United States
                    Environmental Protection
                    Agency
Risk Reduction
Engineering Laboratory
Cincinnati OH 45268
                    Research and Development
 EPA/600/S2-89/023 Jan. 1990
v°/EPA         Project Summary
                    Synthetic  Organic Compound
                    Rejection  by Nanofiltration

                    J. S. Taylor, S. J. Duranceau, L. A. Mulford, D. K. Smith, and W. M. Barrett
                     A study was conducted to evaluate
                    the rejection of six synthetic organic
                    compounds (SOCs) from a  potable
                    water source  by a  nanoflltration
                    membrane process. The SOCs were
                    ethylene dlbromide (EDB), dibromo-
                    chloropropane (DBCP), chlordane,
                    heptachlor,  methoxychlor, and ala-
                    chlor. To investigate SOC rejection, a
                    membrane  pilot  plant was  con-
                    structed that utilized a single,  4- by
                    40-inch FllmTec N 70* spiral wound,
                    thin film composite membrane with a
                    molecular weight  cutoff of 300. The
                    effects of different operating  pres-
                    sures and membrane feed  stream
                    velocities on membrane rejection of
                    SOCs are reported. Trihalomethane
                    formation potential (THMFP),  total
                    organic  halide formation  potential
                    (TOXFP) and general water quality in
                    and out of the membrane are also
                    reported. Accurate organic and inor-
                    ganic mass balances  were  con-
                    ducted on solutes.
                     This Project Summary was devel-
                    oped by EPA's  Risk Reduction  Engi-
                    neering Laboratory, Cincinnati, OH, to
                    announce key findings of the research
                    project that is fully documented In a
                    separate report of the same title (see
                    Project Report ordering Information at
                    back).

                    Introduction
                     The purpose of this cooperative agree-
                    ment was to determine the capability of a
                    nanofilter membrane to reject SOCs from
                    a potable water source.
                     The scope of work involved selecting a
                    potable water site, building a membrane
                    "Mention of trade names on commercial products
                     does not constitute endorsement or recom-
                     mendations for use
pilot plant, securing  and  preparing the
SOC feed, operating the pilot plant,
analyzing  the data and reporting.  Only
one nanofilter membrane  was used  for
this project because of economic con-
straints;  however, the selected mem-
brane, a FilmTec  N 70 nanofilter with
molecular weight cutoff (MWC) of 300,
had been used at four sites  on other
projects because the N  70  controlled
permeate  THMFP to  less  than the THM
MCL of 0.10 mg/L and was as productive
as any membrane that successfully con-
trolled THMFP.

Site Selection
  The initial site selected for this project
was at Flagler Beach, Florida, so that the
project could be done at the same time
as another project investigating the long-
term cost and performance of membrane
processes to control THMFP at the same
site.The Flagler  Beach water treatment
plant had, however, no means to accept-
ably  discharge  the SOC-contaminated
stream.  Because complete containment
of the SOCs was not feasible, the SOC
project  site  was at the  University  of
Central  Florida  (UCF) in  Orlando,  FL.
After two attempts  to use  the  UCF
irrigation  water storage tanks,  the pilot
plant was moved to a site adjacent to the
UCF wastewater treatment plant. A  4-
inch-diameter  206 foot-cased  deep well
was drilled into the Floridan aquifer—the
same aquifer used  by UCF  and the
majority of Florida utilities for drinking
water. The SOC-contaminated membrane
streams were discharged  to the UCF
wastewater treatment plant.

