31    EFFECT OF COAGULATION ON
FOULING RATE AND CLEANABILITY OF
ULTRAFILTRATION MEMBRANES
Weiming Ying, Research Associate
Berrin Tansel, Assistant Professor
Department of Civil and Environmental Engineering
Florida International University
University Park, Miami, Florida 33199
INTRODUCTION
Membrane filtration process has recently received more and more importance in waste water
treatment applications, such as volume reduction of aqueous wastes, recovery of precious chemicals from liquid industrial wastes, and purification of drinking water.'--3 Among the membrane
filtration techniques, continuous cross-flow ultrafiltration (UF) is an innovative method to separate solid/liquid or liquid/liquid phases at a lower pressure of 5-150 psi compared to reverse osmosis (RO) in which the applied pressure is an order of magnitude higher.4 The application of
UF to the removal of oil contaminants from oily wastewater streams has been extensively studied in theoretical aspects.58 The practical use of UF technology has been reported also in various circumstances.eg- 2-9-10 Recently, attempts have been made to combine processes of UF and
other treatments for many applications. Watters et al. (1987) demonstrated the combination of
emulsion solvent extraction and UF to remove toluene." Adham et al. (1991) used a bench-scale
UF and powdered activated carbon to remove organic contaminants from groundwater.12 UF has
also been reported to be combined with the emulsified ion exchangers and surfactants for the
metal ion removal from aqueous solutions.1314 However, there is very little knowledge about the
filtration process which combined coagulation and UF, and very few attempts have been made to
apply coagulated UF to the treatment of fuel oil contaminated water.
During the UF treatment of organic contaminants, especially for filtering oil contaminated
water, rapid declines in flux will occur due to the membrane fouling.15 Oil as a foulant plays an
important role in the flux decrease. However, there are very limited pretreatment processes
which can effectively remove fuel oil from water and hence solve the fouling problem;16 besides,
the addition of complicated pretreatment processes will make UF less cost-effective. Therefore,
simple and effective methods need to be developed to reduce membrane fouling caused by oil
foulant.
The purpose of the study was to examine the effectiveness of a simple method for reducing UF
membrane fouling which is caused by fuel oils in feed water. In this simple method, a coagulant
was added into the feed water contaminated by fuel oils during the cross-flow UF treatment (coagulated UF). In this investigation, turbidity and petroleum hydrocarbon removal efficiency, permeate flux and membrane fouling potential were evaluated by a series of batch experiments. The
mechanisms by which the membrane fouling was significantly reduced by coagulation were discussed.
MATERIALS AND METHODS
Ultrafiltration System
The ultrafiltration experiments were conducted using a laboratory scale continuous cross-flow
membrane filtration unit manufactured by Desalination Systems, Inc. (DSI). Schematic of the
unit set-up is shown in Figure 1. Test water in feed tank first flows through a filter; if feed water
50th Purdue Industrial Waste Conference Proceedings. 1995, Ann Arbor Press, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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