United States
                  Environmental Protection
                  Agency      	
Risk Reduction
EngineeringLaboratory
Cincinnati OH 45268
                  Research and Development
EPA/600/S2-89/022 Jan. 1990
4>EPA         Project Summary
                  Cost and Performance  of
                  Membranes for Organic
                  Control  in Small  Systems:
                  Flagler Beach  and Punta Gorda,
                  Florida

                  J. S. Taylor, L. A. Mulford, W. M. Barrett, S. J. Duranceau, and D. K. Smith
                    A membrane pilot  study  was
                  conducted to determine if membrane
                  processes could  remove trihalo-
                  methane (THM) precursors from
                  highly organic surface and ground-
                  waters and consistently maintain
                  water production for 1  yr at each
                  location. The scope of this 33-month
                  project involved: site selection, mem-
                  brane selection, 1  yr of  membrane
                  pilot plant operation at each site, and
                  a cost comparison of the membrane
                  process and the conventional water
                  treatment process at each site.
                    The highly organic Florida waters,
                  a  groundwater and a surface water,
                  were selected. Several membranes
                  were tested for pilot use by short-
                  term testing at each site. Although
                  four membranes controlled THMs to
                  less  than  the  THM   Maximum
                  Contaminant Level (MCL),  the
                  FilmTec N 70* nanofilter was selected
                  at  each  site for  long-term  use
                  because of both  productivity and
                  THM  control.  A  three-stage
                  membrane  pilot  plant operated at
                  each site controlled THM formation
                  potential (THMFP) to  less than 0.10
                  mg/L. Organic and  inorganic water
                  quality, water production, and cost of
                  treatment were   reported  for
                  membrane utilization at both sites.
                  •Mention of trade names or commercial
                    products does not constitute endorsement
                    or recommendation for use.
  This  Project  Summary  was
developed by EPA's Risk Reduction
Engineering 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 project was to
determine if a membrane process  could
maintain  consistent water production
while keeping permeate THMFP below
the 0.10 mg/L THM MCL. The scope of
the  project was  to  select both  a
groundwater and surface water site that
had a highly organic raw water, select a
membrane for extended operation  on
based on THM control  and water
production, operate  a  membrane pilot
plant for  1  yr  at  each site, monitor
THMFP as well as other water quality
parameters and water  production, and
compare  the cost of  membrane and
conventional processes at each site.
  The groundwater site selected for 1 yr
of  pilot plant operation was Flagler
Beach. The 0.4 mgd Flagler  Beach water
treatment  plant (FBWTP), which utilizes
conventional lime softening, is located on
the east coast of Florida near Daytona
Beach and serves a population of 3,000.
The THM concentration in  the Flagler
Beach distribution system averages more
than 300 jig/L. Punta Gorda, located on
the west coast of Florida about 80 miles

-------
south of  Tampa,  was selected  for the
surface water site and used Shell Creek
as a raw water source. At the start of the
1 yr of pilot plant operation at this  site,
the Punta Gorda  water treatment  plant
(PGWTP) used an  alum-coagulation
process that was being operated  in a fill-
and-draw mode. While the pilot plant was
in  operation,  a new  PGWTP, using  a
continuous alum-coagulation process,
was placed in operation. At the PGWTP,
the average daily flow was 2.7 mgd for a
service population  of about  17,000. At
present, the PGWTP uses  chloramines
for disinfection,  and THMs  in  the
distribution  system average  80 jig/L.
Before the switch  from a free  chlorine
residual  to  chloramines,  distribution
system THMs exceeded 300 ng/L.


