75    REVERSE OSMOSIS REMOVALS OF CHLORINATED
HYDROCARBONS
Riley N. Kinman, Professor
Janet Rickabaugh, Research Associate
Janette Martin, Graduate Research Assistant
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
Ronald F. Lewis, Microbiologist
U.S. EPA-ORD-HWERL
Cincinnati, Ohio 45268
INTRODUCTION
Background
In the past few years, the contamination of water and groundwater supplies with toxic organic
compounds has challenged scientists and engineers with the task of finding innovative treatment
techniques to remove these hazardous constituents. The ideal solution would be to treat the contaminated water in such a way that the organics were completely destroyed. This could be accomplished by
biological, physical or chemical methods. Prior to treatment, the concentration of the contaminants
into as small a volume as possible would be highly desirable. Reverse osmosis (RO) is a unit process
that is used to separate solute from solvent. RO concentrates and isolates the contaminants in the
solution, reducing the volume which must be treated.
Purpose and Scope
The purpose of this study was to determine the effectiveness of reverse osmosis treatment in
removing chlorinated hydrocarbons and pesticides from a hazardous waste leachate. The leachate was
produced by passing water through columns packed with 25 kg of contaminated soil collected from
the Chem-dyne site in Hamilton, Ohio. These soil columns generated a leachate which contained
significant (although low) concentrations of various chlorinated hydrocarbons and pesticides. In
order to manage the waste produced from the column study, reduction of the volume of contaminated
leachate was necessary. Spiral wound cellulose-acetate (CA) and polyamide thin film composite (PA)
membranes were used to treat the leachate in a reverse osmosis unit. Their contaminant removal
capabilities were compared, but the mechanism for the removal was not investigated.
METHODS AND MATERIALS
Equipment
The reverse osmosis unit used in this study was a pilot scale Osmonics OSMO 1919-SB equipped
with a 100 mesh prefilter screen and operated at a pressure of 190 psi. Two different membranes were
used. The first was a cellulose acetate spiral wound membrane model SEPA-97E manufactured by
Osmonics, with approximately 19 sq.ft. of surface area. The manufacturer's specifications for this
membrane predicts a 94 to 97% salt rejection and a lower molecular weight cut off of 200 for
organics. This type of membrane is typically used for desalination of water, salt recovery, organic
removal, BOD and COD reduction [I]. The system could operate between a pH range of 6 and 8, at
approximately 22% permeate recovery per pass when using the CA membrane. The second membrane
was a spiral wound polyamide thin film composite membrane. It also had approximately 19 square
feet of surface area and was manufactured by Osmonics, Inc. The PA membrane is used primarily for
desalination of water with a salt rejection of greater than 99%. It is also used for removal of organic
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