Section Four
PROCESSES-C. PHYSICAL/CHEMICAL
40    REVERSE OSMOSIS TREATMENT FOR NITRATE
REMOVALS IN HIGH SOLIDS WASTEWATER
Riley N. kinman. Professor
Department of Civil and Environmental Engineering
University of Cincinnati
Cincinnati, Ohio 45221
David L. Ntitini, General Manager
RNK Environmental, Inc.
Covington, Kentucky 41017
INTRODUCTION
A wide range of industrial wastewaters have, in addition to specific hazardous substances in lower
concentrations, high levels of other solids which increase the difficulty of treatment. Our group has
been looking at these high solids wastewaters as candidates for RO treatment. Newer membranes
operated at lower pressures with better washing procedures make the RO process more attractive for
hazardous waste, leachates and other high solids wastewaters. High solids chrome bearing wastewater
has been processed full scale, high solids wastewater with high levels of ammonia are under study and
this particular work involves high solids wastewater with nitrates the ion of interest for removal.
The feasibility of using reverse osmosis (RO) technology to treat and concentrate nitrates (N03-N)
and other nitrogen forms from high solids wastewaters was investigated. The project objectives
included: 1) a single pass of the wastestream through the RO; and 2) a double pass of the wastestream
through the RO. THe data were to provide information necessary to design a pilot or full scale RO
Unit.
METHODS AND MATERIALS
RO Unit
The RO used for the project was an OSMO Orion Laboratory Model. The dimensions of the Unit
were: height —46 inches; width—17.5 inches; and depth—15 inches. The weight of the unit was 105
pounds. The membranes consisted of two replaceable polyamide (PA) spiral wound membranes with
36.8% recovery capability. This PA membrane handled a pH range of 5.5 to 10.0 The membranes
provided a surface area of 38 ft2 (each membrane has 19 ft2 of area). Electrical requirements were for
115 V, 60 cycle, standard plug. The unit was enclosed in an insulated housing to minimize the noise
from the unit during operation. The unit was provided with a feed line, a permeate line, and a
concentrate line (each about 10 ft in length). Each line had a quick connect fitting for easy installation
and /or maneuvering of these lines.
The specified flow rate of the unit was 29.4 gph at 77°F for the permeate and 50.4 gph for the
concentrate. The minimum and maximum operating pressure for the unit was 50 and 235 psig,
respectively. A 0.5 micron prefilter was provided with the unit.
Controls consisted of an on-off switch, membrane flush switch, dual pressure gauges (post filter
pressure and final pressure) and percent rejection indicator. The RO lab model design is shown in
Figure 1.
44th Purdue Industrial Waste Conference Proceedings, © 1990 Lewis Publishers, Inc., Chelsea, Michigan 48118.
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