United States
Environmental Protection
Agency
Office of
Drinking Water IWH-550)
Washington, DC 20460
Nitrate Removal
for Small Public
Water Systems
EPA 570/9-83-009
June 1983
-------
United States
Environmental Protection
Agency
Office of
Drinking Water (WH-550)
Washington. DC 20460
EPA 570/9-83-009
June 1983
&EFK
Nitrate Removal
for Small Public
Water Systems
-------
NIIRATE RFI ’OVAL F(I
SMALL PUBLIC WATER SYSTEMS
Piepared by:
SMC -MARTIN
900 W. Valley Foige Road
Valley Fotge, PA 19482
PLepared for:
U.S. Envitorinental Ptotection Agency
Office of Drinking Water Water
Chester Pauls, Ptoject Officer
401 M Street, SW
Washington, DC 20460
Contact No. 68-01-6285
-------
D IS CLAIMER
THIS HANDBOOK HAS BEEN REVIEWED BY THE U.S. ENVIRONMENTAL PROTECTION
AGENCY AND APPROVED FOR PUBLLCATION. APPROVAL DOES NOT SIGNII Y THAT
THE CONTENTS NECESSARILY REFLECT THE VIEWS AND POLICIES OF THE U.S.
ENVIRONMENTAL PROTECTION AGENCY, NOR DOES MENTION OF TRADE NAMES OR
COMMERCIAL PRODUCTS CONSTITUTE ENDORSEMENT OR RECOMMENDATION FOR USE.
-------
CONTENTS
Page
I. SUMMARY AND OVERVIEW I—i
Purpose I—i
When Nitrates are a Problem I—i
Alternative Methods Used to Reduce Excess Drinking
Water Nitrates 1—2
Treatment Methods 1—2
Designing an Ion Exchange Nitrate Removal System 1—4
Cost Estimating Procedures and Funding Sources 1—4
Operation and Maintenance of Nitrate Removal Systems 1—7
Summary 1—7
II. INTRODUCTION 1 1—i
Nitrate: What It is and Where It Comes From 1 1—i
Nitrates and Health: Why the Concern 11—2
How Nitrates Get Into Water Supplies 11—3
The Safe Drinking Water Act 11—4
Analyzing for Nitrates 11—6
Units of Nitrate Measurement 11—9
III. WHAT TO DO IF THE CONCENTRATION OF NITRATE IN THE WATER
SUPPLY IS EXCESSIVE 1 1 1—i
Nontreatment Alternatives 1 1 1—i
Treating Water Supplies for Nitrate Removal 111—2
IV. DESIGNING A NITRATE REMOVAL SYSTEM IV—i
Abbreviations, Units and Conversion Tables IV—i
Analysis of Raw Water Supply IV—i
Pilot Testing IV—1
Pretreatment Requirements IV—4
Anion Exchange Unit Design IV—4
V. COST ESTIMATING PROCEDURES AND FUNDING SOURCES V—i
Construction Costs V—i
Operation and Maintenance Costs V—7
O&M Cost Basis and Assumption V—7
Funding Sources V—16
VI. OPERATION AND MAINTENANCE VI—l
Operator Requirements VI1
Manuals, Equipment and Supplies Needed VI—1
Monitoring VI—2
Preventive Maintenance VI—4
Emergency Procedures VI—8
Safety Procedures VI—9
Record Keeping VI—9
VII. CASE HISTORIES Vu—i
CurryvilLe, Pennsylvania Vu—i
McFarland Mutual Water Company VII—5
REFERENC ES
APPENDIX
-------
LIST OF FIGURES
Number Page
1 Nitrate Control for Community and Noncommunity Water
Systems 1—3
2 Ion Exchange Unit at Curryville, Pennsylvania 1—5
3 The Ion Exchange Process 1—6
4 The Nitrogen Cycle Il—i
5 Typical Sources of Nitrates in Raw Water Supplies 11—5
6 Hach Kit Calibration Curves Used at McFarland,
California 11—8
7 Bead of Ion Exchange Resin 111—4
8 Ion Exchange Process Cycle 111—5
9 Selectivity of Strong Base Anion Exchange 111—8
10 Fixed Bed Ion Exchanger 111—8
ha Continuous Ion Exchange Processes (Pulsed) 1 1 1—11
lib Continuous Ion Exchange Processes 111—12
12 Nitrate Removal System Design Steps IV—2
13 NO /TA vs. Unadjusted Resin Capacity for A—104 Resin IV—13
14 Su fate Correction Curve for A—104 Resin IV—14
15 Bed Expansion Curve for A—104 Resin IV—15
16a Protective Monitors IV—22
16b Protective Monitors IV—23
17 Construction Cost Curves for ton Exchange Nitrate
Removal V—6
18 Operation and Maintenance Costs for Ion Exchange
Nitrate Removal V—9
19 Regeneration Costs vs. SO 4 and NO Concentration V—1O
20 Curryville, Pennsylvania, Equipme t Housing VII—2
21 Curryville, Pennsylvania, Nitrate Removal System VII—3
22 Pilot Scale Test Unit Used at McFarland VII—7
-------
LIST OF TABLES
Number Page
1 Federal Financial Assistance Programs 1—8
2 Occurrence of Nitrate Induced Illness vs. Nitrate
Concentrations 11—3
3 Partial List of U.S. Suppliers of Field Test Kits 11—7
4 Partial List of U.S. Ion Exchange Resin Producers 111—9
5 Partial List of U.S. Suppliers of Fixed Bed Ion
Exchange Systems 111—10
6 Partial List of U.S. Suppliers of Continuous Ion
Exchange Systems 111—10
7 Raw Water Constituents that Should be Quantified IV—3
8 Some Pilot Testing Guides Available from Resin
Manufacturers IV—3
9 Pretreatment Requirements IV—5
10 Equivalent Weights IV—7
11 Some Strongly Basic Resins and Their Suppliers IV—7
12 Suggested Design Parameters for A—104 Resin IV—12
13 Conceptual Design for Pressure Ion Exchange
Nitrate Removal V—5
14 Construction Cost for Pressure Ion Exchange Nitrate
Removal V—5
15 Capital Recovery Factors V—7
16 Operation and Maintenance Summary for Pressure Ion
Exchange Nitrate Removal V—li
17 Sample Monthly Data Sheet VI—3
18 Sample Periodic Equipment Check List for a Small ton
Exchange Unit Vt—S
19 Design and Operating Data for the Curryville, PA
Nitrate Removal System VII—4
20 Pilot Column Data vn—6
21 McFarland, California 0.5 mgd System Design Parameters VII—8
22 McFarland, California Cost Estimate for 0.5 mgd System VII—9
-------
I. SUMMARY AND OVERVIEW
PURPOSE
This Handbook for Nitrate Removal
has been prepared to aid water
utility owners, engineers, opera-
tors, and municipal managers in
understanding and dealing with
excessive nitrate levels In their
water supply. It is intended to
be used for defining the problem,
developing or evaluating proposed
solutions, and explaining to
water consumers why nitrates are
controlled and what the approxi-
mate costs of control will be.
Although the handbook may be
useful to larger utilities, It is
intended primarily to support the
water quality improvement efforts
of smaller utilities that may
lack the technical and financial
resources of the larger systems.
This handbook Is designed as a
technical guide to nitrate removal
for those smaller size systems
that have decided that nitrate
control is desirable. This
document contains no regulatory
policy and does not obligate
systems to use any treatment or
nontreatment technique to reduce
nitrate concentrations. If
appropriate, those regulatory
requirements are or will be
established by the primacy agency
as part of its Implementation of
the Primary Drinking Water
Regulations.
The handbook is divided into
seven sections, plus references,
as follows:
Section Subject
I Summary and Overview
II Introduction — Discusses
nitrate sources and origin
of nitrate in drinking
water, health effects,
federal laws, and methods
for detecting nitrate In
water.
III Nontreatment and Treatment
Alternatives — Different
approaches to solving
excess nitrate problems.
IV Design of Nitrate Removal
Systems — Ion exchange
system types, suppliers.
Example of design calc-
ulations. Waste disposal.
V Cost Estimating Procedures
and Funding Sources —
Capital capacity. Sources
of loans, grants and other
financial assistance.
VI Operation and Mainten-
ance — Basic guidelines
for operating nitrate
removal systems, including
water quality monitoring
and equipment maintenance.
VII Case Histories — Experience
of two utilities which are
treating the water supply
to remove excess nitrates.
WHEN NITRATES ARE A PROBLEF 1
Nitrate is both a natural and a
synthetic ion which Is made up
of one nitrogen (N) atom and
three oxygen (0) atoms; its
chemical symbol is (NO . ).
Under natural conditions,
nitrate usually does not occur
I—i
-------
in drinking waters at levels
which are of concern to water
utilities. However, heavy use of
nitrate fertilizers, septic tanks
for sewage disposal, or animal
feedlots may cause high local
levels of nitrates in soils.
Rainfall then washes the nitrate
from the soil into streams and
groundwater which may then con-
taminate these sources of drink-
ing water supplies.
Beginning in the late 1940s,
health research linked high
levels of nitrates in drinking
water with an illness called
methemoglobinemia, a type of
anemia. Victims of the disease
were likely to be very young
babies. About forty deaths were
attributed to the disease, largely
as a result of feeding babies
with polluted well water. Based
on these findings, the 1962 Public
Health Service Drinking Water
Standards set a maximum limit of
10 milligrams of nitrate—nitrogen
per liter of water (mg/i NO —N)
in public water supplies. urther
reasearch supported this standard
which was adopted unchanged in
the National Interim Primary
Drinking Water Regulations.
ALTERNATIVE METHODS USED TO REDUCE
EXCESS DRINKING WATER NITRATES
If nitrates in the drinking water
supply exceed 10 mg/i (or 20 mg/l
for certain non—community systems)
steps to reduce the level to
10 mg/I or less are generally
recommended. Figure 1 depicts
the steps recommended to define
and eliminate nitrate problems.
As explained later in this text,
treatment for nitrate removal may
involve significant costs.
Before buying a nitrate removal
system, the utility should also
study all nontreatrnent approaches.
Often, nitrate problems are
limited to one well or stream,
or a localized land area. An
alternate source of water may
eliminate the problem. Cooper-
ation and regionalization
options that may be useful are
discussed in the following
reference:
R gionalization Options For
Small Water Systems U.S. EPA
Office of Drinking Water,
401 M St., SW Washington, DC
20460.
It may also be possible to
blend a water containing exces-
sive nitrates with one having
little or no nitrates to produce
a blended water of acceptable
quality. It may also be possible
to reduce the nitrate concentra-
tion with time by controlling
the source of contamination.
For example, more careful
application of nitrogen contain-
ing fertilizers or elimination
of septic tanks may reduce
contamination of ground water
supplies in time. This is
supported by a statistical
comparison of nitrate concentra-
tions from wells for a sewered
area that previously contained
septic tanks. The comparison
showed significantly decreasing
nitrate coi ij ytrations over the
long term.
TREATMENT METHODS
At the present time, nitrate
removal can generally be achieved
by two classes of treatment
technologies: anion exchange
and membrane processes such as
reverse osmosis. At the present
time, membrane systems and
membranes per se are evolving
and improving rapidly. Because
of their relatively high cost
1—2
-------
START
EXCEED
10 mg/I
NO 3 - N
YES
‘ S
Watershed Management
• new/reworked well
• new/relocated surface intoke
• import row water
• blend existing/new sources
join/form regional system
• cooperate with other utilities
COMPARE COSTS
RELIABILITY
OPERATIONAL
CONSIDERTIONS
STUDY
TREATMENT
ALTS.
E’° exchange
Reverse
osmosis
Other
‘SELECT AND IMPLEMENT
BEST SOLUTION
Figure 1. Nitrate Control for Community and Non—community Water Systems
MONITOR
NITRATE
LEVELS
NO
I
0’
1—3
-------
and need for more sophisticated
operation, membrane systems have
not been routinely employed in
small systems specifically for
nitrate removal. Accordingly,
this document will not discuss
and detail Information on these
systems. It should be noted,
however, that these processes may
be particularly applicable to
those water systems that contain
excessive nitrate concentrations
and contain high concentrations
of dissolved solids or other
undesirable consitutents. Reverse
osmosis information is provided
In a document titled: “Radio—
nuclide Removal for Small Water
Systems” currently being prepared
by U.S. EPA Office of Drinking
Water.
The ion exchange processes use
equipment and technologies sim-
ilar to those used for home water
softeners. This equipment is
available from numerous suppliers,
a partial list of which is provided
in Tables 5 and 6 of this handbook.
Figure 2 depicts the ion exchange
unit at Curryville, Pennsylvania
that has been adapted for nitrate
removal.
DESIGNING AN ION EXCHANGE NITRATE
REMOVAL SYSTEM
Design of an ion exchange system
for nitrate removal involves two
main considerations:
1. Characterization of the
water to be treated and
selecting the ion exchange
resin.
2. Designing the tanks, plumbing
and controls.
The ion exchange resin is the
heart of the process. In the
resin bed, located in the exchanger
tank as shown In Figure 3a,
nitrate is removed from the
water by an exchange process
whereby nitrate ions In the
water are replaced by chloride
ions from the resin bed.
When the replacement or exchange
capacity of the bed is exhausted,
it must be regenerated by
pumping a brine solution (usually
sodium chloride, NaCl) from the
brine tanks through the resin
bed (Figure 3b). The resin
tanks, brine tanks and plumbing
are sized depending on the
amount of nitrate to be removed,
the presence of competing ions
particularly sulfate, and the
characteristics of the resin
selected. The design procedure
is based on manufacturer’s
recommended parameters which
can also be determined and
possibly optimized, by pilot
testing.
COST ESTIt1ATING PROCEDURES AND
FUNDING SOURCES
Section V explains the procedure
that can be used for estimating
treatment and operation and
maintenance costs.
Currently (1981), there is only
one nitrate removal Ion exchange
system in continuous operation
in the continental United
States at a water utility.
This system, operating at less
than 10% of its nominal 40,000 gpd
capacity, was installed in 1979
for $30,000. (See Section VII
for Details.) Costs cited In
the examples provided in this
handbook are estimated data
generated from a variety of
sources. Adjusting cost figures
for inflation is also discussed
in Section V.
1—4
-------
I I—.
t
Figure 2.
Ion Exchange Unit at Curryville,
1—5
Pennsylvania
-------
To Distribution
System
REGENERANT
(WATER + C L)
Figure 3.
iN
RESiN
BED
b
REGENERANT
Regenerating the Resin Bed
The Ion Exchange Process
a
Removing NO 3 from the Water
cs -
N _ 1 NOs-
-1
CI No
C l-
CI
hoC’
BRINE
TANK
To Waste
1—6
-------
Sources of financial assistance,
in the form of loans, loan guaran-
tees, or outright grants, are
very limited. The principal
federal financial assistance
programs available are shown in
Table 1.
OPERATION AND MAINTENANCE OF
NITRATE REMOVAL SYSTEMS
In general, ion exchange systems
for nitrate removal share the
very low maintenance requirements
of similarly sized water softeners.
Regeneration is initiated by
simple, highly reliable flow
meters and controlled by timers
and automatic valves known for
their trouble—free operation.
Unlike water softeners, which are
designed to treat a nuisance——hard
water, nitrate ion exchangers are
designed to remove a substance
capable of producing a health
hazard——nitrate. Thus, the
nitrate ion exchangers require
more safeguards in their design
and operation. This generally
includes a requirement for the
ability to monitor for nitrate
breakthrough. Even so, operator
time required to run the system
will not exceed several hours per
day in most cases. Operators do
not require highly specialized
skills, but they must understand
fundamental chemistry and be able
to perform accurate nitrate
analyses and be familiar with
pumps, controls, plumbing and
electrical systems and know how
to keep basic records.
SUMMARY
handbook describes the design
steps used for developing a
simple, reliable and cost
effective system for nitrate
control. Suggestions for
nontreatment approaches by
individual water utilities are
also offered and a reference
that discusses nontreatment
approaches in detail is provided.
Systems faced with the need to
reduce excessive nitrates in the
water supply can use a variety of
nontreatment approaches, or
install a treatment system. This
1—7
-------
TABLE 1
FEDERAL FINANCIAL ASSISTANCE PROGRAMS
ency Program Description
Farmers Home Administration 1. Cooperative grants up to 75 per-
cent of project cost for public—
ly owned rural systems serving
fewer than 10,000 persons.
2. Loan guarantees up to 90 per-
cent of loan face value for
public or private rural
utilities, emphasizing those
serving fewer than
2,500 persons.
3. Direct loans up to 75 percent
of project cost.
Department of Interior 1. Direct loan programs for non—
federal entities in the
17 western states.
2. Financial assistance for
systems serving American
Indians.
