title: Degradation of extracellular polymeric substances (EPS) extracted from activated sludge by low-concentration ozonation.
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.
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, 100084 Beijing, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Meng
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, 100084 Beijing, China. Electronic address: xijinying@tsinghua.edu.cn.
authors.forename: Jinying
authors.initials: J
authors.lastname: Xi
authors.affiliation: Environmental Simulation and Pollution Control State Key Joint Laboratory, School of Environment, Tsinghua University, 100084 Beijing, China.
authors.forename: Marvin
authors.initials: M
authors.lastname: Yeung
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D002850:Chromatography, Gel; D008401:Gas Chromatography-Mass Spectrometry; D008970:Molecular Weight; D016877:Oxidants / Q000737:chemistry*; D010126:Ozone / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D012722:Sewage / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods
chemical_list: D001704:Biopolymers; D016877:Oxidants; D011134:Polysaccharides; D011506:Proteins; D012722:Sewage; D010126:Ozone
keywords: Extracellular polymeric substances (EPS); Ozone; Polysaccharide; Protein