title: Effect of carbon to nitrogen ratio on the physical and chemical properties of activated sludge.
abstract: The effect of carbon to nitrogen ratio (C/N) of the feed on the physical and surface chemical properties of activated sludge is investigated. Semi-continuous reactors with 2 liters volume were operated at a mean cell residence time of 8 days. These mixed culture reactors were operated at 3 different carbon to nitrogen ratio. The operation of conventional activated sludge plants treating municipal wastewater is represented with reactors having a C/N ratio of 21 (in terms of the ratio of COD to TKN). Carbon and nitrogen limited activated sludge systems are represented by reactors with a C/N ratio of 9 and 43, respectively. The results show that C/N ratio has a profound effect on the ultimate physical and surface chemical properties of activated sludge. Both the steady state microorganism concentration and the amount of microbial extracellular polymers produced increase with increasing C/N ratio. The sludge becomes much harder to dewater and settle and it becomes more viscous as the C/N ratio increases. A decrease in surface hydrophobicity and an increase in surface charge of the sludge accompany these physical changes.
authors.affiliation: Middle East Technical University, Department of Environmental Engineering, 06531 Ankara, Turkey.
authors.forename: B
authors.initials: B
authors.lastname: Durmaz
authors.forename: F D
authors.initials: FD
authors.lastname: Sanin
mesh_terms: D019149:Bioreactors; D002244:Carbon / Q000737:chemistry*; D006801:Humans; D009584:Nitrogen / Q000737:chemistry*; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods
chemical_list: D012722:Sewage; D002244:Carbon; D009584:Nitrogen