Department of Housing and Urban 1. Community Block Development
Development Grant Program
1—8
-------
II. INTRODUCTION
NITRATE: WHAT IT IS AND WHERE IT
COMES FROM
Nitrate is a nitrogen—oxygen ion
that occurs frequently
in nature as the result of the
interaction between nitrogen in
the atmosphere and living things
on earth. This interaction is
described pictorially by the
nitrogen cycle (Figure 4).
decay, the nitrogen compounds
are constantly cycled among
various forms. When plant and
animal proteins are broken down
by digestion or decay, ammonia
(NH 3 ) and nitrogen gas (N 2 ) are
released to the atmosphere or
to the land. Ammonia in the
air is returned directly to the
earth in rain, as It readily
combines with water. Nitrogen
LIVING MATERIAL
(complex molecules
containing nitrogen —
human and onimol
wastes)
ATMOSPHERE
N 2 NH 3
PLANT_METABOLISM
DECAY
Figure 4. The Nitrogen Cycle
At any time, nitrogen gas and its
compounds with hydrogen and
oxygen exist in the atmosphere,
on the surface of the earth, and
in the soil. Through the action
of plants, animals, and the
microscopic organisms that effect
gas is taken from the air and
converted to proteins and other
compounds containing nitrogen
by nitrogen fixing bacteria
that live on the roots of a
class of plants called legumes
(e.g., alfalfa). The action of
WATER 8
NH 4 NO 3
SOIL
,N0 2
II—’
-------
Lightning in storms and high
temperature combustion processes
cause nitrogen and oxygen to
combine to nitrous oxide (NO)
which quickly oxidizes to nitrogen
dioxide (NO 2 ). The latter combines
with_rain water to form nitrates
(NO ) and nitrites (NO ) which
soa into the soil. Th cycle is
completed by plants which take
the nitrogen compounds from the
soil and, through photosynthesis,
create plant proteins which man
and animals then digest and
decay, releasing ammonia and
nitrogen gas anew.
NITRATES AND HEALTH: WHY THE
CONCERN
Nitrogen and its compounds are
clearly necessary in human metab-
olism. Why then, are nitrates of
concern in drinking water? The
answer is that, while we need
some nitrate to live, too much is
not beneficial. In other words,
if people and animals consume
food or water that contain excessive
nitrate, it can make them sick.
Left untreated, nitrate caused
illness can be fatal, particularly
for the very young.
The illness resulting from too
much nitrate usually takes the
form of methemoglobinemia, in
which nitrates interfere with the
body’s ability to take oxygen
from their air and distribute it
to body cells. Bacteria that are
normally present in the body —
convert ingested_nitrate (NO 3 )
to nitrites (NO ), which in turn
replace oxygen n the blood. This
condition is exhibited as a type
of oxygen starvation, similar to
anemia. The victim often takes
on a pale, bluish coloration. If
not recognized and treated, death
can result, particularly if the
victim is an infant.
Methemoglobinemia was first
identified with polluted drinking
water supplies by H. H. Comly
of the U.S. Publ , Hea1th
Service in 1949. / Further
work finnl 3 stab1ished the
connection and led to the
1962 U.S. Public Health Drinking
Water Standard for nitrates.
The standard was adopted without
major changes in the Interim
Primary Drinking Water Regula-
tions that resulted from the
Safe Drinking Water Act.
A 1974 sç y for the State of
Illinois’ reviewed the PHS
standard and noted that certain
groups of people are more
vulnerable to nitrate induced
sickness, including the following;
1 Infants under 3 months in
age
2. Infants with respiratory
illness or diarrhea
3. Individuals with enzyme
deficiencies that increase
their vulnerability to
nitrate ingestion related
illness
4. Individual . i a lack of
free hydrochLoric acid in
the stomach (achiorhydria)
due to gastric diseases
This study noted that methemo—
gLobinema can occur in infants
at relatively low nitrate
conditions when the other
contributing factors are present.
Table 2, published in the
I1lin y study from another
work, il lustrates this point.*
* These data are drawn from
the earlier work by Walton
and the American gublic
Health Assocation 5 and
summarized by Lee
11—2
-------
TABLE 2
OCCURRENCE OF NITRATE INDUCED ILLNESS VS. NITRATE CONCENTRATI0N 5
Number
Number of
cases
associated with
of cases
Methemoglobinemia
indicated
ranges
of nitrate!
for which
Reported Reported
nitrogen
(ppm)
data are
State Cases Deaths
0—10 11—20
21—30
31—50 51—100
100+
available
California 1 0
0 0
0
0 1
0
1
Georgia 6 3
— —
—
— —
—
0
Illinois 75 6
0 1
2
2 12
li.
28
Indiana 1 0
0 0
0
0 3
0
1
Iowa Several 11
0 0
0
0 1
1
2
Kansas 13 3
0 0
1
1 2
8
12
Michigan 7 0
0 0
0
0 0
7
7
Minnesota 139 14
0 2
25
29 53
49
129
Missouri 2 0
0 0
0
0 0
2
2
Nebraska 22 1
0 1
0
4 9
8
22
New York 2 0
0 0
0
0 1
0
1
North
Dakota 9 1
0 1
1
0 0
5
8
Ohio 0 0
0 0
0
0 0
0
0
Oklahoma 0 0
0 0
0
0 0
0
0
South
Dakota Several 0
— —
—
— —
—
Texas 0 0
0 0
0
0 0
0
0
Virgina 1 0
0 0
0
0 1
0
1
278 39
0 5
29
36 83
91
214
The National Academy of Science
documented in its recent rep
“Drinking Water and Health, t
that nitrates in food and drinking
water have also been implicated
in the formation of nitrosamines,
known human carcinogens. It is
theorized that nitrates are
reduced to nitrites by bacteria
in the body, with nitrites then
available to combine with naturally
occuring amines in the 9 mach to
produce the carcinogen. /
However, there is no evidence
directly relating human cancer to
nitrates in drinking water and
this point is raised here only
to underscore the advisability
of limiting nitrate consumption
from water and other sources.
HOW NITRATES GET INTO WATER
SUPPLIES
Nitrates occur in our bodies,
our foods, and the plants,
animals and soils around us.
Normally, nitrate concentration
is limited by the natural
action of the nitrogen cycle,
avoiding buildup to levels of
11—3
-------
THE SAFE DRINKING WATER ACT
concern in water supplies.
Runoff from undisturbed natural
areas rarely contain more than a
trace of nitrates. Ground waters
from the same areas approach
nitrate free conditions.
Human interaction with and alter-
ation of the environment can
create elevated nitrate levels in
streams and wells. Figure 5
illustrates some of the routes
contamination can take. Agricul-
tural activities, such as fertil-
izer use and animal feedlots, can
cause substantial quantities of
ammonia and nitrate to be washed
of f and through the soil with
rainfall. The nitrate polluted
water can then flow into local
streams or percolate into ground
water.
Use of septic tanks with drain
fields in close proximity to
ground water supplies is another
important source of nitrate
pollution. Reference 2 reported
specifically on illness caused in
infants from septic tank polluted
ground water.
The severity of contamination
caused by these sources can be
increased if faulty well construc-
tion and protection practices
provide a direct link to the
ground water.
There may be other isolated
sources of nitrates in water
supplies. However, fertilizer and
septic tanks have been foun 4 o
be the most common sources.
Hence a community water system
drawing its raw water from sources
likely to be affected by these
factors should be particularly
alert to the possibility of
nitrate pollution.
The Safe Drinking Water Act
(SDWA) became law on Decem-
ber 16, 1974. It directed the
U.S. Environmental Protection
Agency (EPA) to develop National
Interim Primary Drinking Water
Regulations (NIPDWR) which
became mandatory for public
water supplies, as defined below:
“A public water system is any
publicly or privately owned
drinking water supplier with
at least 15 service connections
or which regularly serves at
least 25 persons daily at
least 60 days per year.”
The regulations are being put
into force into two stages:
o Interim Regulations —
effective June 24, 1977
o Revised Regulations —
effective as health studies
on various contaminants
are completed
The NIPDWR sections of prime
interest to the small water
system can be categorized as
follows:
o Maximum contaminant levels
(MCLs)
o Monitoring
o Record keeping
o Reporting
o Variances and exemptions
o Citizen’s lawsuits
o Emergency powers
o Site requirements
The regulations apply to public
water systems including both
community and noncommunity
water systems.
11—4
-------
OQ
P1
(D
I-I.
(3
I-I
C13
0
1
(3
(D
03
0
z
I .
‘1
p3
0 3
‘ -I .
Ln
Percolation
Municipal
-------
A community system is a public
water system which has at least
15 servIce connections used by
year—round residents or regularly
serves at least 25 year—around
residents. Noncommunlty water
systems are public systems that
serve travellers or other inter-
mittent users for at least 60 days
out of the year. The SDWA requires
promulgation of minimum federal
regulations. A state, in order
to have primary enforcement
responsibility (primacy) must
have primary drinking water
regulations at least as stringent
as the federal regulations.
The NIPDWR adopted without change
the limit for nitrate establishd
In the earlier 1962 Public Health
Service Drinking Water Standard:
“Nitrate—nitrogen in the final
treated water must be 10 milli-
grams per liter or less, as
measured by laboratory analysis.”
Since that time the regulations
have been amended to establish a
limit of 20 mg/i NO —N for non—
community systems uader certain
conditions.
Any water supply covered by the
SDWA must monitor and report
nitrate levels once per year, if
using surface water, or once
every 3 years, If using ground-
water. States may, and often do,
require more frequent monitoring
and reporting.
Recommended Reading
A detailed but concise synopsis
of the Safe Drinking Water Act
and the NIPDWR, written spectf I—
cally for water system owners and
operators is available:
The Safe Drinking Water Act--
Self Study Handbook, Community
Water Systems , available from
the American Water Works
Association, 6666 W. Quincy
Avenue, Denver, Colorado 80235.
Specific regulations applicable
to a particular utility should
be obtained from the agency
that has primary enforcement
authority under the SDWA.
ANALYZING FOR NITRATES
There are three general classes
of analytical methods which can
be used for nitrate analysis:
o Laboratory tests using
Standard Methods (U.S. EPA
approved)
o Packaged test kit (pre—
measured dry chemical)
o Measurement with nitrate
ion selective electrode
An EPA approved laboratory
analysis must be used for
complying with nitrate testing
required by the EPA and state
agencies. The other methods
are useful for research or
control of operating systems
and can be useful because of
their relative simplicity
if a correlation to the results
obtained by the approved test
can be achieved .
Packaged Test Kits that can
approximate nitrate levels
quickly and inexpensively are
available from a number of
vendors (Table 3). Two nitrate
test kits from Hach, Model NI—12
and NI—14 were tested and cali-
brated as part of the treatment
study underc at McFarland,
California. / The NI—l2 is
designed for use In the range
of 1—50 mg/i nitrate (as nitro-
gen) while the N—l4 is used in
a range of 1—10 mg/i nitrate
It—6
-------
Si pplier
PARTIAL LIST OF U.S.
F. S. Brainard & Co.
Captial Controls Co.
Hach Chemical Co.
Mid West Instrument
Sherman Machine &
Iron Works
Taylor Chemicals Inc.
Virgina Chemicals Inc.
TABLE 3
SUPPLIERS OF NITRATE FIELD TEST KITS
(as nitrogen). It was found
for the water at McFarland , that
the Hach kits tended to give
readings on the high side; hence,
the calibration curves 9 wn In
Figure 6 were prepared. They
are included here as an example
of how field test kits can be
calibrated. The field test kit’s
principal advantages are low
cost, speed and ease of use. It
is not a substitute for the
accurate laboratory analysis
required for MCL compliance
monitoring and reporting. How-
ever, the kits do provide a
valuable tool for checking and
controlling system performance
and are accurate to about +5 per-
cent when properly calibrated.
Nitrate ion selective electrodes
are useful for checking nitrate
levels under controlled, labora-
tory conditions. They require
frequent calibration and the
electrode is subject to interfer-
ences from chlorides, fluorides
and many other substances. The
electrode is therefore most
useful for waters of low mineral
content. Electrodes currently
available are best applied at
concentrat B, over 10 mg/i (as
nitrogen). Approved methods
for nitrate MCL compliance
analyses require laboratory
facilities and trained personnel.
Approved methods are published
by EPA and are available upon
request from the Agency or
state organization which imple-
ments the SDWA.
Two references on EPA (NIPDWR)
acceptable laboratory procedures
are available:
o Standard Methods for the Ex-
amination of Water and
Wastewater , available from
the Water Pollution Control
Federation, 2626 Pennsyl-
vania Avenue, NW, Washington,
DC 20037.
o Manual of Methods for Chemical
Analysis of Water and Wastes ,
Address
231 Penn St., Burlington, NJ 08016
Advance Lane, Box 211, Colmar, PA 18915
Box 289, Loveland, CO 80537
286 Executive Dr., Troy, MI 48084
26 E. Main Str., Oklahoma City, OK 73104
7300 York Rd., Baltimore, MD 21204
3340 W. Norfiok Rd., Portsmouth, VA 23703
11—7
-------
0.8
0.6
0.4
0.2
z
4
a’
-JE
4—
30
I
U
4
I
20
‘5
I0
5
0
0 5 10 15 20
ACTUAL N0 3 -N (mg/I)
Figure 6. Hach Kit Calibration Curves Used at McFarland, California
MODEL N- 14
0.2 0.4 0.6 0.8 1.0 1.2
ACTUAL NO 3 — N (mg/I)
MODEL Nl- 12
11—8
-------
available at no charge from
the U.S. EPA, 26 West St. Clair
St., Cincinnati, Ohio 45268.
A complete list of EPA—approved
methods is available from the EPA
or from the state agency that has
primary enforcement responsibility
for the SDWA.
UNITS OF NITRATE MEASUREMENT
When a laboratory analyzes drinking
water for nitrate, it typically
reports the results in the metric
units of mass (milligrams) per
unit volume (liters), milligrams
per liter (mg/l) as nitrate—
nitrogen (NO 2 —N). In other
words, the nftrate (NO 3 ) concen-
tration is expressed as though it
is in the form of nitrogen (N).
The NIPDWR maximum contaminant
level for nitrate is expressed in
this manner as 10 mg/l N0 3 —N.
How to convert nitrate analyses
reported as nitrate to a result
as nitrogen is explained in
Section IV.
11—9
-------
III. WHAT TO DO IF TUE CONCENTRATION OF NITRATE
IN THE WATER SUPPLY IS EXCESSIVE
If it has been determined that
the nitrate concentration in the
water supply is excessive, two
general approaches to reduce the
concentration should be evaluated:
o Nontreatnient alternatives
o Treatment for nitrate removal
Each is discussed in this section.
Economic and engineering data
which further aid in the analysis
of treatment and nontreatment
alternatives is given in Section IV.
NONTREATMENT ALTERNATIVES
Four options are covered in this
category:
o Raw water source substitution
o Blending with low nitrate
waters
o Connection to an existing
regional system
o Organizing a regional system
Inherent In all of these options
Is the usually correct assumption
that the nitrate problem is
localized. Thus, It may be
possible to find acceptable
ground water from other nearby
wells or surface sources. Also,
the existing well might be modified
to draw water from different
aquifiers (water bearing levels).
Surface water users may find It
feasible to draw from other
streams, or may find that reLoca-
tion of the intake will solve the
problem. Substitution of sources
should receive early consideration
in the search for solutions. The
MCL for nitrates applies to the
water as it is delivered to the
user. This means that water that
exceeds the nitrate standard
might be used if it is blended
with other, low nitrate supplies.
For example, a water supply
could be made up of equal
portions of two raw supplies
containing 5 mg/i and 15 mg/i
of nitrate—nitrogen respectively,
and still meet the 10 mg/i
standard.
It may also be cost effective
to obtain all or at least a
sufficient amount of water for
blending from an outside supplier,
perhaps a nearby city or regional
system. Regional systems are
becoming more attractive as
their advantages become more
apparent. Larger systems can
spread the costs of water
quality monitoring and analysis,
and operation and maintenance,
over a larger user base, thereby
lowering per capita costs. The
analysis of nontreatment alterna-
tives Is not complete without
taking a look at regional
alternatives. Joining an
existing regional system, or
forming a new regional utility
by joining with other nearby
systems which may be having
similar water quality problems
should be considered.
A broad range of reglonalization
alternatives is explained In
the following reference:
Regionalization Options For Small
Water Systems , U. S. EPA Office
of Drinking Water, 401 M Street
SW, Washington, DC, 20460.
It should be noted that whether
a source of water high in
nitrates Is treated to reduce
the nitrate or blended to
reduce the nitrate, a failsafe
‘Il—i
-------
monitoring system should be
incorporated into the design and
operation of the system. This
will protect users in the event
the treatment or blending process
malfunctions. It Is also important
to note that water sources high
in nitrate point to the possibility
that the sanitary quality of the
source is In question. This
aspect of the problem should be
investigated. The agency with
primary enforcement authority
could be requested to perform a
sanitary survey leading to recom-
mendations for future action to
resolve the entire water quality
problem.
TREATING WATER SUPPLIES FOR
NITRATE REMOVAL
Nitrate can be removed from
drinking water reliably using
currently available technology.
It Is not removed by the standard
water treatment processes, such
as coagulation, settling, filtra-
tion, carbon adsorption, chlorina-
tion or ozonation. Thus, nitrate
removal generally requires instal-
lation of specialized equipment
for either new or existing plants.
Six technologies for nitrate
removal have or are being studied
by public and private researchers:
o Ion exchange
o Reverse osmosis
o Electrodialysis
o Biological denitrification
o Chemical reduction
Of these, only ion exchange has
at this time been applied success-
fully to full scale drinking
water systems specifically for
nitrate removal. Reverse osmosis
and electrodialysis have been
applied primarily for desalting
saline or brackish waters and
will also remove 60 to 70 percent
of nitrates. At this time,
captial and operating costs for
both processes exceed that for
ion exç ge under most condi-
tions. ‘ / However, site
specific conditions, such as in
areas where brine disposal i 8
difficult or where other constit-
uents require reduction, may
make these the systems of
choice. In addition, these
technologies are evolving and
improving and their effectiveness
and costs may change substantially
in the near future.