Pilot Plant Construction
  A 14- by 12-foot by 3-inch concrete
pad was  poured adjacent  to  UCF

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wastewater treatment plant and the  Civil
and  Environmental  Engineering  field
laboratory (CEEFL)  building. A 10-foot
cube,  steel  research  building   was
assembled on the  pad.  The  research
building had  a 110/220 amp power  line,
lighting, ventilation fans, a locked fence,
and raw  water. A flow diagram of the
membrane pilot plant built  for  SOC
removal is shown in  Figure 1. Well water
was pumped through one  of two parallel
1 p prefilters, a totalizer, and  back  flow
prevention device. Following prefiltration,
H2S04  was  added  to control CaC03
scaling and the desired SOC was added.
The acid and SOC-containing water  then
passed through a high pressure pump
that  pushed the  water  through  the
membrane. Chlordane,  heptachlor,  me-
thoxychlor, DBCP and  EDB feed stock
was prepared by first dissolving the SOC
in an  organic  solvent,  acetone or
methanol, and  then diluting  the  SOC
solution  in  permeate  water.  Organic
solvents  were necessary because the
pure SOCs  were  insoluble  in water.
Alachlor was  obtained as a water-soluble,
formulated compound and was directly
            dissolved in  water  for SOC feed  stock
            preparation.


            Operation
              The  membrane  was  installed  in  a
            donated  custom Mitco* skid, which
            consisted of flow and pressure gauges on
            feed, permeate, and  concentrate  lines;
            the  pressure  vessel;  and  the  high
            pressure pump  with concentrate  and
            pump recycle  lines, all  of which  were
            mounted  on  a steel frame.  Flow and
            pressure  readings were monitored  daily
            by  gauge readings and direct  flow
            measurement  of the concentrate  and
            permeate streams. The membrane  feed,
            permeate, and  concentrate stream  SOC
            concentration was monitored  13 times
            during a 31-day period that was divided
            into  four  different recovery periods and
            one  flushing period. The membrane pilot
            plant  was operated  at approximate
            recoveries of  10% (10%R), 30% (30%R),
            30% with recycle  (30% RR) and 50% with
            recycle (50% RR). Samples were taken
            after the end  of each period of operation
            to determine if any adsorbed SOCs  could
                                                           be flushed  from  the  membrane. 0
                                                           solutes in the membrane feed, perm-
                                                           and concentrate streams were monito
                                                           once during each  recovery period. Tr
                                                           were THMFP, TOXFP, dissolved org
                                                           carbon (DOC), color, total hardness ('
                                                           calcium hardness (CaH), alkalinity (i
                                                           pH, total dissolved solids (TDS), sod
                                                           (Na), sulfates (S04) and iron (Fe).
                                                             The  feed  permeate and concenti
                                                           stream flows were typically 4.8, 4.3,
                                                           0.5 gpm for 10%R; 3.3, 2.3, and 1.0 £
                                                           for 30%R;  3.6, 2.3,  and 1.3  gpm"
                                                           30%RR; and 2.8, 1.4, and 1.4 gpm
                                                           50%RR. The approximate pressure dn
                                                           and membrane feed stream velocities
                                                           each recovery were 62 psi and 1 f/sec
                                                           10%R, 93 psi  and  0.6  f/sec  for  30°.
                                                           107 psi and 1.1  f/sec for 30%RR,  i
                                                           150 psi and 1.0  f/sec for 50% RR. "
                                                           membrane flux ranged from 10 g/sfd
                                                           30 g/sfd,  increasing  with recovery.
                                                           water  mass  transfer  coefficient  (M"
                                                           averaged  0.21  g/sfd-psi (0.021 day
                                                           The water production  was very const
                                                           from the  membrane, which  operal
                                                           5137.7 hr out of a total 5202.5  availa
                                                           hr  during  the  SOC project. Only 14.C
                Surge
                Tank
         206'
             Well
       Stainless
       Steel Screen
                  113 hp
                  Pump on
                  Bottom of
                  Well
  Parallel
 Filter Tanks
84 Sq. Ft of
Surface Area
                                                                       Emergency Bypass
                                             Totalizer
                                            —<$—
                                                              Manifold
                                                  /
                                               Back-Flow
                                               Prevention
                                                Oewce
                                                          Sealed
                                                          Mixing
                                                           Tank
                                                           H2SO4
                                                           Feed
                                 55 Gallon
                                  Nalgene
                                   Tanks
          Permeate
 Permeate
Sample Port
    A  p%rte KSS
    t   Ce    G«**
           Concentrate
                         I  Concentrate .  * ,  A
                        n     Flow   Concentrate
                        &   Gauge    Pressure
                   Concentrate           Gauge
                   Sample Port
                  t
                       N 70 Pressure Vessel

