,5709
MICROORGANISM REMOVAL FOR SMALL WATER SYSTEMS
Prepared by:
SMC Martin Inc.
900 West Valley Forge Road
P. 0. Box 845
Valley Forge, Pennsylvania 19482
Prepared for:
U.S. Environmental Protection Agency
Office of Drinking Water
Chester Pauls, Project Officer
401 M Street, SW
Washington, DC 20460
Contract No. 68-01-6285
June 1983
-------
-------
ACKNOWLEDGEMENT
This manual was prepared for U.S. Environmental Protection Agency under
Contract No. 68-01-6285. Mr. Chester Pauls, EPA Project Officer, provided
valuable guidance to the project. The manual was compiled by SMC Martin
Inc. in cooperation with the following:
G. Wade Miller
Wade Miller Associates
Arlington, VA
Rip G. Rice
Rip G. Rice, Incorporated
Ashton, MD
C. Michael Robson
Purdue University and
City of Indianapolis, IN
Daniel C. Houck
D.H. Houck Associates
Silver Spring, MD
The authors are particularly grateful to Prof. Harold W. Wolf, of Texas
A&M University, College Station, Texas, for his significant assistance
in developing and reviewing sections of this document dealing with
waterborne diseases, health and safety aspects of disinfectants, and
disinfection using chlorine and chloramines.
In addition, thanks are due to Craig A. Reynolds of Aqua Media Corpora-
tion for his significant assistance in sections of this report dealing
with disinfection using ultraviolet radiation.
-------
-------
CONTENTS
I. SUMMARY AND OVERVIEW
Purpose
Sources and Significance of Waterborne Disease
Methods of Reducing Risks of Occurrence of Waterborne
Diseases
Non-Treatment Alternatives
Treatment Methods
National Interim Primary Drinking Water Regulations
(NIPDWR)
Disinfectant Costs
Funding Sources
Operation and Maintenance (O&M)
Health and Safety Aspects of Disinfectants
II. INTRODUCTION
Sources of Waterborne Diseases
Kinds of Waterborne Disease
The National Interim Primary Drinking Water
Regulations (NIPDWR)
The Maximum Contaminant Level (MCL) for Bacterio-
logical Contaminants
NIPDWR Mandated Coliform Sampling and Reporting for
Small Systems
Recordkeeping Requirements for Results of
Microbial Analyses
Significance/Implications of the Presence of
Coliforas and Disinfectant Residuals
Bacteriological Analyses
Disinfectant Residual Analysis
III. ASSURING SAFE, PATHOGEN-FREE DRINKING WATER
Non-Treatment Alternatives
Treatment Alternatives
Disinfection
Introduction
Disinfection With Chlorine
Disinfection With Chloramines
Disinfection With Chlorine Dioxide
Disinfection With Ozone
Disinfection With Ultraviolet Radiation
IV. DISINFECTION SYSTEM DESIGN
Introduction
Optimal System Design
Selection of a Disinfectant
Chlorination System Design
Chlorine Dioxide Systems Design
Chloramination Systems Design
1-1
1-1
1-1
1-2
1-3
1-3
1-4
1-5
1-5
1-7
1-7
II-1
II-l
II-1
II-2
II-4
11-5
II-7
11-13
11-14
11-15
II I-1
III-l
III-5
III-5
II1-5
III-6
111-16
111-20
111-24
111-29
IV-1
IV-1
IV-1
IV-2
IV-3
IV-10
IV-17
-------
CONTENTS
(Continued)
IV. (Continued)
Ozone Disinfection Systems Design
Ultraviolet Radiation Systems Design
Safety Provisions For Working With Disinfectants
Associated Design Considerations
V. COST ESTIMATING PROCEDURES AND FUNDING SOURCES
Cost Estimating Procedures
Construction Costs
Operation and Maintenance Costs
O&M Cost Basis and Assumptions
Funding Sources
VI. OPERATION AND MAINTENANCE
Introduction
Operation and Maintenance Practices
Manuals, Equipment, and Supplies Required
Monitoring
Preventive Maintenance
Emergency Procedures
Good Sanitary Practices
Safety Procedures
NIPDWR Compliance
VII. CASE HISTORIES
White Haven, Pennsylvania
Hamilton, Ohio
Strasburg, Pennsylvania
REFERENCES
IV-17
IV-26
IV-27
IV-30
V-l
V-l
V-l
V-4
V-4
V-8
VI-1
VI-1
VI-1
VI-3
VI-3
VI-6
VI-6
VI-7
VI-9
VI-11
VI I-1
VI I-1
VI1-4
VI I-7
APPENDICES
-------
LIST OF FIGURES
Figure
1
6
7
10
11
12
13
Reporting procedures - Microbiological
Contaminants - Membrane Filter for
Single Samples
Reporting Procedures - When Calculating
Monthly Membrane Filter Results
Reporting Procedures - Microbiological
Contaminants - Multiple-Tube
Fermentation Method (10 mL) '.
Reporting Procedures - When Calculating
Monthly Multiple-Tube Fermentation
(10 mL) Results
Reporting Procedures - Microbiological
Contaminants - Chlorine Residual
Factors Contributing to Assuring Safe,
Pathogen-Free Drinking Water
Distribution of Hypochlorous Acid and
Hypochlorite Ions in Water at Different
pH Values and Temperatures
Graphical Representation of the Breakpoint
Chlorination Reaction
Concentration of Chlorine as HOC1 Required
for 99 Percent Kill of E. Coli and Three
Enteric Viruses at 0 to 6°C
Comparison of the Germicidal Efficiency of
Hypochlorous Acid, Hypochlorite Ion and
Monochloramine for 99 Percent Destruction
of E. Coli at 2 to 6°C
Proportions of Mono- and Dichloramine
(NH Cl and NHC1 ) in Water Chlorination
witn Equimolar Concentrations of Chlorine
and Ammonia
Typical Corona Cell Ozone Generator Configuration
Schematic Diagram of Ultraviolet Radiation
Disinfection Systems
11-8
II-9
11-10
11-11
11-12
III-2
III-8
III-10
III-ll
111-13
111-18
IH-25
111-31
-------
LIST OF FIGURES
(Continued)
Figure
14 Solution Feed Gas Chlorination System
15 Automatic Flow-Proportional Chlorine Dioxide
System; Generation from Chlorine and
Sodium Chlorite
16 Equipment Arrangement for Generating Chlorine
Dioxide from Hypochlorite and Acid
17 CIFEC Chlorine Dioxide System
18 Rio Linda Chemical Company, Inc. Acid/NaCIO
CIO Generator 2
19 Preengineered, Skid-Mounted Ozone Generation
system
20 Different View of Skid-Mounted Ozone
Generation System
21 The Four Basic Components of an Ozonation
System
22 Air Preparation Unit for Ozone Generation
23 Two-Compartment Ozone Contactor Using Porous
Diffusers
24 Schematic of Treatment Process at
White Haven, PA
25 Schematic of Treatment Process at Hamilton, OH
26 Schematic of Treatment Process at
Strasburg, PA
Page
IV-5
IV-11
IV-13
IV-15
IV-16
IV-19
IV-20
IV-21
IV-22
IV-24
VI1-3
VI1-5
VII-9
-------
LIST OF TABLES
Table
I Comparison of Water Disinfectants !
II Some Waterborne Illnesses and Causative Agents
III Bacteriological Samples Required Per Served
Population
IV MPN Index and 95% Confidence Limits for Various
Combinations of Positive and Negative Results
When Five 10-mL Portions Are Used
V Some Suppliers of Chlorine Residual Test Kits
VI Major Manufacturers of Gaseous Chlorine
VII Some Gas Chlorinator Manufacturers
VIII Partial Listing of Chlorine Dioxide Equipment
Suppliers
IX U.S. Ozonation Systems Suppliers
X Major Suppliers of Ultraviolet Radiation Equipment
XI Physiological Effects of Chlorine, Ammonia and Ozone
XII Example of a Partial Functional Numbering System
For a Water Treatment Plant
XIII Capital Recovery Factors for Some Combinations
of Interest (i) and Financing Period (n)
XIV Availability of Disinfection System Documents
Page
1-6
II-3
11-6
11-16
11-17
IV-4
IV-6
IV-12
IV-27
IV-28
IV-30
IV-32
V-5
VI-4
-------
-------
I. SUMMARY AND OVERVIEW
This section provides a summary
of all the information which
follows in the remaining chapters.
The document itself is divided
into eight sections plus appen-
dices. It traces pertinent
subjects from microorganism
control in sources of raw water
supply, through treatment control
technologies, cost estimating
techniques, and proper operation
and maintenance procedures for
each control technique discussed.
It concludes with a series of
short case histories representing
"success stories" of the control
technologies discussed herein for
small water systems.
PURPOSE
This document is designed pri-
marily for use by owners and
operators of small water systems,
those producing 500,000 gallons
per day or less and serving less
than 5,000 persons. Other ex-
pected users are municipal man-
agers and consulting engineers
retained by utilities. Its
primary purpose is to assist
personnel of small water systems
to understand the importance of
microorganism control and to
explain the design concepts, cost
estimating techniques, and opera-
tional considerations associated
with current technological ap-
proaches for maintaining such
control.
