Enhanced short-chain fatty acids production through a short-term anaerobic fermentation of waste activated sludge: Synergistic pretreatment of alkali and alkaline hydrolase blend

• Published in: Journal of cleaner production Vol. 342; p. 130954
• Main Authors: Pang, Heliang, Jiao, Qiangqiang, He, Junguo, Zhang, Zhiqiang, Wang, Ling, Yan, Zhongsen, Lu, Jinsuo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.03.2022
• Subjects: Alkaline hydrolase blend; Anaerobic fermentation; Carbon recovery; Carbon-emission reduction; Short-chain fatty acids; Waste activated sludge; Short-chain fatty acids; Anaerobic fermentation; Waste activated sludge; Carbon-emission reduction; Carbon recovery; Alkaline hydrolase blend
• ISSN: 0959-6526; 1879-1786
• DOI: 10.1016/j.jclepro.2022.130954

Short-chain fatty acids (SCFAs) recovery through anaerobic fermentation is a promising pathway to achieve economic benefits and carbon-emission reduction in waste activated sludge management. Although numerous pretreatment approaches have been investigated, alkaline hydrolase blend (AHB) incubation at initial pH 10.0 condition for enhancing anaerobic fermentation has rarely been reported. In this study, the sludge flocs were disintegrated into electronegative particle fragments with extracellular polymeric substance disruption and microbial cell lysis, owing to the synergistic effect of alkali-triggered sludge solubilization and AHB-catalyzed hydrolysis. Substantial sludge hydrolysis and biodegradable organic matter release were thereby induced. After pH 10 + AHB pretreatment for 2 h, numerous SCOD release of 5109 mg/L was achievable, which was approximately 12.4, 2.02, and 1.19 times higher than those in control, pH 10 and pH 10+alkaline protease pretreatments, respectively. Meanwhile, the AHB boosted hydrolysis and biodegradation of dissolved organic matters, promoting a low molecular weight shift in molecular weight distribution. The dissolved organic matter compositions tended to low molecular weight organic matters, accelerating the overall anaerobic fermentation process. Correspondingly, considerable SCFAs of 528.9 mg COD/g VSS was produced through a short-term anaerobic fermentation (3 days), which was 5.6, 1.7 and 1.1 times higher than the maximum SCFAs production by control, pH 10 and pH 12–10+alkaline protease pretreatments, respectively. The produced SCFAs were mostly composed of acetate (58.7%), which could be recovered as biodegradable carbon source. By adopting the AHB-based strategy, economic benefits of 392.4–580.6 CNY/ton sludge SS and carbon-emission reduction of 0.207–0.521 ton CO2/ton sludge SS were achievable. Apparently, the AHB-based strategy is a cost-effective and carbon-beneficial technology for sludge management. [Display omitted] •pH 10 + AHB pretreatment induced remarkable sludge hydrolysis (SCOD/TCOD = 32.5%).•AHB facilitated DOMs hydrolysis and biodegradation with low molecular weight shift.•Alkali-triggered sludge solubilization and AHB-catalyzed hydrolysis was proposed.•SCFAs of 349.9 mg COD/g SS was produced by a short-term anaerobic fermentation.•Carbon recovery with economic and carbon-emission reduction benefits were assessed.