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Ultrasonic measurement of membrane fouling during microfiltration of natural brown water
Author(s)
Mbanjwa, Mesuli Bonani
Date Issued
2007
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The removal of the colour-eausing natural organic matter (NOM) from natural
brown water (NSW) to be used for drinking purposes is of paramount
importance. One of the methods available to remove NOM from NSW is the use
of pressure-driven membrane separation systems. One of the limitations in
efficiently applying membrane filtration in the treatment of NOM-eontaining
water is membrane fouling that is caused by foulants, such as NOM, that
accumulate on the membrane surface and in the membrane pores.
Microfiltration (MF), as a membrane separation system, is susceptible to severe
membrane fouling during membrane filtration of NSW. Fouling is characterized
by a rapid decline in permeate flux and loss of productivity.
Progress in developing more effective control and prevention of fouling is
impeded by the absence of suitable fouling measurement and characterization
techniques. An in situ method for measuring membrane fouling is necessary for
detection of membrane fouling during MF of NSW at the eartiest stages so that
the corrective actions can be taken before fouling is permanently adsorbed onto
the membrane surface.
In this study, an ultrasonic-based method was effectively used to detect and
measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling
exp~riments results showed the formation of a new peak on the ultrasonic
response echo signal due to the presence of a fouling layer on the surface of
the membrane. The ultrasonic signals acquired during the in-situ detection of
membrane fouling were analysed using wavelet transforms (WTs). Wavelet
analysis was applied to differential signals to obtain additional information about
fouling. Differential signals were calculated by subtracting the baseline
measurement signals from the test signals. The presence of the fouling layer on
membranes was verified by atomic force microscopy (AFM) and scanning
electron microscopy (SEM) analyses of the fouled membranes.
brown water (NSW) to be used for drinking purposes is of paramount
importance. One of the methods available to remove NOM from NSW is the use
of pressure-driven membrane separation systems. One of the limitations in
efficiently applying membrane filtration in the treatment of NOM-eontaining
water is membrane fouling that is caused by foulants, such as NOM, that
accumulate on the membrane surface and in the membrane pores.
Microfiltration (MF), as a membrane separation system, is susceptible to severe
membrane fouling during membrane filtration of NSW. Fouling is characterized
by a rapid decline in permeate flux and loss of productivity.
Progress in developing more effective control and prevention of fouling is
impeded by the absence of suitable fouling measurement and characterization
techniques. An in situ method for measuring membrane fouling is necessary for
detection of membrane fouling during MF of NSW at the eartiest stages so that
the corrective actions can be taken before fouling is permanently adsorbed onto
the membrane surface.
In this study, an ultrasonic-based method was effectively used to detect and
measure the growth of membrane fouling dUring MF of NSW, in situ. Fouling
exp~riments results showed the formation of a new peak on the ultrasonic
response echo signal due to the presence of a fouling layer on the surface of
the membrane. The ultrasonic signals acquired during the in-situ detection of
membrane fouling were analysed using wavelet transforms (WTs). Wavelet
analysis was applied to differential signals to obtain additional information about
fouling. Differential signals were calculated by subtracting the baseline
measurement signals from the test signals. The presence of the fouling layer on
membranes was verified by atomic force microscopy (AFM) and scanning
electron microscopy (SEM) analyses of the fouled membranes.
Additional information
Thesis (MTech (Engineering))--Cape Peninsula University of Technology, 2007
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