There are many small water systems
that each year exceed the bacter-
iological Maximum Contaminant
Level (MCL) contained in the
National Interim Primary Drinking
Water Regulations (NIPDWR).
Recognizing this as a critical
problem, the Environmental Protec-
tion Agency has sponsored the
development of this document to
explain:
1) why microorganism control is
important;
2) theories of microorganism
control;
3) process options for micro-
organism control;
4) design procedures for micro-
organism control;
5) process control methods;
6) operation and maintenance
procedures;
7) methods of estimating costs
for control processes.
This document discussing microor-
ganism control is one of a series
of five such documents being
developed by EPA* The other four
deal with turbidity removal,
radionuclide removal, nitrate
removal, and regionalization of
small water supply systems.
SOURCES AND SIGNIFICANCE OF
WATERBORNE DISEASE
Waterborne diseases can result
when humans come into contact
with waters which contain harmful
microbial organisms called pathogens.
These organisms may overcome the
natural defenses of the body and
cause disease. Prior to the
introduction of chlorine as a
water disinfectant in this country
in 1908 and its subsequent wide-
spread use in the U.S. and other
countries, waterborne diseases
such as cholera and typhoid fever
were prevalent. Other ailments
and infectious diseases also can
1-1
-------
result from consumption of con-
taminated drinking waters. The
most common of these are gastro-
enteritis, dysentery, and infec-
tious hepatitis. Whereas these
infections are less likely to be
fatal for the general public than
are typhoid fever or cholera,
they can cause prolonged illness
and severe discomfort to the
individuals infected, and death
among sensitive individuals, such
as infants, the already infirm,
and the elderly.
The fact that each of these
diseases can be transmitted by
drinking water is well known.
Typically, the disease-causing
organisms various types of
bacteria, viruses, and cysts
enter the water as a result of
unsanitary practices. The most
common causes of contamination
are from human and animal waste
deposits in the watershed, leaking
sewers or septic tanks, cross-
connections with other sources of
water, and back-siphonage resulting
from negative pressure in the
water distribution system.
As a way of illustrating the
widespread nature and significance
of waterborne diseases, consider
that in 1980 more than 580 small
water supply systems were persist-
ent violators (were in violation
more than four months during the
year) of the national bacteriolog-
ical MCL, and another 5,400 were
intermittent violators (were in
violation less than four months
during the year). During the
period 1946-1970, there were
53 outbreaks of waterborne infec- ,
tious disease due to typhoid, but
there were 297 outbreaks attrib-
uted to other bacterial or viral
agents; these numbers probably
represent only the "tip of the
iceberg", however, since sporadic,
random cases of gastroenteritis
generally go unreported (1), A
General Accounting Office report
on drinking water (2) notes that
the incidence of waterborne
diseases has increased since the
early 1950's. "From 1961 through
1978 drinking water caused 407 out-
breaks of disease or poisoning
resulting in 101,243 recorded
illnesses and at least 22 deaths",
the GAO report states.
METHODS OF REDUCING RISKS OF
OCCURRENCE OF WATERBORNE DISEASES
Some organisms which cause disease
in man originate with the fecal
discharges of infected individuals.
Since it is not practical to
monitor and control the activities
of human disease carriers, it is
necessary to exercise precautions
against contamination of a normally
safe water source, to institute
treatment methods which will
produce a safe water, and to
insure protection of the treated
water during storage and distribu-
tion from becoming recontaminated (3).
Protection of the water source is
the first line of defense against
microbial pollution. In protecting
a water source, whether it be a
ground or surface source, the
importance of conducting periodic
sanitary surveys cannot be over-
emphasized. Such sanitary surveys
consist of thorough investigations
of the essential elements which
are a part of or can impact on a
water supply.
Water distribution systems also
may be potential sources of
bacterial contamination. The
three most common ways for bac-
teria or viruses to enter the
distribution network are through
treated water which has not been
1-2
-------
adequately disinfected, by cross-
connections, or by broken or
leaking water lines. Other
points of potential contamination
are back-siphonage and openings
or defects in storage reservoirs
which allow entrance of small
animals, such as rodents, snakes,
birds, or insects.
Source protection, conducting
sanitary surveys, protection of
storage reservoirs, working to
eliminate cross-connections and
back-siphonage, and prompt repair
of broken or leaking water lines
all help to prevent contamination
and reduce risks of waterborne
diseases. Pretreatment techniques
to remove suspended particulate
matter (turbidity) from the raw
water and disinfection to kill
living microbes are necessary to
reduce risks to a minimum, however.
NON-TREATMENT ALTERNATIVES
Installment of a complete treat-
ment process to solve a micro-
organism problem may not always
be economically feasible. If
this is the case, two non-treatment
alternatives should be investi-
gated. The first is to try to
find a new water source. This
might be difficult and expensive
for larger water supply systems,
but may be quite feasible for
small systems which have ground-
water sources. The problem may
be solved by locating wells in an
area removed from the source of
contamination (e.g., leaking
sewer line or adjacent sanitary
landfill).
The second alternative is to
consider joining a regional
system. Regionalization is a
concept which has been successful
in several states, particularly
in Pennsylvania, Washington,
Texas, and Alabama. The concept
is one of sharing resources in
order for the smaller water
supply system to be able to
afford highly skilled personnel
on a part-time basis and thereby
reduce operating and management
costs. Regionalization does not
necessarily mean loss of decision-
making authority for a municipality,
as has been implied in the past.
The subject of regionalization is
discussed in detail in a companion
EPA document entitled, Regionaliza-
tion for Small Water Systems.
TREATMENT METHODS
The "conventional" water treatment
process employed widely in the
United States consists of chemical
coagulation, settling or clarifica-
tion, filtration, and disinfection.
The basic objective of the first
three unit processes is to remove
solid or colloidal particles from
the raw water. Detailed discus-
sions of filtration and other
treatment processes can be found
in a companion EPA treatment
document entitled, Turbidity
Removal for Small Water Systems.
The most important fact for the
reader to retain is that the
effectiveness of the disinfection
process increases with the effi-
ciency of the turbidity removal
processes. Microorganisms can
become attached to the surfaces
of turbidity-causing solid par-
ticles (adsorbed), or be enveloped
by these particles, thereby being
protected from contact with the
disinfecting agent. Thus, the
disinfection process may not
produce a finished water of
acceptable quality unless the
turbidity-causing contaminants
are removed from the water.
It also should be appreciated
that costs to disinfect turbid
waters are higher than costs to
1-3
-------
treat clear waters. This is
because the chlorine or other
disinfectant employed can react
with the organic and other mate-
rials contained in the solid
particles. Thus, instead of
attacking only the microorganisms,
some quantity of the disinfectant
will be consumed in extraneous
reactions which have no relation-
ship to disinfection.
Disinfection
Once the turbidity-causing sus-
pended matter has been removed,
the treated water can be disin-
fected efficiently. Disinfection
can be defined as the removal or
inactivation of infectious
microorganisms.
As a result of its relatively low
cost and other desirable proper-
ties, chlorine currently is the
most commonly used disinfectant.
However, chlorine reacts with
certain organic constituents of
raw water supplies (humic and
fulvic acids, for example) to
produce halogenated compounds
which impart undesirable tastes
and odors (chlorophenols, for
example) to the treated water.
Also, trihalomethanes (THMs) may
be formed as a result of chlori-
nation. Because THMs currently
are of public health concern and
are regulated at a level of
0.10 mg/L MCL (4) for large water
supply systems, there is consider-
able interest in the use of
so-called "alternative disinfec-
tants". None of these have as
many desirable properties as does
chlorine; therefore the use of
each should be assessed by each
water supply system in terms of:
o need to modify the pre-
and/or post-disinfection
processes;
o ability of alternative
disinfectant/modified treat-
ment process to meet all
required standards;
o costs.
Disinfectants other than chlorine
or hypochlorites, currently in
use include
o chlorine dioxide,
o chloramines,
o ozone, and
o ultraviolet light.
The number of water treatment
facilities using these alternative
disinfectants is small when
compared to the number using
chlorine. However, each disinfec-
tant has grown in popularity in
recent years, and their use can
be expected to continue to increase
as more data demonstrating their
advantages and disadvantages are
developed. A detailed discussion
of the chemistry, theory of use,
and methods of application of
each disinfectant is included in
Section 3, DISINFECTION. Methods
for estimating the costs associated
with each of these disinfectants
are provided in Section 5, COST
ESTIMATING TECHNIQUES AND FUNDING
SOURCES, and Appendix A.
NATIONAL INTERIM PRIMARY DRINKING
WATER REGULATIONS (NIPDWR)
The NIPDWR were promulgated by
the Environmental Protection
Agency in 1975 as part of the
Safe Drinking Water Act, and
became effective in June 1977 (5).
Maximum Contaminant Levels (MCLs)
are provided for five general
categories of impurities found in
raw water supplies. To date,
more than 20 MCLs have been
established, one of which deals
with bacteriological contaminants.
