Abstract
Electrolysis zero-valent iron activated peroxymonosulfate (EZVI-PMS) was applied to enhance sludge dewaterability and disintegration performance. Sludge dewaterability was characterized by capillary suction time (CST), specific resistance to filtration (SRF), and disintegration performance was explored by measuring sludge DNA content, ammonia nitrogen, chemical oxygen demand (COD), extracellular polymeric substances (EPS) and dissolved organic carbon (DOC). EPS, including soluble EPS (SB-EPS), loosely bound EPS (LB-EPS), and tightly bound EPS (TB-EPS) were analyzed by three dimensional fluorescence excitation-emission spectrum (3D-EEM) to confirm the proteins' transformation tendency. DOC, protein and polysaccharide in EPSs were quantified to investigate the conditioning mechanism. The results showed that sludge CST and SRF were reduced significantly when the current was 0.2 A and PMS dosage was 130 mg/gDS with the reductions of 43.8% and 74.1%, respectively, and DNA was released from sludge cells to the liquid phase. Mechanically, sludge TB-EPS converted to SB-EPS with DOC in TB-EPS decreasing from 367.0 mg/L to 210 mg/L, while DOC in SB-EPS increased from 44 mg/L to 167.4 mg/L. Besides, the changes of protein and polysaccharide contents in SB-EPS and TB-EPS were similar to DOC, and protein in TB-EPS transformed to other protein-like or organic substances obviously.
Highlights
With the increase in the amount of sewage treatment, the waste activated sludge produced by waste water treatment plants (WWTPs) is huge in China (Wang et al 2018; Gao et al 2021), the moisture content of which reaches more than 99% (Liang et al 2020), and is still about 96% even after the thickening process
Effect of electro-oxidation on sludge filterability The effects of EZVI-PMS on sludge dewaterability in terms of capillary suction time (CST) and specific resistance to filtration (SRF) under different current intensities are shown in Figures 2(a) and 1(b)
The results indicated that EZVI-PMS has a remarkable influence on sludge dewaterability
Summary
With the increase in the amount of sewage treatment, the waste activated sludge produced by waste water treatment plants (WWTPs) is huge in China (Wang et al 2018; Gao et al 2021), the moisture content of which reaches more than 99% (Liang et al 2020), and is still about 96% even after the thickening process. Extracellular polymeric substances (EPS), as the main component of sludge flocs, account for 80% of sludge solids (Yang et al 2017), and are mainly microbial metabolites, such as proteins, polysaccharides and humic substances (More et al 2014). These substances are highly hydrophilic (Yuan et al 2017), making EPS able to wrap up a large amount of water and impede the separation of sludge particles and water. Destroying EPS structure does not necessarily improve the dewatering performance: if the properties
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