REVERSE OSMOSIS MEMBRANE FOULING BY SANITARY LANDFILL
LEACHATE AND COPPER PLATING SOLUTIONS
Riley N. Kinman, Professor
James W. Stamm. Graduate Student
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
David Nutini, General Manager
RNK Environmental, Inc.
Covington, Kentucky 41017
INTRODUCTION
Reverse osmosis is a pressure driven membrane separation process which may be used for desalination of water, water reclamation from various pollutional sources, concentration of metals from
dilute waste streams, and the production of high quality water comparable to distilled water. Engineers and process designers have been attracted to the potential of this process that is simple to design,
has low energy requirements, high recovery and minimum maintenance in a contaminated water
setting.
Design and operation of the process is not without problems. Perhaps the most challenging of
these problems associated with R.O. use is fouling of the membrane. Fouling may be simply described
as reduction of permeate flux with time caused by constituents in the feed water or changes in the
membrane structure. Fouling of the membrane causes a degree of uncertainty for the engineers or
designers as to the useable life of the membrane, need for pretreatment of the feed water, and the
degree of pretreatment required.
Relationships between specific ions or compounds in the water and fouling of the membrane have
not been fully explained [1]. Currently, the results of the simple filtration test, the Silt Density Index
and more recently the permanganate demand test [2) has been used to determine if the process can
be reasonably operated for an extended period of time without fouling. Because the S.D.I, could not
predict the expected life span of the membrane, nor did it react linearly with concentration of potential fouling agents, we prepared the permanganate demand test as a replacement for the S.D.I,
and reported the basic procedure out at this conference last year. May 1984 (2). Our research has
continued to explore the fouling of R.O. membranes by various pollutants. This presentation includes
recent work with copper plating solutions and sanitary landfill leachates.
Specific objectives of this work included: I) Further evaluation of the permanganate demand test
and the silt density index was carried out on two industrial waste streams; 2) an attempt was made
to determine linear relationships between S.D.I, and the permanganate demand test and fouling by
the two wastes, and 3) an attempt was made to develop an equation which would predict where a
membrane has fouled beyond its useful operation (minimum flux) for these two wastes.
PERMANGANATE DEMAND TEST
Permanganate ion is a wide spectrum oxident which follows a variety of reaction pathways. These
pathways depend on the pH at which the reaction occurs and the structure of the material that is to
be oxidized [3]. A typical reaction in weakly acidic solutions and neutral solutions is illustrated by
the reaction of permanganate ion with soluble manganese ion to form manganese dioxide:
2M„G,    + 3 M„ + 2 + 40H" - 5 Mn02 + 2 H20 (1)
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