Hollow fiber membrane microfiltration has been widely applied in wastewater treatment. Recently, in this field, there is a strong trend to use submerged membranes as filtration medium. However, the pressure driven submerged membrane processes suffer from membrane fouling much more heavily than cross flow filtration, a very important drawback that remains one of the most challenging issues facing further development of this technology.Induced surface shear by introducing gas flow into liquid system is a major strategy to control membrane fouling. The input gas is not only used as an alleviator, but also easily separated from the process stream. In some hybrid membrane process, such as membrane bioreactors (MBR), gas sparging is required for aeration, therefore it serves a double purpose.This study proposed a novel submerged hollow fiber membrane module to better control membrane fouling in gas bubbling enhanced microfiltration. Using yeast as model particle in water, the performance of this module was tested by measuring the transmembrane pressure (TMP) under constant flux.It was found that the nozzle size at the base end of the module greatly affected the size and shape of created bubbles, and with the increase of the nozzle size and after exceeding one threshold value, the gas flow pattern transformed from bubble flow to the single bullet-shaped slug flow. The observed membrane fouling performance coincided with the observed two-phase flow characteristics and the results of critical flux experiments. Nevertheless, the relative efficiency of membrane fouling control by gas sparging depended on not only the nozzle size, but also the suspension concentration and gas flowrate. By limiting rising bubble around the fibers or creating slug flow, the novel module presented in this study showed some advantage over conventional submerged module in membrane fouling control.In this study, the effect of the feed concentration, gas flowrate and permeate flux on the rate of TMP increase were also examined. The experimental results indicated that TMP increase faster with higher feed concentration, permeate flux and lower gas flowrate.The cake filtration under constant pressure was taken to determine the relationship between the cake specific resistance r and the filtration pressure△P, and to guide the researching of the mathematic model.A mathematical model for constant flux filtration using dead-end hollow fiber membranes has been developed by combining the Hagen-Poiseuille equation and the filtration equation to describe the time dependence of the filtration behavior of hollow fiber membranes experiencing particle deposition on their surface. Introducing a parameter D, it can characterize the influence of gas sparging to the back diffusion of the accumulative particles on the membrane surface. The developed model has been used to simulate the transmembrane pressure rise rate under varied operation conditions, and to simulate the distribution of TMP and flux along the hollow fiber membrane.

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