title: Effect of carbon to nitrogen ratio of feed wastewater and sludge retention time on activated sludge in a submerged membrane bioreactor.
abstract: This paper investigated the effects of extracellular polymeric substances (EPS) on the activated sludge rheology in a submerged membrane bioreactor (sMBR) operated at different sludge retention time (SRT) values and different carbon to nitrogen ratios (C/N) of feed wastewater. The C/N ratios of the feed were adjusted accordingly so that synthetic wastewaters prepared simulated municipal wastewater, non-toxic wastewater with high C/N ratio and non-toxic wastewater with low C/N ratio. A number of important operational parameters such as mixed liquor suspended solid (MLSS), protein fraction of EPS (EPSp), carbohydrate fraction of EPS (EPSc), protein fraction of soluble microbial product (SMPp), carbohydrate fraction of SMP (SMPc), apparent viscosity, critical flux and hydrophobicity in mixed liquor and their correlations were investigated in the sMBR systems operated. The statistical analysis indicated that the C/N ratio of feed, SRT, MLSS and SMPc were found to have positive effects on apparent viscosity at three different shear rates. On the other hand, a negative impact was detected between the apparent viscosities and the critical fluxes. It was also observed that there is a significant positive correlation between hydrophobicity and both EPSp and SMPp.
authors.affiliation: Department of Environmental Engineering, Faculty of Civil Engineering, Yildiz Technical University, 34220 Davutpasa, Esenler, Istanbul, Turkey. hsari@yildiz.edu.tr.
authors.forename: Hanife Sari
authors.initials: HS
authors.lastname: Erkan
authors.affiliation: Department of Environmental Engineering, Faculty of Civil Engineering, Yildiz Technical University, 34220 Davutpasa, Esenler, Istanbul, Turkey.
authors.forename: Guleda
authors.initials: G
authors.lastname: Onkal Engin
authors.affiliation: Department of Environmental Engineering, Faculty of Civil Engineering, Yildiz Technical University, 34220 Davutpasa, Esenler, Istanbul, Turkey.
authors.forename: Mahir
authors.initials: M
authors.lastname: Ince
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, Gebze Technical University, 41400, Gebze, Kocaeli, Turkey.
authors.forename: Mahmut R
authors.initials: MR
authors.lastname: Bayramoglu
mesh_terms: D001704:Biopolymers; D019149:Bioreactors; D002244:Carbon / Q000032:analysis*; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D009584:Nitrogen / Q000032:analysis*; D014783:Viscosity; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000032:analysis*
chemical_list: D001704:Biopolymers; D002244:Carbon; D008567:Membranes, Artificial; D009584:Nitrogen; D062065:Wastewater
keywords: Activated sludge; C/N ratio; Critical flux; Extracellular polymeric substances; Membrane bioreactors; Rheology