The rernaIntng processes listed
above, chemical reduction and
biological denitrification,
must be regarded as experi-
mental (although, biological
denitrification is being con-
sidered in England for remova 19 )
of nitrate from surface water ).
This document focuses on ion
exchange theory, design and
methods of cost approximation.
As more experience becomes
available on the other technolo—
gies, this handbook may be
updated. Specific information
on reverse osmosis systems is
provided in a document entitled
“Radionuclude Removal for Small
Water Systems” currently being
prepared for EPA ODW.
How Ion Exchange Works
Ions in water are molecules or
particles that exist in solution
as semi—independent, electrically
charged entities that can give
noticeable properties to water.
For example, calciu +and mag sIum
Ions, denoted as Ca and Mg
are largely responsible for the
characteristic called hardness.
The higher the concentration of
these positively charged Ions,
the harder the water. Ion
111—2
-------
exchange technology was developed
largely out of the desire to
control hardness and its undesir-
able effects.
Overall, any water solution has
to be electrically balanced;
i.e., the solution must contain
the same number of positively
charged ions (cations) as nega-
tively charged ions (anions).
The most co on cations are ++
calcium (Ca ) magnesium (Mg )
and sodium (Na ) and the most
common anions are chlorides
(Cl ), bicarbonate (HCO ) and
sulfates (SO 4 or HSO 4 . Nitrate
(N0 3 ) is an anion as well.
Ion exchange treatment does
exactly as the name Implies: it
trades one ion for another. The
exchange process can be tailored
to remove cations, by cation
exchange, or to remove anions, by
anion exchange. The latter
process is used to remove nitrate
from water solutions.
The actual removal of the nitrate
ion occurs in a bed of ion exchange
resin through which the water is
passed. Resin beds are made up
of millions of tiny, spherical
beads which usually are about the
size of medium sand grains. The
resin beads are very homogeneous
in size and color. Each bead
(Figure 7) is, in effect, a
skeleton on which exchange sites
are available. The ion exchange
media or resin bed is enclosed in
an ion exchanger which consists
of the tanks, piping, valves,
monitors and controllers needed
to operate the process.
Figure 8 depicts the full cycle
of the Ion exchange process as It
would occur in an individual bead
of resin. The process proceeds
in four stages:
o In Stage I the ion exchange
resin is fully recharged,
or regnerated, and ready
to remove ions.
o In Stage II the ion exchange
resin is exchanging chloride
ions for sulfate and
nitrate ions, releasing
chloride Ions Into the
water and retaining sulfate
and nitrate.
o In Stage III all of the
exchange sites have been
used up and the resin is
said to be “exhausted” or
“spent.”
o In Stage IV the resin is
regefle ated I by passing a
strong salt water (brine)
solution of sodium chloride
(NaC1) through the resin
bed. The very high relative
chloride concentration
displaces the sulfate and
nitrate ions from the
exchange sites on the
resin beads. After a
short washing to remove
the salt water from the
resin, the resin is ready
to operate again, at
Stage I.
Out of this highly simplified
scheme of anion exchange, some
points need particular emphasis:
o Ion exchange does not
break up or convert the
nitrate to another form.
It merely removes It from
the product water and
deposits It first on the
resin then ultimately in
the spent reagenerant
(water brine) stream
during the regeneration
cycle.
111—3
-------
Long—chain organic moJecule has positive charged sites C®)
to which •xchangable anions(Ř) are “loosely” bonded. In our example,
the exchongab le onions ore chloride (C1), which exchange for
nitrate (NO ).
Figure 7. Bead of Ion Exchange Resin
111—4
-------
loosely bound
•zchongobls Ion
(provided by
09Sf. Font)
anion (K) such
as NO 3 and
su’fate
__ K-.
— A
STAGE 3 — spent-
site on resin
STAGE I — fresh — resin has anionic sites occupied
by regenerant anions,(a)
i __řI.o_
— regenerant anions (a) ore
progressively displaced
by onions In the process
woter(nltrote and suifote,A)
all sites on resin ore filled
with anions from process
water,(A)
— process Is reversed and
previously exchanged ions
from process water ore
displaced by regeneront
anions, (o)
Figure 8. Ion Exchange Process Cycle
0 -ř.i
STAGE 4 —
K-anion (nitrate or sulfate)
(— r,generont onion
STAGE 2—
111—5
-------
o Ion exchange produces a
waste flow which must be
disposed of. The waste flow
is about 4 to 10 percent of
the treated flow. Approxi-
mately 60 percent of the
waste volume consists of
concentrated (10—12 percent)
brine solution which must be
disposed of properly.
o There are currently no
commercially available anion
exchange resins that remove
nitrate selectively over
other anions.* In fact,
sulfate ions are removed
first. Therefore, if an
anion exchanger is _ operated
beyond bed exhaustion without
regeneration, sulfate will
dislodge nitrate from the bed
and force It back into the
product water stream. Under
this condition the product
water can contain higher con
centrations of nitrate than
were origInally resent in
the raw water .
o There are a number of sub-
stances which can foul an
anion exchange bed including
suspended solids, iron and
organic compounds.
o The chloride concentration
of the finished water will
be increased proportionately
to the amount of sulfate and
nitrate removed.
* Research on special resins
that preferentially remove
nitrate over sulfate is
being performed under US EPA
cooperative agreement
CR 808902—0. Results when
available will be published.
Exchange Resins for Nitrate
Removal
There are five general classes
of ion exchange resins:
o Strongly acidic
o Weakly acidic
o Weakly basic
o Strongly basic
o Ion specific
Acidic resins are used to
remove cations. Basic resins
are used to remove anions such
as nitrate. The terms strongly
and weakly relate to the strength
of the ionic forces in the
resin and their ability to
exchange various ions. Strongly
basic resins are recommended
for use in nitrate removal as
they can effectively exchange
nitrate from potable water at
very low concentrations. Ion
specific resins are formulated
to maximize exchange of a
target ion. There are currently
no commercially available
nitrate ion specific resins.
To be suitable for long term
potable water service, an Ion
exchange resin shou] 25 ieet five
basic requirements:
1. It should have high total
capacity as evidenced by
its ability to exchange
large numbers of ions
throughout the volume of
the bed.
2. It should have the proper
chemical structure for the
Intended application. The
resin should be designed
to operate In the expected
pH range with adequate
selectivity to remove most
of the target Ions without
being overly difficult to
regenerate.
111—6
-------
3. It should be very insolubLe
in potable water. A major
value of ion exchange resins
lies in their reusability.
Low solubility also avoids
leaching of impurities into
the treated product.
4. It should have good physical.
and chemical stability. It
should resist attack by the
regenerant or any substances
in water. It should be
capable of withstanding
turbulence and abrasion
within the bed and not be
broken down by contact with
the exchanger walls or
plumbing.
5. It must be nontoxic and must
not release organic compounds
to the water stream. Many
states require that resins
used in potable water systems
be approved by the state.
EPA provides guidance to
state primacy agents regarding
acceptability of resins for
use in potable water service.
Resins approved for use by
the Food and Drug Administra-
tion (FDA) in accordance
with federal. regulations 21
CFR 173.25 are generally
acceptable for use in potable
water systems.
Selectivity defines the affinity
of a particular resin for a
particular Ion. It depends on
ionic charge, molecular weight,
and solution concentration. For
a strong base resin in a weak
solution, such as potable water,
the resin selectivity would
operate as shown in Figure 9.
Thus, the resin would take up
sulfate along with nitrate and
would have some preference for
the former. If the ion exchanger
is operated beyond exhuastion, no
more nitrate will be taken up
and, in addition, sulfates will
displace nitrates from the bed
causing the bed effluent to
have more nitrates than the
Inf luent. When de j nIn 1 a
system, it Is impe ra
this o le rating_characteristic
be recogn ize _ a4 aes -
rdsbe rovided.
There are currently four major
resin producers in the United
States. They all distribute
resin under their own and other
trademarks (Table 4). All
currently provide strongly
basic resins for nitrate removal.
Ion Exchange Plant_Desctlon
The term “plant” as used here
describes the tanks, piping,
valving, monitors, controllers
and other hardware needed to
operate the ion exchange bed.
Two types of plants are cur-
rently available In the U. S.
o Fixed bed exchangers
o Continuous Ion exchangers
Fixed bed exchangers, shown in
Figure 10, are the units most
commonly used for Industrial
and private systems. The home
water softener follows the same
basic design. The unit is
controlled by a flow totalizer
which is set to initiate an
automatic regeneration cycle at
about 75 to 80 percent of the
theoretical bed capacity.
During regeneration, the regener—
ant is pumped through the bed
for a preset period, followed
by a rinse to cleanse the bed.
Many systems also incorporate
backwashing to “fluff” up the
bed, remove trapped solids and
thereby reduce pressure drop
through the exchanger.
ii i—i
-------
Most Preferred
I
Least Preff erred
IODIDE
SULFATE
NITRATE
CHLORIDE
BICARBONATE
HYDROXIDE
FLUORIDE
BISIL ICATE
Figure 9. Selectivity of Strong Base Anion Exchange
Resin level
Resin packing
space
for bed expansion
support and
collecting system
(13)
Figure 10. Fixed Bed Ion Exchanger
system
111—8
-------
TABLE 4
PARTIAL LIST OF U.S. ION EXCHANGE RESIN PRODUCERS
Company
Location
Trademark
Diamond Shamrock
Cleveland, Ohio
Duolite
Dow Chemical Company
Midland, Michigan
Dowex
lonac Chemical Corporation
Birmingham, New Jersey
lonac
Rohm and Haas Company
Philadelphia, Pennsylvania
Amberlite
A typical fixed bed exchanger
usually consists of a cylindrical
tank having four essential features:
o Sufficient space above the
bed for expansion during
backwash ing.
o A feed distribution system
to spread the influent water
across the surface of the
bed.
o A bed support system that
collects the product water
uni’ r ’ly and prevents
leakage of the resin.
o An internal lining that
protects the containing
vessel from corrosion from
the process water and regener-
ating chemicals.
Where semi—continuous output is
needed, the use of two fixed bed
units, each sized for full flow,
allows full operation on one bed
while the second is being regen-
erated or is held in ready condi-
tion to replace the first when it
becomes exhausted. Process
interruption is limited to the
few seconds needed to switch the
process flow between beds.
Suppliers of fixed bed equipment
are numerous, with equipment
ranging in size from simple
one—bed home water softeners to
very large industrial and
municipal systems. Some sup-
pliers are listed in Table 5.
Continuous ion exchangers were
developed for larger installa-
tions where continuous output
is required and minimizing bed
volumes is desired. While
treating product water, these
units periodically move the
resin bed through a cycle in
which a portion of the bed is
withdrawn and regenerated
outside of the main exchange
vessel, while regenerated resin
is returned in fresh condition.
There are several versions of
this equipment available in the
U.S. (Table 6) and it has
largely been applied to indus-
trial water treatment problems.
Figure 11 (a and b) depicts the
operation of the units provided
by these two companies listed
in Table 6. The Chemical
Separations Corporation unit is
based on the Higgins process
and has been successfully
applied to nitrate removal from
drinking water in a 2.0 mgd
installation at Garden City
Park, New York.
111—9
-------
TABLE 5
PARTIAL LIST OF U.S. SUPPLIERS OF FIXED BED ION EXCHANGE SYSTEI1S
Company Location
Culligan Company Northbrook, Illinois
Envirex Waukesha, Wisconsin
Graver Company Ames, Iowa
General Filter Clayton, New Jersey
Hungerford & Terry Richmond, Virginia
Illinois Water Treatment Rockford, Illinois
Infilco—Degremont Richmond, Virginia
Ionics Watertown, Massachusetts
Permutit Company Paramus, New Jersey
TABLE 6
PARTIAL LIST OF U.S. SUPPLIERS OF CONTINUOUS ION EXCHANGE EQUIPMENT
Company
Location
Chemical Separations
Infilco—Degremont
Corporation
Oak Ridge,
Richmond,
Tennessee
Virginia
111—10
-------
Resin storage area
Resin movement
Resin is pulsed periodically in the hydraulically operated pulse section.
As it travels around the exchanger, the resin passes through successive
stages of backwashing, regeneration and process water treatment.
Figure ha. Continuous Ion Exchange Process (Pulsed)
Contacting section
Regeneront flow
ill—li
-------
The anion and cation exchange resin mixture is continuously with-
drawn from the bottom of the service (water treatment) vessel, and
hydraulically separated into anion and cation resin regeneration
vessels. In these vessels the anion and cation exchange resins are
regenerated individually by the appropriate regenerants. The fresh
resins are finally reiuixed in a resin mixing tank prior to being
reintroduced to the service vessel.
Figure llb. Continuous Ion Exchange Process
‘: W- Wastewater
111—12
-------
IV. DESIGNING A NITRATE RF !OVAL SYST 1
This section is intended as a
primer covering the fundamentals
for evaluating process proposals
from design consultants and/or
equipment vendors. The actual
design will be a function of the
raw water characteristics and
flow, type of equipment selected
and site requirements. Pilot
testing to select a resin and to
determine design parameters Is
recommended for larger systems as
currently there is very limited
design and operating experience
with nitrate removal systems for
domestic water supplies. Figure 12
illustrates the steps used to
design the nitrate removal system.
ABBREVIATIONS, UNITS AND CONVER-
SION TABLES
The abbreviations and units used
throughout this section are defined
in Appendix A. Metric unit
conversion tables are also provided.
Units used in this document
follow typical U.S. practice for
ion exchange system design and
general water supply.
ANALYSIS OF RAW WATER SUPPLY
The first step Is to fully charac-
terize the water supply and
determine, where possible, the
nitrate source. If the nitrates
are entering the water supply as
a result of inadequately treated
sewage or septic tank leakage,
continued use of the water supply
may pose severe health risks
other than those related to
nitrates. Nitrate level as a
function of time is also quite
important. Increasing nitrate
levels will shorten the run time
between regenerations and may
render system design obsolete,
particularly where blending of
treated and nontreated water is
practical.
Raw water constituents of prime
interest are shown in Table 7,
along with their principal
relationship to system design.
Of course, the water should
also be checked to determine if
it is bacteriologically accept-
able.
PILOT TESTING
Pilot testing, using scale
model ion exchange reactors, is
recommended by resin manufac-
turers to establish key design
and operating parameters for
individual systems. It is also
generally advisable to perform
a pilot study of treatment
processes that are not well
understood or not widely used
in order to avoid costly errors
in treatment process design.
Pilot testing may be cost
effective for larger systems or
in situations where the water
treatment problem is excep-
tionally difficult. Specific
guidebooks for pilot testing
are available from resin manu-
facturers (Table 8).
Extensive pilot testing of five
strong base ion exchange resins
has been carried out at MacFarland,
California, using 2—inch test
colums 4 feet in height containing
1,245 cubic centimeters
(0.44 cu.ft.) of resin. This
work, outlined in Section VII,
(and described in detail in
Reference 16) produced more
IV— 1
-------
RAW
WATER
ANALYSIS
— —
T PILOT STUDY
I (OPTIONAL BUT
L RECOMMENDED)
— — — — —
Figure 12. NItrate Removal System Design Steps
IV—2
-------
TABLE 7
RAW WATER CONSTITUENTS THAT SHOULD BE QUANT [ FlED
Name Symbol Why Needed
Bicarbonate HCO 3 Interacts with strong basic resins
Nitrate NO 3 To be removed
Sulfate SO 4 Interferes with nitrate removal by
competing for exchanged anions
Iron Fe+ Can coat resin and lower efficiency
Chloride Cl Released during exchange process,
therefore, concentration increased
by process
Suspended Solids SS May plug ion exchange bed
Total Organic Carbon TOC Some organics can foul resins
TABLE 8
SOME PILOT TESTING GUIDES AVAILABLE FROM RESIN MANUFACTURERS (9)
Company/Location Guide/Author
Diamond Shamrock “Ion Exchange Polymers”
Functional Polymers Division I. M. Abrams, et.al.
1100 Superior Avenue
Cleveland, Ohio 44114
Dow Chemical Company “A Basic Reference on Ion Exchange”
Functional Products and Dow Chemical Company
Systems Department
Midland, Michigan 48640
Rohm and Haas “A Laboratory Manual on Ion Exchange”
Fluid Process Chemical Department “Amberlite Ion Exchange Resins
Philadelphia, Pennsylvania 19105 Laboratory Guide”
IV— 3
-------
optimized design parameters with
resulting lower costs than those
expected from the guidelines
normally used by resin and ion
exchange equipment manufacturers.
Ion exchange equipment suppliers
will usually analyze a water
sample and make recommendations
for pretreatment requirements and
anion exchange system sizing.
The cost of this service is
minimal, usually less than $50.
In lieu of an on—site pilot study
which may be uneconomical for
very small systems, this alterna-
tive Is recommended. Analyses
and recommendations by at least
two vendors Is suggested. In
addition, the Agency that imple-
ments the SDWA should be contacted
for guidance and facility approval.
