Aged refuse enhances anaerobic digestion of waste activated sludge. (15th October 2017)

• Record Type: Journal Article
• Authors: Zhao, Jianwei; Gui, Lin; Wang, Qilin; Liu, Yiwen; Wang, Dongbo; Ni, Bing-Jie; Li, Xiaoming; Xu, Rui; Zeng, Guangming; Yang, Qi
• Is Part Of: Water research. Volume 123(2017)
• Page Start: 724
• Page End: 733
• Publication Date: 2017-10-15
• Subjects: Waste activated sludge -- Anaerobic digestion -- Aged refuse -- Hydrolysis -- Acidogenesis; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2017.07.026
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: In this work, a low-cost alternative approach (i.e., adding aged refuse (AR) into waste activated sludge) to significantly enhance anaerobic digestion of sludge was reported. Experimental results showed that with the addition dosage of AR increasing from 0 to 400 mg/g dry sludge soluble chemical oxygen demand (COD) increased from 1150 to 5240 mg/L at the digestion time of 5 d, while the maximal production of volatile fatty acids (VFA) increased from 82.6 to 183.9 mg COD/g volatile suspended solids. Although further increase of AR addition decreased the concentrations of both soluble COD and VFA, their contents in these systems with AR addition at any concentration investigated were still higher than those in the blank, which resulted in higher methane yields in these systems. Mechanism studies revealed that pertinent addition of AR promoted solubilization, hydrolysis, and acidogenesis processes and did not affect methanogenesis significantly. It was found that varieties of enzymes and anaerobes in AR were primary reason for the enhancement of anaerobic digestion. Humic substances in AR benefited hydrolysis and acidogenesis but inhibited methanogenesis. The effect of heavy metals in AR on sludge anaerobic digestion was dosage dependent. Sludge anaerobic digestion was enhanced by appropriate amounts of heavy metals but inhibited by excessive amounts of heavy metals. The relative abundances of microorganisms responsible for sludge hydrolysis and acidogenesis were also observed to be improved in the system with AR addition, which was consistent with the performance of anaerobic digestion. Graphical abstract: Image 1 Highlights: Aged refuse accelerated sludge solubilization, hydrolysis, and acidogenesis. Enzymes and anaerobes in aged refuse were the primary reason. Humic substances in aged refuse benefited hydrolysis and acidogenesis. The effect of heavy metals in aged refuse on hydrolysis and acidogenesis was dosage dependent.