v-xEPA
United States
Environmental Protection
Agency
Municipal Environmental Research*-'
Laboratory
Cincinnati OH 45268
i
Research and Development
EPA-600/S2-82-042 August 1982
Project Summary
Removal of Nitrate from
Contaminated Water
Supplies for Public Use:
Final Report
Gerald A. Outer
Three treatment processes (reverse
osmosis (RO), ion exchange, and the
combination of RO followed by ion
exchange) to remove nitrate from
public water supplies obtained from
wells were evaluated. Laboratory size
and field-test equipment was used to
establish design criteria and operating
experience useful for designing a full-
scale plant of approximately 1-million
gal per day (mgd) capacity. An interim
report (EPA-600/2-81-029) on this
project was published in February
1981 and is available from the National
Technical Information Service, Spring-
field, Virginia; and the final report is
summarized herein.
The program was conducted by the
McFarland Mutual Water Co. at well
No. 3 in McFarland, California. Ion
exchange column tests were conducted
with five strong-base anion exchange
resins on nitrate-laden waters of
various anion compositions. From this
work, estimates of product water
quality and the bed volume capacity
for feedwater of any composition can
be made. A working hypothesis was
developed from an analysis of the data
about how the chemical structure of
resins can be practically altered to
obtain nitrate selectivity. As a result, a
series of resins was synthesized to
study the effect of molecular structure
on nitrate selectivity. Two of the resins
showed selectivity of nitrate in prefer-
ence to sulfate ion. Others in the series
showed enhanced sulfate selectivity.
A 20-in. diameter pilot anion exchange
column was designed and operated
for over 1 year at well No. 3. Data from
this column operation was used to
verify estimates of pilot column
performance and to project the cost
for equipment and regenerant for a
well site installation to treat up to
1 mgd. An RO system having a pro-
duction capacity of 76 mVday (20,000
gpd) was operated for over 1,000
hours until excessive nitrate passage
was obtained.
This Project Summary was developed
by EPA's Municipal Environmental
Research 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
The small community of McFarland,
California, in the heart of the intensive
agricultural/industrial area of the San
Joaquin Valley in central California, is
faced with declining water quality and
increased demand on their groundwater
supply. This problem is typical of many
communities not only in the United
States but throughout the world. If the
development of new water sources from
surface supplies or deep aquifers or the
use of centralized treatment is economi-
cally unfeasible, well site treatment for
contaminant removal is an alternative
to be considered. This study concerns
-------
applying treatment processes to a well
site situation — and improving water
quality without constructing new wells,
modifying old wells, or altering the
distribution system.
Well site treatment to remove nitrate
is not considered to be standard
practice; only a few such installations
can be cited throughout the world, and
no detailed operating data or costs have
been published. Although ion exchange
and reverse osmosis (RO) are familiar
and widely used processes in industrial
water treatment, their use to remove
specific contaminants from community
water supplies is new and requires the
traditional demonstration project to
advance widespread use of these
processes. This study provides both
engineering and scientific aspects
information and data to aid the planning
of a demonstration project. The engi-
neerng aspects deal with design para-
meters, conceptual designs, operation,
and process reliability derived from
actual hands-on experience. The scien-
tific aspects deal with ion exchange
theory of resin selectivity and the
testing of new resins that show nitrate
selectivity in presence of sulfate and
other common anions. It is believed this
work has resulted in a major break-
through in development of nitrate-
selective resins having the potential to
lower costs of nitrate removal for many
communities. The method used to
derive the nitrate-selective resins can
be used to derive resins selective for
other inorganic contaminants.
Methods and Materials
All tests were conducted at a well site
(No. 3) owned and operated by the
McFarland Mutual Water Company.
Nitrate-nitrogen levels for this water
were 16 to 23 mg/L, well above the 10-
mg/L maximum contaminant level
Sulfate levels were greater than 300
mg/L.