PRETREATMENT REQU IREMENTS
Ion exchange systems have one
principal function——to exchange
undesirable dissolved ions (such
as nitrate) in the process water
stream for ions which are less of
a problem. They are not filters,
even though some filtration may
occur in the bed. Suspended
solids, iron and organics are
some of the more common contami-
nants that foul ion exchangers
and for which pretreatment is
required. These contaminants can
occur in either surface or ground
water.
Suggested action levels and pre-
treatment alternatives for common
contaminants are shown in Table 9.
ANION EXCHANGE UNIT DESIGN
After detailed water analyses and
Identification of any pretreat-
ment requirements, the nitrate
removal (anion exchange) unit is
designed. Largely, the design
is based on nitrate concentra-
tion, total anion concentration
(including nitrate and sulfate)
and conservative design guide-
lines provided by the supplier
of the exchange unit and/or
resin. The specific design
steps are outlined below using
examples to illustrate actual
computations required.
1. Develop system design
parameters
2. Select resin and determine
capacity
3. Size ion exchange bed
4. Size regeneration system
Develop System Design Parameters
System design parameters are
based on known (or calculated)
quantities such as required
water production and nitrate
reduction, combined with design
assumptions. The process of
defining the key design param-
eters is illustrated using
examples below.
o SYST 4 OPERATING FLOW
Known Data:
— daily, weekly, monthly,
seasonal and annual water
production required.
— maximum, minimum and
average raw water nitrate
concentration.
Assumed Data:
— daily and weekly exchanger
operating time.
IV—4
-------
TABLE 9
PRETREATMENT REQUIREMENTS FOR COMMON CONTAMINANTS
Contaminant
Action Level
Pretreatment Alternatives
Iron (Fe)
0.1 mg/i or
greater as Fe
1. Chlorination to 1 mg/i
residual followed by
20 minutes retention
and sand filtration
2. Potassiuim permanganate
treatment followed by
filtration
3. Aeration in basin with
20 minute detention time
followed by sand filtration
Suspended Solids
2 NTU* turbidity
or greater
1. Sand filtration
2. If over 20 NTU, coagulation,
settling, sand filtration
Organics
Any measurable
concentration
1. Pilot test resin for fouling
2. Analyze for specific known
interfering organics
* Nepholometric Turbidity Units
Calculated Data:
— blending ratio*
— flow rate through ion exchange
unit.
Discussion:
Using standard design practice
for consumer water demand for
new systems, or measured flow
data from an existing system,
the flow rate through the ion
exchange system is derived.
The system is sized for flow
based on maximum needs, consid—
* Ratio of the treated flow
rate to the total flow rate.
ering adequate safety factors,
and the possibility of blending.
It will usually not be required
to treat all of the flow to
achieve the 10 mg/i NO 3 —N
standard. The anion exchanger
will reduce nitrate to 0.5 mg/i
NO 2 —N. Accordingly, the
effluent from the exchanger
can be blended with the raw
water thus reducing the
volume that must be treated.
Based on the utility’s specif-
ic needs and capabilities,
some assumptions about the
ion exchanger operating
schedule are needed. Unless
the unit is operated continu-
ously, to meet the instan-
taneous water demand, the
operating schedule will
IV— 5
-------
reflect the availability of
maintenance and supervisory
personnel, and the availability
of finished water storage
(reservoirs). Typically, a
small system may elect to
operate the unit during the
normal 6 to 8 hour working day
for 5 or 6 days a week, drawing
on stored water when not operat-
ing. The System Operating Flow
Example shows how to make these
computations.
o WATER ANALYSIS DATA
Known Data:
— maximum concentrations of
nitrate, sulfate, chloride,
bicarbonate.
Calculated Data:
— total anion, sulfate and
nitrate concentrations ex-
pressed in terms of a common
base.
— ratio of sulfate and nitrate
concentrations to total
anion concentration.
— nitrates to be removed.
Discussion:
Water chemistry analytical
results are typically given in
terms of concentration, in
milligrams per liter, as a
function of the molecular
weight of the particular com-
pound. In order to compute
total anions and anion ratios
(needed for resin quantity
calculations), all anions must
be expressed to a common base.
This is usually the equivalent
weight, or since the concentra-
tions are so low, the mijliequiv—
alent weights (milli =
Table 10 provides equivalent
weights for common water constitu-
ents. To obtain the number of
milliequivalents per liter of a
substance, its concentration in
mg/l is divided by its mule—
quivalent weight ( .—).
meq
Ion exchange resin capacity may
also be given by the supplier’s
guides in units of grains of
calcium carbonate (CaCO 3 ), per
gallon; so, it may necessary to
restate nitrate data in this
form for later determination of
ion exchange resin capacity.
Since 1 grain equals 65 mg the
conversions from grains to mg
is made simply by multiplying
grains by 65. Then the proced-
ures in Appendix B can be used
to determine the capacity in
units of meq/1. The Water
Analysis Data Conversion Example
shows the procedure and general
equations that are used to
evaluate the required calculated
data.
Resin Selection
Resin selection is a function
of water analysis, pilot testing
(if any) and manufacturer’s
recommendations. There are a
number of strong base anion
exchange resins available.
Table 11 lists these resins and
their suppliers. Considerable
pilot test data on the perform-
ance of these resins is given
in Reference 12. In addition,
the manufacturers will provide
detailed application guides for
each resin. Factors to be
considered in choosing the
resin include initial cost and
capacity, life, regeneration
efficiency and pretreatment
requirements.
IV—6
-------
TABLE 10
EQUIVALENT WEIGHTS
Compound Equivalent ( Grams Milliequivalent ( Milligrams
Weight Equivalent ) — Weight Mu l ie u1va lent)
N 14.007 14.007
NO 3 62. 005 62. 005
Cl 35. 453 35. 453
so 4 48.031 48.031
1 1C0 3 61.017 61.017
CaCO 3 50.045 50.045
TABLE
11
SOME STRONGLY BASIC RESINS
AND THEIR SUPPLIERS 12
Company Resin
Diamond Shamrock Company Duolite A—l0l—D
Duolite A—102—D
Duolite A—104
Dow Chemical Company Dowex SBR—P
Dowex SAR
Dowex SER
Dowex 11
lonac Division of Sybron Corp. lonac ASB—1
Ionac ASB—1P
lonac ASB—2
lonac A—540
lonac A—550
lonac A—641
lonac AFP—l00
Rohm and Raas Company Amberlite IRA—400
Amberlite IRA—402
Amberlite IRA—410
Amberlite IRA—900
Amber]J.te IRA—910
IV- 7
-------
SYSTF 4 OPERATING FLOW EXAMPLE
CALCULATION OF BLENDING RATIO AND ION EXCHANGER FLOW RATE
Known or Assumed Information:
Maximum daily flow 100,000 gallons/day
Maximum weekly flow 500,000 gallons/week
Maximum nitrate level 15 mg/l
1. Assume:
The unit will be sized to treat the maximum daily flow of
100,000 gallons by routinely operating 6 hours per day, 5 days
per week (presumes sufficient storage capacity for weekend demand).
Produced water at 0.5 mg/i N0 3 —N will be blended with untreated
water at 15 mg/l N0 3 —N to provide a finished water of 9 mg/i
NO 3 —N or less.
2. Calculate quantity of water which must be treated to produce
100,000 gpd of blended water with no more than 9 mg/ 1 N0 3 —N
using the following general equation:
Q treated = Q Total _ [ Total x ( Final N0 3 —Treated NO 3 )
L (Untreated N0 3 —Treated N0 3 )J
Therefore:
Q Treated = 100,000 gpd —rioo,ooo gpd x ( 9 mg/i — 0.5 mg/l )
L (15 mg/i — 0.5 mg/i)
Q Treated = 41,380 gpd
3. Calculate Blending Ratio
The blending ratio is obtained by dividing the treated flow rate
by the total daily flow rate = 41,380
100,000 Blending Ratio 0.414
4. Calculate anion ion exchanger flow rate in gallons per minute .
Although the unit will treat 41,380 gallons each day, it will
only operate 6 hours per day. Thus the flow rate while opera-
ting must be calculated:
Unit Flow Rate (gpm) =
Q Treated x 24 hours/day x 1 day —
Daily Operating Time 1440 mInutes
= 41,380 gpd x 24 hours x 1 day
6 hours 1440 minutes
Ion Exchanger Flow Rate (gpm) = 115
IV-8
-------
WATER ANALYSIS DATA CONVERSION EXAMPLE
EXPRESSING ANION CONCENTRATIONS TO VARIOUS BASES AND CALCUL&TING TOTAL
ANIONS
Note: See Appendix B for more detailed explanation of Equations
used in these samples.
Given the following analysis:
Constituent* Concentration (mg/l) Expressed As
N0 3 —N 15 Nitrate Nitr gen (N0 3 —N)
SO 4 50 Sulfate (SO 4 ) —
HCO 75 Bicarbonate (HCO 3 )
c1 25 Chloride (Cl )
* ionic charge deleted for clarity.
1. Express N0 3 —N (nitrate as nitrogen) in terms of N0 3 —N0 3
(nitrate as nitrate)
General Equation:
ConcB = ConcA x Equivalent Weight B
Equivalent Weight A
Given the N0 3 concentration expressed as nitrogen is known to be
15 mg/i. It is desired to express the concentration not in terms
of nitrogen but as nitrate. Use the general equation above, Table 10
(equivalent weights) and the given water analysis as follows:
Let: Cone = Conc of NO as N (N0 3 —N) (from chemical analysis) =
b mg/i for th s example
Equivalent weight B = Equivalent weight Nitrate* = 62.005
Equivalent weight A = Equivalent weight Nitrogen = 14.007
* From Table 10
Therefore, to change the concentration of nitrate expressed as nitrogen
to nitrate (as nitrate) the general equation beomes:
mg/i (N0 3 —N0 3 ) = mg/i (N0 3 —N) x ! ivalent weight NO 3
Equivalent weight N
mg/i (N0 3 —N0 3 ) = 15 mg x 62.005
14. 007
mg/i (N0 3 —NO 3 ) = 66.4
IV- 9
-------
WATER ANALYSIS DATA CONVERSION EXAMPLE
(Continued)
2. Calculate total anions
Total anion concentration, used in design of the resin bed, is
determined by adding up the individual anion concentrations, ex-
pressed to a common base.
Milliequivalent Concentration
Anion* Concentration mg/i weight (mg/meg) meq/**
N0 3 —N 15 14. 007 • g 1.07
meq
SO 50 48.031 1.04
HC 6 75 61.017 1.23
c . 25 35. 453 0. 71
Total Anions 4.05 meq/l
* Ionic charge deleted for clarity
** See Appendix B for a detailed explanation of computation
3. Calculate ratio of sulfate and nitrate to total anions. This
calculation is made using the general equation below. The
concentration of all constituents used in the equations must be
expressed to the same base, such as milliequivalerits per liter.
Ratio (%) = Single Anion Concentration 100
Total Anion Concentration
Using the information from Step 3.
Sulfate Ratio % = Sulfate Conc as meq/l 100%
Total Anion Conc as meq/l
1.04 x 100% = 26%
Nitrate Ratio % = Nitrate Conc as meg/i
Total Anion Conc as meq/l
Nitrate Ratio % = 1.07
x 100% = 26.4%
4. Daily nitrates to be removed
The total quantity of nitrates to be removed daily by the
exchanger depends upon the initial concentrations of nitrate
in the raw water, the concentration in the effluent and the
total volume of water treated. The general equation below
describes the relationship:
IV— 10
-------
WATER ANALYSIS DATA CONVERSION EXAMPLE
(Continued)
Nitrate Removed (meq) = Initial Conc (meq/l) —
(meq/l) x Daily Volume Treated in Liters
final Conc
This equation can be written so that the daily volume treated
can be entered in the equation in gallons:
Nitrate Removed (meq) = Initial Conc (meq/l) — final Conc
(meq/l) x gallons treated x 3.785 liters
gallon
For our example:
Nitrate Removed = (1.07 meq/l — 0.04 meq/l x 41,380 gpd x
3.785 liters = 161,996 meq per day
gallon
If the system is going to operate with only one regeneration
cycle per day, the nitrate to be removed per cycle is also
161,996 meq.
Determining Resin Capacity, Bed
Dimensions and Regenerant
Requirements
o Resin Capacity
Resin capacity determines the
amount of resin needed In the ion
exchanger and Is calculated from
pilot test data and/or data
provided in the manufacturer’s
manual. For purposes of illustra-
tion, resin capacity in this
example Is based on the Diamond
Shamrock A—104 strongly basic
resin. Characterisitics and
manufacturer’s recommended prac-
tices are shown in Table 12 and
are given 4 he A—104 resin
guidebook.
This resin can be used for nitrate
removal and is described as a
chloride cycle resin. This means
that it Is regenerated by a salt
(NaC1) brine solution in an
operation much like that of a
typical water softener.
The operating capacity of
A—104 resin for nitrate removal
is quite dependent on the
sulfate, nitrate and total
anion concentrations. These
were calculated in the example
on the previous page.
Known, Assumed or Previously
Calculated Data:
— design flow rate through
exchanger
— influent nitrate and
sulfate, as meq/1
— total anions (TA) as meq/l
— suggested operating condi-
tions for resin (Table 12)
Data yet to be Determined:
— Corrected resin capacity.
IV— 11
-------
TABLE 12
SUGGESTED DESIGN PARAMETERS FOR A—104 RESIN 14
Minimum bed depth
Backwash flow rate
Regenerant concentration
Regenerant concentration
Regenerant temperature
Regenerant flow rate
Rinse flow rate
Rinse volume
Service flow rate
pH limitation
Operating temperatures
30 inches
2 to 3 gpm/sq.ft.
15 to 18 lb sodium chloride
(NaC1)/ft resin
10 to 12 percent NaCl (by weight)
Up to 120°F (49°C)
0.5 gpm/cu.ft.
2 gpm/cu.ft.
50 to 70 gals./cu.ft.
Up to 5 gpm/cu.ft.
None
Salt form — up to 185°F (85°C)
Using the known data and the
manufacturer’s product informa
tion, the corrected resin capac-
ity can be determined.
First, determine the raw, or
uncorrected resin capacity from
the manufacturer’s data. This is
generally available from a graph
such as Figure 13. This capacity
must be adjusted downward to
reflect the presence of sulfate
in the water supply. Since
sulfate anions will be exchanged
before nitrate, the final resin
capacity used for design must be
reduced accordingly. This is
accomplished with the aid of
another graph such as the one
reproduced as Figure 14.
o Bed Dimensions
Once the adjusted resin capacity
is determined for the specific
water to be treated, the required
volume of ion exchange resin (bed
volume) can be calculated. Bed
volume is determined by dividing
the amount of nitrate that must
be removed each cycle by the
adjusted resin capacity. (See
Step 2 of the exchanger sizing
example.) Using this bed
volume, the remaining bed
dimensions are determined by
using the manufacturer’s minimum
depth and adjusting first the
surface area to get a standard
size containment vessel and the
height of the vessel to allow
for bed expansion during backwashing
(Steps 3 and 4 of sizing example
and Figure 15).
o Regenerant P oirements
Once the bed volume and dimen-
sions are available, the regener-
ation system requirements can
be calculated using these and
additional information provided
by the manufacturer. Required
manufacturer’s information may
include:
Backwash flow rate
Regenerant dosage
Regenerant concentration
Regenerant temperature
Regenerant flow rate
The regeneration system design
must determine:
IV— 12
-------
0
tO 20 30 40 50 60 70 80
% N0 3 [ ]X 100
Figure 13. N0 3 /TA vs. Unadjusted Resin Capacity for A—104. Resin
0
0
0
0
—
E
0
a
‘ S
C )
C
a.
C
C)
4
0.25
IV—13
-------
0 20 40 60
0/ SO4 100
1.0
0.8
0
0.6
z
00.4
I-
C)
w
0.2
0
U
0
80
Figure 14. Sulfate Correction Curve for A—104 Resin
I
Iv— 14
-------
BACK WASH
NOTE :
FLOW RATE, GPM/SQ. FT.
— 35°F
— 50°F
— 70°F
— 100°F
Figure 15.
Bed Expansion Curve for A—104 Resin
I-
2
‘ Ii
U
w
0
z
0
U)
2
x
w
0
w
100
80
60
40
20
0
0 I 2 3 4 5
Curve I
Curve 2
Curve 3
Curve 4
IV - 15
-------
1. the amount of salt used each
regeneration cycle,
2. the volume of brine used
each cycle,
3. the total volume of the
brine storage tank, and
4. the time required for the
regeneration process.
The amount of salt required is
based on the volume of the resin
in use and the manufacturer’s
information which specifies
pounds of salt required for
regeneration per cubic foot of
resin. Knowing the total pounds
of salt used and the required
concentrations of the salt brine
regenerant as specified by the
manufacturer, the corresponding
volume of brine required for each
regeneration can be calculated
(see Steps 5 and 6 of the sizing
example). Holding tanks generally
are designed to provide sufficient
volume for 2—3 regeneration
cycles. Finally, the time required
for regeneration can be determined
by dividing the volume of brine
required per regeneration cycle
by the regeneration flow rate
specified by the manufacturer.
