Solid-liquid redistribution and degradation of antibiotics during hydrothermal treatment of sewage sludge: Interaction between biopolymers and antibiotics

Siying Cai; Xinyu Zhang; Shuaiyu Chen; Sainan Peng; Tong Sun; Yu Zhang; Peng Yang; Hongxiang Chai; Dongsheng Wang; Weijun Zhang

doi:10.1016/j.watres.2024.121759

Solid-liquid redistribution and degradation of antibiotics during hydrothermal treatment of sewage sludge: Interaction between biopolymers and antibiotics

Water Res. 2024 May 9:258:121759. doi: 10.1016/j.watres.2024.121759. Online ahead of print.

Authors

Siying Cai¹, Xinyu Zhang¹, Shuaiyu Chen¹, Sainan Peng¹, Tong Sun¹, Yu Zhang¹, Peng Yang², Hongxiang Chai³, Dongsheng Wang⁴, Weijun Zhang⁵

Affiliations

¹ School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China.
² School of Civil Engineering and Architecture, Northeast Electric Power University, Jilin 132012, Jilin, China.
³ Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), College of Environment and Ecology, Chongqing University, Chongqing 400045, China.
⁴ Department of environmental engineering, Zhejiang University, Hangzhou 310058, Zhejiang, China.
⁵ School of Environmental Studies, China University of Geosciences, Wuhan 430074, Hubei, China; National Engineering Research Center of Industrial Wastewater Detoxication and Resource Recovery, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: zhangweijun@cug.edu.cn.

PMID: 38754299
DOI: 10.1016/j.watres.2024.121759

Abstract

Waste activated sludge serves an important reservoir for antibiotics within wastewater treatment plants, and understanding the occurrence and evolution of antibiotics during sludge treatment is crucial to mitigate the potential risks of subsequent resource utilization of sludge. This study explores the degradation and transformation mechanisms of three typical antibiotics, oxytetracycline (OTC), ofloxacin (OFL), and azithromycin (AZI) during sludge hydrothermal treatment (HT), and investigates the influence of biopolymers transformation on the fate of these antibiotics. The findings indicate that HT induces a shift of antibiotics from solid-phase adsorption to liquid-phase dissolution in the initial temperature range of 25-90 °C, underscoring this phase's critical role in preparing antibiotics for subsequent degradation phases. Proteins (PN) and humic acids emerge as crucial for antibiotic binding, facilitating their redistribution within sludge. Specifically, the binding capacity sequence of biopolymers to antibiotics is as follows: OFL>OTC>AZI, highlighting that OFL-biopolymers display stronger electrostatic attraction, more available adsorption sites, and more stable binding strength. Furthermore, antibiotic degradation mainly occurs above 90 °C, with AZI being the most temperature-sensitive, degrading 92.97% at 180 °C, followed by OTC (91.26%) and OFL (52.51%). Concurrently, the degradation products of biopolymers compete for active sites to form novel amino acid-antibiotic conjugates, which inhibits the further degradation of antibiotics. These findings illuminate the effects of biopolymers evolution on intricate dynamics of antibiotics fate in sludge HT and are helpful to optimize the sludge HT process for effective antibiotics abatement.

Keywords: Antibiotics; Biopolymers; Hydrothermal treatment; Molecular simulation; Wastewater sludge.