                     
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of maintenance were needed for prefilter
replacement and small  repairs. The  re-
mainng  50.8 hr were spent waiting  on
lighting installation which was not attribu-
table to the mechanical  operation  of the
membrane pilot plant.
  Following NaCI injection, the  transient
response of the membrane was  deter-
mined to be accurately modeled by a first
order system with a time constant of 2
min. Although initial sampling for each
new SOC was done at least 4.0 hr after
operation  had  begun,  99.9% of any
permeate or concentrate  concentration
change would be  complete in 13.8 min
following initiation of the change.
  The smallest  molecular weight  (MW)
SOC was EDB (187.9). EDB feed stream
concentration  ranged from 260 to 22.4
iig/L during 785.1 hours  of operation and
from 88.4 to 22.4 ng/L in the final 443.5
hr,  after the operation  was  stabilized.
Some EDB rejection was observed  for
the first four samples collected; however,
the membrane  had been  permanently
fouled at the initial UCF  location and was
replaced after the  second sample had
been collected.  Only 66% of the EDB
had been accounted for  when the  fouled
membrane was  used. Routine operation
of the  membrane  pilot  plant  was not
achieved until after the fourth sample was
collected.  Some  EDB  may  have  ad-
sorbed onto the  fouled membrane  during
a period that was not representative of
normal operation. No EDB rejection was
observed for  the  final  seven  samples
taken  over the  last 443.5  hr  of EDB
operation. Ninety four % of all the EDB
input to  the membrane was recovered in
the concentrate  and permeate  streams
for the entire EDB operation.
  DBCP (MW 236.4)  was  fed to  the
membrane in concentrations varying from
41.5 to 83.5 pg/L  over 667.1  hr  of
operation.  Partial rejection  of DBCP  by
the membrane varied from  19.6  to  60
ng/L in the permeate stream or 19% to
52%.  DBCP  permeate concentrations
varied inversely  with the water  flux and
could  be described  by  a diffusion pro-
cess. The DBCP MTC varied from 2.79 to
7.43 f/day and averaged 4.27 f/day.
  The membrane,  under all operating
conditions, completely rejected  the four
remaining SOCs: chlordane (MW 409.8),
heptachlor  (MW 373.3),  methoxychlor
(MW 345.7), and  alachlor (MW 269.8).
The detection limit  for each  of  these
SOCs was 0.6 iig/L. The absence of any
SOC concentration in the permeate indi-
cates they  were sieved from permeate
and were too large to pass through the
yore of the membrane.
  The cumulative recovery of SOC in the
membrane  output was, in order of their
MW, 94% for EDB (MW 187.9), 96% for
DBCP  (MW 236.4), 100%  for alachlor
(MW 269.8), 91% for methoxychlor (MW
345.7), 92% for heptachlor  (MW  373.3),
and 90% for chlordane (MW 409.8). Only
EDB was found in any flushing samples;
this amounted  to less than 0.01%  of the
total EDB and  was only 0.2 ng/L  in the
flushing sample taken 46  hr after EDB
feed was discontinued. No previously fed
SOCs were ever found in any succeeding
SOC analysis.  The  SOC mass balance
indicated the  higher  MW  SOCs were
adsorbed onto  the membrane and did not
release during  operation. If adsorption is
a SOC  removal  mechanism, however,
then SOC breakthrough  could occur fol-
lowing longer periods of operation.
  The  summary  of the SOC-rejection
membrane  project is shown  in Table 1.
The average MTC for  30R and 30RR is
shown because recycling the concentrate
had  little  effect  on  the MTCs. The
membrane  rejection of TOXFP, THMFP,
and DOC was greater  than  90%  when