Another deals with trihalomethanes.
1-4
-------
Water suppliers are required by
the NIPDWR to collect a minimum
number of water samples each
month (depending on system size)
and have them analyzed for bac-
teriological contamination by a
state or EPA-approved laboratory.
The regulations also define the
steps which suppliers must take
in the event that test results
indicate contamination. These
steps include retesting and State
and possibly public notification.
DISINFECTANT COSTS
Total costs for the installation
and use of disinfection systems
are a function of capital costs,
operation and maintenance costs,
and chemical costs. Chapter 5
discusses these costs and pro-
vides a method to estimate total
disinfectant costs.
Of the disinfectants discussed in
this document, chlorine currently
is the least expensive, especially
in terms of capital equipment
costs. Chlorination systems also
are less expensive to operate
than are systems involving chlor-
amines and chlorine dioxide.
This is because these latter two
disinfectants, generated on-site
as required, involve the reaction
of chlorine with additional
chemicals, ammonia and sodium
chlorite, respectively.
Generally speaking, chlorine
dioxide generating systems are
about twice as expensive to
purchase and install as are
chlorination or chloramination
systems. Generation of chlorine
dioxide requires the reaction of
sodium chlorite solution with
hypochlorite solution or gaseous
chlorine. Formation of chloramines
requires simple addition of
either gaseous ammonia or a
solution of ammonium sulfate to
process waters containing hypo-
chlorite. Alternatively, hypo-
chlorite solution can be added to
process water containing ammonia
or ammonium sulfate. Thus, the
primary cost difference between
chlorination and chlorine dioxide
or chloramination systems is the
cost of additional chemicals.
Ozone currently is the most
expensive of the four chemical
disinfectants in terms of initial
capital equipment costs, which
amount to four to six times those
of gaseous chlorination systems.
However, once installed, ozone
generation equipment operates
solely by means of electrical
energy. Chemical costs are nil
and operating labor costs can be
very low, especially if a high
degree of instrumentation is
installed.
Ultraviolet radiation also is
generated on-site without chemi-
cals, requires electrical energy
only and little operating labor
and maintenance (cleaning of the
UV lamps). The life of UV gener-
ating bulbs is about one year,
after which their efficiency
decreases and new bulbs must be
installed. Installing a new bulb
is roughly equivalent to changing
a light bulb in terms of effort.
Table 1 shows various comparative
relationships between the disin-
fectants discussed in this report.
FUNDING SOURCES
Federal Sources
Federal funding programs for
support of local water systems
are few, the most prominent being
1-5
-------
TABLE 1
COMPARISON OF WATER DISINFECTANTS*
i
ON
Disinfectant
chlorine
(C12)
sodium
hypo chlorite
(NaOCl)
calcium
hypo chlorite
[Ca(OCl)2]
chloramine
chlorine
dioxide
(cio2)
ozone
(03)
ultra-
violet light
* These comoa
How Purchased
compressed
gas - 100%
available Cl
aqueous
solution -
5-15% avail-
able ci2
solid
prepared on-
site in
product
water
generated on-
site in
solution
generated on-
site in air
generated on-
site
risons eeneral 1 <
Equipment Required Capital Cost
to lower pressure
and add to water low
to meter
solution low
to prepare and
meter solution low
a) to lower pressure low
and add ammonia to
water; or
b) to meter aqua NH ;
c) to prepare and meter
ammonium sulfate
solution
CIO generator
system iow_
medium
air preparation,
ozone generator,
contactor and off-
gas destructor high
UV generating
system medium
7 a TO Kfl aarl r*r» K-a />+«*! « 1 J-J«4-.C _^.^^__
Operating
Chemical Cost Cost
low low
low low
low low
low low
medium low
low
nil (power)
low
nil (power)
Bacterial
Disinfection
Efficiency
high
high
high
lowest
second
highest
highest
high
applicable to cysts, such as Giardia lamblia.
-------
the Farmers Home Administration
(FmHA) combination grant/loan
program for financing of small,
rural water and sewer systems.
The total program funding level
in fiscal year 1982 (October 1,
1981-September 30, 1982) was
about $400 million. Most of this
money is made available through
state FmHA. offices in the form of
long-term, low interest loans.
Typical financial terms in the
past consisted of 40-year loan
periods at 5 to 7 percent interest
rates.
Little federal assistance other
than the FmHA program is expected
in the foreseeable future.
State Sources
As many as 17 states have some
type of funding program for water
systems and there is an increasing
trend developing in this area.
In 1981, the voters of both
Pennsylvania and New Jersey
approved sizeable state bond
issues for water supply improve-
ments. The State of Washington's
program to assist water systems
has been on-going since 1972.
Other states are expected to
develop funding mechanisms for
small water supply systems in the
near future.
OPERATION AND MAINTENANCE (O&M)
None of the systems discussed in
this document will operate contin-
uously without some regular and
planned attention from a water
treatment plant operator. There-
fore, the prudent water supplier
will require the disinfection
system vendor to provide start-up
assistance and training, and to
provide detailed O&M manuals for
the equipment. A schedule of
preventive maintenance activities
for the equipment should be
developed and plant operators
should be required to follow it.
Section 6 contains a discussion
of desirable operation and mainte-
nance procedures.
HEALTH AND SAFETY ASPECTS OF
DISINFECTANTS
Since disinfectants used in
potable water systems also are
strong chemical oxidants, operators
must learn to handle these toxic
and potentially injurious sub-
stances properly. Safety training
and emphasis on precautionary
plant operating measures to
ensure personnel safety are of
extreme importance. Of the
chlorination chemicals discussed,
sodium and calcium hypochlorites
generally are the safest to use
because they are purchased in
liquid and solid forms,
respectively.
Gaseous chlorine was used as a
chemical warfare agent during
World War I. Short exposure to
gaseous vapors of chlorine can
cause injury or even death.
Emphasis on correct methods of
chang-ing chlorine cylinders,
ensuring proper ventilation and a
separate room for handling chlorine
which has provisions for rapid
access to the outdoors, and
having safety equipment such as
gas masks readily available are
of utmost importance.
Sodium chlorite, the chemical
from which chlorine dioxide is
generated, is incendiary in its
pure, dry state. Thus, any
spills of chlorite solutions
should be cleaned up quickly, but
never with paper or rags, which
1-7
-------
after contacting the wet chlorite
can become combustible after the
water has evaporated.
Once generated, chlorine dioxide
should remain in aqueous solution
and not be allowed to escape into
the air, where it can present an
explosion hazard.
Ammonium sulfate is a harmless
powder which exhibits no unusual
hazards, such as toxicity, fire
or explosion. Liquid ammonia is
supplied in cylinders under
pressure from which the gaseous
material is volatilized. Gaseous
ammonia is a choking gas, ingestion
of which can cause temporary
upsets to human digestive systems.
Precautions should be taken to
avoid breathing either ammonia or
chlorine vapors.
Ultraviolet radiation can be very
damaging to the skin and especially
damaging to human eyes. This
fact is recognized by UV systems
suppliers, who normally design
their systems so that it is not
possible to see any light emanating
from the unit during its operation.
Since the UV portion of the
spectrum is invisible, care
should be taken to avoid looking
into UV generating units unless
the power is turned off. Light
generated by UV systems during
operation is similar in effect,
although not as intense, as that
given off during arc welding of
metals.
Ozone is a very powerful oxidizing
agent which can cause temporary
upsets to human digestive systems
in low concentrations, but can be
fatal at high concentration. On
the other hand, commercially
available ozone generating systems
are safe to operate since the
operator never has to come into
contact with the chemical. If a
leak of ozone is detected, simply
shutting off the electrical power
to the generator will halt the
production of ozone. An instru-
ment to monitor the level of
ozone in ambient air in the room
housing the ozone generation
and/or contacting equipment can
be installed. Exposure to as
little as 0. 3 to 0.4 ppm concen-
trations of ozone in air can
cause light-headedness and nausea.
However, recovery from short term
exposures to ozone, even for
periods up to an hour, to date
has not been reported to be other
than complete.
1-8
-------
II. INTRODUCTION
This section discusses sources
and kinds of waterborne diseases,
the National Interim Primary
Drinking Water Regulations, and
the requirements for sampling and
monitoring, types of microbio-
logical analysis, record keeping
and reporting of results, and the
concept of disinfectant residuals.
SOURCES OF WATERBORNE DISEASES
Waterborne illness may occur when
water containing a sufficient
concentration of harmful microbial
organisms (called pathogens) is
consumed or otherwise contacted
intimately. The pathogens of
concern may be one or more
species of bacteria, viruses,
protozoa, or even other forms
such as fungi, rickettsia, or
helminths. Typically, they enter
a raw water supply as a result of
wastewater discharges, waste
deposits, or leaking sewers or
septic tanks. Sometimes they may
even enter a finished water
distribution system via a connec-
tion with a contaminated source
or system (cross-connection)
which subsequently allows reversal
of flow (back-siphonage).
