Enhancement of waste activated sludge hydrolysis and decomposition by combined free nitrous acid and sodium citrate pretreatment

• Published in: Journal of water process engineering Vol. 54; p. 103945
• Main Authors: Zhou, Wu-yang, Fang, Qian, Ding, Wen-xue, Xiao, Zi-long, Luo, Fan, Ren, Peng-fei, Wang, Guang-hua
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.08.2023
• Subjects: Free nitrous acid; Microbial community; Short-chain fatty acids; Sodium citrate; Waste activated sludge; Short-chain fatty acids; Waste activated sludge; Free nitrous acid; Sodium citrate; Microbial community
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2023.103945

Hydrolysis of waste activated sludge (WAS) is the limiting step in the anaerobic fermentation process. In view of this, this study evaluated the feasibility of a combination of free nitrous acid (FNA) and sodium citrate (SC) pretreatment to promote WAS hydrolysis and anaerobic fermentation. The results showed that the combined treatment of FNA and SC could promote the decomposition of WAS. Under the conditions of 2.504 mg/L FNA and 0.25 g/g total suspended solids of SC pretreatment for 5 h, the soluble chemical oxygen demand release rate (DDSCOD) was 1.86 and 1.42 times that of FNA and SC pretreatment alone. Meanwhile, the contribution rate of intracellular organic compounds reached 84.18 %. The maximum short-chain fatty acids yield was obtained at the 8th day of fermentation, which was 580.34 mg COD/g volatile suspended solids. The protein utilization rate of combined pretreatment was increased to 74.10 %, which was much higher than that of single treatment. Moreover, FNA-SC also changed the activities of key enzymes, increasing the activities of protease and α-glucosidase but inhibiting the activities of coenzyme F420. Microbial analysis showed that the combined pretreatment significantly changed the composition of microbial community and effectively enriched acid-producing bacteria (such as Petrimonas and Macellibacteroides). [Display omitted] •DDSCOD of FNA-SC was 1.86 and 1.42 times that of FNA and SC treatment alone.•FNA coupled SC pretreatment can enrich acid-producing bacteria of the genus.•The protein utilization of the combined pretreatment was increased to 74.10 %.•The co-pretreatment increased the activity of three key enzyme.•The combined pretreatment enhanced the EPS structure and cell wall disruption