Site improvements were designed for
well No. 3 to accommodate equipment
for conducting both field and laboratory
scale experiments Water was supplied
directly to a concrete pad and trailer
from an existing hydropneumatic tank.
All product and wastewaters were
discharged from the pad directly into the
city sewer system. The 9 1- x 9.8-m
(300- x 32-ft) pad was large enough to
accommodate a field test ion exchange
system, a field test RO system, and a
single module RO system with the
necessary tanks for temporary water
storage. A trailer adjacent to the pad
housed a field office and limited
laboratory facilities.
A source of well No. 3 water was
available in the trailer for experimental
tests which were conducted on various
ion exchange resins in 5.1-cm (2-m.)
diameter columns Synthetic mixtures
were prepared and pumped directly at
measured flow rates through the ion
exchange columns Five commercially
available exchange resins were studied
along with eight specially prepared
resins. Because only the single-bed
process was chosen for this study, tests
were limited to strong-base anion
exchange resins.
A Culligan HI-FLO 5 Water Softener
Model 150* was installed and operated
on the pad at well No 3. The completely
automatic water softener was converted
to a semiautomatic anion exchanger by
installing an industrial timer and anion
exchange resin (Duolite A-101D). The
system incorporated a 50.8-cm (20-in.)
diameter bed that contained 123L(4.36
ft3) of anion exchange resin.
A pilot scale RO system producing 7.6
mVday (20,000 gpd) was operated on
pretreated well No. 3 water. Cellulose
acetate spiral wound elements were
used in this system
Discussion of Results and
Conclusions
Engineering Aspects
Ion Exchange
1. Design parameters for application
of a conventional fixed single-bed ion
exchange process with downflow re-
generation for removal of nitrate from
well waters were developed and tested
using laboratory columns and a modified
conventional automatic water softener
converted to a 20-in. diameter anion
exchange pilot column. The process is
depicted in Figure 1 for a well water of
moderate nitrate and sulfate levels. Pilot
column tests were conducted using a
Type I strong-base anion exchange
resin (Duolite A-101D) at well 3.
Because well No. 3 is high in nitrate (ca
20.3 mg/L NO3-N) and sulfate (ca 320
mg/L), it is a useful research well.
2. The study showsthat automatic ion
exchange equipment, which is com-
monly used by the water softening
industry, can be adapted for nitrate
removal The equipment can be installed
'Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use
at a well site for direct treatment of well
water and operated on demand without
storage.
3 The selected resin was effective for
the nitrate removal for flow rates over
45 gpm/ft2 of bed area (2.75 BV per
minute). Forty five gpm/ft2 was the
upper limit of the test equipment used.
These high flow rates bring the cost of
capital equipment and resin quantities
to low practical levels.
4. When sulfate is present in raw
water, operating the ion exchange
column in a partial regeneration mode is
more economical than in the complete
regeneration mode because the resin
concentrates nitrate near the down-
stream end of the column from which it
is easily removed. Salt requirements for
McFarland wells ranged from 2.5 to 5 Ib
of sodium chloride/ft3 of resin. In
comparison, complete regeneration
would require 18 to 20 Ib/ft3. The
extended bed life and lower nitrate
leakage does not justify the added salt
costs for complete regeneration. Partial
regeneration also produces a water less
corrosive than the high chloride water
produced by complete regeneration.
5. Capital equipment costs of an ion
exchange system for treating a Vz mgd
production well are estimated to be less
than $100,000 installed (1981 costs).
This estimate is based on moderate
nitrate levels (less than 13.5 mg/L NOs-
N) in well water and sulfate levels less
than 200 mg/L and on blending (50/50)
treated water with raw water to produce
a water less than 10 mg/L NOa-N (see
Figure 1). Equipment cost for a system
to treat all water from a 1-mgd produc-
tion well is estimated at less than
$160,000.
The total water cost including amortized
capital and operating costs are estimated
to be 17.3 cents/1,000gal (4.6 cents/m3)
of treated water. This is based on raw
water nitrate-nitrogen levels of 13.5
mg/L, sulfate levels of 200 mg/L, and
treated water nitrate-nitrogen levels of
6.8 mg/L with all sulfate removed.