Water supplies should be obtained
from the best water source avail-
able. It may be a surface or a
groundwater source or even a
combination of the two. The
source water should be consist-
ently adequate in quality and
quantity. Quality character-
istics might be especially criti-
cal during periods of unusual
stress, such as during heavy
rainfall runoff, extensive drought,
or upstream spills. Wastewater
discharges into sources of drinking
water must comply with all local,
state, and federal regulations.
This includes appropriate disinfec-
tion for contaminated or poten-
tially contaminated discharges.
Most outbreaks of waterborne
illness occur when using untreated
or inadequately treated ground-
water supplies. Popular myths
about the purity and safety of
groundwaters tend to lull users
into a false sense of security.
Although the various states have
different regulations concerning
water treatment and disinfection,
the strategy recommended by water
supply professionals is to disinfect
all groundwater supplies and to
clarify, filter, and disinfect
all surface water supplies and
groundwater supplies containing
excessive turbidity.
KINDS OF WATERBORNE DISEASE
Present day control strategies
for the prevention of waterborne
disease historically are linked
to the control of typhoid fever,
which is caused by a bacterium.
However, it is now known that
organisms such as cysts and
viruses are active agents in
waterborne disease outbreaks.
Both treatment and monitoring
techniques must be designed to
accommodate these differences
successfully.
Even in a contaminated raw water
source, the causative agent, such
as the typhoid organism, would be
extremely difficult to locate
among the myriad of other organisms
that would be present. Hence, an
easily found substitute (called a
II-1
-------
'surrogate') was developed to
indicate the likely presence of
disease-causing organisms. The
coliform group of organisms,
which are common inhabitants of
the intestinal tracts of mammals
(warm blooded animals) was chosen.
This surrogate approach is based
on the theory that if coliform
organisms are present at a high
enough concentration, then some
intestinal pathogen also might be
present, and therefore the bac-
terial quality of the water is
questionable.
The surrogate approach has been
highly successful in helping
overcome the scourge of waterborne
typhoid fever. As waterborne
typhoid fever gradually came
under control over the years, it
was observed that the incidence
of other illness also decreased (1).
This occurred because many other
disease-causing intestinal microbial
agents are destroyed during the
disinfection process, in spite of
the fact that some are more
resistant to disinfection methods
than is the coliform indicator
organism, when pure strains of
organisms are tested.
Table II shows some common water-
borne illnesses and the agents
that cause them (6). The organism
most commonly implicated in
recent documented waterborne
outbreaks is Giardia, an organism
of which very few people are even
aware. Giardiasis is usually a
relatively mild illness causing
cramps, diarrhea, and the typical
distress of intestinal upset.
However, in some individuals it
is a very severe, debilitating
disease.
Other diseases also can be water-
borne under unusual circumstances.
For example, tuberculosis has
occurred in children who fell
into a sewagecontaminated canal (7),
Nosocomial infections (hospital
infections) have occurred because
Pseudomonas aeruginosa developed
in hospital water systems (8). A
few strains of the coliform
bacterium Escherichia coli
called 'opportunistic pathogens'
may cause diarrhea and other
diseases.
Because there is so much variabil-
ity among people and organisms,
there can be no "safe" level of
contamination. Transmission of
waterborne disease can be minimized
by appropriate treatment and
disinfection, protected water
supply distribution systems
always under adequate pressure,
and a vigilant program against
cros sconnect ions.
THE NATIONAL INTERIM PRIMARY
DRINKING WATER REGULATIONS (NIPDWR)
When Congress enacted the Safe
Drinking Water Act in 1974, it
included as one of five major
provisions the development of
primary regulations for the
protection of public health. As
part of Section 1412 of the Act
directing it to develop such
regulations, EPA promulgated the
National Interim Primary Drinking
Water Regulations (5) in 1975,
which became effective on June 24,
1977. The NIPDWR established
maximum contaminant levels (MCLs)
for several general categories of
contaminants commonly found in
raw water supplies. A maximum
contaminant level is defined as
"the maximum permissible level of
a contaminant in water which is
delivered to the free flowing
outlet of the ultimate user of a
public water system". The only
exception to this definition is
II-2
-------
TABLE II
WATERBORNE ILLNESSES AND CAUSATIVE AGENTS (6)
Illness
Agent
Typhoid fever
Paratyphoid fever
Bacillary dysentery
Cholera
Amoebic dysentery
Infectious hepatitis
(Hepatitus A)
Giardiasis
Gastroenteritis
Salmonella typhi, (bacterium)
Salmonella paratyphi, (bacterium)
Shigella spp., (bacterium)
Vibrio cholerae, (bacterium)
Endamoeba histolytica, (protozoan)
Hepatitis A Agent (virus)
Giardia lamblia, (protozoan)
Rotavirus, Norwalk Agent (viruses)
Campylobacter jejuni, Yersinia
enterocoliticus (bacteria), as
well as other bacteria and viruses
that turbidity levels are measured
at the point of entry to the
distribution system as opposed to
the extremities.
As part of the implementation
strategy for the regulations,
each state and territory has been
given the option of accepting
primary enforcement responsibil-
ity (primacy) for the regulations.
As of mid-1982, more than 50 of
the 57 states and territories had
assumed primacy. In those few
states which have not assumed
primacy, EPA operates the program
and enforces the regulations.
The NIPDWR sets limits on the
kinds and amounts of contamina-
tion allowed in drinking water,
defines monitoring and reporting
requirements, and requires systems
that do not meet the regulatory
requirements to publicly notify
users. MCLs have been established
for more than 20 selected organic
chemicals, inorganic chemicals,
turbidity, microbiological and
radiological contaminants. These
contaminants were selected because
their presence in concentrations
above their respective MCLs are
known, or are strongly suspected,
to cause adverse effects on human
health.
Each contaminant has specific
monitoring and reporting require-
ments. By law, all water systems
are responsible for collection of
finished water samples, for
having them tested by an EPA or
state approved testing laboratory,
and for having copies of the
results sent to the appropriate
state or federal agency.
II-3
-------
The NIPDWR makes a distinction
between the monitoring and report-
ing requirements applicable to
community and non-community
systems. A community system is
defined as one having at least
15 service connections used by
year-round residents or regularly
serving at least 25 year-round
residents. Mobile home parks,
small residential areas, and
apartment communities fall into
this category. A non-community
system has at least 15 service
connections used by travelers or
intermittent users at least
60 days per year, or serves an
average of at least 25 individuals
at least 60 days per year. Water
supplies for campgrounds, some
restaurants, motels, factories,
service stations, and schools
fall into this category.
Community water systems must
monitor and report levels of all
contaminants listed in the NIPDWR.
For coliforms, community systems
must test monthly; however the
State may reduce the sampling
frequency, based on a sanitary
survey of a system that serves
less than 1,000 persons from a
groundwater source, except that
in no case shall it be reduced to
less than once per quarter.
Non-community public water systems
must monitor and report levels of
nitrate, turbidity (where surface
waters are used) and microbial
contaminants. Coliform analyses
must be conducted quarterly, but
this frequency may be modified by
the State based on the results of
sanitary surveys. For the non-
community systems, the remaining
contaminants must be monitored
and reported at intervals speci-
fied by the State. Generally,
states require reporting on a
timely basis, depending upon the
contaminant.
THE MAXIMUM CONTAMINANT LEVEL
(MCL) FOR BACTERIOLOGICAL
CONTAMINANTS
In reviewing this discussion of
the bacteriological MCL, the
reader should be aware that
individual states may have regu-
latory requirements in addition
to those of the NIPDWR.
The NIPDWR allows approved labora-
tories to analyze bacteriological
samples using one of two methods,
either the membrane filter technique
or the multiple tube fermentation
method, and MCLs have been estab-
lished for both methods. The
multiple tube fermentation method
allows either 10 mL or 100 mL
sample portions to be used in the
coliform multiple tube fermentation
test. The regulations establish
requirements both for single
samples and for the average
arithmetic mean of all samples
tested each month regardless of
which method is used. The require-
ments when using each method of
analysis are summarized below:
MCL Using the Membrane Filter
Method
o For all systems, the number
of coliform bacteria shall
not exceed one colony per
100 mL as the arithmetic
mean of all samples examined
per month.
o For systems which collect
and examine less than 20 sam-
ples per month, the coliform
level must not exceed four
colonies per 100 mL sample
in more than one sample per
month.
o For systems that collect and
examine more than 20 samples
II-4
-------
per month, the coliform
level must not exceed four
colonies per 100 ml in more
than five percent of the
samples.
MCL Using the Multiple Tube
Fermentation Method (10 mL sample
portions)
o For all systems, coliforras
must not be present in more
than 10 percent of the total
tubes per month.
o For systems which examine
fewer than 20 samples per
month, coliform bacteria
shall not be present in
three or more portions in
more than one sample, or
o For systems that examine
more than 20 samples per
month, coliform bacteria
shall not be present in
three or more portions in
more than five percent of
the samples.
