Novel thermodynamic mechanisms of co-conditioning with polymeric aluminum chloride and polyacrylamide for improved sludge dewatering: A paradigm shift in the field

Yansha Zeng; Zhe Wang; Zhenxiang Pan; Liguo Shen; Jiaheng Teng; Hongjun Lin; Jianzhen Zhang

doi:10.1016/j.envres.2023.116420

Novel thermodynamic mechanisms of co-conditioning with polymeric aluminum chloride and polyacrylamide for improved sludge dewatering: A paradigm shift in the field

Environ Res. 2023 Oct 1:234:116420. doi: 10.1016/j.envres.2023.116420. Epub 2023 Jun 14.

Authors

Yansha Zeng¹, Zhe Wang², Zhenxiang Pan³, Liguo Shen⁴, Jiaheng Teng⁵, Hongjun Lin⁶, Jianzhen Zhang⁷

Affiliations

¹ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: zengyansha@zjnu.edu.cn.
² College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: wangzhe321000@zjnu.edu.cn.
³ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: 838265202@zjnu.edu.cn.
⁴ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: lgshen@zjnu.cn.
⁵ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: tengjiaheng@zjnu.edu.cn.
⁶ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: linhonjun@163.com.
⁷ College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, China; Key Laboratory of Watershed Earth Surface Processes and Ecological Security, Zhejiang Normal University, Jinhua, 321004, China. Electronic address: zjz@zjnu.cn.

PMID: 37327838
DOI: 10.1016/j.envres.2023.116420

Abstract

This study investigated the combined effects of polymeric aluminum chloride (PAC) and polyacrylamide (PAM) on sludge dewatering, aiming to unveil underlying mechanisms. Co-conditioning with 15 mg g^-1 PAC and 1 mg g^-1 PAM achieved optimal dewatering, reducing specific filtration resistance (SFR) of co-conditioned sludge to 4.38 × 10¹² m^-1kg^-1, a mere 48.1% of raw sludge's SFR. Compared with the CST of raw sludge (36.45 s), sludge sample can be significantly reduced to 17.7 s. Characterization tests showed enhanced neutralization and agglomeration in co-conditioned sludge. Theoretical calculations revealed elimination of interaction energy barriers between sludge particles post co-conditioning, converting sludge surface from hydrophilic (3.03 mJ m^-2) to hydrophobic (-46.20 mJ m^-2), facilitating spontaneous agglomeration. Findings explain improved dewatering performance. Based on Flory-Huggins lattice theory, connection between polymer structure and SFR was established. Raw sludge formation triggered significant change in chemical potential, increasing bound water retention capacity and SFR. In contrast, co-conditioned sludge exhibited thinnest gel layer, reducing SFR and significantly improving dewatering. These findings represent a paradigm shift, shedding new light on fundamental thermodynamic mechanisms of sludge dewatering with different chemical conditioning.

Keywords: Coagulation/flocculation; Extracellular polymer; Sludge dewatering; Specific filtration resistance; Thermodynamic mechanism.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aluminum Chloride
Filtration
Flocculation
Polymers / chemistry
Sewage*
Thermodynamics
Waste Disposal, Fluid*
Water / chemistry

Substances

Sewage
Aluminum Chloride
polyacrylamide
Polymers
Water