Anaerobic fermentation of aerobic granular sludge: Insight into the effect of granule size and sludge structure on hydrolysis and acidification

Jinte Zou; Lei Cai; Jianrui Lin; Ruyi Wang; Jun Li; Mingsheng Jia

doi:10.1016/j.jenvman.2023.118202

Anaerobic fermentation of aerobic granular sludge: Insight into the effect of granule size and sludge structure on hydrolysis and acidification

J Environ Manage. 2023 Oct 1:343:118202. doi: 10.1016/j.jenvman.2023.118202. Epub 2023 May 24.

Authors

Jinte Zou¹, Lei Cai², Jianrui Lin², Ruyi Wang³, Jun Li², Mingsheng Jia⁴

Affiliations

¹ College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China; Shaoxing Research Institute, Zhejiang University of Technology, Shaoxing, 312000, China.
² College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
³ School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, 310012, China. Electronic address: wangry@zjgsu.edu.cn.
⁴ Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium.

PMID: 37229861
DOI: 10.1016/j.jenvman.2023.118202

Abstract

Aerobic granular sludge (AGS) has different physicochemical properties and microbial communities compared to conventional activated sludge (CAS), which may result in different behaviors during anaerobic fermentation and require further investigation. This study investigated the effect of granule size and sludge structure on the hydrolysis and acidification of AGS. Experimental results show that AGS exhibited significantly higher soluble chemical oxygen demand (SCOD) dissolution and total volatile fatty acids (TVFA) production (330.6-430.3 mg/gVSS and 231.0-312.5 mgCOD/gVSS) compared to conventional activated sludge (CAS) (167.0 mg/gVSS and 133.3 mgCOD/gVSS). This is because AGS (90.6-96.9 mg/gVSS) had higher extracellular polymeric substances (EPS) content than CAS (81.2 mg/gVSS). EPS can not only serve as substrates but also release the trapped hydrolases. Moreover, the relative abundances of hydrolytic/acidogenic bacteria and genes were higher in AGS (0.46%-3.60% and 3.01 × 10^-3%-4.04 × 10^-3%) than in CAS (0.30% and 1.23 × 10^-3%). The optimal granule size for AGS fermentation was found to be 500-1600 μm. The crushing of granule structure promoted the dissolution of small amounts of EPS and the release of some trapped hydrolases, thereby potentially enhancing the enzyme-substrate contacts and bacteria-substrate interactions. Therefore, the highest SCOD dissolution (510.6 mg/gVSS) and TVFA production (352.1 mgCOD/gVSS) from crushed 500-1600 μm AGS were observed. Overall, the findings of this study provide valuable insights into the recovery of organic carbon from AGS via anaerobic fermentation.

Keywords: Aerobic granular sludge; Anaerobic fermentation; Extracellular polymeric substances; Granule size; Granule structure.

MeSH terms

Anaerobiosis
Bacteria
Bioreactors*
Fatty Acids, Volatile
Fermentation
Hydrogen-Ion Concentration
Hydrolases
Hydrolysis
Sewage* / chemistry
Waste Disposal, Fluid / methods

Substances

Sewage
Hydrolases
Fatty Acids, Volatile