Other Design and Purchase
Cons ide rations
Other factors effect the design,
purchase and operation of the
system. These include:
o Process control and monitoring
o Equipment redundancy
o Salt handling and storage
o Materials of construction
o Spent regenerant disposal
o PROCESS CONTROL AND MONITORING
As noted earlier, the operation
of small ion exchange systems
for nitrate removal is quite
similar to that of the more
common water softener. Thus,
nitrate ion exchangers can be
controlled by flow totalizers
just as water softeners are. A
flow totalizer is a device
included in an accurate water
meter/controller that can be
set to trigger regeneration
after a given quantity of water
has passed through the unit.
Regeneration, backwashing and
flushing then proceed automati-
cally, controlled by a t1n r
activated switch that operates
a motorized valve. The technolo-
gy of this control system is
well established and highly
reliable. However, because of
the potential dangers associated
with a failure of the nitrate
removal system, additional
safeguards are warranted to
ensure the exchanger is not
operated to resin exchange
capacity exhaustion:
1. The process stream flow
totalizer should have a
warning light and/or bell
to alert the operator when
regeneration Is automati-
cally Initiated. If
possible, the operator
should be present during
the regeneratIon cycle,
observing that regeneration
is proceeding correctly.
2. Salt brine feed during
regeneration should be
visually observed by the
operator and quantities
checked during and after
regeneration.
3. Regenerant flow should be
metered to ensure that the
IV— 16
-------
SIZING THE ION EXCHANGE UNIT EXAMPLE
1. Determine the uncorrected volume of exchange resin required:
a. Using the nitrate to total anion ratio (7.) of 30 from the
previous example, use Figure 13 to determine the uncorrected
resin capacity of 0.51 meq N0 3 /mi resin.
This is not the final capacity; it must be adjusted for sulfate
concentration as shown below:
b. Using the sulfate ratio (%) of 25 from the previous example
and Figure 14, determine the resin capacity correction factor
of 0.7.
c. Multiply the uncorrected resin capacity by the correction factor
to determine the corrected or adjusted resin capacity = 0.7 x
0.51 = 0.357 meq/ml.
d. Convert these units from meq/ml to meq/ft 3 :
0.357 meq/ml x 3785 mi/gal x 7.48 gal/ft 3
= 10,107 meq/ft 3
2. Using milliequivalents nitrate to be removed each cycle and the
adjusted resin capacity per cubic foot, determine the bed volume (By)
of resin required:
BV = 161,996 meg — 3
10,107 meq/ft
3. Check to make 5 ertain that the manufacturer’s maximum service flow
rate (5 gal/ft from Table 12) is not exceeded:
Service Flow Rate Ion Exchange Unit Flow Rate
Ion Exchange Unit Volume
= l l5gpm 3
16.1 ft 3 = 7.1 gpm/ft
Since the maximum allowable flow rate would be exceeded, either
the exchanger operating time per cycle would have to be increased
to reduce the service flow rate, or the bed volume must be adjusted.
Both methods are demonstrated below:
a. The adjusted operating time can be determined by using the
following equation:
IV— 17
-------
SIZING THE ION EXCHANGE UNIT EXAMPLE
(Continued)
A4justed Service Time = Design Time Calculated_Service Flow
cycle cycle X Max. Allowed Service Flow
= 6 hours 7.1 gpm/ft
cycle X 5.0 gprn/ft
= 8.5 hours/cycle
The adjusted flow rate during this cycle would be
41,380 gal
cycle = 81 gpm
8.5 hours/cycle x 60 miii .
hour
b. As an alternative, the initial flow rate can be retained, but
the ion exchange bed volume can be adjusted to make sure the
service flow rate does not exceed the manufacturer’s recom-
mendations. Bed volume can be adjusted as follows:
Adjusted BV = Design BV x Calculated _ Unit Service Flow Rate
Max. Allowable Unit Service Flow Rate
Adjusted BV = 16. 2 ft 3 x 7.1 gpm/ft 2
5 gpm/ft 2
Adjusted BV = 23 ft 3
For the purpose of this example, It will be assumed that it
is more desirable to be able to complete the treatment and
regeneration cycle during the normal 8 hour shift than it
is to save the capital costs by minimizing the size of 3 the
resin exchange bed. BV is therefore taken to be 23 ft
4. Determine Bed Dimensions
Minimum bed depth (Table 12) is 30 inches or 2.5 feet. Since
Volume = Area x Depth, Area = Volume . Using a minimum depth of 2.5 ft.
Depth 3
the area can be calculated as 23 ft — 9 2 f 2
2.5ft • t
For a circular vessel, Area = P1 (Diameter) 2
4
- S
Therefore: Diameter =114 x Area
V P1
IV— 18
-------
SIZING THE ION EXCHANGE UNIT EXAMPLE
(Continued)
For this example:
Diameter x9.2 2 = 3.42 ft
A reactor vessel of circular cross section would have a diameter
of 3.42 feet and most likely, the closest premanufactur d site
would be 3.25 feet with a corresponding area of 9.62 ft . The
bed d pth would then be adjusted so the required volume of
23 ft would be available:
Volume = Area x Depth, therefore Depth = Volume
Area
Depth = 23 ft 3 2
9.62 ft
= 2.4 ft
Adjusting for Expansion During Backwash
The bed depth must be adjusted to allow sufficient room for bed
expansion during the backwash cycle. This design adjustment is
accomplished with the aid of Figure 15 and manufacturer’s data from
Table 12. If we assume that the backwash flow rate is 2 gpiu/ft
(Table 12) and that under the worst temperature condition, the
backwash water temperature will be 35°F, the percent bed expansion
of 56% is determined from the graph in Figure 15. Then the follow-
ing equation can be used to determine the final vessel depth:
Adjusted bed depth equals unadjusted bed depth + unadjusted
depth x % expansion
100
For this Example:
Adjusted bed depth = 2.4 ft + 2.4 (56) = 3.74 ft
100
5. Regeneration System:
Salt required per regeneration cycle: From Table 12,
Regeneration dosage = 15 to 18 pounds sodium chlorid (NaCl)
per cubic foot of resin. For this example, 18 lb/ft is
assumed.
Salt required = 18 lbs x 23 ft 3 = 414 lbs/cycle
cycle ft 3
IV—19
-------
SIZING THE EON EXCHANGE UNIT EXAMPLE
(Continued)
6. Volume of brine required per regeneration cycle:
Salt concentration % Wt. of Salt
Total Weight Brine X 100
10 (from Table 12) = 414 lb 100
Total Weight Brine
Total Weight Brine = 4140 lbs.
Weight of Water = Total Wt. — Wt. of Salt
= 4140 lbs. — 414 lb.
= 3726 lbs.
Volume of Water (ft 3 ) = Wt. Water (lbs) 3
Density (lb/ft )
= 3726 lbs
62.4 lb/ft
= 59.71 ft 3
Volume of Salt (ft 3 ) = Wt. Salt — 414
Density — (62.4) x (2.165)
= 3.06 ft 3
Total Volume = Water & Silt = 59.71 + 3.06
= 62.78 (ft )
Total Volume (gallon) = 62.78 ft 3 x 7.48 gallon = 470 gallons
(ft 3 )
This brine tank should contain sufficient volume for 3—4 regen—
erations. If 3 regenerations used, the total brine tank volume
must be 470 gal/cycle x 3 = 1410 gal.
7. Regeneration Cycle Operating Time
Regeneration time = Volume of Brine
Flow Rate of Brine
Flow rate of brine = 0.5 gpm/ft resin ( rom Table 12)
= 0.5 gpm/ft x 23 ft
= 11.5 gpm
Regeneration time = 470 gal
11.5 i = 41 minutes
mm
IV—20
-------
brine actually passes through
the bed in the required
quantities. A sight glass
or break in the drain line
should be provided so that
waste flows can be visually
observed.
4. Protective instrumentation,
as illustrated in Figures l6a
and 16b, should be incorpor-
ated in the system.
5. Spot checking of product
water for nitrate removal,
using a calibrated field
test kit, should be rou-
tinely performed by the
plant operator (see Sec-
tion V I, Operation and
Maintenance).
All systems should also
consider using a continuous
on—line nitrate analyzer
which will actuate alarms
and initiate automatic
system shutdown in case of
nitrate breakthrough.
Reference 15 describes an
analyzer/ controller in use
by the Garden City Park
Water District, of New York
(Long Island).
o Equipment Redundancy
The need for backup equipment is
determined largely by state and
local regulatory requirements and
the consequences of main system
shutdown for repair. If the
water supply is quite high in
nitrate and no backup water
supply or large reserve is avail-
able, two fully equipped parallel
systems are justified. At the
opposite extreme, a very small
system with raw water quality
near the standard (i.e., Curry—
ville, PA, described in Sec-
tion VII) can get by with a
single system.
Typically, a system could have
two parallel exchanger vessels
sewed by a single regeneration!
backwash system.
o Salt Handling and Storage
Regeneration for nitrate removal
requires a considerable amount
of rock salt (NaC1) which must
be stored in a cool, dry place.
Salt is corrosive but is other-
wise nontoxic and can be readily
handled. Storage and brine
solution tanks should be construct-
ed of highly corrosion resistant
materials and operators should
wear gloves when handling the
salt simply to avoid skin
irritation.
o Materials of Construction
Although the process water
stream will usually be only
slightly corrosive, the regener—
ant stream, at 10 to 12 percent
salt content, will be highly
corrosive (similar to sea
water). Use of more expensive
but corrosion resistant mate-
rials will be very cost effective
over the life of the system.
For example:
o High strength PVC (polyvinyl
chloride) piping should be
used, where system pressures
permit, as this material
is corrosion free. Fittings
should be of the same
material or better.
o Plastic epoxy lining or
galvanizing for vessels is
suggested. The brine
tank, where the rock salt
and water are mixed,
should be galvanized
and lined , or protected by
a plastic liner. Smaller
IV—21
-------
VALVES
- OPEN
-4-CLOSED
Flow In -line mechanical
recorder I lowmetef
controller
Sewer
etc.
—
Free space • Product
water-filled Water
N 0 3 -N
recording
controller
(optional)
I
Normal Operation Cycle
Backwash Cycle
Figure 16a. Protective Monitors
Backwash
Timer
to control
Velvil
pumps SIC.
discharge
4
r
erote
Water
•
Backwash
water
BackwasP 1 .
— discharge
Feed
I4
Regenerate
Water
rinse
?4
Timer Flow In-line mechanical
wcofflrolr eC? p Wmeter
• Free space u Product
I water-filled 1 Water
NOçN
recording
controller
E.i (optional)
Backwash
water
VALVES
- OPEN
‘•4- CLOSED
IV—22
-------
Backwash -.
discharge
Feed
F
Regenerate ,_
Water
VALVES
- OPEN
1-CLOSED
Timer
to Control
volvil
purnps .tc.
Flow
r•corder
controller
Free space
water-filled
I
r
Figure 16b. Protective Monitors
F
Product
I I Water
N0 3 -N
recording
controller
(optional)
—
Backwash
water
Regeneration Cycle
Backwash
Timer
to control
valves
p mpi .tc.
line mechanical
recorder
controller
Flow 1 owmete
Product
Water
VALVES
-OPEN
- CLOSED
Rinse Cycle
IV—23
-------
systems may be able to use
all plastic or fiberglass
brine tanks.
o Meters and other instruments
should be designed and
warranted for corrosive
service.
o Spent Regenerant Disposal
Ion exchange systems do not
provide ultimate disposal of the
nitrate removed from the process
water stream. They simply move
nitrate, sulfate and a substantial
amount of spent brine to the
waste stream. In the process
design example, the hypothetical
100,000 gpd (after blending)
system would use about 410 pounds
of salt every day, and generate a
waste stream of approximately
400 gallons per day having a
total dissolved solids concentra-
tion exceeding 12,000 mg/i.
There are currently few practical
means of removing the water or
otherwise treating this waste
stream. Thus, disposal alterna-
tives are generally limited to
the following:
o Direct discharge to a stream
or other surface water——the
spent brine can be diluted
in the stream flow so that
final total dissolved solids
(TDS) and nitrate levels are
acceptable. This may have
an adverse effect on a fresh
water stream. A discharge
permit from the state water
pollution control authority
may be required.
o Direct discharge to a sewer
system——again, the spent
brine must be diluted so
that the resultant salt and
nitrate levels do not interfere
with the waste treatment
system or violate treatment
facility discharge permit
requirements.
o Evaporation in a lined
pond——it may be possible
in dry climates to evaporate
the water from the salt in
a simple holding pond
located on—site or nearby.
The dried salt can be
periodically removed and
disposed in an approved
landfill.
o Truck spent brine to an
acceptable off—site disposal
site.
o Ocean discharge for coastal
facilities.
Generally, septic tank disposal
or disposal in unlined ponds
will be unacceptable as it may
lead to salt and nitrate pollu-
tion of adjacent ground waters.
IV—24
-------
V. COST ESTIMATING PROCEDURES AND FUNDING SOURCES
This section provides a summary
of the kinds of costs that are
likely to be encountered in any
treatment facility construction
project and outlines a procedure
to estimate costs associated with
treatment for nitrate removal.
It also summarizes some estimated
construction and operating cost
projections which have been made
for ion exchange nitrate removal
systems, explains how to update
costs, and provides an overview
of potential funding sources for
small water utilities.
Costs depend largely on site—
specific conditions some of which
may change over time. The cost
estimates in this report were
based on assumptions made when
the cost curves were developed
(1976—78). In this regard, other
projects are currently in progress
to refine and improve the accuracy
of cost estimating procedures.
As these projects are completed
they should be consulted for more
accurate cost estimation procedures.
The total cost estimate for a
water treatment facility is
generally the sum of the costs
associated with two major categor-
ies: (1) construction costs aud
(2) operation and maintenance
costs. Each of these major cost
categories Is composed of individual
costs for a number of components.
To arrive at a total cost estimate
for a given facility, the component
costs are evaluated, adjusted as
necessary for site—specific
considerations and Inflation,
then summed. Costs can be expressed
many ways: annual cost and cost
per thousand gallons treated are
two of the most common. The
latter can be used directly to
estimate the effect the project
will have on the individual
consumer’s water bill. However,
cost curves are generally most
useful for comparing relative
costs of the treatment alterna-
tives and for approximating the
general cost level to be expected
for a proposed treatment system.
CONSTRUCTION COSTS
Introduction
Whenever treatment costs are
determined, whether from a
published report or a vendor’s
estimate, it is extremely
important to establish exactly
what components and processes
the cost estimate Includes.
Different cost estimates based
ofl different basic assumptions
(such as water quality) and
different components (such as
housing) have in the past
resulted in many misunderstandings.
In addition, If the costs are
taken from a report, it Is
important to be sure they apply
to the size category of your
system. Once this has been
ensured, cost comparisons
between alternatives can be
made using the process outlined
above. To Illustrate this
procedure, the cost information
developed by the EPA Municipal
Environmental Research Laboratory
[ presented in a 4—volume report
titled: Estimating Water Treat 1)
ment Costs (EPA—600/2—79—162)].
can be used. This report
presents cost curves for 99 unit
processes useful for removing
contaminants covered by the
N IPDWR.
V-i
-------
The construction cost curves in
Reference 1 were developed by
using equipment cost data supplied
by manufacturers, cost data from
actual plant construction, pub-
lished data, and estimating
techniques from Richardson Engi-
neering Services Process Plant
Construction Estimating Standards,
Mean’s Building Construction Cost
Data, and the Dodge Guide for
Estimating Public Works Construc-
tion Costs. The construction cost
curves were then checked and
verified by an engineering con-
sulting firm.
Although the cost data in Refer-
ence 1 may be somewhat outdated,
the method used to generate those
costs provides an outline of the
things you should consider when
developing your own estimates.
For example:
o Excavation and Site Work
This category includes work
related only to the applic-
able process and does not
include any general sitework
such as sidewalks, roads,
driveways, or landscaping
which should be itemized
separately.
o Manufactured Equipment
This category includes
estimated purchase costs of
pumps, drives, process
equipment, specific purpose
controls, and other items
that are factory made and
sold with equipment.
o Concrete
This category includes the
delivered cost of ready—mix
concrete and concrete—forming
materials.
o Steel
This category includes
reinforcing steel for
concrete and miscellaneous
steel not included within
the manufactured equipment
category
o Labor
The labor associated with
installing manufactured
equipment, and piping and
valves, constructing
concrete forms, and placing
concrete and reinforcing
steel are included in this
category
o Pipe and Valves
Cast iron pipe, steel
pipe, valves, and fittings
have been combined into a
single category. The
purchase price of pipe,
valves, fittings, and
associated support devices
are included within this
category.
o Electrical Equipment and
Instrumentation
The cost of process electri-
cal equipment, wiring, and
general instrumentation
associated with the process
equipment is included in
this category.
o Rousing
In lieu of segregating
building costs into several
components, this category
represents all material
and labor costs associated
with the building, including
heating, ventilating, air
conditioning, lighting,
V-2
-------
normal convenience outlets,
and the slab and foundation.
To the subtotal for construction
costs is normally added 15 percent
for contingencies.
The total construction cost is
obtained by adding in the follow-
ing items:
Special sitework
General contractor overhead and
profit
Engineering
Interest
Land
Legal, fiscal, administrative
services
These are not directly applicable
to the costs for specific processes.
Rather, when using these cost
curves, they should be added in
after process costs have been
estimated. Typically, these will
average 30 to 35 percent of the
total construction cost. The
cost curves of Reference 1 do not
include these items; they must be
added on to arrive at a total
cost estimate.