Membrane Selection
   Eight spiral-wound, thin-film composite
membranes were tested at Flagler Beach
for THM  precursors  and  permeate
productivity.  Single 4-in. diameter by 40-
in. length membranes were installed in a
small-scale test unit and tested  at  feed
pressures of 105 to 140 psi at a recovery
of 75%.  Four of  the  membranes
produced a permeate with a THMFP of
less  than the 0.10 mg/L THM MCL. Of
these four, the FilmTec N 70 membrane
was  selected for the 1  yr  pilot  plant
operation  because its solvent  (water)
mass transfer coefficient (MTC) of 0.0137
day1 was the highest of all membranes
tested at this site.  Membrane testing at
Flagler Beach showed that a membrane
molecular weight cutoff (MWC) of 500 or
less  was  needed to remove sufficient
THM precursors  for the  permeate
THMFP to  be less than the 0.10  mg/L
THM  MCL. Similarly,  an MWC of 300 or
less  was  needed  to reduce  permeate
total hardness to 150 mg/L as CaC03.
   Ten spiral-wound,  thin-film composite
membranes were tested at Punta Gorda
for removal  of  THM precursors  and
permeate  productivity. With  the use of
the  small-scale test unit, the single
membranes  were tested  under similar
operating conditions using both raw and
alum-coagulated feed waters. Four of the
membranes were  able  to reduce the
THMFP of the feed waters  to less  than
the 0.10 mg/L THM MCL. Of these four
membranes, the FilmTec  N 70  had the
highest solvent MTC (0.0106 day1 with a
raw-water feed, 0.0048 day1  with an
alum-coagulated feed) at this location and
was  again selected for the 1  yr pilot  plant
trial.  Permeate  solute concentrations
were lower for all membranes when the
feed  had  been  alum coagulated  first;
however, all membranes whose permeate
THMFP could meet the THM MCL using
alum-coagulated  feed, could also  meet
the THM  MCL  using  raw-water  feed.
Since  the  FilmTec  N 70 membrane
showed greater  permeate  productivity
(higher solvent MTC) on raw-water feed
than on alum-coagulated feed,  a raw-
water feed was chosen  to begin the
Punta Gorda  pilot  plant  operation.  All
membranes with  an MWC of 500 or less
were able to produce a permeate THMFP
that could meet the  THM  MCL  at the
Punta Gorda site.


Pretreatment
   The silt density index (SDI) was used
to determine  pretreatment requirements
to prevent membrane fouling  at Flagler
Beach. The average  of three SDI tests
conducted  on the Flagler Beach raw
water was 2.2, which is less than the 3.0
maximum  recommended  for membrane
plant  feed  waters.  The  solubility
calculations  made  to define scaling
problems  indicated that  calcium
carbonate was the salt limiting recovery.
Based on  the  manufacturer's recom-
mendations, an  initial  dose of  6 mg/L  of
Pfizer FloCon 100 antiscalent was  used.
A flow diagram  of the membrane pilot
plant is shown in  Figure 1.
   The mini-plugging  factor index (MPFI)
and the SDI were used at Punta Gorda to
determine  pretreatment  requirements.
Several different pretreatment schemes
were investigated, including:
   -untreated raw water (R)
   -raw water plus sand filtration (RSF)
   -alum coagulated  and  settled  water
    (ACS)
   -alum coagulated  and  settled  water
    plus sand filtration (ACSSF)
The lowest acceptable MPFI and SDI test
values for membrane  processes were for
the RSF pretreatment option, which was
selected for use at pilot  plant start-up.
Limiting salt  calculations  indicated that
calcium carbonate  also controlled
recovery at Punta Gorda. A 5-mg/L dose
of FloCon 100  was initially selected  to
control scaling.


Operation at Flagler Beach
   The FBWTP personnel  who operated
the pilot plant at  Flagler Beach kept daily
records of pressure and flow.  Pilot plant
repairs, makeup of feed chemicals, and
bi-weekly collection of samples were the
responsibility of personnel  from the
University  of  Central  Florida. The pilot
plant only  operated  when  the FBWTP
operated, generally about 16 hr per day.
From November 1986 to November 1
the pilot plant operated for 5,098 hr,
64 needed for  maintenance.  Additi
operating time was lost because of re
delays.
   Water production  for the  year of
plant  operation at  Flagler  Bead
summarized in Table 1. The average 1
pressure was 141 psi, and  the avei
recovery was 79%.  The  average  w
flux from stage 1 (S1), stage 2 (S2),
stage  3 (S3) was 12.5,  15.3, and
g/sfd,  respectively. Overall  system
averaged 12.8 g/sfd. As shown in Fie
2(a),  system  flux was  very consis
during the year of operation.
   Average values of the  concentrati
of selected water quality  parameters
the raw water, the FBWTP finished  we
and the membrane pilot plant perme
are listed  in Table  2.  The  perme
THMFP  averaged  20 ng/L  and v
consistently low  throughout  the year
shown  in  Figure 2(b). Stage  perme
concentrations were typically in the or
S2 < S1 < S3, which was the inverse
the stage  order water flux (S3 <  S1
S2) as one would expect in a diffusi
controlled process.
   The membranes  were  cleaned  tw
during the year at Flagler Beach. The f
cleaning  at 280 hours was necess,
because iron  fouled  the FloCon 1
antiscalent and  the  antiscalent  lost
ability  to prevent calcium carbon;
scaling.  The  membranes  were clean
with sulfuric acid, and a sulfuric acid fe
was substituted  for  the  FloCon 100
prevent  scaling.  The membranes th
operated until 3,891  hr when the seco
cleaning was  done  to remove  visit
biological growths in the pressure vesse
and transmission lines; it was not do
because of any change in water quality
production. If sulfuric acid  had  been us
initially for the antiscalent feed, there
no evidence that a cleaning to maint.
water  quality  or production would ha
been  necessary during  the year
operation.