MCL Using the Multiple Tube
Fermentation Method (100 mL
sample portion)
o For all systems, coliforms
must not be present in more
than 60% of total tubes in
any month.
o For systems that examine
less than five samples per
month, coliforms shall not
be present in more than one
sample, as indicated by gas
in all five tubes.
o For systems that examine
five or more samples per
month, coliforms shall not
be present in more than 20%
of the samples, as indicated
by gas in all five tubes.
For community and non-community
systems that are required to
sample at a rate of less than
four per month, compliance shall
be based upon sampling during a
3-month period, except that, at
the discretion of the State,
compliance may be based upon
sampling during a one-month
period.
Significant Facts For the Small
System Owner/Operator
The wording of the bacteriological
MCL is very complex. Since most
small systems are expected to
retain an outside certified
laboratory to collect and analyze
the samples, attempts to under-
stand all the complex language
may appear to be superfluous.
However, it is the owner of the
system who is responsible for
ensuring compliance with the law.
Therefore, some degree of under-
standing is necessary to insure
that:
1) the proper number of samples
is collected;
2) the meaning of test results
is comprehended; and
3) correct results are reported
to appropriate state and/or
federal offices.
NIPDWR MANDATED COLIFORM SAMPLING
AND REPORTING FOR SMALL SYSTEMS
The minimum number of routine
monthly coliform samples currently
required by the NIPDWR is given
in Table III. The number of
samples required is based upon
the population served. Although
the table shows that no less than
one sample is required each
month, it is possible for small
supplies serving 25 to 1,000 people,
II-5
-------
TABLE III
BACTERIOLOGICAL SAMPLES REQUIRED PER SERVED POPULATION
Served Population
Minimum Routine Monthly
Samples
25
1001
2501
3301
4101
4901
5801
- 1000
- 2500
- 3300
- 4100
- 4900
- 5800
- 6700
1
2
3
4
5
6
7
which use groundwater, and having
a history of little or no coliform
contamination, to obtain their
state's approval to sample and
report only quarterly. Two types
of reports are required by the
NIPDWR:
1) suppliers must report the
results of routine bacterio-
logical analyses to the
state on a timely basis;
2) if the MCL is exceeded and
confirmed by a follow-up
check sample, suppliers must
notify both the state and
the water consumers.
The public notification require-
ments for community and non-
community systems differ signifi-
cantly. See Reference 5 for a
detailed discussion of these
requirements.
A positive coliform sample is not
a matter to be taken lightly
it is a basis for genuine concern.
Good sanitary engineering prac-
tices dictate a series of succes-
sive steps to determine the
seriousness of the problem. In
addition, the NIPDWR requires the
following minimum procedures:
1) when the number of coliforms
exceeds four per 100 mL,
when using the membrane
filter procedure, at least
two consecutive daily check
samples shall be collected
and examined from the same
sampling point. Additional
check samples shall be taken
daily until the results from
at least two consecutive
check samples show less than
one coliform per 100 mL;
2) when coliforms occur in
three or more 10-mL portions
of a single sample, when
using the multiple tube
procedure, the same procedure
as above shall be followed
until the check samples show
no positive tubes;
3) when coliforms occur in all
five of the 100-mL portions
of a single sample, at least
two daily check samples
shall be collected plus
additional check samples
daily until two consecutive
II-6
-------
samples show no positive
tubes.
If the check samples persist in
being positive, a process of more
intensive sampling and system
checking must begin if it has not
already been initiated.
Some states allow water systems
to reduce the number of bacterio-
logical samples normally required
by up to 75%, provided that
certain other conditions are met:
1) the system must undergo a
sanitary survey;
2) chlorine residual samples
are to be taken at points
representative of the distri-
bution system at a frequency
of at least four per substi-
tuted coliform sample;
3) chlorine residuals are
determined at least daily;
4) no less than 0.2 mg of free
residual chlorine* per liter
of water shall be maintained
throughout the distribution
system;
5) when a free chlorine residual
of less than 0.2 mg/L is
found, the chlorine residual
of the water must be retested
at the same point within the
hour;
* After the chlorine demand of a
water has been satisfied, the
amount of chlorine which can be
measured in solution is called
'free residual chlorine*. This
concept will be discussed later
in this Section.
6) if the resampling shows a
residual of less than 0.2 mg/L,
the state shall be notified
and a sample for coliform
analysis must be collected
at that same point, also
within the hour. These
results must be reported to
the state in a timely manner.
Figures 1 and 2 summarize the
current reporting procedures for
single samples and arithmetic
mean values for samples analyzed
monthly, respectively, by the
membrane filter method. Figures 3
and 4 summarize the current
reporting procedures for the
corresponding samples analyzed by
the multiple tube fermentation
method (10 mL). Figure 5 summarizes
the current reporting procedures
for chlorine residuals (9) when a
water supply system elects to
substitute chlorine residual
monitoring for bacteriological
monitoring.
RECORDKEEPING REQUIREMENTS FOR
RESULTS OF MICROBIOLOGICAL ANALYSES
Good recordkeeping is the corner-
stone of effective long-term
operation of quality drinking
water supplies. Records provide
historical bases from which to
interpret current data and help
prevent recurring problems.
Records provide a basis for
answering information requests
from the public, and may prove
invaluable in the event of legal
action.
It is the responsibility of every
water supplier to keep adequate
records and to ensure that the
reporting requirements of the
primary drinking water regulations
are met. Results of bacteriological
II-7
-------
r
1 If 4 colonies)!
is not exceede
»
Routine
reporting
required
Take Sample
!
1
30m llf 4 colonies/100ml
d is exceeded
1
At least two consecutive
daily check samples must
be taken from the same
sampling point
1
If none of the check
samples contain one or
more colonies/100 ml
1
Routine
reporting
required
I
If any of the check
samples contain one or
more colonies/100 ml
Report this to
the state with-
in 48 hours
1
Collect additional check samples
on a daily basis or at a frequency
established by the state, until the
results obtained from at least 2
consecutive check samples show
less than one conform colony/100 ml
Figure 1. Reporting Procedures - Microbiological Contaminants
Membrane Filter (7) for Single Samples
II-8
-------
I. Calculate
the Monthly
Average
Value
Using values from original
samples ONLY,' calculate
the monthly average value
II the monthly average of
the daily samples does not
exceed 1 colony/100 ml
If the monthly average of
the daily samples exceeds
1 colony/100 ml
II. Determine the
Number of Times
4 Colonies/ml
Was Exceeded
Using values from original
samples ONLY, determine the
number of times 4 colonies/
100 ml was exceeded"
If the MCL'"
is not exceeded
If theMCL"'
is exceeded
Check sample values are not to be used when calculating the monthly average. ,Reler to the mem-
brane (liter recordkeepmg form shown in Appendix 4 J
For systems taking fewer than 20 sample* per month, merely count the number ot samples
exceeding 4 colonies/100 ml.
For systems taking 20 or more umptn pet month, calculate the percentage of samples exceed-
ing 4 colonies/tOO ml. (Refer lo the membrane luler recordkeepmg lorm shown tn Appends 4}
"TheMCL states that conform presence shall not exceed 4 colonies/100 ml in more than one sam-
ple If fewer than 20 samples collected per month or 4 colonies /100 ml in more than 5% of the
simples if 20 or more are examined per month. Refer to the multiple-lube recordkeepmg form
shown in Appendix 4.
Figure 2. Reporting Procedures - When Calculating
Monthly Membrane Filter Results (7)
II-9
-------
I Take sample
At least two consecutive
daily check samples
must be taken from the
same sampling poiint
If none of the check
samples contain one or
more positive tubes
If any of the check
samples contain one or
more positive tubes
Collect additional check samples
on a daily basis or at a frequency
established by the state, until tne
results obtained from at least 2
consecutive check samples show no
positive tubes.
Figure 3. Reporting Procedures - Microbiological Contaminants
Multiple-Tube Fermentation Method (10 mL) (7)
11-10
-------
I. Calculate The
Monthly
Percentage
II. Determine the
Number of Times
3 or More Tubes
Were Positive
Using values from original
samples ONLY', calculate the
monthly percentage
Using values from original
samples ONLY*, determine the
number of times 3 or more
tubes were positive."*
If *0°b or less of the
tubes forthe month are
positive
If more than 10% of the
tubes for the month are
positive
II the MCL*"
is not exceeded
If the MCL"*
is exceeded
*ChecV7 sample values are not to be used where calculating the monthly percentages. (Refer to
Ihe mulliple lube recordkeeping lorm shown in Appendix 4.)
"For systems taking fewer than 20 sample* p«r month, merely count the number of samples
which contained 3 or more positive portions.
For systems taking 20 or more umples per month, calculate the percentage of samples con-
taining 3 or more positive portions.
The MCL stales thai no! more than 1 sample mav have 3 of more portions positive when lewe-
than 20 samples are examined per monlh OR not more than 5 ol the samples mav have 3 01
more portions positive when 20 or more samples are examined per month
Figure 4. Reporting Procedures - When Calculating Monthly
Multiple-Tube Fermentation (10 mL) Results (7)
-------
Take Sample
If the free chlorine
residual is 0.2 mg/i or
greater
If the free chlorine
residual is less than
0.2 mg/1
A check sample must be
taken within one hour
*
If check sample 1
indicates that the free
chlorine residual is 0.2
mg/l or greater |
*
Routine
reporting
required
1
If check sample indicates that
the free chlorine residual is
less than 0.2 mgn
1
Report this to
the state with-
in 48 hours.