The costs from Reference 1 are
based on October 1978 dollars and
can be updated by using the
Engineering News Record (ENR)
Construction Cost Index (CC I), or
Building Cost Index (BCI).
The following formula can be used
to update construction costs:
Updated Cost = Cost from Curve x
(Current ENR Construction Cost
Index [ CCI])
(ENR CCI When Costs were Determined)
The cost curves used in this
document from Reference 1 are
based on October 1978 costs
when the ENR* CCI was 265. 38.
As of June 1982, the ENR CCI
was 352.92. Thus to update the
Reference I cost estimates,
they must be multiplied by the
ratio of 352.92/265.38 which
equals 1.33.
Note that this is the average
of the 20 city construction
cost index——there is wide
variation between individual
cities and regions of the U.S.
For example, the August 1981
index varied from a low of 274
to a high of 360 among the
20 cities, about a 31 percent
difference. As a result,
updated cost figures using this
adjustment may tend to over-
estimate or underestimate
costs, depending on construction
costs in the locality of interest.
More sophisticated cost esti-
mating techniques are available;
they are described in Reference 1.
Reference _ i Construction Cost
Basis and Assumptions
Reference 1 costs were developed
for treatment of a water supply
with the following anion content:
Nitrate—nitrogen = 22.2 mg/i,
sulfate = 80 mg/i, other anions
120 mg/i. The work assumed a
strongly basic anion exchange
resin operated with sodium
chloride regenerant. Note that
other water supplies with
different quality may cause the
resin to have significantly
different exchange capacities,
* Engineering News Record,
(ENR), is a McGraw—Hill
Publication which summa-
rizes periodically updated
construction cost indices
weekly.
V-3
-------
depending generally on the nitrate—
to—sulfate ratio.
Regenerant required was assumed
to be 15 pounds salt/cu.ft. of
resin. A total regeneration time
of 54 minutes was assumed.
Backwash required 10 minutes, the
brine contact and slow rinse
24 minutes and the fast rinse an
additional 20 minutes.
Construction costs were developed
for pressure anion exchange
systems using the de8ign basis In
Table 13. Contact vessels were
fabricated steel, with a 100—psi
working pressure and a baked
phenolic lining. A 6—foot bed
depth was utilized, and tanks
were sized for up to 80 percent
resin expansion during backwash.
A gravel layer between the resin
and the underdralns was not
assumed.
Regeneration facilities include
two salt storage/brining basins,
which are open, reinforced con-
crete structures, constructed
with the top foot above ground
level. A salt storage capacity
of 4 days was provided. A satur-
ated 26 percent brine is pumped
from these storage basins to the
contact vessel using an eductor
to dilute the brine to 10 percent
concentration as It Is being
transferred.
Brine, transfer, and backwash
pumping facilities are included
in the cost estimate. Costs
for spent regenerant disposal are
not Included as they are highly
site—specific. They must not be
ignored, however, if true cost
estimates are to be prepared.
Construction costs are presented
in Table 14 and In Figure 17.
Annualizing Construction Costs
To determine the true total
yearly cost of owning, maintaining,
and operating a nitrate removal
system, all costs must be
stated on an annualized basis.
As shown later herein, 0&M
costs are normally stated on
this basis. Capital costs can
be annualized as a series of
equal payments needed to recover
the Initial expenditure over
the life of the project, plus
interest costs.
The size of the annual payment
needed to recover the initial
capital cost can be determined
by multiplying the lump sum
amount times a capital recovery
factor (CRF).
Annualized Construction Cost
= Construction Cost x CRF
The CRF is a function of the
interest rate “i ” (cost of
money) and the lIfe( 1 )the
system in years (n)
CRF = 1(1 + I) ”
(1 +
Many economics handbooks provide
tables of CRF values corresponding
to various combinations of
interest and financing period.
Table 15 is an abbreviated
example of this type of table,
from Reference 16. The cost
example beginning on page V—12
shows how this can be used to
find the annual cost of a
proposed system’s capital cost
based on the expected financing
term and interest cost.
V—4
-------
TABLE 13
CONCEPTUAL DESIGN FOR PRESSURE ION EXCHANGE NITRATE REMOVAL*
Treatment Capacity Number Diameter of
(gpd) of Contactors Contactors (ft.)
Housing
sq.ft.
70,000 2 2
132
270,000 2 4
210
425,000 2 5
255
TABLE 14
CONSTRUCTION COST FOR PRESSURE ION EXCHANGE NITRATE
REL4OVAL*
Capacity
(gad) -
Cost Category 70,000 270,000
425,000
Excavation and Sitework 50 110
140
Manufactured Equipment:
Equipmeru. 11,860 16,500
19,090
Media 5,460 21,860
34,160
Concrete 280 490
550
Steel 420 680
950
Labor 4,770 5,990
6,880
Pipe and Valves 9,650 12,440
13,600
Electrical and Instrumentation 18,390 21,460
23,070
Housing 7,600 900
9,800
Subtotal 58,480 88,430
108,240
Miscellaneous and Contingency 8,770 1 ,160
Total $67,250 $101,690
$124,480
ENR CCI October 1978 — 265.38
* Reference 1.
V - 5
-------
‘ I__hull
I I I 1.111
I —
I I I
10,000 100,000
1,000,000
PLANT C
APACITY— gpd
I I
I I
100 1000
PLANT CAPACITY— m 3 /day
+
10,000
Figure 17. Construction Cost Curves for Ion Exchange Nitrate Removal
1,000,000
F
I-
U)
0
U
I00’c
I-
U
I-
(I )
2
0
I -)
DO
—
a
10,00 0
V—6
-------
TABLE 15
CAPITAL RECOVERY FACTORS FOR SOME COMBINATIONS
OF INTEREST (1) AND FINANCING PERIOD (n)
6%
OPERATION AND MAINTENANCE COSTS
To obtain a total operation and
maintenance (O&M) cost, the
individual costs for energy
(process and building heating),
maintenance material, and labor
must be determined and summed.
Total operation and maintenance
costs from a reference document
or previous contractor’s estimate
can be updated and adjusted to
local conditions by updating and
adjusting the operation and
maintenance cost components:
energy, labor, and maintenance
material. Energy and labor
requirements are generally provided
in kilowatts per year and hours
per year, respectively, and cost
curves are developed by multiplying
these requirements by the cost of
power and labor respectively. To
update such a curve, the cost per
year is multiplied by the ratio
of current energy or labor costs
divided by the respective unit
cost used to develop the original
cost curve. For example, assume
an available energy cost curve is
based on an energy cost of $0.03
per kilowatt hour; If electricity
now costs $0.05 per kilowatt hour
the current annual energy cost
for a given facility can be
determined by multiplying the
annual cost from the graph by the
0.05
ratio of;
Likewise maintenance material
costs are related to the Producer
Price Index (PPI) for Finished
Goods. To update this component,
the PPI at the time the original
cost estimates were made must
be known. Then the new annual
cost Is determined by multiplying
the cost from the graph by the
ratio of the new PPI divided by
the PPE at the time the graph
was prepared. The technique is
also demonstrated in the example
(page V—12).
O&M COST BASIS AND ASSUMPTIONS
O&M costs were also estimated
In Reference 1 and are included
In this section. The basis and
assumptions used are outlined
below.
Electrical costs inclue backwash,
rinse, and regenerant pumping,
building heating, lighting and
ventilation. Backwash pumping
was based on a 10—minute wash
at 3 gpm/sq.ft. Regenerant
pumping was based on a rate of
6 gpm/sq.ft. of resin for
24 minutes, and fast—rinse
pumping was based on a rate of
8 gpm/sq.ft. of resin for
20 minutes. All pumping was
n Years
7% 8% 9% 10% 12%
5
0.237396
0 243891
0 240456
0 257092
0 263797
0 277410
10
0.135868
0.142378
0 149029
0.155820
0.162745
0.176984
15
0.102963
0 109795
0.116830
0.124059
0.131474
0.146824
20
0.087185
0 094393
0.101852
0.109546
0.117460
0.133879
25
0.078227
0.085811
0.093679
0.101806
0.110168
0.127500
V- 7
-------
assumed to be against a 25—foot
total developed head. Feed water
pumping requirements are not
included.
Maintenance material costs for
periodic repair and replacement
of components were estimated
based on 1 percent of the con-
struction cost plus the cost of
resin replacement. Resin replace-
ment costs are for resin lost
annually by physical attrition as
well as loss of capacity as a
result of chemical fouling. An
anion resin is typically replaced
every 3 to 5 years; a 25 percent
annual resin replacement was
included to account for resin
fouling and resin loss. Regenerant
costs may be significant but are not
included in the maintenance material
costs provided . These must be
included to determine total O&M
cost.
Labor requirements are for opera-
tion and maintenance of ion
exchange vessels and the pumping
facilities. Hours were estimated
based on filtration plants and
filter pumping facilities of
comparable size which generally
require the same level of labor
attention.
Labor requirements are also
included for periodic media
addition and replacement of the
media every 4 years. No costs
are included for spent brine
disposal . These costs may be
significant and are highly site—
specific. They must be considered
to deterniine total 0&M costs.
Operation and maintenance
curves are presented in Figure 18
and are summarized in Table 16.
Energy costs are based on
$0.03 per kilowatt hour, labor
costs are based on $10.00 per
hour and maintenance material
costs are based on a PPI of 199.7.
The above costs do not include
an estimate of the costs associated
with regeneration of the media.
This cost is highly dependent
upon system throughput and the
sulfate and nitrate concentration
of the raw water.
Figure 19 relates regeneration
cost to sulfate and nitrate
concentrations. One hundred
percent efficiency of sulfate
and nitrate removal is assumed.
Salt cost is assumed to be
1.5 cents per pound. For other
salt costs, multiply the regen-
eration costs from Figure 19 by
the ratio of actual cost in
cents divided by 1.5.
To use Figure 19, determine sul-
fate and nitrate concentration
of the raw water. Enter the graph
at the sulfate concentration and
read the regenerant cost for the
standard 33.3 mg/i NO 3 —N concen-
tration. Determine your cost
using the following equation:
your cost (cost from Figure 19 for 33.3 mg/i N0 3 —N
times (the number of thousand gallons treated)
times (the ratio of your nitrate—nitrogen concentration
in mg/l divided by 33.3)
times (the ratio of your salt cost divided by 1.5 cents
per pound)
OR
your cost = (Figure 19 cost) x
your NO —N conc.
( gallons treated) ( 3 ) ( your salt cost )
( 33.3 mg/i N0 3 —N) ( 1.5Q/lb. )
V—8
-------
10029
LABOR—hr/yr
I00 00 , IC
PROCESS ENERGY—
—
-
—
— /hr/Yr
—
— C, • 4
• lii
z
4 • IU ____________
/ ‘MAINTENANCE
w
10000 100
2 I / MATERIAL— $/.yr
-
uJ.o. /
U - a) /
Z - 4
4 -J /
z — —
w
________________ BUILDING ENERGY
/ OOO kw-hr./yr.
2 -
0
IOQQ_ . I C I I. 1111111 I I I 111111
10,000 100,000 - 1,000,000
PLANT FLOW RATE- gpd
I 10100 IO)OO
100
PLANT FLOW RATE - m 3 /doy
Figure 18. Operation and Maintenance Costs for Ion
Exchange Nitrate Renioval
V— 9
-------
I-
I,
•0
0
0
0
0
0
8
z
0
L i i
z
I i i
16
15
14
13
12
II
I0
9
8
7
6
5
4
3
0 50 100 150 200 250 300
SULFATE CONCENTRATION OF RAW WATER, mg/I
Figure 19. Regeneration Costs vs. SO 4 and NO 3 Concentratjon 1
Resin Capacity 1.2 meg/nil
Soil Usage - 15 lbs R uin
Salt Cost — 1.5 $ /ib
v—i 0
-------
TABLE 16
OPERATION AND MAINTENANCE COST SUMMARY FOR PRESSURE ION EXCHANGE NITRATE REMOVAL 1
Plant Flow Rate
(gpd)
Electrical
Building
Energy (kw—hr/yr)
Process Total
Maintenance
Material ($/year)
Labor
(hr/yr)
Total Cost*
($/yr)
70 000
13,540
126
13,666
$ 1,890
1,000
$12,300
270,000
21,550
510
22,060
6,340
1,400
21,000
425,000
26,160
790
26,950
9,660
1,550
25,970
* Calculated using $0.03/ky—hr and $10.00/hr of labor.
-------
EXAMPLE OF APPROXIMATING COSTS
FOR A 100,000 GPD* NITRATE REMOVAL SYSTEM
STEP 1: Calculate cost adjustment factors as of June 1982
A. Construction Cost Current ENR CCI
Escalation Factor (CCEF) = Base ENR CCI
The cost curves of Reference 1 are based on October 1978 costs,
when the ENR Construction Cost Index (CCI) was 265. 38. The
June 1982, ENR CCI was 352.92.
Therefore, CCEF = = 1.33
B. Maintenance Material Current PPI
Cost Escalation Factor (MMCEF) Base Year PPI
The October 1978 Producer Price Index (PPI), issued by the U.S.
Department of Commerce, was 199.7. The June 1982 PPI was 299.4.
Therefore MMCEF = = 1.50
STEP 2: Estimate Construction Cost Using Figure 17
From Figure 17, construction cost in October 1978 dollars is $65,000.
June 1982 Construction Cost = $65,000 x CCEF
= $65,000 x 1.33
= $86,450
STEP 3: Estimate Annual O&M Cost
A. Maintenance Material
From Figure 18, October 1978 annual maintenance material cost
is $2,800.
June 1982 Maintenance Cost = $2,800 x MMCEF
= $2,800 x 1.50
= $4,200
* Note that this is treated flow, before blending. Refer to
Section IV for a discussion of total blended flow computations.
v-i 2
-------
EXAMPLE OF APPROXIMATING COSTS
FOR A 100,000 GPD NITRATE REMOVAL SYST 4
(Continued)
B. Energy Cost
Energy Use = Process Energy + Building Energy*
From Figure 18:
Energy Use = 200 kwh/year (process) +
16,000 kwh/year (building)
= 16,200 kwh/year
Energy Cost/Year = kwh/year x energy cost
kwh
For this example, assume energy cost of $0.05/kwh
Energy cost/year = 16,200 x $0.05
= $810
C. Labor Cost
From Figure 18, labor, hour/year = 1,100 for a 100,000 gpd system.
If labor costs $12.00/hour (including fringe costs), annual labor
cost is calculated as follows:
Annual Labor Cost = 1,100 hr/yr x $12.00/hr.
= $13,200
D. Regenerant (salt) cost per day (assume sulfate concentration of
100 mg/i and nitrate concentratioQ of 30 mg/i N0 3 —N).
From Figure 19, unadjusted cost for 100 mg/i sulfate is 8.6Q/i,000 gal.
If salt costs 3 /lb:
Cost/day = 8.6 x 100,000 gpd x 30.0 x 3
1,000 gal.. 33.3 1.5
= i550c/day or $15.50
Cost/year = $15.50 x 365
= $5,658
* Building energy is very dependent on climate. If possible, estimate
this directly for your area.
V-i 3
-------
EXAMPLE OF APPROXIMATING COSTS
FOR A 100,000 GPD NITRATE REMOVAL SYSTEM
(Continued)
STEP 4: Annualize Construction Cost
If the cost of money is 10 percent, and the project has a 20—year
financing period, the annualized construction cost Is determined as
follows:
Annualized Capital Cost Capital Cost x
Capital Recovery Factor, 10 percent, 20 years
The capital recovery factor from Table 15 for 10 percent and
20 years is 0. 117460.
Annual Capital Equivalent $86,450 x 0.117460
= $10,154/year
STEP 5: Determine Total Annual Costs by Stimmfng the Annual Costs of
Construction with O&M and Determine Cost per 1,000 Gallons
Treated
A. Annual Cost Summary
Capital
O&M
Maintenance Material
Energy
Labor
Regenerant
$10,154
$ 4,200
$ 810
$13,200
$ 5,658
TOTAL $34,022
B. Annual Treated Flow, Thousands of Gallons
Annual Treated = 100,000 gal/day , 1 365
Flow (1,000 gal) 1000
= 36,500
per 1000 gallons treated
Cost/1000 gal = Annual Cost
Annual Treated Flow (1000 gal)
= $34,022
36,500 thousand gal/year
Cost! 1000 gal — $0.93
C. Cost
V-i 4
-------
EXAMPLE OF APPROXIMATING COSTS
FOR A 100,000 GPD NITRATE REMOVAL SYSTEM
(Continued)
NOTE THAT THIS IS THE UNBLENDED TREATMENT COST. IN MOST CASES,
ONLY A PORTION OF THE FLOW WILL BE TREATED. THE COST PER
THOUSAND GALLONS OF TOTAL FLOW WOULD THEREFORE BE LESS. FOR
EXAMPLE:
If the water in this example has a NO —N of 30 mg/l and the system
will remove all but 0.5 mg/i of the n trate from the treated flow,
the potential total system flow, after blending, and the cost per
1000 gallons of total (treated + blended) flow can be determined
using the following formulas.
