title: Experimental evidence for osmotic pressure-induced fouling in a membrane bioreactor.
abstract: A lab-scale membrane bioreactor (MBR) was continuously operated to investigate the membrane fouling. A new membrane fouling mechanism: osmotic pressure mechanism in cake layer filtration process was identified. Osmotic pressure was proposed to stem from the retention of counter-ions in the matrix of biopolymers in cake layer. Through Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyzes, it was found that functional groups were abundant in the surface of cake layer. Batch filtration tests showed that soluble microbial products (SMP) and biopolymer clusters (BPC) in the supernatant played key roles in osmotic pressure mechanism, and were thus largely responsible for the high cake resistance. The chemical potential of water varied along with cake depth. The formed cake layer was found to be much hydrated and elastic. These findings provided the direct evidence for the existence of osmotic pressure mechanism.
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China. Electronic address: hjlin@zjnu.cn.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Lin
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Meijia
authors.initials: M
authors.lastname: Zhang
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Fangyuan
authors.initials: F
authors.lastname: Wang
authors.affiliation: Department of Materials Physics, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Yiming
authors.initials: Y
authors.lastname: He
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Jianrong
authors.initials: J
authors.lastname: Chen
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Huachang
authors.initials: H
authors.lastname: Hong
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Aijun
authors.initials: A
authors.lastname: Wang
authors.affiliation: College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua 321004, PR China.
authors.forename: Haiying
authors.initials: H
authors.lastname: Yu
mesh_terms: D019149:Bioreactors; D008567:Membranes, Artificial; D009997:Osmotic Pressure; D056951:Photoelectron Spectroscopy; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D008567:Membranes, Artificial
keywords: Chemical potential; Membrane bioreactor; Membrane fouling; Osmotic pressure; Soluble microbial products