1 AND
Take a sample coliform
bacteria! analysis from
that sampling point,
preferably within one hour
AND
Report the results of the
coliform test to the stale
within 48 hours
Figure 5. Reporting Procedures - Microbiological
Contaminants - Chlorine Residual (7)
11-12
-------
tests must be retained for at
least five years. The following
information must be collected to
meet minimum requirements:
1) date, place, time of sampling;
2) name of person who collected
the samples;
3) sample disinfectant concentra-
tion, whether it is routine
or a check, raw or treated
water, etc.;
4) date and place (laboratory)
of analysis, test method
used, results, and person
who performed the analysis.
A supplier may develop his own
form for this purpose or use the
standard forms included in Refer-
ence 5 and reproduced in Appendix B.
SIGNIFICANCE/IMPLICATIONS OF THE
PRESENCE OF COLIFORMS AND DISINFEC-
TANT RESIDUALS
There are two important indicators
of bacteriological safety in
drinking water systems:
o presence or absence of
coliforms;
o concentration of disinfecting
agent.
Presence Or Absence Of Coliforms
As stated previously, the coliform
organism normally is present in
the intestinal tract of all
mammals. Hence, whenever coliforms
are found to be present in drinking
water, the assumption can be made
that the possibility of intestinal
pathogens being present also
exists. The absence of coliforms,
however, does not guarantee that
pathogens are absent. The finding
of any coliforms in a finished
drinking water sample requires an
immediate response from the
operator to ensure that a more
significant problem does not
exist. Therefore, to assure good
quality of the water, plant
operating personnel must be
capable of obtaining routine and
check samples, reviewing treatment
facility operations, and checking
distribution system integrity.
A related matter of primary
importance is to determine if the
coliforms found actually were
present in the water system
sampled, or if they gained entry
to the sample via some pathway of
contamination unrelated to the
quality of the drinking water. A
possible source of bad samples is
a customer's faucet, either an
inside or outside tap, in which
coliforms have become established
in the faucet gasket material or
aerator. For this reason, proper
sampling technique is essential.
The NIPDWR requires sampling at
the tap, except for turbidity,
which should be measured at the
point of entry of treated water
into the distribution system.
For operational control, however,
the sampling locations chosen for
monitoring coliforms and disinfec-
tant residuals should include a
point where the water leaves the
treatment plant and enters the
distribution system and another
point in the distribution system
at the greatest distance from the
treatment plant. "The greatest
distance" usually implies that
the water also takes the longest
time to reach that point. It is
best to make calculations to
ensure this is true, because it
is important to sample the "longest
11-13
-------
flow" points. The samples withdrawn
at these most distant points must
meet the criteria for coliforms
and/or disinfectant residuals.
The prudent operator will use the
bacteriological sampling program
to help develop data that provide
a background of information for
the entire distribution system
through a pattern of representative
samplings.
Concentration Of Disinfectant
Residual
Drinking water supplies are
disinfected for one principal
reason: to kill or inactivate
pathogens. The disinfection
process occurs mainly in the
treatment plant where concentra-
tions, contact times, and other
conditions are controlled so that
bacterial and other waterborne
pathogens are dramatically reduced.
This does not mean that the
treated water is sterile; it is
not. However, sufficient disin-
fecting chemical usually is
added, not only to eliminate
pathogens, but also to help
control the possible growth of
other microorganisms which may be
present.
If the treated water enters a
distribution system and there is
no residual disinfectant remaining
in the water, those surviving
organisms that find a suitable
living environment in pipeline
sediment, crevices at pipe joints,
or packing materials, may grow
and reproduce. This situation
can result in undesirable conse-
quences, such as slimes breaking
loose and entering the consumer's
drinking water, foul tastes and
odors, and increased corrosion
and pipeline deterioration.
Providing a residual of disin-
fecting agent throughout the
distribution system minimizes the
possibility of such events.
BACTERIOLOGICAL ANALYSIS
Bacteriological analyses are
performed by State or EPA approved
private laboratories or by State
operated laboratories, depending
upon the preference of the State.
Many state health department
laboratories do not charge for
routine bacteriological analyses
of public water supply system
samples. Commercial, State, or
EPA-certified labs charge from
$5 to $25 per sample, plus the
costs of sample transportation.
Results are reported in one of
two ways, depending on the ana-
lytical method used. If the
membrane filter test is used, the
results will be expressed as
coliform colonies per 100 mL of
sample. If the multiple tube
fermentation method is used, the
results will be reported as a
most probable number (MPN) of
coliform organisms (per 100 mL)
of sample or in terms of the
number of tubes positive.
Membrane Filter
The bacteria in a measured sample
are filtered onto the surface of
a thin membrane which is trans-
ferred to a culture dish containing
nutrients for coliforms to grow
and then placed in a 35°C incubator.
Any coliforms present will grow
into visually observable differ-
entiated colonies which if of
the appropriate type are
counted. Each colony is presumed
to come from a single viable
bacterium in the sample.
11-14
-------
Multiple Tube Fermentation
Each of five sterile culture
tubes containing a suitable
lactose or lauryl tryptose broth
and an inverted tube (to demon-
strate gas production) are inocu-
lated with 10 mL of the water
sample. These are placed in an
incubator (35°C). Any coliforms
will grow, and in growing will
produce gas which is trapped in
the inverted tube. Thus, a
visual observation of gas in the
tubes is an indication of coliform
presence. If only one tube has
gas and the other four do not, it
can be presumed that the sample
of water used to inoculate the
tubes (50 mL) contained at least
one coliform (or 2 per 100 mL).
Since it is possible that two
coliforms could have been in that
one tube but not in the other
four, a statistical correction is
applied and called a most probable
number (MPN).
Table IV shows the relationships
between the Most Probable Number
Index per 100 mL determined by
the multiple tube fermentation
method (using five 10-mL samples)
and the 95% confidence limits to
be applied. For example, if
three tubes are found to give
positive reactions, the MPN index
per 100 mL is 9.2, and one can be
95% confident that the true MPN
falls between 1.6 as the lower
limit and 29.4 as the upper
limit.
For the most part, routine testing
using these methods will indicate
whether the drinking water supply
is reasonably safe from waterborne
illnesses. It does not, however,
provide positive proof of a safe
system, nor is it all that a
responsible operator should be
concerned about. Continuing
efforts must be directed at
maintaining pressure, eliminating
and insuring against cross-
connections, keeping the system
tight, maintaining an adequate
level of residual disinfectant,
being alert for changes in water
quality, keeping the chemical/
physical systems operating to
remove contaminants, maintaining
adequate supplies of chemicals,
maintaining proper records, and
monitoring the water source
itself.
DISINFECTANT? RESIDUAL ANALYSIS
The current primary drinking
water regulations specify one
method for analyzing chlorine
residual in finished drinking
water. This is the DPD colori-
metric method which is described
in detail in Reference 10.
Analytical methods for measuring
residuals of other disinfectants
are not yet specified in the
primary drinking water regulations.
The primary reason for this is
the current lack of sufficient
experience in the United States
with other disinfectants and
their analyses. Various methods
exist for determining chlorine
dioxide and ozone, and each
method is characterized by problems
of interference by other oxidants,
difficulties in attaining accurate
measurements, or complexities in
the procedures themselves.
Methods for analyzing residuals
of each disinfectant chlorine,
chlorine dioxide and ozone are
described below. Methods for
analyzing ultraviolet residuals
are not discussed because ultra-
violet radiation does not leave a
residual; this is one of its
shortcomings. Chloramine residuals
11-15
-------
TABLE IV
MPN INDEX AND 95% CONFIDENCE LIMITS FOR VARIOUS
COMBINATIONS OF POSITIVE AND NEGATIVE
RESULTS WHEN FIVE 10-mL PORTIONS ARE USED (10)
No. of tubes giving
positive reactions
out of five of 10-mL
each
MPN Index/100 mL
95% Confidence Limits
Lower Upper
0
1
2
3
4
5
<2.2
2.2
5.1
9.2
16.
>«.
0
0.1
0.5
1.6
3.3
8.0
6.0
12.6
19.2
29.4
52.9
infinite
can be determined by using the
DPD method, as can chlorine
dioxide.
It is not important that the
reader understand fully the
procedures or chemistries of the
analytical methods discussed.
However, it is extremely important
to have knowledge of the limita-
tions of analytical procedures
and to know which methods can be
relied upon. Only through this
knowledge can the owner/operator
be assured that a disinfectant
residual is being maintained and
customers protected.
Chlorine
Chlorine residual tests must be
conducted immediately after
sampling, since agitation or
exposure to sunlight will cause
the chlorine residual to disappear
rapidly. Tests can be carried
out at the sampling location
using a portable field test kit
which uses the DPD colorimetric
method. This is the only chlorine
residual test procedure currently
approved for use in connection
with compliance monitoring under
the primary drinking water regula-
tions. It is a simple method
based on color comparisons that
can be carried out in about five
minutes.
