.0% and 22.3% respectively. At the molecular level, a large amount of residual polycyclic steroid-like matters, alkanes and aromatics were identified. Specific higher MW residual compounds, e.g. polar metabolites (like dipeptide, benzene and substituted derivatives), and non-polar lipids (like diacylglycerols, long chain fatty acids, alkenes, flavonoids, sphingolipids, glycerolipids, glycerophospholipids and their derivatives) were also identified. The results indicate that further polishing steps should be considered to remove the remaining soluble recalcitrant compounds. This study helps to understand the insight of sludge treatment from macro to micro level.

研究了碱（ALK），超声（ULS）和碱-超声联合（ALK-ULS）预处理释放的可溶性有机化合物，以及它们在厌氧消化系统中的转化。最大甲烷产量为197.1±3.0 mL CH ₄ / g tCOD_进料用ALK-ULS预处理的污泥（pH 12和比能量输入为24 kJ / g TS）观察到。联合处理可能会增强污泥的溶解度，并产生更多的低分子量（LMW）物质，这有利于提高沼气的产生率。但是，这种预处理不仅释放出易于生物降解的物质，而且释放出更多的顽固性物质，例如腐殖质（HS）和复杂的高分子量（HMW）蛋白。因此，消化后检测到更多的残留溶解有机物（DOM），这可能对下游水处理产生不利影响。难熔HS和疏水性溶解有机碳（HO DOC）是残留DOM中的主要成分，分别占35.0％和22.3％。在分子水平上，大量残留的多环类固醇样物质，确定了烷烃和芳烃。还鉴定了特定的较高分子量残留化合物，例如极性代谢物（如二肽，苯和取代的衍生物）和非极性脂质（如二酰基甘油，长链脂肪酸，烯烃，类黄酮，鞘脂，甘油脂，甘油磷脂及其衍生物）。结果表明，应考虑采取进一步的抛光步骤以除去残留的可溶性顽固性化合物。这项研究有助于从宏观到微观理解污泥处理的见识。还鉴定了甘油磷脂及其衍生物。结果表明，应考虑采取进一步的抛光步骤以除去残留的可溶性顽固性化合物。这项研究有助于从宏观到微观理解污泥处理的见识。还鉴定了甘油磷脂及其衍生物。结果表明，应考虑采取进一步的抛光步骤以除去残留的可溶性顽固性化合物。这项研究有助于从宏观到微观理解污泥处理的见识。