Operation at Punta Gorda
   The membrane pilot plant operated
total of 6,676 hr from November 1987
November 1988 at  Punta Gorda. Pit
plant  maintenance required 198  hr
downtime, and  additional time was lo
with PGWTP  shutdowns  and   repa
delays.  The pilot plant was operated t
PGWTP personnel, with maintenance ar
other duties shared between PGWTP ar
University personnel.
   Pilot  plant operation was much
difficult  at the  surface water  site. Th

-------
      Supply
      Pump
uptionai
Holding
lank

C



)


Optional
Sand Fitten
                                             Alum
                                              or
                                          Raw Water
                                           Feed Line
                                                                 Concentrate
                                                                    Line
                                                                                       Sample Point  n Valve
           High
         Pressure
          Pump
                                                                                                   Permeate
                                                                                                   Discharge
                                                                                                     Pump
 Figure 1.    Flow diagram For the F/lmTec N 70 Membrane System.
pretreatment indices (SDI and MPFI)  did
not accurately predict  the  extent of
membrane fouling  that  occurred. The
membranes  were  cleaned   on  20
occasions because of low flux caused by
organic fouling.  Several pretreatment
changes were made during the year in an
attempt to maintain the average system
flux above 10 g/sfd. The most significant
of these changes were: (1) the addition of
a second  sand pre-filter, (2) a  change
from an antiscalent feed to a  dispersant/
antiscalent  feed,  (3)  use  of  alum-
coagulated and settled  water  from the
PGWTP for the membrane  feed, and (4)
use of a sulfuric acid feed to dissolve any
                         aluminum hydroxide colloids remaining in
                         the alum-coagulated water after settling.
                           The most successful pretreatment
                         configuration was found to be the use of
                         alum-coagulated and  settled water from
                         the  PGWTP, following  by two sand
                         prefilters in series with sulfuric  acid
                         addition and 5-u  final filtration. The
                         average flux and average rate of flux loss
                         for this pretreatment configuration  was  8
                         g/sfd and 0 05 g/sfd2,  respectively. Under
                         these  operation conditions, membrane
                         cleaning was required  about every 16
                         days to avoid a production loss of greater
                         than  10%.  Product recovery was also
                         varied from  80%  down to  40%  in an
attempt to maintain a  higher velocity
across the membrane  surface to  scour
out foulants. Operation at 40% recovery
produced  the  lowest  average flux (7.1
g/sfd), but also least rate of flux loss.
   Water production for  the year of pilot
plant  operation at Punta Gorda  is also
summarized in Table  1.  As shown  in
Figure 2(c), system flux at Punta Gorda
varied greatly because of  numerous
membrane cleanings and changes in the
pretreatment configuration in  an  attempt
to stabilize water production.
   Average values of the concentrations
of selected water quality parameters for
the raw water, the  PGWTP finished water,
     Table 1
Average Water Flux, MTC and Pressure Drop by Stage for Flagler Beach and Punta Gorda FilmTec N 70
Membrane Plants.
                                        Flagler Beach
Location
Stage 1
Stage 2
Stage 3
System
Flux
glsfd
125
15.3
11 1
128
MTC"
1/day
0.015
0.009
0.008
0.005
Recovery
%
38
38
43
79
Pressure Drop
psi
57
101
100
141
     "Mass Transfer Coefficient
                                                                    Punta Gorda
Flux
glsfd
8.0
8.0
9.0
8.2
MTC"
1/day
0.003
0.003
0.040
0.003
Recovery
%
22
17
22
56
Pressure Drop
psi
134
132
119
152