These costs do not include brine
disposal costs, which are variable and
community dependent. Brine disposal
costs can be proportional to regeneration
chemical costs if disposed to local
landfills and could increase the above
unit quantity costs by 30 to 50 percent.
6. Regenerant costs alone over a 20-
year plant life can be more than double
the first equipment costs of the plant.
Because of the significance of regen-
erant costs, a method is presented to
estimate the sodium chloride require-
-------
ments for regenerating the resin used in
nitrate removal from waters of various
composition. Because anion exchange
resins are quite selective for sulfate ion,
the presence of sulfate in raw water
decreases the efficiency of the resin to
absorb nitrate In this study, however,
the sodium chloride regenerant easily
removed sulfate from the spent resin in
nearly stoichiometric proportions where-
as excess regenerant is required for
nitrate removal. The overall effect of
sulfate, however, is to increase the salt
required to remove nitrate per unit
quantity of water treated. This study
also confirmed that large quantities of
regenerant (20 Ib/ft3 of resin) are
required to remove most of the nitrate
from the spent resin. Not all nitrate need
be removed, however, to reduce nitrate-
nitrogen levels in treated water to below
10 mg/L
For McFarland wells, the salt require-
ments for lowering nitrate levels to
between 6.8 and 10 mg/L NCVN range
between an estimated 2.48 to 4.48
Ib/ft3 of resin. The salt costs range
between 2.31 cents/1,000 gal of
blended (50/50) water for well No. 2 to
12.28 cents/1,000 gal of treated water
for well No. 3. Well No. 3 represents a
particularly difficult water to treat as
nitrate-nitrogen levels are near 23 mg/L
and sulfate levels are above 300 mg/L.
Nitrate-nitrogen levels in well No. 2 are
near 13 5 mg/L and sulfate levels are
near 200 mg/L. Salt requirements for
waters of other compositions are given
(Table 1).
7. To achieve efficient nitrate removal,
good brine and influent flowdistribution
are essential and may require modifica-
tion in commercially available softening
equipment. A method of declassification
(thorough mixing) of the resin after
downflow regeneration should also be
incorporated in the regeneration cycle.
8. Wastewater produced during the
regeneration cycle has an enriched
composition of sodium sulfate, chloride,
and nitrate. Continuous operation of
well No. 2 would produce over 12,000
gal of wastewater/day (see Figure 1).
Continuous operation of well No. 3
would produce an average of 39,000
gal of wastewater/day
Reverse Osmosis
1. An RO system, operated on well No.
3 for over 1,000 hr, contained spiral
wound cellulose acetate membranes
and produced 15 gpm of treated water
with 75 percent water recovery. Of the
major groundwater anions, nitrate is
__ 1,000 gal
well water
/VOJ< 57 ppm
HCO3 = 72
Cl~ = 61
SOf = 197
500 gal
Regenerant
NaCI
1.25 Ib
\
500
gal
Strong
base
anion
exchanger
(type 1)
Chloride
form
V^
\
\
\
Raw water \^
^
Ion exchange
column effluent
NOy = 30 ppm
HCOz = 72 ppm
cr= 221
SOf = 0
I
Bypass
NO =4,9OOppm
S0f= 8,200
N0j = 1,200
Cl~= 800
I
Spent regenerant
and rinse
12 gal
1,000 gal
blended product water
NOy < 44 ppm
HCOj= 72
CL~ =141
SOf = 96
Figure 1. Conventional single-bed ion exchange process.
