Comparison of different sewage sludge pretreatment technologies for improving sludge solubilization and anaerobic digestion efficiency: A comprehensive review

Pan Zhou; Dunjie Li; Cong Zhang; Qian Ping; Lin Wang; Yongmei Li

doi:10.1016/j.scitotenv.2024.171175

Comparison of different sewage sludge pretreatment technologies for improving sludge solubilization and anaerobic digestion efficiency: A comprehensive review

Sci Total Environ. 2024 Apr 15:921:171175. doi: 10.1016/j.scitotenv.2024.171175. Epub 2024 Feb 24.

Authors

Pan Zhou¹, Dunjie Li¹, Cong Zhang¹, Qian Ping², Lin Wang², Yongmei Li³

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
² State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China.
³ State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, PR China. Electronic address: liyongmei@tongji.edu.cn.

PMID: 38402967
DOI: 10.1016/j.scitotenv.2024.171175

Abstract

Anaerobic digestion (AD) of sewage sludge reduces organic solids and produces methane, but the complex nature of sludge, especially the difficulty in solubilization, limits AD efficiency. Pretreatments, by destroying sludge structure and promoting disintegration and hydrolysis, are valuable strategies to enhance AD performance. There is a plethora of reviews on sludge pretreatments, however, quantitative comparisons from multiple perspectives across different pretreatments remain scarce. This review categorized various pretreatments into three groups: Physical (ultrasonic, microwave, thermal hydrolysis, electric decomposition, and high pressure homogenization), chemical (acid, alkali, Fenton, calcium peroxide, and ozone), and biological (microaeration, exogenous bacteria, and exogenous hydrolase) pretreatments. The optimal conditions of various pretreatments and their impacts on enhancing AD efficiency were summarized; the effects of different pretreatments on microbial community in the AD system were comprehensively compared. The quantitative comparison based on dissolution degree of COD (DD_COD) indicted that the sludge solubilization performance is in the order of physical, chemical, and biological pretreatments, although with each below 40 % DD_COD. Biological pretreatment, particularly microaeration and exogenous bacteria, excel in AD enhancement. Pretreatments alter microbial ecology, favoring Firmicutes and Methanosaeta (acetotrophic methanogens) over Proteobacteria and Methanobacterium (hydrogenotrophic methanogens). Most pretreatments have unfavorable energy and economic outcomes, with electric decomposition and microaeration being exceptions. On the basis of the overview of the above pretreatments, a full energy and economy assessment for sewage sludge treatment was suggested. Finally, challenges associated with sludge pretreatments and AD were analyzed, and future research directions were proposed. This review may broaden comprehension of sludge pretreatments and AD, and provide an objective basis for the selection of sludge pretreatment technologies.

Keywords: Biogas yield; Economy assessment; Energy assessment; Microbial community; Sludge pretreatment; Sludge solubilization.

Publication types

Review

MeSH terms

Anaerobiosis
Bioreactors
Hydrolysis
Methane / chemistry
Sewage* / microbiology
Ultrasonics*
Waste Disposal, Fluid

Substances

Sewage
Methane