-------
                Table 2.     Average Values for Raw, Finished Plant and Membrane Water Quality at Flagler
                            Beach and Punta Gorda FilmTec N 70 Membrane Pilot Plant Operations.
Flagler Beach
Parameter
THMFP (itg/L)
TOXFP (ng/L)
Color (cpu)
DOC (mg/L)
TDS (mg/L)
A/a (mg/L)
TH (mgIL CaCOs)
CaH (mg/L CaCOy)
Cl (mg/L)
Alk (mg/L CaCOJ
PH
Raw
367
1186
30
8.9
625
49
352
327
122
338
7.9
Finished
350
1105
5
7.6
530
49
111
91
122
98
8.3
Membrane
20
33
29
6.8
105
22
35
31
102
35
5.5"
Raw
880
2737
46
20.6
411
44
227
165
85
121
7.4
Punta Gorda
Finished
3821/80"
1414
3
6.4
473
57
222
161
105
116
8.1
Membrane
37
53
3
0.6
99
51
31
24
35
20
3.8"
                  t THMs formed with free chlorine present over 96 hours
                  " THMs formed in distribution system with chloramme disinfectant
                  " Prior to stabilization
and the membrane pilot plant permeate
are listed in Table  2.  The  feed and
permeate  THMFP concentrations are
shown  in  Figure  2(d) for the  year  of
operation at  Punta Gorda. The permeate
THMFP exceeded the THM MCL on only
one occasion when the new PGWTP was
put on-line. The permeate  THMFP
averaged 37 ug/L, which was less than
the average THM concentration  of 80
vig/L in the Punta  Gorda  distribution
system.
   An  upward  shift occurred in the
concentrations of  all  organic  and
inorganic permeate parameters when the
pretreatment was changed  to  alum-
coagulated  and  settled  feed water
Although  alum  coagulation removed
many foulants  that impeded water flux,
the presence of these foulants may have
resulted in the formation of a tighter
secondary  layer on the  membrane
surface that would have  increased  solute
rejection and decreased concentrations in
the permeate.
   The order of stage  flux before and
after the change to alum-coagulated and
settled-feed  water was  S1 > S2  > S3
and S3 > S1  = S2, respectively. The
stage  order for  permeate concentration
before and  after  the change  to  alum-
coagulated and  settled-feed  water was
typically S3  >  S2 > S1  and 81  > 82 >
S3,  respectively. The  stage  pressure
drops  after the  pretreatment  change
indicated  that  less fouling material was
reaching S3, therefore  S3 productivity
was  increased and  S3  permeate
concentrations  were decreased.  As at
Flagler Beach, the stage  and system
solute concentrations were indicative of a
diffusion-controlled process.

Cost
   With  the use  of information obtained
from  the pilot  plant  operation,  the
estimated capital and  O&M  costs for
installing a membrane  water  treatment
plant of  equivalent capacity (0.7 mgd) to
the existing lime softening plant at Flagler
Beach  are  shown  in  Table  3.  A
membrane  plant (including  concentrate
disposal) installed at the Flagler Beach
groundwater  site would cost  less  to
operate  but would require more to build
because the  existing  0.70  MGD  lime
softening plant is debt free. Installation of
a membrane plant (including concentrate
disposal) at Flagler Beach with a  2.7
MGD capacity to meet the future demand
for 20 years  would essentially cost the
same  to build and   operate  as  an
equivalent capacity lime softening plant.
The  membrane  plants  would produce
better  water quality  than  the  lime
softening plants.
   Similar cost information for the surface
water site at Punta Gorda is given (Table
3). Here, the use of a membrane process
essentially requires the construction  of a
complete alum coagulation,  sedimenta-
tion, and filtration  plant to  be  used as
pretreatment  in front of the membranes.
Thus,  the costs  for  the membrane
operation  are  considerably higher.
Operating  a  membrane plant  on  the
highly organic  surface waters found  in
Florida  would require lower design flux
and  recovery, more frequent  membrane
cleanings, and  very  extensive  pre-
treatment  than would a  plant at
groundwater site. The cost of membre
treatment for this type of  surface wa
may be unreasonable unless futi
regulations  for  THMs  and disinfecti
byproducts  force further consideration.