Table 1. Regeneration Requirements for Waters of Various Compositions
Water Composition NO3 rrieq/L
HCOl
cr
Operating SOI
Parameter Total Anion
NOl in product water ppm
Bed volumes treated to breakthrough
Salt loading Ib/ft3
Salt requirement Ib/ 1.000 gal
1
1
1
5
35
30
423
2 15
0.68
1
1
1
3
60
30
229
3.73
218
1.5
1
1
3
6.5
30
207
413
2.67
1.5
1
1
2
5.5
30
247
3.67
1.98
1.5
1
1
1
4.5
30
307
3.36
1.46
15
1
1
.5
4.0
30
347
3.22
1.24
-------
the most difficult to remove by RO.
During the operation of the system,
nitrate passage rose from 33 to 65
percent.
2. Because operation of the RO
system was plagued with several
electrical and mechanical failures, its
use is questionable for well site removal
of nitrate insmallcommunitieswithfew
or no maintenance personnel.
3. The most serious trouble experienced
with the RO system was failure of 0-
ring seals between the high pressure
brine and low pressure product channels
This was presumably due to lateral
movement of membrane elements
during the system start and stop that is
required to follow the start and stop of
the well pump. This difficulty can be
avoided by providing sufficient well site
storage to allow continuous system
operation.
4. Capital equipment costs for treating
water by RO for nitrate reduction from a
1 -mgd production well are over $800,000.
Estimates of water costs including
amortized equipment and operating and
maintenance costs are 99.2 cents/1,000
gal of water produced (26.2 cents/m3).
5. Twenty-five percent of the well
capacity becomes waste brine from the
RO system — for a 1 mgd well, 250,000
gal of wastewater per day. This quantity
would use one-half of the municipal
waste treatment capacity of McFarland's
wastewater treatment plant and would
add approximately 2 tons of dissolved
solids/day to the local disposal area if
operated at well No. 2 (compared with 1
ton for ion exchange — same basis).
However, no outside source of sodium
chloride is needed as is the case with
ion exchange
6. The advantages of RO over ion
exchange are that fewer processing
chemicals need be brought to the locale
and the product water is considerably
deminerahzed
Reverse Osmosis Followed by
Ion Exchange
1. For small communities, there
appears to be few advantages to using
RO followed by ion exchange polishing
to produce water of low nitrate content
(less than 1 mg/L NO3-N). Because RO
brine was ineffective for regenerating
the nitrate-loaded resin, some salt was
still required. The added complexity and
cost of operating an RO system in
conjunction with ion exchange at the
well site appears to outweigh any
advantages of producing a less minera-
lized water. Water costs by operation of
such a system are estimated to be at
least $1.12/1,000 gal of low nitrate
content water that could be blended
with other well water. If blended (two
volumes raw water to one of treated
water), the cost per 1,000 gal would be
37 cents plus brine disposal costs. Resin
regeneration requirements would be
substantially reduced, to below 10
percent of their value, if ion exchange
alone would be used. Volume of
wastewater would be about 115,000
gal of mainly RO brine per 1 mgd of
blended product
2. RO followed by ion exchange may
be cost effective for large scale systems;
these were not a subject of this
investigation. Economies of scale could
lower RO costs and advantages of
demmeralization may be highly desir-
able Large communities with high
nitrate, high TDS groundwater can treat
with RO and polish by ion exchange and
could blend the product with raw water
and may find the process cost effective.
Theoretical Aspects
1. A special series of strong-base
anion exchange resins, synthesized
especially for this program, shows a
striking correlation between nitrate-to-
sulfate selectivity and the molecular
structure of the alkyl substituents on the
quaternary amine ion exchange sites.
Some of the resins are nitrate-to-sulfate
selective. The normal increasing order
of ion selectivity for available anion
exchange resins at normal ground-
water concentrations is bicarbonate,
chloride, nitrate, sulfate. As the number
of carbon atoms around the ammonium
nitrogen increase in the R groups of the
resin structure.
