title: Influence of COD:N ratio on sludge properties and their role in membrane fouling of a submerged membrane bioreactor.
abstract: The effect of COD:N ratio on sludge properties and their role in membrane fouling were examined using a well-controlled aerobic membrane bioreactor receiving a synthetic high strength wastewater containing glucose. Membrane performance was improved with an increase in the COD/N ratio (100:5-100:1.8) (i.e. reduced N dosage). Surface analysis of sludge by X-ray photoelectron spectroscopy (XPS) indicates significant differences in surface concentrations of elements C, O and N that were observed under different COD/N ratios, implying changes in the composition of extracellular polymeric substances (EPS). Fourier transform-infrared spectroscopy (FTIR) revealed a unique characteristic peak (CO bonds) at 1735 cm(-1) under nitrogen limitation conditions. Total EPS decreased with an increase in COD/N ratio, corresponding to a decrease in the proteins (PN) to carbohydrates (CH) ratio in EPS. There were no significant differences in the total soluble microbial products (SMPs) but the ratio of PN/CH in SMPs decreased with an increase in COD/N ratios. The results suggest that EPS and SMP composition and the presence of a small quantity of filamentous microorganisms played an important role in controlling membrane fouling.
authors.affiliation: Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Hao
authors.affiliation: School of Environmental Studies and Department of Chemical Engineering, Queen's University, Kingston, ON K7L 3N6, Canada.
authors.forename: S N
authors.initials: SN
authors.lastname: Liss
authors.affiliation: Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, ON P7B 5E1, Canada. Electronic address: bliao@lakeheadu.ca.
authors.forename: B Q
authors.initials: BQ
authors.lastname: Liao
mesh_terms: D057919:Biological Oxygen Demand Analysis; D019149:Bioreactors; D002241:Carbohydrates / Q000737:chemistry; D008567:Membranes, Artificial; D009584:Nitrogen / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D011108:Polymers; D011506:Proteins / Q000737:chemistry; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology; D017550:Spectroscopy, Fourier Transform Infrared; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology
chemical_list: D002241:Carbohydrates; D008567:Membranes, Artificial; D009584:Nitrogen; D011108:Polymers; D011506:Proteins; D012722:Sewage; D062065:Wastewater
keywords: COD:N; Extracellular polymeric substances; Industrial wastewater; Membrane bioreactor; Membrane fouling; Sludge properties