acetone or methanol was not used  to
prepare  SOC feed stock.  Permeate
TOXFP, THMFP,  and DOC  concentra-
tions averaged 35 ng/L,  6 iig/L, and 0.1
pg/L; this represented 93%, 95%, and
95% rejection,  respectively. The recovery
of all DOC  in the  membrane output was
102%.
  As shown in Table 1, the  rejection of
the inorganic  solutes  increased by
species charge and  molecular  weight.
The rejection of the highest charged and
largest MW species (SO4-2)  was  100%.
Rejection of the lowest MW and  lowest
charged species  (Na*)  was 64%,  the
least of any inorganic species monitored.
Recovery of inorganic species mass was
102% for all species except  Fe and Alk
which were 104% and 98%.
  The percent rejection  versus MW for
inorganic solutes  and  organic SOCs  is
shown in Figure 2. Membrane rejection of
SOCs is  controlled by species MW. All
SOCs with  MW greater than  269.8 were
completely  rejected. The SOC with MW
187.8 was not rejected, and the SOC with
MW  236.4  was partially rejected.  More
highly charged inorganic species with
MWs  less  than 187.8  (EDB) were re-
jected  by  the same  membrane. The
permeate  stream concentration   of all
partially  rejected  species  tended  to
decrease as water flux increased  and to
increase  as feed  stream concentration
increased, as  would be expected  in a
diffusion controlled process.  Velocity  of
the  membrane feed streams correspond-
ed to Reynolds numbers of less than 113.
Flow velocity within the membrane varied
from 0.6 to 1.1 f/sec and had no effect on
permeate concentration.
  Solute passage through the membrane
involved convection, sieving and  diffu-
sion.  The mass  transport  of a  small
uncharged SOC that passed completely
through the membrane  could  be  de-
scribed by convection. The  mass  trans-
port of any partially rejected organic or
inorganic species could be described by
diffusion. The  mass transport of SOCs
too large to pass through the membrane
could be  described by sieving.  The
FilmTec N  70 nanofiltration  membrane
had sieving properties of an ultrafilter and
diffusion properties of a reverse osmosis
membrane.
Conclusions
 1.  The membrane  rejected  certain
    SOCs for a one month period from a
    potable water source which indicates
    SOC rejection by membranes  is a
    feasible  potable  water treatment
    process.
 2.  The rejection of SOCs by  the
    membrane was dependent on SOC
    MW and  increased  as SOC  MW
    increased.
 3.  SOCs with MWs of 269.8 or more
    were  completely rejected  by the
    membrane for all operating  condi-
    tions by sieving.
 4.  The rejection  of DBCP, molecular
    weight 236.4, increased as water flux
    increased  and recovery decreased,
    and could be described by diffusion.
 5.  EDB, the smallest molecular  weight
    SOC (187.9), was  not  rejected by
    the membrane, which indicated the
    mass transport of EDB  through the
    membrane pores was by convection.
 6.  The SOC MW determined whether
    diffusion could be used to describe
    mass  transport through  the  mem-
    brane pores.
 7.  Charged   inorganic  solutes were
    rejected by the membrane at much
    lower  molecular weights than were
    the uncharged SOCs, possibly be-
    cause of the electrostatic repulsion
    between the ion and membrane.
 8.  SOC mass  balances showed  that
    SOCs with MWs of more than 345.7
    were not completely recovered and
    were indicated to have  adsorbed
    onto the membrane.
 9.  Solute rejection by  the  membrane
    increased  as solute  MW or charge
    increased.

