Current Status and Prospects of Environmentally Friendly Sludge Dewatering, Solidification and Stabilization Technology

A special issue of Separations (ISSN 2297-8739). This special issue belongs to the section "Separation Engineering".

Deadline for manuscript submissions: 10 March 2026 | Viewed by 677

Special Issue Editors

State Key Laboratory of Water Pollution Control and Green Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
Interests: solid waste management; solid–liquid separation; hazardous waste disposal

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Guest Editor
College of Mechanical and Electrical Engineering, China Jiliang University, Hangzhou 310018, China
Interests: sludge dewatering; drying; solid–liquid separation; porous media; energy-saving and efficient equipment

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Guest Editor
Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
Interests: municipal solid wastes; solid waste management; dewatering; rheological characterization; solid waste resource

Special Issue Information

Dear Colleagues,

Sludge is an inevitable by-product generated by the transformation of pollutants or sediments converted from pollutants during wastewater treatment or water environment remediation processes. Various toxic substances, such as pathogens, heavy metals, and organic pollutants, make the safe disposal of sludge a crucial step for the secondary pollution control of water pollution control.

High moisture content is one of the main limiting factors of the resource/energy recovery and disposal of sludge. Dewatering can minimize the sludge volume, facilitate the transportation, and increase the calorific value. Thus, dewatering commonly acts as the essential step of different sludge treatment routines. However, sludge presents a stable state with water–solid infiltration, which is difficult to be dewatered without pretreatment.

Aiming at highly efficient dewatering of sludge, the multiple influencing factors on sludge dewaterability should be systematically analyzed and more efforts should be devoted to improving sludge dewaterability by various approaches with minimal consumption of chemicals and energy.

Therefore, this Special Issue aims to consolidate and disseminate knowledge in the field. We invite you to contribute your research article, communication, or review related to the basic theory and technical inovation of sludge dewatering processes.

Dr. Boran Wu
Prof. Dr. Binqi Rao
Dr. Houfeng Wang
Guest Editors

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Keywords

  • sewage sludge
  • hazardous waste
  • dewatering
  • solidification
  • stabilization

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Published Papers (1 paper)

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Research

14 pages, 2613 KB  
Article
Synergistic Enhancement of Sludge Deep Dewatering via Tea Waste and Sludge-Derived Biochars Coupled with Polyaluminum Chloride
by Qiang-Ying Zhang, Geng Xu, Hui-Yun Qi, Xuan-Xin Chen, Hou-Feng Wang and Xiao-Mei Cui
Separations 2025, 12(9), 229; https://doi.org/10.3390/separations12090229 - 27 Aug 2025
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Abstract
Although coagulation can enhance sludge dewatering performance, it often leads to dense flocs, hindered water release, and secondary pollution of the sludge cake. In this study, three types of biochar-based skeleton materials, tea waste-derived biochar (TB), PAC sludge-derived biochar (PB), and their mixture [...] Read more.
Although coagulation can enhance sludge dewatering performance, it often leads to dense flocs, hindered water release, and secondary pollution of the sludge cake. In this study, three types of biochar-based skeleton materials, tea waste-derived biochar (TB), PAC sludge-derived biochar (PB), and their mixture (MB), were employed in combination with polyaluminum chloride (PAC) to improve sludge permeability and water release capacity. The results showed that PAC alone reduced the water content (Wc) and capillary suction time (CST) of raw sludge (RS) from 79.07% and 97.45 s to 69.45% and 42.30 s, respectively. In contrast, biochar–PAC composite conditioning achieved further enhancement. Among them, the TBP group (10% DS TB + 4% DS PAC) exhibited the best performance, with Wc and CST reduced to 58.73% and 55.65 s, reaching the threshold for deep dewatering (Wc < 60%). Low-field nuclear magnetic resonance (LF-NMR) analysis revealed an enhanced transformation from bound to free water, improving water mobility. Zeta potential and particle size analysis indicated that biochar promoted electrostatic neutralization and adsorption bridging. Rheological and EPS measurements demonstrated significant reductions in yield stress and apparent viscosity, alongside the enhanced release of proteins and polysaccharides into soluble EPS (S-EPS). Scanning electron microscopy and pore structure analysis further confirmed that biochar formed a stable porous skeleton (pore diameter up to 1.365 μm), improving sludge cake permeability. In summary, biochar synergizes with PAC through a “skeleton support–charge neutralization–adsorption bridging” mechanism, reconstructing sludge microstructure and significantly improving deep dewatering performance. Full article
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