Several suppliers of chlorine
residual test kits are listed in
Table V.
Analysis of residual chlorine is
based on the instantaneous reaction
of free available chlorine with
the DPD indicator to produce a
red color. The depth of this
color can be converted into a
free chlorine value using a
visible light spectrophotometer
11-16
-------
TABLE V
SOME SUPPLIERS OF CHLORINE RESIDUAL TEST KITS
Capitol Controls Co., Advance Lane, Box 211, Colmar, PA 18915
Chemply, Division of United Chemicals, Inc., Box 18049, Pittsburgh,
PA 15236
Fischer & Porter Co., Environmental Division, County Line Rd.,
Warminster, PA 18974
Hach Co., Box 389, Loveland, CO 80537 (Branch Offices in
Santa Clara, CA; Orlando, FL; Tucker, GA; Palatine, IL;
Ames, IA; Lake Charles, LA; Cherry Hill, NJ; Chapel Hill,
NC; Cleveland, OH; Houston, TX; and Olympia, WA.
Wallace & Tiernan, Div. of Pennwalt Corp., 25 Main St.,
Belleville, NJ 07109
as provided in a standard field
kit.
Chloramines also can be determined
using the DPD method by adding a
second reagent (potassium iodide)
after taking an initial photometer
reading. After adding a small
amount of potassium iodide,
another reading is taken to
measure chloramines.
Chlorine Dioxide
Although several methods are
specific for pure solutions of
chlorine dioxide, in actual
practice chlorine dioxide typi-
cally is generated in the presence
of free residual chlorine. In
addition, small concentrations of
chlorite ions (the starting
material) and chlorate ions
(resulting from the dispropor-
tionation (simultaneous oxidation
and reduction) of chlorine dioxide
will be present.
The DPD procedure is not selective
for chlorine dioxide alone; it
will measure the total concentra-
tion of all the above oxidants
which may be present. When
chlorine dioxide is generated in
the presence of significant
quantities of free residual
chlorine, addition of ammonia
will destroy the free residual
chlorine, leaving chloramines,
chlorine dioxide, and chlorite
and chlorate ions, the sum total
of which can be determined upon
addition of DPD and conducting
the analysis in the same manner
as for free residual chlorine.
Standard Methods (10) contains
descriptions of four other ana-
lytical methods, each of which
has specific advantages and
disadvantages. These methods,
all of which will also measure
total oxidants in addition to
CIO , are:
o iodometric;
11-17
-------
o orthotolidine-oxalic acid;
o amperometric titration with
phenyl arsine oxide;
o DPD-ferrous ammonium sulfate.
In order to determine chlorine
dioxide selectively and accurately
currently requires a complex
sequence of analyses, which would
place a great analytical burden
on small water supply systems.
On the other hand, EPA currently
recommends a maximum dosage of
1 mg/L of chlorine dioxide for
use in water treatment (11). If
this recommendation is followed,
there will be no necessity to
determine specific chlorine
dioxide residuals. Instead, the
DPD (or other) method can be used
to measure and control total
residual oxidants in the treated
water. If chlorine dioxide is
the only oxidant added, and at a
maximum dosage of 1 mg/L, then
the concentration of total residual
oxidants will not exceed 1 mg/L.
Ozone
In solution, dissolved ozone is
very reactive and, except in
triple-distilled water near its
freezing point, quickly decomposes
into oxygen from which it is
generated. Therefore, when ozone
is utilized as a terminal disin-
fectant, it produces a short-lived
residual which disappears in a
matter of minutes in the storage
tank. However, ozone can be used
as the primary disinfectant, with
the ozonized water being treated
with chlorine, chlorine dioxide,
or chloramine later in the process
to produce a residual.
During ozonation for disinfection,
however, dissolved residual ozone
is sufficiently stable so that
its concentration can be analyzed
accurately, provided the analysis
is conducted quickly on samples
taken in or close to the contact
chamber. In fact, many European
and Canadian water supply systems
which utilize ozonation for
disinfection, control the amount
of ozone added by monitoring the
dissolved residual obtained after
the initial ozone demand of the
process water has been satisfied.
Two primary methods for measuring
residual ozone in water are
applicable to small water systems.
These are:
o iodometric (wet chemical,
manual)
o ampe rome tr ic (ins trumental,
manual or automatic)
Iodometric Procedure
To a sample of water containing
ozone, a solution of starch and
potassium iodide is added.
Dissolved ozone is destroyed
while oxidizing iodide ion to
free iodine which, in turn, forms
a deep blue-colored complex with
the starch. This is titrated to
colorless with standardized
sodium thiosulfate solution, and
the amount of dissolved ozone is
calculated from the quantity of
thiosulfate required. This is
the cheapest method, but requires
manual chemical analysis.
Amperometric Procedure
This method requires purchase of
an in-line instrument which
continuously samples the water
and monitors total oxidant concen-
trations colorimetrically.
Several current suppliers of
amperemeters (which also can be
used to measure free and combined
11-18
-------
chlorine residuals and chlorine
dioxide) are Fischer & Porter,
Wallace & Tiernan, Infilco-
Degremont, Hach Co. , and Ionics,
Inc. The basic principles of
operation of the first three of
these instruments are described
by Parg (12).
The choice between use of the
manual iodometric method and the
automatic amperometric titration
method involves consideration of
cost and available skills. If a
trained laboratory technician is
on staff, the manual iodometric
method is sufficient. However,
if trained personnel are not
available, the automatic analyzer
should be purchased along with
the ozone system. If a small
water system is financially able
to purchase an ozonation system,
it should seriously consider
purchase of an automatic residual
ozone monitor.
11-19
-------
-------
III. ASSURING SAFE, PATHOGEN-FREE DRINKING WATER
Providing the public with a safe,
pathogen-free drinking water is
the shared responsibility of
system designers, owners, and
operators. Public health officials
assist by providing professional
advice and technical guidance
based on local experience.
Ensuring quality potable product
water begins with the protection
of source waters and includes
programs and efforts designed to
maintain that protection through-
out its treatment, transportation,
and use. The other factors
involved in supplying safe drinking
water are diagrammed in Figure 6.
They include a quality system
which is well operated and main-
tained, and properly staffed, and
capable of complying with the
National Interim Primary Drinking
Water Regulations.
Source waters can be either
surface or groundwater, or a
combination of the two. The
majority of small public water
supplies utilize groundwaters,
and groundwater protection has
received increasing emphasis in
recent years as society has
learned to appreciate its value.
This section presents summary
discussions of non-treatment and
treatment alternatives. Detailed
discussions of system designs for
specific disinfectants, and
operation and maintenance are the
subjects of Sections 4 and 6,
respectively.
NON-TREATMENT ALTERNATIVES
Watershed Management
In general, the better the quality
of the raw water supply (source
waters), the easier and cheaper
it is to treat and the better
will be the final product quality.
Protecting the source of a drinking
water supply is the first step to
quality water. For example:
o Uncontrolled development
leads to erosion, paving
over of groundwater recharge
areas, and more polluted
runoff. Runoff from roadways
carries oils, trash, and
sediment. Erosion from
disturbed, developing areas
increases turbidity which
requires more expensive
treatment processes. Water-
shed protection starts with
land use planning and control
of development.
o Dumping (whether intentional
or; accidental) of inadequately
treated, potentially toxic
solid and liquid wastes onto
the land or into water may
lead to serious, sometimes
irreversible pollution of
the watershed and source
waters. Accidents with the
potential for damage and
outright violations should
be reported promptly to the
authorities that have
jurisdiction.
o Poorly constructed septic
tank systems and collector
sewers often are identified
with fecal contamination of
groundwaters and water
systems. This problem can
be especially severe in
limestone areas and wherever
fissured rocks permit the
unrestricted movement of
underground water. Local
and state health officials
need public help for effective
III-l
-------
WATERSHED
MANAGEMENT
NON-TREATMENT!
ALTERNATIVES
TREATMENT
ALTERNATIVES
OPTIMAL
SYSTEM
DESIGN
STAFFING
a
TRAINING
OPERATION
a
MAINTENANCE
NIPDWR
COMPLIANCE
PATHOGEN-FREE
POTABLE
WATER
Figure 6. Factors Contributing to Assuring Safe,
Pathogen-Free Drinking Water
III-2
-------
septic tank system controls
and sewer maintenance programs.
o A few small communities draw
their water supplies from
surface sources into which
contaminants have been
discharged, surreptitiously,
accidentally, or legally.
Any surface source must be
considered potentially
contaminated; contaminated
discharges simply render
them more so. Failure to
effectively treat waste
discharges generally will
result in increased treatment
costs to subsequent users.
