Critical, sustainable and threshold fluxes for membrane filtration with water industry application...

Title: Critical, sustainable and threshold fluxes for membrane filtration with water industry application

Journal: Advances in Colloidal and Interface Science

Authors: Robert W. Fielda, Graeme K. Pearceb

Corresponding author Robert W. Field



aDept of Engineering Science , University of Oxford, United Kingdom

bMembrane Consultancy Associates, United Kingdom


The original and creativity of paper: This paper discussed about concept of critical, sustainable and threshold flues for ultrafiltration process. The paper reviewed the concept of the fluxes and discussed which one is suitable for the real practice.




The concept of critical, sustainable and threshold flues was explained;

-          Critical flux: The flux at which fouling is first observed for a given feed concentration and cross-flow velocity. The term “sustainable flux” has been used to describe the flux above which membrane system will have a sharp increase in fouling as evidence by a sharp increase in the rate dTMP/dt. At the flux below sustainable flux, the operation of the filtration system will generate much slower fouling rate that is sustainable in real practice.

-          Limiting flux: The plateau flux which is achieved at high TMP; further increases in TMP do not increase the flux

-          Sustainable flux: The flux at which a modest degree of fouling  occurs, providing  a compromise between capital expenditure and operating costs

-          Threshold flux: The flux at or below which a low and near constant rate of fouling occurs but above which the rate of fouling increases markedly. The concept of this flux also provides the sufficient guidance for the membrane plant designer or operator in the water industry.

For the real practice, the authors suggested that;

-          The concept of threshold flux is meaningful to distinguish between regions of low fouling and high fouling.

-          The concept of sustainable flux embodies economics factors. Thus, in order to operate the filtration system under the sustainable flux, the system will be operated at the acceptable degree of fouling. Moreover, fouling is easily removed in a cleaning procedure of acceptable frequency.

-          The concept of sustainable flux recognizes a degree of fouling and also allows designer as well as operator to accept a degree of fouling resulted from a higher flux.

-          The sustainable flux represents the tradeoff between capital cost and operating cost.

-          According to concept of sustainable flux, it is the one that meet a cost objective over the projected life of the membrane plant.




Application & further study: The information obtained from the paper is meaningful to develop the similar concept for reverse osmosis process. Then, we can provide the procedure to the operator to operate the plant under the appropriate flux.

By Monruedee Moonkhum

Email: moon@gist.ac.kr

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