Combined microbial transcript and metabolic analysis reveals the different roles of hydrochar and biochar in promoting anaerobic digestion of waste activated sludge

Zhijian Shi; Muhammad Usman; Jun He; Huihui Chen; Shicheng Zhang; Gang Luo

doi:10.1016/j.watres.2021.117679

Combined microbial transcript and metabolic analysis reveals the different roles of hydrochar and biochar in promoting anaerobic digestion of waste activated sludge

Water Res. 2021 Oct 15:205:117679. doi: 10.1016/j.watres.2021.117679. Epub 2021 Sep 24.

Authors

Zhijian Shi¹, Muhammad Usman², Jun He¹, Huihui Chen³, Shicheng Zhang⁴, Gang Luo⁵

Affiliations

¹ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China.
² Bioproducts Science and Engineering Laboratory, Washington State University (WSU), Tri-Cities, WA 99354, United States.
³ College of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
⁴ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
⁵ Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China; Shanghai Technical Service Platform for Pollution Control and Resource Utilization of Organic Wastes, Shanghai 200438, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China. Electronic address: gangl@fudan.edu.cn.

PMID: 34600232
DOI: 10.1016/j.watres.2021.117679

Abstract

Hydrothermal pretreatment of waste activated sludge (WAS) could eliminate the rate limiting step of anaerobic digestion (AD) -hydrolysis. However, the high organic loading rate may cause acid accumulation, thus leading to an unstable system. This study compared the effect of different hydrochar (HC2-260°C and HC3-320°C) and biochar (BC5-500°C and BC7-700°C) on AD of hydrothermal pretreated WAS (HPS). Results demonstrated that hydrochar was superior to biochar in the methane yield and production rate, especially HC2. HC2 had the highest surface oxygen-containing functional groups that could facilitate direct interspecies electron transfer (DIET). The enhanced methane yield was related with the increased protein utilization, and hydrochar and biochar enriched different microbes related to protein degradation. Metabolomic analysis showed the significantly changed metabolites induced by hydrochar and biochar were involved in fatty acids and amino acids-related metabolism, indicating the rapid conversion of intermediated products, which was consistent with the microbial community structure results. Hydrochar and biochar also induced upregulation of metabolites related to microbial metabolic activity and extracellular electron transfer. Although biochar induced the same metabolic changes, the alterations of these metabolites were weaker than those of hydrochar. The results of this study offered new insights into the molecular mechanisms of enhanced AD of HPS by hydrochar and biochar.

Keywords: 16S rRNA transcript analysis; Biochar; Hydrochar; Metabolomic analysis; Methane.

MeSH terms

Anaerobiosis
Bioreactors
Charcoal*
Methane
Sewage*

Substances

Sewage
biochar
Charcoal
Methane