United States
 Environmental Protection
 Agency
  Municipal Environmental Research
  Laboratory
  Cincinnati OH 45268
 Research and Development
 EPA-600/S2-81-115  Oct. 1981
 Project  Summary
 Inorganic  Contaminant
 Removal  from  Drinking
 Water  by  Reverse  Osmosis
 Martin R. Huxstep
  The removal of inorganic contami-
 nants from drinking water was studied
 using two reverse osmosis (RO) treat-
 ment systems. A high pressure (400
 psi) and low pressure system (200
 psi). each having a rated capacity of
 1.82 L/sec (28.9 gpm) of product
 water, were used to evaluate their
 capability for removing various inor-
 ganic contaminants.' A groundwater
 was spiked with varying concentra-
 tions of fluoride, nitrate, arsenic III,
 and arsenic V, and runs of 2 to 5 days
 ware conducted to determine rejec-
 tions. Removal data were also col-
 lected on the natural constituents in
 the  feed water of total dissolved
 solids, hardness, calcium, magnesium,
 chloride, sodium, and sulfate.
.  For all contaminants and natural
 constituents measured, the high pres-
 sure system operated at 265 to 359
 psig more effectively removed the
 inorganic contaminants than did the
 low pressure system operated at 163
 to 187 psig. High pressure system
 removals ranged from 80 to 99 per-
. cent; low pressure, from 10  to 85
 percent. Percent removals varied with
 the ion measured, but the order, from
 best to worst, was about the same for
 each system. The order for  the high
 pressure system was: (1) arsenic V, (2)
 fluoride, (3) nitrate, and (4) arsenic III.
 For the low pressure system: (1) arsenic
 V, (2) fluoride, (3) arsenic III, and (4)
 nitrate.  Percent removal was also
 independent of the initial concentra-
 tion.
   This Project Summary was devel-
 oped by EPA's Municipal Environmen-
 tal Retearch Laboratory. Cincinnati,
 OH. to announce key findings of the
 research project that is  fully docu-
 mented in 'a separate report of the
 same title (see Project Report ordering
 information at back).

 Introduction
   RO has been used successfully for
 desalting sea waterand brackish waters
 for many years. Compared with other
 drinking water treatment methods,  its
 relatively high cost has limited  its
 application in this field. Technological
 advances,  however, have generated
 considerable interest for use on drinking
 waters with high total dissolved solids
 and on those having specific contami-
 nants that cannot be easily removed by
 other methods.
   One  major advantage of RO is  its
 effectiveness to remove almost all
 inorganic substances. Information is
 generally available on the rejection
 capabilities for the common natural
. constituents in drinking water, such as
 sodium, chloride, or sulfate, but lacking
 on the rejection of specific contaminants
 such as arsenic and selenium.
   This study was undertaken to develop
. data on removing the inorganic con-
 taminants included in EPA National
 Interim Primary Drinking Water Regula-
 tions by RO. Tests were  conducted
 using two parallel pilot plant RO sys-
 tems: (1) a low pressure (200 psi)
 system housing low rejection mem-

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    branes and (2) a high pressure (400 psi)
    system with high rejection membranes.
    Test runs lasting from 1 to 5 days were
    carried out by spiking a natural ground-
    water with known concentrations of
    contaminants and measuring their
    removal by each RO system. Removal
    data were also obtained on some of the
    natural constituents in  the feed water
    such as total  dissolved solids, calcium,
    magnesium, chloride, sodium, and
    sulfate. The results of the first series of
    tests for the removal of fluoride, nitrate,
    arsenic III, and arsenic V are reported in
    this first progress report.

    Results
      Because of several problems, unre-
    lated to the RO systems, the two systems
    were operated under  three slightly
    different sets of operating conditions
    (pressure). The test data on the natural
    substances suggest, however, that
    these changes did not significantly
    influence the performance of the sys-
    tems for removing the spiked contami-
    nants.
      As was anticipated, the test data
    show a very significant difference in the
    capabilities between the two RO sys-
    tems for removing all spiked and natural
    constituents monitored. The low pres-
    sure system, which requires about one-
    half the energy used by the high pressure
    system, achieved rejections of about 50
    percent or less than that achieved by the
    high pressure system. Data also show
    that rejection of the contaminants on a
    percent basis was  independent of the
    feed concentration and the order of
    effectiveness  for removing spiked and
    natural constituents was nearly the
    same for each system (Table 1).
    Conclusions
      The investigation clearly indicated
    that the high pressure  system was
         Table 1.
Percentage Removal of Natural and Spiked Constituents Monitored

                       Reverse Osmosis Systems, % Removal
Constituents
                                          High Pressure
Low Pressure
          Natural
           Sulfate
           Magnesium
           Calcium
           Total Hardness
           Radium-226
           Total Dissolved Solids
           Chloride
           Sodium
                           >99
                          96-98
                          96-98
                          97-98
                            97
                          93-96
                          87-95
                          88-93
   82-84
   63-67
   64-67
   64-66
     62
   45-52
   42-45
   36-44
Spiked
Arsenic V
Fluoride
Nitrate
Arsenic III
91 -98
90-93
76-80
63 - 70
77-81
56-62
6-24
12-35
         significantly more effective for removing
         all substances measured. The low pres-
         sure system achieved a very wide range
         of removals and was very ineffective for
         removing nitrate and arsenic III.
           Because of its  low rejection charac-
         teristics, the low pressure system is
         ofily effective on source water having
         contaminant concentrations slightly
         above the maximum contaminant levels
         (MCL).  The high  pressure system, al-
                             though  it requires about twice the
                             energy,  is much more effective, and
                             blending of feed and  product waters
                             could be accomplished to affect the
                             difference in energy costs.
                               The full report was submitted in ful-
                             fillment of Cooperative Agreement No.
                             RC-805207 by Charlotte Harbor Water
                             Association, Inc., under the sponsorship
                             of the U.S. Environmental Protection
                             Agency.
           Martin R. Huxstepis with the Charlotte Harbor Water Association, Inc., Harbour
             Heights, FL 33950.
           Thomas J. Sorg is the EPA Project Officer (see below).
           The complete report, entitled "Inorganic Contaminant Removal from Drinking
             Water by Reverse Osmosis," (Order No. PB 81-224 420; Cost: $8.00, subject
             to change) will be available only from:
                   National Technical Information Service
                   5285 Port Royal Road
                   Springfield, VA2216t
                   Telephone: 703-487-4650
           The EPA  Project Officer can be contacted at:
                   Municipal Environmental Research Laboratory
                   U.S. Environmental Protection Agency
                   Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
                                           Postage and
                                           Fees Paid
                                           Environmental
                                           Protection
                                           Agency
                                           EPA 335
Official Business
Penalty for Private Use $300

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