Summary
   A  membrane  plant,  operati
noncontinuously for a year on a grour
water source at Flagler Beach,  Floric
produced a permeate of high chemk
quality  while  maintaining  consiste
production.  The permeate THMFP w
always less than the current THM MCL
0.10 mg/L.  On a unit cost basis, the cc
of constructing  and operating equivale
capacity lime  softening  and membrai
plants  would be nearly equal,  and  tt
membrane  plant would produce superi
quality drinking water.
   At the Punta Gorda,  Florida,  surfa<
water source site, the membrane pil
plant could not maintain  consiste
production  because  of  severe organ
fouling problems. The permeate THMF
concentration consistently averaged lei
than the current THM MCL, however, ar
was also less than the distribution systei
THMs  produced by  the existing alui
coagulation  plant using chloraminatioi
Additional  pretreatment involving alui
coagulation,  pH  control,  and san
filtration was needed  to improve  produt
tion and lessen  the  rate  of  flux los
between membrane cleanings. The Punl
Gorda data indicate  that  a membran
process designed  for a  highly  organi
surface water source  must be based onf
lower design  flux  and  recovery, mor

-------
           I
           3
           1

           I


           1
           I
           0.

           I
 600
 500
 400

 300
 200
 100

  15

  12

   9

   6

   3

1500

1200

 900

 600

 300
                                                                                          Operating
                                                                                            Year
                                                                                          Complete
                                                                                          Operating
                                                                                            Year
                                                                                          Complete
                                  Permeate THMFP
                                   Flux
                                                                                                 Operating
                                                                                                    Year
                                                                                                 Complete
Punta Gorda
                                Feed THMFP
                                                              Punta Gorda
                                    Operating
                                      Year
                                    Complete
                                Permeate THMFP
                                                                                                               (A)
                                                 (B)
                                                 (C)
(D)
                                 1000        2000         3000         4000

                                                         Hours of Operation
                                                                5000
                               6000
                                                                                        7000
Figure 2.     Water flux and permeate THMFP for the FilmTec N 70 Membrane System at Flagler Beach and Punta Gorda, Florida.
frequent membrane cleanings, and exten-
sive pretreatment. Although  constructing
and operating a membrane plant at Punta
Gorda was shown to be more than twice
as costly as the existing alum coagulation
                           process, the plant would produce a better
                           quality drinking water.

                              The  full report  was submitted in  ful-
                           fillment of CR 813199 by  the  University
                        of Central Florida under the sponsorship
                        of the  U.S.  Environmental  Protection
                        Agency.
    Table 3.     Capital and Operation and Maintenance (O&M) Costs for the Present (1988) and Future (2008) Flagler Beach and Punta
                Gorda Water Treatment Plants and Equivalent Capacity Membrane Plants.
                                       Present
Location Capacity
Flagler Beach
Punta Gorda
MGD
0.7
8.0
Conventional
O&M
$11000
gal
1.21
0.99
Capital
$
0
3,500,000
Membrane
O&M
$11000
gal
1 09
1.86
Capital
$
1,437,000
12,966,000
Future
Capacity
MGD
2.7
8.0
Conventional
O&M
$11000
gal
0.69
0.99
Capital
$
3,951 ,000
6,971.000
Membrane
O&M
$11000
gal
0.72
1.86
Capital
$
3,840,750
16,338,500

-------
  J. S. Taylor, L A. Mulford, W. M. Barrett, S. J. Duranceau, and D. K. Smith  are
        with the University of Central Florida,  Orlando, FL 32816.
  J. Keith Carswell is the EPA Project Officer (see below).
  The complete report, entitled "Cost and Performance of Membranes for Organic
        Control in  Small Systems: Flagler  Beach and Punta Gorda,  Florida,"
        (Order No. PB 89-190 367/AS; Cost: $28.95, subject to  change) will be
        available only from:
            National Technical Information Service
            5285 Port Royal Road
            Springfield, VA22161
            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
US.OFFiCiALMAiL
                                                                                  ,,•:,; 4' M   i W/ATI-
Official Business
Penalty for Private Use $300

EPA/600/S2-89/022
                                                             -SI'/ATI-         _  r -.
                                                            ,'ji£S3CC|   II  ^  *1 -
                                                           /»     » j -• U  «J  »* -
                                                 V      ,  /- a  METER
                                                  v  C.'  \^s  :;jro4'i41
        00005833     S              GE»C,

-------