Degradation of extracellular polymeric substances (EPS) extracted from activated sludge by low-concentration ozonation. (March 2016)

• Record Type: Journal Article
• Authors: Meng, Lu; Xi, Jinying; Yeung, Marvin
• Is Part Of: Chemosphere. Volume 147(2016)
• Page Start: 248
• Page End: 255
• Publication Date: 2016-03
• Subjects: Extracellular polymeric substances (EPS) -- Ozone -- Protein -- Polysaccharide; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.12.060
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Reaction mechanisms between ozone and extracellular polymeric substances (EPS) can be the key of understanding the improvements in microbial aggregates properties by low-concentration ozonation. In this study, EPS are extracted from activated sludge and treated continuously by ozone gas at 270 ± 41 ppm. The reaction between ozone and EPS was investigated by observation of EPS component concentrations, functional groups and molecular weight distributions using UV–Vis spectrometry, excitation-emission matrix fluorescence spectroscopy (EEM), high performance size-exclusion chromatography (HPSEC) and gas chromatography-mass spectrometry (GC–MS). In a 12-hour-ozonation experiment, significant ozone consumption was observed in the first 4 h and protein concentration in EPS solution was reduced by 30 ± 12%. However, the polysaccharides concentration only had a slightly decrease at the end of the ozonation process. UV–Vis spectra and EEM spectra results suggest that ozone removed protein and fluorescent matters (SMP and tryptophan-like aromatic protein) rapidly by attacking specific amino acid residues on polypeptide chain. After ozonation, the molecular weight of polysaccharide and protein dropped by 4 orders of magnitude according to HPSEC results. TOC concentration of EPS solution was reduced by 13 ± 2% after ozonation. The loss in TOC could be explained by the observation of volatile organic compounds such as carboxylic acids, aldehydes and ketones in the off-gas detected by GC–MS. The results in this study can provide a better understanding towards the mechanisms of improvements in activated sludge properties by ozonation. Highlights: Degradation of EPS by ozonation was studied to understand activated sludge property. Ozone reacts with protein in EPS by attacking amino acid residue on polypeptide chain. The polysaccharides/protein molecular weights decreased significantly after ozonation.