Q Total = Q Treated
1 — ( Final NO 3 —N — Treated N0 3 —N )
(Untreated N0 3 —N — Treated NO 3 —N)
For a final blended water of 9 mg/i N0 3 —N:
Q Total = 100,000
1 — ( 9.0 — 0.5 )
(30.0 — 0.5)
= 100,000
0.712
Q Total = 140,450 gpd
Cost per thousand gallons of total flow then becomes:
Cost/1000 gal — Cost/1000 gal Q Treated
(Total Flow) — (Treated Flow) X Total
= $0.93 x 100,000
140,450
Cost/1000 gal = $0 66
(Total Flow) ______
V-is
-------
FUNDING SOURCES
The principal financing options
available to small water systems
for treatment process improvement
can be categorized as follows:
o Self financing
— User charges and fees
— Bonding/loans
o Direct grant programs
o Subsidized/assisted loan
programs
o Other assistance programs
— Labor sharing with other
systems
— EPA technical assistance
activities
These are discussed in turn
below.
Self Financing
Water utilities process, deliver
and charge consumers for potable
water. In this, they bear close
resemblance to other businesses
that also produce and sell a
product. Most of these utilities,
publicly or privately owned, do
not normally have problems financ-
ing needed capital improvements
either through user fees or
changes 63 he water rate, or by
bonding. However, the financing
needs for constructing and operating
nitrate removal systems may
strain the resources of small
community water systems, either
by requiring capital expenditures
beyond their ability to finance,
or by causing large incremental
increases in user charges. The
latter course may incur substantial
consumer resistance to
improvement program, a
impediment in the case
publicly owned systems. Very
small systems may be particularly
vulnerable to problems in this
regard -
The prime considerations for
self f inanftg include the
following:
o Amount of revenues available
for payment of interest
costs
o Ratio of new treatment
capital costs to existing
assets
o Percent rate increase
needed to finance and
operate treatment
o Ratio of the typical
residential water bill to
the community’s median
family income
In competing for funds on the
private capital markets, the
larger utility is expected to
have a debt service ratio
(ratio of income after operating
expense to interest costs)
of 1.3 and income at least
twice that of interest charges.
Private utiLities must be
showing a net profit, after
taxes, of 10 to 13 percent.
User bills should run less than
1.5 to 2.0 pero g of median
family income.
Smaller utilities may be substan-
tially less robust financially,
and sti1l be able to raise
money locally. Utility customers
may be wi1ling and able to put
up the needed capital. Even
so, the utility should have a
debt service ratio of at least
1.0 so interest and bond repay-
ment schedules can be met.
the
major
of
V—I 6
-------
Grant Programs
The principal financial assistance
program available to small com-
munity water systems (public or
private nonprofit) is operated by
the Farmers Home Administration
(FmHA) of the Department of
Agriculture. FmHA can grant up
to 75 percent of the cost for
installation, repair or upgrading
community water systems that
serve fewer than 10,000 people
with emphasis on farmers and
other rural residents.
Program aid priorities are estab-
lished considering the following
criteria:
o Public bodies and towns with
emphasis to those serving
5,500 people or less
o Systems that will achieve
compliance with Safe Drinking
Water Act as a result of the
improvements
o Low income communities
o Systems proposing to merge
and/or regionalize
o State recommended projects
o Projects promoting water
energy conservation
FmHA can be contacted for further
information at any one of 340 offices
nationwide.
The Department of Housing and
Urban Development (DHUD) has a
program of Community Development
Block Grants (CDBG), funds from
which local water treatment
projects can be funded. The CDBG
program combines a wide range of
public construction and allocation
of funds is normally carried out
by local committees, with Federal
oversight. The program is
usually operated at the county
or city level and these sources
can provide the information
needed to apply for funds.
Direct Loan Programs
Two federal agencies currently
operate direct loan programs:
o Department of Interior —
has two programs available
to public nonfederal
entities in the 17 western
states.
o Farmers Home Adminstration —
has loan program with
similar criteria to those
used in their grant program.
The loan can be for 100 per-
cent of the project cost.
Loan Guarantee Programs
The Farmers Home Administration
has a Business and Industry
Loan program available to
public or private organizations,
particularly those located in
rural areas and serving fewer
than 50,000 persons. Loan
guarantees range up to 90 percent
of face value.
Other Forms of Assistance
Other ways of reducing financing
and/or operating costs include
the following:
o Bond banks — Several
states have central bond
banks that assist localities
in the mechanics of bond
financing. By aggregating
small bonds into larger
ones, interest costs may
be reduced and bond place-
ment enhanced.
v—i 7
-------
o Research and development —
The U.S. Environmeta]. Protec-
tion Agency (EPA) has funded
a few pilot and demonstration
projects for water and
wastewater systems using
uncommon technology. Pilot
studies at McFarland, Cali-
fornia, were carried out as
part of an EPA research
project.
o State loan programs — Several
states provide direct loans
for construction of public
water and sewer projects.
The programs are normally
operated under the aegis of
state economic development
offices.
o Shared operator costs with
other nearby utility(s) —
Ion exchange nitrate removal
does not require full time
supervision; hence, operator
costs could be divided
between two or more utilities
where travel distance permits.
Regionalization is one
approach to shared operating
expenses.
V- 18
-------
VI. OPERATION AND MAINTENANCE
Nitrate removal using salt regen-
erated strong base ion exchange
will provide long service, with
low maintenance providing that
precautions are taken to prevent
excess raw water turbidity or
fouling of the resin. The equipment
is widely used for water softening
and industrial water treatment
and does not require continuous
operational supervision. Preven-
tive maintenance (PM) is the key
to long trouble—free performance.
This section sets out recommended
monitoring and PM activities for
a typical small nitrate removal
system.
OPERATOR REQUIREMENTS
Operation of an ion exchange
system does not require special-
ized operator skills. The operator
should be reasonably proficient
in plumb 4 “ce and electrical skills
and shou1 . ‘rstand the operation
and repair of simple pumps,
valves, water meters and electrical
controls. He or she must be
capable of carrying out a program
of periodic sampling and be able
to use a packaged test kit, make
simple calculations and record
results. The operator should be
of sufficient intelligence and
schooling so that he or she can
be trained in the fundamentals of
process operation and be able to
fully grasp the importance of
avoiding nitrate breakthrough.
Operator time requirements are
dependent on system size. However,
it is not likely that the operator
will spend more than several
hours per day carrying out the
monitoring and PM activities
described herein.
MANUALS, EQUIPMENT AND SUPPLIES
NEEDED
Provide the system operator
with the guide manuals, tools,
analytical equipment and supplies
needed to properly maintain the
system. For example:
o System operation and
maintenance manual for
each individual piece of
equipment and the system
as a whole which describes:
— Startup and test procedures,
routine (preventative)
maintenance procedures,
and troubleshooting
guide.
— Schedule of routine
maintenance activities
and tools/supplies for
each task. Schedule
should include daily,
weekly, monthly, quarterly
and annual activities
as needed.
— Sources, incLuding
name, address and
telephone numbers, for
emergency parts and
service. This should
also be posted near the
equipment.
— Operational directions,
including detailed
control settings for
electrical controls,
motorized valves,
flowmeters, pumps, etc.
— Sampling and test
procedures and schedules
for process monitoring
VI— 1
-------
and reporting to the
state.
— Appropriate forms for
recording maintenance and
water quality data.
Format of recommended
record keeping.
o Recommended tools and critical
spare parts for each item,
such as lubricants, valve
and pump gaskets and packing,
electrical fuses. Stock key
spare parts that are not
available locally or overnight
from manufacturer’s warehouse.
o Field test kits for process
control:
— turbidity
— nitrate
— chlorides
— sulfates (if high or
variable)
o Sample bottles, mailing
packages and complete mailing
instructions including name,
address, telephone number of
state approved laboratory.
o Supply of regenerant chemicals
(e.g., salt).
MONITORING
Monitoring encompasses two
activities:
1. Monitoring to satisfy Federal
or State requirements under
the National Interim Primary
Drinking Water Requirements
(NIPDWR) of the Safe Drinking
Water Act (SDWA)
2. Monitoring for process
control
Monitoring/Reporting requirements
for nitrates under the Safe
Drinking Water Act are quite
minimal. Community water
systems using surface water
must report the result of
nitrate analyses to the State
or EPA every year; those using
ground water must report nitrates
to EPA only once every 3 years
unless otherwise specified.
For non—community systems state
health departments may require
more frequent reporting.
Illinois, where nitrate pollution
of ground and surface water
occurs as a result of heavy
agricultrual activity, requires
monthly reporting of nitrates.
Note that test kit data do not
satisfy this requirement.
You must have these analyses
performed by a state approved
laboratory . When drawing a
sample for certified analysis,
you should simultaneously check
nitrate levels with your field
test kit. This will give a
laboratory check against test
kit results. Table 17 illus-
trates a sample form that could
be used to record test kit and
laboratory analyses. A permanent
record and file for both test
kit data and lahcr ory analysis
reports should be maintained.
Approved monitoring for process
control can be carried out
using a calibrated field test
kit (Table 3). A sample schedule
of monitoring activities is
given below. Table 17 is a
sample data sheet that might be
used to record these data.
Daily
o Use nitrate test kit to
check
— Raw water nitrates
VI— 2
-------
ThBLE 17
SAMPLE MONTHLY DATA SHEET
( I)
(2) I (3) I (4) I (5) I (6)
(7) I (8) I (9) I (10)
(II) I (12) I (13) I (14) I (IS) I (16)
FLOW METER READINGS
140 - N IN SERVICE
I GENERATI0N CYCLE CHECK
Treated
tsr
Previous
Day
Blend
Wat
Previous
Day
Total
Woim
Raw
N0 1 -N
Escllanaer
Out NOj-N
Blend
N0 5 -N
Chlorides
Out
Check
Dais /TIms
N0 5 -N
Out
Chlorides
Waits Flow
Meter Dspd.nas
Salt
Added
Lbs
Start
Finish
MONTHLY LAB DATA
ROUTINE
CHECK____
OTHER_ANALYSES
Dais
—
i !
Date
Item
Rsadinq
Date
.
CALCULATIONS
Treated Flow • column 2 — column 3
Blended Flow - column 4 — column 5
Total Flow - Treated Flow + Blended Flow
Wast.woter Flow column 6 — column 14
I I I I I I
U I U U U I
I
-------
— Exchanger product water
nitrate
— Blended water nitrate*
o Use chloride test kit to
check
— Raw water chlorides
— Exchanger product water
chlorides
o Use turbidity test kit to
check
— Exchanger feed water
turbidity
— Product water turbidity
o Check and record treated
flow, blended flow, waste
flow and total flow.
Regeneration Cycle Check**
o Verify operation of full
cycle of back wash
— Time each phase of cycle
and compare to set times
on time clock.
— Verify brine flow during
brine cycle. Visually
check that brine level
lowers in salt tank when
back wash valve is in
brine position.
— Check flow meter on waste
line to verify water flow
for each cycle and visually
observe flow at waste
line.
* Continuous nitrate monitoring
may be required by the State.
**Check frequency determined by
manufacturer’s recommendation
and back wash cycle frequency.
o Use test kits to check.
— Nitrate and chloride
levels in feed and
product water after
unit returns to normal
operation.
PREVENTIVE MAINTEN&NC E
Preventive maintenance (PM) is
the key to reliable service and
long equipment life. Close
attention to PM activities will
reduce annual costs and minimize
system failure. Summarized
below are typical PM activites
for a nitrate removal system.
A schedule of PM tasks should
be included in the plant O&M
manual. Table 18 is a PM
equipment check list that could
be applied to a small system
such as the one at Curryville,
Pennsylvania (also see Section VII).
Typical Daily PM Checks
o Pumps (if any):
— Overheating.
motor should
hot nor burn
when touched.
— Noisiness/vibration.
Rattling and grinding
noises may indicate
serious bearing problems
and/or shaft misalignment.
— Water leaks from packing
glands and fittings.
— Loose hardware, mountings,
electrical connections.
— Surface rusting/corrosion.
— Motor ventilation
ports. Ports should be
clear and free of dirt,
oil and moisture.
The pump
not smell
the hand
VI—4
-------
TABLE 18
SAMPLE PERIODIC EQUIPMENT CHECK LIST FOR A SMALL
ION EXCHANGE UNIT
I. In Service Operation
1. Brine Tank
Float valve / / OK / / Leaking / / Other
Salt level I / OK / / add salt _________
(Amount )
Sump/draw line I / OK / / needs cleaning
Container / / OK / / not OK _______________
(describe)
2. Motorized valve
Leaking I / NO I / Yes __________________
(where)
Noisy f/NO//Yes
Oil level / / OK I / Oil added _____________
(amount)
In correct position / / NO I / Yes ___________________
(position)
Water leak at waste
line i/NO//Yes ____________
(amount)
3. Flow totalizer
Sensor leaking / / NO / / Yes
Check against main / / OK I / Reading high
flow meter / / OK I / Reading low
Unusual noises / / NO / / Yes
II. Regeneration Cycle Check
1. Brine Tank
o Does brine level lower at a rate which corresponds to
the rate required for regeneration when motorized
valve in tbrinet position?
I / Yes / / NO——Inches/minute ___________
If no — check:
Supply pressure ______________________________________
Waste line clear _____________________________________
Brine suction line clear _____________________________
Valve malfunction __________________________________
Air leak in brine suction line _______________________
VI—5
-------
o Check brine flow rate during brine cycle.
Start Finish
Inline meter reading (gallons) _________ __________
Flow rate = ( finish) — (start ) = — gpm
12 minutes
NOTE: Correct flow rate is 11 gpm (for Permutit
ED—20 System).
2. Motorized valve
o Elapsed Time
Actual (Minutes) Correct (Minutes)
Backwash ________________ __________________
Brine draw ________________ __________________
Slow rinse ________________ __________________
Fast rinse _________________ ___________________
o Observe operation
Yes No
Oil leaking _________________ ___________________
Water leaking ________________ ___________________
Noisy ________________ __________________
Correct position for
each cycle ________________ ___________________
3. Waste flows
o Observe free flow at waste line for each part of regener-
ation cycle
4. Flow totalizer
Inline meter readings:
Regeneration:
Start of cycle ________________________ (gallons)
End of cycle _________________________ (gallons)
Difference ________________________ (gallons)
NOTE: Should be about 670 gallons (for Permutit
ED—20 System).
VI—6
-------
In Service Cycle
Start of cycle ___________________________ (gallons)
(End of last regeneration cycle)
End of cycle ___________________________ (gallons)
(Beginning of regeneration cycle)
Difference ___________________________ (gallons)
Totalizer Trip Setting ___________________ (gallons)
NOTE: These should be approximately equal. If more than
10 percent difference, check both flow meters per
manufacturer’s recommendations.
VI— 7
-------
o Motorized flow valves: o Check automatic valve for:
— Water, oil leaks. Leaking
Sticking
— Rough operation, noisiness Complete cycling
during regeneration
cycle. o Check brine system for:
— Leaks from waste line Flow meter operation
when valve is in the Adequate salt in brine
“off” or “In service” tanks
position.
o Waste flow:
— Proper valve positioning.
Free flowing
o Flow meter/flow totalizers: Evidence of resin in
waste flow
— Comparison of main flow
meter and check flow Other Periodic Activities
meter for equivalent
recordings. 0 Pumps/niotors:
— Leaking, moisture under Lubricate in accordance
meter glass, sticking of with manufacturer’s
meter In operation. recommendation
o Blending flow valve/flow o Flow meters:
meters:
Calibrate in accordance
— Check daily for correct with manufacturer’s
flow splitting recommendation
o Brine/salt storage: o Time clock/relays/automatic
valve
— Salt level in brine tank.
— Lubricate, adjust in
— Stored salt quantity. accordance with manufac-
turer’ s recommendation
o Tanks, pipes and appurtenances:
— Leaks, cracks, corrosion. EMERGENCY PROCEDURES
Checks During Regeneration Salt regenerated ion exchangers
do not use or give off dangerous
o Check t1 ne clock and relays chemicals or fumes. The principal
for: hazard to operators associated
with their use is the result of
Noisiness skin or eye contact.
Sticking
Overheating or hot smell Operation beyond nitrate break—
Time accuracy through, however, will result
in elevated product water
nitrate levels. After resin
VI—8
-------
exhaustion, the influent sulfates
will replace nitrates in the bed.
As a result, the product water
will have MORE nitrate than the
raw water. This could be highly
dangerous to the consumers.
Should this situation occur:
SHUT THE SYSTEM DOWN IMMEDIATELY.
Check stored water for high
nitrates. If high, notify the
public and state representatives
immediately. Prevent stored
water from being distributed if
possible, recognizing the poten-
tial hazards associated with
insufficient capacity in case of
fire. Regenerate exchanger
immediately, checking each step
in the regeneration process.
When water processing resumes,
check for correct effluent nitrate
levels. Flush the system with
the properly treated water and
ensure high nitrate levels are
eliminated in all parts of
the system. Review and change
regeneration program as needed to
avoid a recurrence.
SAFETY PROCEDURES
There are no substantial hazards
associated with the operation or
repair of salt regenerated systems.
Manufacturer’s recommended prac-
tices should be clearly posted on
site and followed. No special
safety equipment is required.
Waterproof gloves may be worn
when working with the brine
system to avoid skin irritation.
RECORD KEEPING
Records of all process monitoring
and PM activities in addition to
the records required by state and
federal regulations should be
organized and retained. Complete,
well organized records create a
historical basis over time that
will provide great assistance
In understanding and dealing
with equipment problems and raw
water quality variations. Keep
records in a central file,
convenient to plant operators,
and protected from extremes of
heat, cold or moisture. Peri-
odically update and cull obsolete
files.