R
(Divmylbenzyl Resin Backbone)—N—R,
R
the increasing order of ion selectivity is
changed to bicarbonate, chloride,
sulfate, nitrate. Where R is methyl, Ks(a
measure of nitrate-to-sulfate selectivity)
is approximately 100; whereas if R is
ethyl, Ks is approximately 1,000 Thus,
in column tests with the triethy I resin on
water having a nitrate plus sulfate
concentration of greater than 8 meq/L,
nitrate is the last ion to breakthrough
Other resins with a total of four and five
carbon atoms show intermediate Ks
values. See Tables 2 and 3 and Figure 2.
The effect of introducing OH groups into
the alkyl substituents is to decrease the
Ks value. For example, if the R groups
are ethoxy, the Ks value is approximately
10.
These structural effects on Ks value
are ascribed to steric strains set up in
the resin by the special (or steric)
requirements of alkyl R groups with
nitrate having capability of decreasing
the steric strain whereas sulfate can
increase strain. Little effect on the KCI
values are noted. All resins are easily
regenerated with chloride brines. This
observed effect of molecular structure
gives rise to a concept of structurally
induced electroselectivity reversal.
2. The net effect of using the triethyl
amme resin as compared with the
commercially available trimethyl resin,
is to increase the bed life BV (N) from
170 to 275, an increase of 62 percent,
when treating a water containing 1.5
meq/L nitrate and 6.5 meq/L sulfate
(see Figure 3). The immediate effect is to
reduce wastewater for processing by
38 percent A second desirable effect
of using the triethyl resin is to reduce by
25 to 50 percent, the amount of
regenerant required to remove an
equivalent amount of nitrate depending
on the mode of operation and level of
regeneration selected. This represents
a projected cost savings of $84,000 to
$168,000 in salt over the 20-year plant
life plus at least equivalent amounts for
brine disposal costs. Special column
operation must be used since the nitrate
breakthrough can be compounded and a
choice is available to operate to the first
or second nitrate breakthrough. A third
advantage in using NSS resins is to
preserve more of the raw water quality
by allowing sulfate to pass through the
column.
3. The structural effects noted above
were found characteristic of a series of
eight special resins that show a trend
toward increased KS (and greater
process efficiency) without any obser-
vable limit. Consequently, it is believed
a continuing study of structure I changes
can produce an optimum resin that will
give an even greater cost saving than
that noted above.
4. The nitrate-to-sulfate selective
(NSS) resins have characteristics that
require special consideration in process
design.
• Anion exchange capacity of NSS
resins is approximately 15 percent
lower than their Type 1 counterpart.
-------
Table 2. Structures of Special Resins
No. Designation Amine
Molecular Structure*
1
R-TM
Trimethyl
R-TE
Triethyl
R-MDE
Methyldiethoxy
R-EDEOH
Ethyldiethoxy
R-TEOH
Triethoxy
R-DMEOH
(same as A-104)
R-DEEOH
Dimethylethoxy
Diethylethoxy
R-N-MM
N-methyl-
morpholine
CH3
R N+ CH3
CH3
CH3
CH2
R N+ CH2 CH3
CH2
CH3
CH3
R /V+ CHz CH2OH
CHZ
CH2OH
CH3
CH2
R N+ CH2 CH2OH
CH2
CH2OH
CH2OH
CH2
R N+ CH2 CH2OH
CH2
CH2OH
CH3
R N+ CH2 CH2OH
CH3
CH3
CH2
R N+ CH2
CH2
CH3
CH3
N
O
*R denotes resin backbone structure.
• Two nitrate breakthrough points
are obtained with partially regen-
erated resin. Nitrate leakage before
the first is determined by chloride
ion-nitrate ion competition for resin
sites. The first breakthrough point
occurs simultaneously with sulfate
breakthrough. Nitrate leakage
after sulfate breakthrough is deter-
mined by nitrate ion-sulfate ion
competition. The first break is
usually sharp; the second is often
indistinguishable.
• To use the triethyl NSS resin
effectively, two columns can be
run out of phase to average the two
levels of nitrate leakage.
