Sludge biodrying coupled with photocatalysis improves the degradation of extracellular polymeric substances

Lu Cai; Meng-Ke Cao; Guo-Di Zheng; Xin-Yu Wang; Han-Tong Guo; Tao Jiang

doi:10.1016/j.jenvman.2023.118590

Sludge biodrying coupled with photocatalysis improves the degradation of extracellular polymeric substances

J Environ Manage. 2023 Nov 1:345:118590. doi: 10.1016/j.jenvman.2023.118590. Epub 2023 Jul 26.

Authors

Lu Cai¹, Meng-Ke Cao¹, Guo-Di Zheng², Xin-Yu Wang¹, Han-Tong Guo², Tao Jiang³

Affiliations

¹ School of Civil and Environmental Engineering, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, China.
² Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
³ School of Civil and Environmental Engineering, School of Physical Science and Technology, Ningbo University, Ningbo, 315211, China. Electronic address: jiangtao@nbu.edu.cn.

PMID: 37499415
DOI: 10.1016/j.jenvman.2023.118590

Abstract

The efficiency of sludge dewatering is limited by extracellular polymeric substances (EPS) during biodrying. This study investigated the effect of photocatalysis-mediated EPS degradation on sludge dewatering performance during the sludge biodrying process. The photocatalysis of municipal sludge was first carried out to choose a cost-efficient catalyst. Then sludge biodrying tests were performed using TiO₂-coated amendment (T_CA) and uncoated amendment (T_UCA) as the control. Municipal sludge photocatalysis results showed that using TiO₂ could efficiently degrade carbohydrates and proteins in the EPS within 60 min. After 20-day biodrying, photocatalysis significantly promoted a reduction in the moisture content and EPS by 17.64% and 6.88%, respectively. The surface-enhanced Raman scattering (SERS) intensities of the C-C-O symmetric stretching vibration peak of D-lactose and the C-S stretching vibration peak of cysteine were significantly decreased by approximately 33.19% and 44.76%, respectively, indicating that photocatalysis indeed promoted the reduction of polysaccharides and cysteine in the EPS, especially after the thermophilic phase. The hydrophilic amino acid content decreased by 23.02%, verifying that photocatalysis could improve EPS hydrophobicity. Consequently, municipal sludge biodrying coupled with photocatalysis promotes sludge EPS degradation and enhances sludge dewaterability, improving the efficiency of sludge biodrying.

Keywords: Biodrying; Extracellular polymeric substances; Hydrophobic amino acid; Sludge dewatering; TiO(2) photocatalysis.

MeSH terms

Cysteine
Extracellular Polymeric Substance Matrix*
Sewage* / chemistry
Waste Disposal, Fluid / methods
Water / chemistry

Substances

Sewage
titanium dioxide
Cysteine
Water