VI— 9
-------
VII. CASE HISTORIES
Use of strong base resins in ion
exchangers for deionization,
including nitrate removal, is
widely practiced in industrial
waste treatment. Experience in
potable water service for removing
nitrate from drinking water
supplies, however, is limited.
The following two localities have
accrued some experience with the
process, using equipment typical
for smaller systems.
Figure 20 shows the equipment
house, which houses a small gas
chlorinator and the ion exchange
unit. Figure 21 is a photograph
of the ion exchange unit inside
the house. The brine tank i 5
in the foreground, nearest the
door. The main flow control
valve, an electrically driven
flow valve, is located atop the
ion exchanger In the rear of
the room. It is controlled by
Locality
System
Curryville, Pennsylvania
3000 gpd fixed bed salt regenerated
anion exchange unit (40,000 gpd
available capacity)
McFarland Mutual Wate 1 9q.
McFarland, California /
Pilot study for 1.0 mgd fixed
bed system
CURRYVILLE, PENNSYLVANIA
Curryville provides an example of
a very small system treating a
water which only slightly exceeds
the standards. Nitrate nitrogen
is only about 11 mg/i N0 3 —N. The
utility’s total daily flow is
less than 45,000 gallons per day
of which about 10 percent is
treated for nitrate removal, then
blended with the main flow to
reduce nitrates to 9 mg/i (N0 3 _N).*
The ion exchanger, a single fixed
bed Permutit water softener style
unit (Model ED2O) was installed
in early 1979 at a cost of $30,000.
* No sulfate data available.
a totalizing flow controller,
located to the right of the
unit.
Table 19 provides pertinent
design parameters for this
unit. As presently operated,
the unit regenerates automati-
cally after 18,000 gallons of
water has been treated, using
about 45 pounds of salt. The
regeneration cycle lasts about
70 minutes and consumes 130 gal—
loris of brine which is wasted
to a septic tank adjoining the
treatment house. (This proced-
ure is not encouraged as it may
lead to ground water pollution.)
The plant operator, employed on
a part time basis, visits the
treatment plant twice weekly,
VII— 1
-------
—
Figure 20. Curryville, Pennsylvania, Equipment Housing
VII—2
-------
Figure 21. Curryville, Pennsylvania, Nitrate Removal System
1 ,I
L i ,
VII—3
-------
TABLE 19
DESIGN AND OPERATING DATA FOR THE CURRYVILLE, PA NITRATE REMOVAL SYSTEM
Type exchange unit Single bed anion exchanger
Manufacturer/Model: Permutit, Model ED2O
Costs (1979 Dollars):
Installed Cost $30,000 (approximate)
Housing $39,100 for building, fencing
and hook up to adjacent well
Engineering $10,000
Resin Manufacturer/Type: lonac, A550 Strongly Basic
Bed Dimensions:
Diameter 20 inches
Height 32 inches
Volume 5.5 cu.ft.
Flow Through Exchanger:
Design — average 28 gpm
— peak 36 gpm
Actual 0.45 gpm*
Average Daily flow treated (gal)
Regeneration Cycle:
Time 70 minutes
Salt Consumption 45 pounds
Pounds Salt/cu.ft. resin 8.2 pounda/cu.ft.
Water Consumption
backwash 200 gallons
brine 130 gallons
slow rinse 190 gallons
fast rinse 150 gallons
Total 670 gallons
* Flow rate on 24—hour/day basis. In practice, unit is operated
6 hours/day or less.
VII—4
-------
spending less than one hour per
visit. The following checks and
maintenance operations are rou-
tinely carried out:
1. Salt level in brine tank is
checked
2. Gear box oil on motorized
valve is checked
3. Setting on flow splitter
valve checked to verify that
10 percent of flow is being
treated
4. Operation of flow recorder/
controller is checked
The operator does not routinely
check the operation of the regen-
eration cycle, due to its infre-
quency. Nitrate samples are
drawn quarterly at a cost of $50
per sample analysis. The utility
does not presently have a field
kit for nitrate analysis, but
plans to purchase one in the near
future. The operator reported
that the unit has been trouble
free after some startup problems
were remedied. No operating cost
data were available at the time
of the site visit.
MCFARLAND MUTUAL WATER COMPANY
In cooperation with the U.S.
EPA’s Drinking Water Research
Division, Cincinnati, Municipal
Environmental Research Laboratory
(MERL), Boyle Engineering Corpora-
tion has carried on extensive
pilot studies at the I ftrland
Mutual Water Company. This
work, developing an optimized ion
exchange nitrate removal system
for a high sulfate well water,
has resulted in several discov-
eries that may be of significance
in designing new systems.
o Nitrate at McFarland was
readily removed from even
high sulfate waters at
flow loading rates greatly
in excess of those normally
recommended by equipment
and resin suppliers.
o High loading rates, coupled
with use of readily available
and adaptable equipment,
substantially reduces
expected capital cost for
a 1.0 MCD system.
o Packaged test kits, such
as manufactured by the
vendors shown in Table 3,
while not accurate enough
for testing for compliance
with standards can be
calibrated and used effec-
tively for pilot work and
process control.
McFarland’s water supply is
drawn from several wells. The
test well that is not presently
used for water supply contains
over 20 mg/i of nitrate nitrogen
and over 300 mg/l of sulfate
(as SO 4 ). Because of its very
high sulfate concentration, the
water would seemingly be quite
difficult and costly to treat
using ion exchange. Results of
the pilot study, however, show
that the water can be treated
economically, largely due to
the discovery that high flow
rate, partial regeneration and
equipment and resins that are
commercially available can be
used successfully.
Column Tests
Column tests, using resin
manufacturer’s recommendations,
were conducted for the 4 resins
tested at McFarland. The columns,
VII— 5
-------
TABLE 20
Item
PILOT COLUMN DATA
Data
Column Size
Bed Depth
Bed Volume
Test Flow Rate
Regenerant Flow Rate
Regenerant Composition
2 inches inside diameter
4 feet high
3.14 square inches cross sectional
area
24 inches
0.044 cubic feet
2.5 to 11.2 gpm/cu.ft. of resin
1.315 gallons/hour, 90 minutes
contact time
6 percent salt (NaC1) solution
2 inches in diameter and over
4 feet tall, were constructed and
operated as described in Table 20.
All of the resins tested were of
the strong base type. However,
they varied as to their specific
resin type. Selectivity and
porosity seems to have been
inconsistent (resistance to water
flow through bed).
Pilot Scale Unit
Based on results from column
testing, a pilot scale unit was
adapted from commercially availa-
ble equipment manufactured by the
Culligan Company. The unit, shown
schematically in Figure 22, Is
designed to handle relatively
high flow rates using a coarser,
semiporous resin. Several modi-
fications were made to the unit
to render it suitable for the
test, including improving the
inlet configuration and brine
consumption monitor. At the high
backwash/regeneration flows used,
it was also found desirable to
screen the inlet/backwash exit
manifold to prevent resin
washout.
Results from the high flow rate
loading of this unit demonstrated
that flows of 6 gpm per cubic
foot of resin are feasible with
this feed water . Other tests
indicated that varying regenera-
tion conditions result in
similar system performance over
a wide range of regenerant
consumption, suggesting that
operating costs could be sub-
stantially reduced with little
loss of efficiency by optimizing
regeneration parameters.
Proposed Design of 500,000 gpd
Full Scale System
Based on the pilot study, a
full scale system design was
developed and costs were esti—
VII— 6
-------
Plastic brine tank
ID. Softner tank
Hondhole
Figure 22. Pilot Scale Test Unit Used at McFarland
No. 2
salt bed
VI 1-7
-------
TABLE 21
Parameter
MCFARLAND, CALIFORNIA 0.5 MCD SYST 4 DESIGN PARAMETERS
Data
0.5 mgd
347 gpm
454 gpm
Resin Bed:
— depth
— diameter
— volume
— loading
— surface flow
— capacity/cycle
Regeneration:
— brine concentration
— brine flow
— rinse flow
— backwash
— total water flow
per cycle (back-
wash recycled)
36 inches
72 inches (each, two tanks)
85 cubic feet
6.67 gpm/cubic foot
20 gpm/square foot
126,500 gallons
6 percent
63 gpm, 846 gallons total, 15 minutes
49 gpm, 2225 gallons total, 45 minutes
140 gpm, 1400 gallons total, 10 minutes
3071 gallons
Flow Rate — average
maximum
VII—8
-------
TAELE 22
MCFARLAND, CALIFORNIA COST ESTIMATE FOR 0.5 MCD SYSTFI4 (1980)*
Number Description Cost
2 Fabricated resin tanks 72” x 60” (including
valves, electrical controls, and flow distri-
butors) $33,117
2 Alternators 640
2 4—inch reset meters 4,893
4 Solenoid kits 122
1 Brine pump 416
1 40—Ton brine maker 10’ X 14’6” (including level
controls, sight glasses) 15,430
170 Cubic feet resin @ $150/cu.ft. 25,500
Plumbing installation 2,000
Concrete pad 2,000
Startup and loading by vendor 1,000
TOTAL $86,818
* Does not include engineering, contingencies and housing. Based
on direct quotations from supplier for commercially available
equipment.
VII—9
-------
mated. Table 21 provides the
design parameters for the
500,000 gpd* system. Cost esti-
mates are given in Table 22, and
provide estimated Installed cost
less engineering and contin-
gencies. Even if these items
cost 30 percent of the capital
cost, the total cost would be
less than $113,000 (1980 dollars).
The cost of the McFarland system
could be much higher if equipment
housing is Included.
Operating costs were not directly
estimated in the report. However,
regenerant costs for the optimized
regenerating system apparently
would range from 4 to 6 cents per
1000 gallons, based on the data
presented.
The McFarland costs assume use of
commerically available equipment
with minimal Installation diff i—
culties. Housing Is not Included .
Costs were estimated In late 1980
based on direct quotations from
suppliers and installers. No
allowance has been made for
contingencies or engineering
costs.
* Treated flow.
v u—b
-------
REFERENCES
1. Hansen, S. P., S. P. Culp, and R. C. Gumerman, Estimating Water Treat
ment Costs: Volume 3 Cost Curves Applicable to 2500 gpd to 1 mgd
Treatment Plants , U.S. EPA 600/2—79—162, Cincinnati, Ohio 1969.
2. Comly, H. H., “Cyanosis in Infants Caused by Nitrates in Well
Water,” Journal of the American Medical Association , 129,
112 (1945).
3. Walton, G., “Survey of Literature Relating to Inf ant Methemoglo—
binemia Due to Nitrate Contaminated Water,” American Journal of
Public Health , 41, 986 (1951).
4. “Advisory Report on Health Effects of Nitrates in Water,” Illinois
Institute for Environmental Quality, January 1974, p. 17.
5. Lee, 0. H. K., “Nitrates, Nitrites and Methemoglobinmeia,” Environ-
mental Research , 3 pp. 484511, 1970.
6. A.P.H.S. Committe, “Water Supply: Nitrate in Potable Waters and
Methemoglobinemia,” APHA Yearbook , 40:110, May 1949—1950.
7. Drinking Water and Health , U.S. National Academy of Sciences,
Washington, D.C., Vol. 1, 1977.
8. Tannenbaum, S. R., A. J. Sinskey, M. Weisman, and W. Bishop,
“Nitrite in Human Saliva. Its Possible Relationship to Nitrosamine
Formation,” Journal of the National Cancer Institute , Vol. 53,
No. 1, July, 1974.
9. Cuter, C.A., “Removal of Nitrate from Contaminated Water Supplies
for Public Use——Interim Report,” U.S. EPA Grant No. R8059000l,
January 1981.
10. Mertens, J., P. Van den Winkel, and D. L. Massart, “Determination
of Nitrate in Water with an Ammonia Probe,” Analytical Chemistry ,
Vol. 4.7, No. 3, March 1975, P. 522.
11. Sorg, T. J., “Compare Nitrate Removal Methods,” Water and Waste
Engineering , December 1980, p. 26.
12. Clifford, D. A. and W. J. Weber, “Nitrate Removal from Water
Supplies by Ion Exchange,” U.S. EPA Grant 600/278052, June 1978,
p. 49.
13. Wheaton, R. M. and A. H. Seamster, A Basic Reference on Ion Exchange ,
Kirk—Othmer Encyclopedia of Chemical Technology , 2nd edition,
Vol. 11, pp. 871—899 (1966).
14. Data Leaflet — Duolite A104 , Diamond Shamrock Company, Functional
Polymers Division, Cleveland, Ohio (1978).
-------
15. Sheinber, M. R. and R. Krumholz, “Nitrate Analyzer Monitors
Ailing Well,” Water and Wastes Engineering Magazine , February 1979,
Pp. 3738.
16. Highway Engineering Handbook , First ed. , McGraw—Hill Book Company,
Inc., New York 1960.
17. Cater, C. A., “Removal of Nitrate from Contaminated Water Supplies
for Public Use, Final Report,” MERL/GRD, U.S. EPA Cooperative
Agreement No. CR—805900—01—02—03, Cincinnati, Ohio, March 1982.
18. Rasonl, Stephen E., B. C. Katz, C. E. Kimmel, J. B. Linder.
Nitrogen in Ground Water and Surface Water from Sewered and
Unsewered Areas, Nassau County, Long Island, NY USGS/WRD/WRI —
81 /022.
19. Gauntlet, R. B. and Craft, D. G., “Biological Removal of Nitrate
from River Water” Water Research Center, Medmenham/Stevenagi Labora-
tory, TR 98, May 1979.
-------
APPENDIX A
Abbreviations
BV bed volume (of resin in ion exchange)
cu. ft. cubic foot (volume)
sq. ft. square foot (area)
gr. grain (unit of mass)
gpm gallons per minute (flow)
gpw gallons per week
GPM gallons per minute based on daily total flow
GPMc gallons per minute based on weekly total flow
JTU Jackson Turbidity Unit
mg/i milligrams per liter (metric)
mgd million gallons per day
Q flow rate, in units indicated
gpm unit flow rate
Conversion Tables
VOLUME
1
Cubic Feet Gallons (U
.S.) Liters
28.3
cu. ft. 1 7.48
1
gallon (U.S.) 0.134 1
3.785
1
liter 0.353 0.264
1
MASS
Pounds Grams
Grains Kilograms
1
pound 1 453.6
7,000 7
1
gram 0.0022 1
15.43 0.01543
1
grain 0.000143 0.065
1 0.001
1
kilogram 0.143 65
1,000 1
CONCENTRATION
1
Gr./gallon Gr./cu.ft.
Lb./ga llon mg/l
0.143 17.17
gr./gal. 1 7.48
1
gr./cu.ft. 0.134 1
0.019 2.30
1
lb./gal. 7 0.936
1 119.841
1
mg/i 0.058 0.436
0.0000083 1
-------
APPENDIX B
The general equation that is used to determine the common basis quantity
of a substance in term of milliequivalents is given below:
Milliequivalents (meg ) — Cone of Substance mg/l
liter (1) — Equivalent Weight of
Substance in Milligrams
per Millequivalent (s—-)
meq
If you know any two of these values in the general equation, you can
determine the value of the third. For this example, the equivalent
weight is known, the concentration is known and by simple division,
the number of milliquivalents/liter can be calculated:
Given the following analysis:
1. Express the NO —N (nitrate as nitrogen) concentration of
15 mg/i as NO. NO 3 from Table 10, and milliequivalents of
nitrate per ifter.
Using the general equation:
(meg/i) = Cone of Substance (mg/i )
Equivalent Weight of
Substance (mg/meq)
Substitute the known values and solve for the unknown value:
meq nitrogen = 15 mg/i (N0 3 —N ) = 1.07
1 14.007 mg/meq
2. Express the milliequivalents of nitrogen as concentration of
nitrate:
meq/l = Conc of Substance
Equivalent Weight
of Substance
Therefore:
Cone of nitrate = meq/l x milliequivalent weight of substance
Cone of nitrate = 1.07 meq/l x 62.005 mg/meq
= 66.3 mg/i NO 3
From the example it can be seen that if it is desired to express the
concentration of one constituent (such as nitrogen) in terms of another
constituent (such as nitrate) two steps are involved:
1. Converting the original concentrations to the common base
mililequlvalents/llter, and
-------
2. Changing the common base to a concentration of the new
constituent.
This process can be simplified by writing one general equation that
combines both steps. The general equation is:
COnCB C0nCA x Nilliequivalent Weight B
Milliequlvalent Weight A
Therfore, to convert a concentration of 15 mg/i nitrate which is
reported as nitrogen to the equivalent concentration of nitrate as
nitrate, substitute the known values into the general equation above
as follows:
ConcB (N0 3 ) = ConcA (Conc as N) x Milliequivalent Weight B (NO 3 )
Milliequivalent Weight A (N)
Conc N0 3 = 15 mg/i ( 62.005 ) = 66.4 mg/i
(14.007)
Grains/gallon, a unit often used in ion exchange practice, is converted
to the meq/ml as follows:
gr (asCaCO)
3 65 mg 1 meg gal 1 .x . =
gal X gr X 50. 045 mg CaCO 3 X 3.78 1 x 1000 ml ml
solving
r (asCaCO)
3 meg
gal =
2910 m
------- |