5. The method used to discover the
nitrate-to-sulfate selective resins was
through observation and analysis of (a)
column breakthrough profiles and
relation to chemical structure; (b)
departure of column behavior from a
mathematical model; (c) the shape of
binary isotherms; (d) effect of structural
changes on primary, secondary, and
tertiary ammonium weak-base resins;
(e) swelling effects of ions on resins; (f)
experiments on nitrate-selective sulfate-
loaded resin; and (g) inferences from
physical organic chemical studies of
effects of structure on chemical equili-
brium. This method may be applied to
studies on selective removal of other
inorganic contaminants.
6. Nitrate-to-sulfate selectivity among
strong-base resins was found to also
increase with the degree of resin cross
linking. The list of resins studied in
increasing order of nitrate-to-sulfate
selectivity are:
Duolite A-101D
Duolite A-104
Amberlite IRA-910
Dowex SAR
Amberlite IRA-900
The literature shows IRA-410 and lonac
A-550 as well as some tertiary amine
weak-base resins to have nitrate-
selective tendencies However, com-
mercially available resins do not show
enough nitrate selectivity to be of
significant value. In this study they are
not NSS resins. Lower anion exchange
capacity is a disadvantage of the higher
cross linked resins and also makes the
ion exchanger appear to be nitrate-to-
sulfate selective through the electro-
selectivity effect. (Activated carbon is a
notable case.) Also, where nitrate and
sulfate are equal in selectivity, the spent
column will have nitrate evenly distri-
buted in the column. This is a dis-
advantage in downflow regeneration
-------
Table 3. Properties of Special Resins'
No. and Designation
1 R-TM
2 R-TE
3 R-MDEOH
4 R-EDEOH
5 R-TEOH
6 R-DMEOW
7 R-DEEOH
8 R-N-MM
(Duolite A-1 '01 D)
Moisture2
Content
51.0
47.9
41.1
38.9
33.1
45.7
43.5
44.6
(48 to 55)
Vol.
Capacity2
(eq/L)
1.41
1.19
1.41
1.30
1.23
1.42
1.29
1.35
(1-3)
(approximate)
100
1,000
10
50
10
50
100
200
(25)
NSS
-0.14
+0.92
-1.15
-0.41
-1.09
-0.45
-0.11
+0.17
-0.7 1
'A II resins synthesized from the resin intermediate used in commercial manufacture
of Duolite A-104.
2Data supplied by Diamond Shamrock.
3Same as Duolite A-104
3.0 r
2.0
§•
-J
1.0
• NO OH group's in fl, R2 R3
O One " " " " "
A Two " " " " "
D Three " " " " "
A-101-D
m
345
No. of carbon atoms in /?, R2 R3
Figure 2. Effect of structure on nitrate to sulfate selectivity.
6
since nitrate must be moved through
the entire column. Consequently, A-
101D resin was chosen for pilot studies
because nitrate concentrates near the
exit end of the column from which it is
more easily removed during regenera-
tion. It is also pointed out in the study
that threshold Ks values must be
reached before a resin can be a nitrate-
to-sulfate selective resin and before
process efficiency can be improved.
7. Use of chemical regenerants other
than sodium chloride was briefly
explored. It was demonstrated that
nitrate can be selectively removed using
sulfate-loaded resins. It is suggested
that dilute calcium sulfate be tested as a
regenerant. Larger volumes of regenerant
using a low IDS water are required.
Such a supply is available in McFarland
as irrigation water. Waste brine would
contain calcium nitrate and sulfate both
of which are disposable to agricultural
lands. Ammonium chloride is also
suggested as regenerant that would
give ammonium nitrate and sulfate as a
disposable brine
8. From these studies and a review of
previous studies on synthesis of resins
with higher nitrate-to-chloride selectivity,
it does not appear regenerant require-
ments can be reduced if nitrate-to-
chloride selectivities are increased.
Available anion exchange resins are
already nitrate-to-chloride selective.
Making them more selective for nitrate
will only add to further regeneration
inefficiencies. This, however, does nol
appear to be the case with the NSS
resins since the nitrate-to-chloride
selectivities did not change substantially
whereas nitrate-to-sulfate selectivitv
did change.
