Fundamental fouling mechanisms of dissolved organic
matter fractions and their implications on the surface
modifications of ceramic nanofiltration membranes:
insights from a laboratory scale application
Welldone Moyo, Machawe M. Motsa, Nhamo Chaukura,
Titus A. M. Msagati, Bhekie B. Mamba , Sebastiaan G. J. Heijman
and Thabo T. I. Nkambule
ABSTRACT
This work reports on the fundamental factors influencing inter-foulant and foulant-membrane
interactions during simulated dissolved organic matter removal using ceramic nanofiltration. Fouling
tests were performed using sodium alginate (SAL), humic acid (HA) and bovine serum albumin (BSA)
as model foulants. Fouling potentials of each foulant and their mixtures were investigated using feed
solutions containing fixed concentrations of K
þ
, Na
þ
, Mg
2þ
and Ca
2þ
with a total ionic strength of
10 mM. The impact of modification by atomic layer deposition on fouling mitigation was also
assessed. The flux decline in the first 100 min for single foulants was 4.16 × 10
2
, 2.69 × 10
2
and
1.60 × 10
2
Lm
2
for SAL, HA and BSA, respectively. These results demonstrated that for the single
foulants, deposition on the membrane surface in the early stages of filtration was primarily governed
by membrane-foulant interactions. Interestingly, cake filtration was the least fouling mechanism in
feed solutions composed of BSA and SAL (R
2
¼ 0.519, 0.374 for BSA þ SAL and BSA þ SAL þ HA,
respectively) and the most favorable fouling mechanism of feed solution which included HA and SAL
(R
2
¼ 0.972). The water contact angle dropped from 58
o
to 35
after coating, thus improving its
anti-fouling properties.
Welldone Moyo
Machawe M. Motsa
Nhamo Chaukura
Titus A. M. Msagati
Bhekie B. Mamba
Thabo T. I. Nkambule (corresponding author)
Nanotechnology and Water Sustainability
(NanoWS) Research Unit,
University of South Africa (UNISA),
Johannesburg,
South Africa
E-mail: nkambtt@unisa.ac.za
Sebastiaan G. J. Heijman
Department of Civil Engineering and GeoSciences,
Technical University of Delft,
Delft,
The Netherlands
Key words | atomic layer deposition, ceramic membrane, dissolved organic matter, membrane
fouling, nanofiltration
INTRODUCTION
There is a continual deposition and accumulation of organic
and inorganic substances in the aquatic systems as a result
of both natural and anthropogenic activities. With water scar-
city and an increase in industrial activities, the concentration
of these compounds and other emerging micropollutants is
intensified, thus compromising the quality of the natural
water streams. Dissolved organic matter (DOM) is one
class of pollutants found in abundance in water sources
(Nkambule ). Previous studies have reported that DOM
compromises the quality of water by giving it color, bad
odor and a foul taste (Chaukura et al. ). Because of
this, there is a need to monitor and remove DOM and its frac-
tions in drinking water. One treatment approach that has
shown good success in removing DOM in water is membrane
technology. However, one of the enduring challenges of
membrane processes is fouling.
While studies on membrane fouling mechanisms are
well documented in the case of polymeric membranes
(e.g. Mahlangu et al. a, b; Shang et al. ; Shen
& Schaffer ), conflicting reports on DOM fractions con-
tributing more to membrane fouling have been reported.
Some studies report that colloidal DOM fraction contributes
more to membrane fouling than other fractions (Kim &
Dempsey ). Other studies reported that aromatic or
hydrophobic compounds (humic and fulvic acids) were the
major DOM foulants on ultra and nanofiltration membranes
1702 © IWA Publishing 2019 Water Science & Technology | 80.9 | 2019
doi: 10.2166/wst.2019.419
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