title: Effect of C/N ratio on extracellular polymeric substances of activated sludge from an anoxic-aerobic sequencing batch reactor treating saline wastewater.
abstract: The effect of C/N ratio on extracellular polymeric substances (EPS) of activated sludge was investigated in an anoxic-aerobic sequencing batch reactor (SBR) treating saline wastewater. The protein (PN) and protein/polysaccharide (PN/PS) ratio in the loosely bound EPS (LB-EPS) increased with the decrease of C/N ratio, whereas the PS in the LB-EPS decreased. The PS, PN and PN/PS ratio in the tightly bound EPS (TB-EPS) were independent of C/N ratio. Two fluorescence peaks in the LB-EPS and TB-EPS were identified at excitation/emission (Ex/Em) wavelengths of 275-280/335-340 nm and 220-225/330-340 nm by three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy, respectively. These peaks in LB-EPS and TB-EPS were, respectively, associated with tryptophan protein-like substances and aromatic protein-like substances. The tryptophan protein-like fluorescence peaks in LB-EPS showed blue shift along the Ex axis and red shift along the Em axis with the decrease of C/N ratio. Fourier transform infrared spectra suggested that the variation of C/N ratio had more distinct effect on the functional groups of protein in the LB-EPS than those in the TB-EPS. The sludge volume index value decreased with the increase of LB-EPS, but there was no correlation between SVI and TB-EPS.
authors.affiliation: a Key Lab of Marine Environmental Science and Ecology, Ministry of Education , Ocean University of China , Qingdao 266100 , People's Republic of China.
authors.forename: Zichao
authors.initials: Z
authors.lastname: Wang
authors.forename: Mengchun
authors.initials: M
authors.lastname: Gao
authors.forename: Yanjun
authors.initials: Y
authors.lastname: Xin
authors.forename: Dong
authors.initials: D
authors.lastname: Ma
authors.forename: Zonglian
authors.initials: Z
authors.lastname: She
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.forename: Changqing
authors.initials: C
authors.lastname: Sun
authors.forename: Yun
authors.initials: Y
authors.lastname: Ren
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001704:Biopolymers / Q000032:analysis*; D019149:Bioreactors; D002244:Carbon / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D011134:Polysaccharides / Q000032:analysis*; D011506:Proteins / Q000032:analysis*; D054712:Salinity; D012722:Sewage; D062065:Wastewater
chemical_list: D001704:Biopolymers; D002244:Carbon; D009584:Nitrogen; D011134:Polysaccharides; D011506:Proteins; D012722:Sewage; D062065:Wastewater
keywords: 3D-EEM fluorescence spectroscopy; C/N ratio; EPS; FTIR spectroscopy; salinity