Recommendations
1. An ion exchange demonstration
plant of '/2- to 1 -mgd capacity should be
installed and operated to obtain actual
operational experience regarding reli-
ability, health, safety, and costs. Com-
mercially available resins should be
used because NSS resins require
further testing.
2. As pointed out above, the cost of
regenerant and brine disposal over the
plant lifetime can be several times the
cost of the plant. Efforts should be made
to reduce regenerant requirements to
the lowest level practicable. This can be
done by recycling portions of brine and
brine rinse as well as backwash waters
in demonstration plant operation and
continuing studies on nitrate-to-sulfate
selective resins.
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400 r-
350
300
250
£
Q>
I
* 200
I
o
S /50
c
.0
5
^
100
50
Influent S04
- Influent NO3
sor
A
A
NO;
•
0
Resin
R-TE
A-101-D
Regenerated IV/4 BV 6% NaCI
runs 09230. 09190
50
100
150 200 250
Bed volumes Well 3
Figure 3. Ion exchange column experiment 09230 and 09190.
300
350
400
3. Studies should be conducted on
use of regenerants other than sodium
chloride for the single-bed process to
produce waste brines more amenable to
disposal on agricultural land.
4. Studies on NSS resins should
continue since further increases in
nitrate-to-sulfate selectivity can be
expected. These resins must also be
characterized as to fouling tendency,
chemical degradation, and acceptance
in water treatment.
5. Brine disposal is the single most
important factor and major expense that
deters widespread use of the ion
exchange process. All future efforts to
improve the process should focus on
this impediment to its application.
6. Ion exchange is recommended over
RO for nitrate removal at remote well
sites in small communities because of
cost and operational problems associated
/ith RO. This study showed that total
oosts for treatment of well No. 2 water
were approximately 18 cents/1,000 gal
for ion exchange versus $1/1,000 gal
for RO. Brine disposal costs were not
included in either estimate.
Summary
The ion exchange process isgenerally
more suitable as a well site treatment
for nitrate removal than RO or a
combination of the two. Ion exchange
requires lower first cost and annual
operating costs, has greater reliability,
uses less energy, requires no additional
well site storage, has higher water
recovery, produces a more concentrated
waste brine, and requires fewer auto-
matic and electrical controls. It can be
operated on demand as required by
distribution system needs. Such on-off
operation is severely detrimental to an
RO system, which operates best on a
continuous basis and, hence, requires
additional storage and repressurization.
Brine disposal is a cost common to both
processes.
Ion exchange resins with altered
chemical structures were formulated
for selective removal of nitrate from
common groundwaters containing
sulfate ions. Projected use of nitrate-to-
sulfate selective (NSS) resins in ion
exchange plants has potential to reduce
operating costs by increasing the
efficiency of the process through
reduced wastewater, reduced brine
requirements, and lower waste brine
disposal costs. These operating cost
savings are estimated to exceed the
equipment costs of the plant over a 20-
year period. The NSS resins, which
require further testing before practical
applications can be made, are presently
not commercially available. Small
quantities were made for this program
by a resin manufacturer using existing
processes and available intermediates.
The NSS resins are examples of struc-
turally induced electroselectivity rever-
sal, a concept that may find applications
in removal of other contaminants.
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The full report was submitted in
fulfillment of Grant No R-805900-01-
02-03 by the McFarland Mutual Water
Co., McFarland, California, under
subcontract to Boyle Engineering Cor-
poration, Bakersfield, California, under
the sponsorship of the U S. Environ-
mental Protection Agency.
Gerald A. Cuter is with Boyle Engineering Corporation, Bakersfield. CA 93302.
Richard Lauch is the EPA Project Officer (see below).
The complete report, entitled "Removal of Nitrate from Contaminated Water
Supplies for Public Use: Final Report," (Order No. PB 82-222 902; Cost:
$18.00, 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:
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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