Membrane fouling in a membrane bioreactor: High filtration resistance of gel layer and its underlying mechanism.
A membrane bioreactor (MBR) was continuously operated to investigate mechanisms of fouling caused by the gel layer in this study. Agar was used as a model foulant for gel layer formation, and filtration resistance of gel layers was systematically assessed. The results showed that gel layer possessed unusually high specific filtration resistance (SFR) and high measured porosity as compared with cake layer. Current knowledge cannot explain the contradiction between high filtration resistance and high porosity of gel layer. A new fouling mechanism based on Flory-Huggins theory was then proposed. Filtration resistance of agar gel layer was found to be independent of pH and ionic strength, but linearly increase with gel thickness. The results are accordant with the mechanism deductions. Simulation of the mechanism model showed that the filtration resistance induced by mixing chemical potential variation was comparable to the experimental data of filtration resistance of agar gel layer, indicating that the proposed mechanism is the predominant mechanism responsible for the high filtration resistance of gel layer. The proposed mechanism was further verified from the bound water viewpoint.
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Jianrong
J
Chen
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Meijia
M
Zhang
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Fengquan
F
Li
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Lei
L
Qian
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China. Electronic address: linhonjun@163.com.
Hongjun
H
Lin
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Lining
L
Yang
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Xilin
X
Wu
College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, 321004, PR China.
Xiaoling
X
Zhou
Department of Materials Physics, Zhejiang Normal University, Jinhua, 321004, PR China.
Yiming
Y
He
Department of Chemical Engineering, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada.
Bao-Qiang
BQ
Liao
D019149:Bioreactors; D005374:Filtration; D008567:Membranes, Artificial; D008962:Models, Theoretical; D016062:Porosity
D008567:Membranes, Artificial
Filtration resistance; Gel layer; Membrane bioreactor; Membrane fouling