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Table 1. Summary of SOC Membrane Operation
Solvent

Parameter
H#





Species
EDB
DBCP
CWordane
Heptachlor
Methoxychlor
Alachlor
THMFP
TOXFP
DOC
Color
TDS
Alk
TH
CaH
SO4
Fe
Na
Pressure
psi
62
93
107
144

Rejection
%
0
35
100
100
100
100
95
93
95
97
85
78
88
89
700
87
64
Recovery
%
70
30
30 Recycle
50 Recycle
Solute
CP" MTC"
mgIL f/day
— —
0.0372 4.27
< 0.0006
< 0.0006
< 0.0006
< 0.0006 -
0.006
0.035 * -
0.7 0.095
2** -
36 0.363
20 0.647
20 0.239
75 0.226
<7
0.06 0.265
3 7.053
Flux
g/sfd
11
19
22
28

Recovery
%
94
96
90
92
97
700
_
-
702
—
702
98
702
102
102
104
702
   *  permeate concentration
  m  mass transfer coefficient
  *  asCI
 * *  as cpu
     as CaC03

10.  Over 90% of the THM and TOX pre-
    cursors were rejected by the mem-
    brane except  when  acetone was
    used to solublize the hydrophobia
    SOCs into feed stock.
11.  Water flux was directly proportional
    to feed pressure.
12.  The membrane system was consist-
    ly productive, operating 5138 hr with
    only 65 hr of downtime.
13.  The transient response of the  N 70
    membrane was accurately described
    by a first order system with a time
    constant of 2.0 min.
14.  The  partial rejection  of  any  solute
    could be described by diffusion.
Recommendations
1.  The disposal of  membrane concen-
   trates containing SOCs  should  be
   investigated.
2.  Longer operating periods with higher
   SOC  feed  stream  concentrations
   should be used to determine if sus-
   tained rejection of  higher MW  SOCs
   can be  attained  and to determine  if
   SOC  adsorption is significant for dif-
   ferent membrane  types  and  mate-
   rials.
3.  Membranes differing  in surface mate-
   rials  and   pore   size  should be
   investigated for SOC rejection  at
   higher operating pressures.
4.  Rejection of  SOCs  by  membrane
   processes should  be investigated in
   water supplies of varying quality that
   are actually  and  artificially  contam-
   inated by SOCs  so that the  effect of
   solvent characteristics and SOC com-
   petition can  be determined.
5.  An accurate  model  for  permeate
   solute concentration  including  mem-
   brane pore  size  and distribution,
   membrane material,  solute and  s<
   vent mass transfer,  recovery, pre
   sure, solute size, solute charge  ai
   temperature should be developed :
   that  the  mechanism  of  solu
   rejection can  be  explained  ar
   permeate water quality predicted.
6.  An assessment  of SOC adsorptk
   onto different membrane  materia
   should be conducted  and  necessa
   SOC adsorption isotherms should t
   developed for  different membrar
   materials  in  order that a  comple
   evaluation of SOC membrane adsorj
   tion can be made.
7.  The  effect of turbulence  within tr
   membrane should be investigated
   reduce membrane fouling and permi
   ate solute concentration.
8.  SOC rejection should  be investigate
   with  a membrane array at recoverie

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  •*d

  I
       100
        so
60
        40
        20
                           Inorganic
                                              Organic (SOC)
                       100          200          300

                                  Solute Molecular Weight
                                                              400
                                                                           500
Figure 2.  Inorganic (A) and organic (*) percent solute rejection versus solute molecular weight
           from the SOC investigation using the FilmTec N 70 membrane.
    normally experienced by actual mem-
    brane plants.
  The full report was submitted in partial
fulfillment  of Cooperative Agreement
CR813199  by the  University  of  Central
Florida under the  partial sponsorship  of
the  U.S.  Environmental Protection
Agency.

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  J. S. Taylor, S. J. Duranceau, L A. Mufford, D. K. Smith, and W. M. Barrett are with
   the University of Central Florida, Orlando, FL 32816.
  J. Keith Carswell is the EPA Project Officer (see below).
  The  complete  report,  entitled  Synthetic  Organic Compound Rejection by
   Nanofiltration" (Order No. PB 89-194 2451 AS; Cost:  $21.95, subject to change)
   will be available only from:
          National Technical Information Service
          5285 Port Royal Road
          Springfield, VA 22161
          Telephone: 703-487-4650
  The EPA Project Officer can be contacted at:
          Risk Reduction Engineering Laboratory
          U.S. Environmental Protection Agency
          Cincinnati, OH 45268
United States
Environmental Protection
Agency
                       Center for Environmental Research
                       Information
                       Cincinnati OH 45268
U.S.OFFICIAL MAIL"
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Penalty for Private Use $300

EPA/600/S2-89/023
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