It is every dischargers'
responsibility to treat the
discharges at least to the
degree required by the
controlling agencies whose
requirements are, in turn,
largely governed by the
downstream uses of the
water.
o Overly intensive agricultural
practices can result in
contaminated surface and
groundwaters. Animal feedlots
and runoff from heavily used
pastures and also from dense
populations of wildlife can
contribute to fecal pollution
of surface waters. Poor
agricultural crop practices
result in increased erosion
and higher turbidity and
sediment trans po rt, wh ich,
in turn, result in filling
in of reservoirs. Over-
fertilization and indiscrim-
inate use of pesticides can
add potentially harmful
substances to runoff waters
and destroy non-target
beneficial organisms and
wildlife. Awareness of
these and other agricultural
practices is essential to
appropriate watershed
management.
Other Non-Treatment Alternatives
Small water systems faced with
the need for upgrading or the
addition of new facilities in
order to provide safe drinking
water should first consider the
possibilities offered by other
approaches herein addressed
collectively as "Other Non-
Treatment Alternatives". In
general, these alternatives mean
the obtaining of water, in whole
or in part, from a different
source or supply superior in
quality.
Examples include:
Source Substitution
Treatment and disinfection costs
are related directly to water
quality. Costs often can be
greatly reduced by switching from
a turbid surface water to a clear
well water. It can be expected
that such a change will reduce
costs of disinfection as well.
There are many other factors that
also must be considered, however,
such as iron, hardness, or
stability.
Blending
A high quality water source of
insufficient capacity to fully
replace an existing water source
of lesser quality still may be
used to advantage to reduce
treatment needs and costs. For
example, blending of waters from
the higher quality source might
reduce the concentrations of
chlorine-demanding substances,
thereby permitting better disin-
III-3
-------
faction with less chlorine. Such
a course of action, however,
requires prudence because other
water quality parameters might be
affected as well such as
stability.
Regional Systems
Regionalization is a concept
which involves sharing of resources
in order for each system to be
able to avail itself of the
services of skilled personnel,
thus lowering operating and
management costs. This concept
has been tried in several states,
and has been most successful in
Pennsylvania, Washington, Texas
and Alabama.
A regional system can be formed
only if the concept has the
support of local political bodies
and the public. Several types of
entities can be formed: these
include formation of a special
district, authority, or associa-
tion, a non-profit water supply
corporation or an investor-owned
(profit making) water system;
entering into informal agreements
or setting up joint service
organizations with other juris-
dictions in the region; or entering
into basic service contracts with
private service organizations.
The type of entity formed depends
entirely on the particular needs
of the local water systems forming
the regional system.
Substantial planning is required
before a regional system can
become a reality. The basic
steps in the planning process are
to decide the following:
o benefits to be derived from
the regional system;
o services and functions of
the entity;
o management structure that
will govern the entity;
o legal structure that will
meet area needs;
o financing needs and plans
for funding.
Once these basic decisions are
made, the process becomes one of
implementation. If most local
political and institutional
bodies are in agreement with the
plan, the process of forming a
regional entity, although time-
consuming, is relatively easy.
However, if some of the local
institutions disagree with the
concept and the plan, the regional-
ization process can become ex-
tremely difficult and time-consuming,
often resulting in failure.
One of the primary reasons that
regionalization has not been more
widely practiced is the fear of
loss of authority by owners of
small water systems, usually
municipalities. In those states
in which regionalization schemes
have been successful, the benefits
derived usually have outweighed
their costs both monetary and
non-monetary. Other barriers may
preclude formation, however.
These include financial and legal
difficulties and geographical
dispersion.
Regionalization often has been
viewed as the total physical
interconnection of a number of
systems. Although this is indeed
its ultimate definition, other
forms of regionalization are
III-4
-------
possible and are more prevalent.
These include:
1) provision of laboratory
services to a number of
utilities by a single central
laboratory;
2) provision of management and
financial services by a
central authority; and
3) operation and maintenance of
facilities by a single set
of operators.
Benefits which can be derived
from regionalization are numerous:
1) Services often can be provided
at lower unit costs as the
quantity of water produced
increases. This is often
referred to as "economies of
scale".
2) Pooling of skills, resources
and knowledge enhances the
ability to deliver services.
3) The number of poorly operated
and maintained systems can
be reduced.
4) The regional entity has
greater capabilities to plan
and design facilities,
secure financing for needed
capital improvements, and
operate and maintain systems.
5) More highly skilled management
and operations personnel can
be attracted and retained.
These concepts are developed in
detail in a companion EPA document
entitled Regionalization for Small
Water Systems.
TREATMENT ALTEKNATVES
Predisinfection
Treatment methods for control of
pathogens in drinking water
inevitably involve some form of
disinfection to inactivate the
microorganisms. However, pre-
treatment may be required to
remove substances which interfere
with the disinfection process.
The most common interfering
substance in potable water treat-
ment is turbidity, caused by fine
particulates suspended in water.
Excessive turbidity interferes
with the action of disinfectants
and is usually associated with
the presence of many extraneous
organic substances which collec-
tively also interfere with the
disinfection process. The subject
of turbidity removal is addressed
in a companion EPA document
entitled Turbidity Removal for
Small Water Systems.
DISINFECTION
Introduction
Disinfection means the destruc-
tion of disease-causing organisms.
It is not the same as sterilization,
which means the killing of all
organisms. Disinfection of
drinking water long has been
measured in terms of the number
of coliform organisms that remain
in the water after it has been
subjected to a disinfection
process. Such treatment does not
render the water sterile, nor is
it necessarily pathogen-free
because a few forms, such as the
hardy cysts and spores of pathogens
might survive if initially present.
III-5
-------
However, substantial experience
has demonstrated that serious
waterborne illness rarely occurs
when disinfection to the coliform
levels specified in the NIPDWR is
carried out meticulously.
This section of the document
presents discussions of factors
known to affect disinfection by
each of the disinfectants. The
chemistry of each disinfectant is
discussed, along with methods for
the application of each, establish-
ment of residuals, factors af-
fecting disinfecting efficiency
of each, formation of by-products,
and availability of commercial
equipment.
Desirable properties for a chemical
disinfectant include:
o non-toxic to humans at
concentrations applied for
disinfection;
o high germidical power (kills
a high proportion of microbes
at low dosages);
o stability (so as to provide
a residual* effect);
o solubility;
* The addition of disinfectant
in excess of the amount required
to disinfect water in the plant
provides a residual quantity of
that disinfectant in the treated
water. The stability of that
residual disinfectant will depend
upon the quality of the water to
which it is added. Ammonia will
react with and destroy free
residual chlorine; some dissolved
organics will react with and
destroy residuals of chlorine,
chlorine dioxide, and ozone. UV
radiation will not produce a dis-
infecting residual concentration.
Residual ozone will disappear
within a few hours of addition.
o economy;
o dependability;
o ease of use and measurement;
and
o ready availability to the
small water system.
Chlorine and its hypochlorite
compounds satisfy all of the
desirable properties of this
list. The other disinfectants
each lack one or more attributes.
Disinfection With Chlorine
Chlorine, symbolized chemically
as Cl , is the disinfectant most
commonly used by U.S. water
utilities. It is available
commercially in three forms:
Form
gas
solid
aqueous
solution
Formula
Cl,
Ca(OCl),
NaOCl
Name
chlorine
gas
calcium
hypochlorite
sodium
hypochlorite
The gaseous form is used most
frequently, especially by larger
water utilities.
Chemistry of Chlorination
Chlorine in the gaseous form will
react with water to form hydro-
chloric acid and hypochlorous
acid:
ci
chlorine
"HC1 +
hydrochloric
acid
water
HOC1
hypochlorous
acid
III-6
-------
The hypochlorous acid then will
react with the water by dissocia-
tion to an extent determined by
the pH:
HOC1-
hypochlorous
acid
denoted in the equations above by
HC1 and H ):
"(OC1)
hypochlorite
ion
H
hydrogen
ion
(pH is a measure of the concentra-
tion of hydrogen ion in the
water. The more hydrogen ion
present, the lower is the pH
value. Conversely, the lower the
hydrogen ion concentration, the
higher will be the pH value)
At neutral pH (pH = 7.0), almost
80% of the hypochlorous acid will
remain in the highly effective
HOC1 form and the remainder will
exist in the less-effective
(OC1)~ form. As the pH increases,
however, an increasing amount of
HOC1 will react with water to
form the (OC1)~ form. At pH 8.0,
for example, almost 80% of the
hypochlorous acid will exist as
the hypochlorite ion, almost a
complete reversal of the situation
which exists at pH 7. Hence,
effective pH control is essential
for good chlorine disinfection.
Figure 7 shows these relation-
ships determined at 0°C and at
20°C.
When the chlorination is conducted
by adding either sodium hypochlor-
ite or calcium hypochlorite, the
chemical reactions result in an
alkaline (basic) product as
compared to the acidic product
obtained when using the gas (as
NaOCl
-HOC1 + NaOH
sodium water hypo sodium
hypo- chlorous hydrox-
chlorite acid ide
Ca(OCl)2 +
calcium
hypochlorite
-~>-2HOCl H
hypochlorous
acid
2H2° "
water
Ca(OH)2
calcium
hydroxide
The resulting hydroxides increase
the pH value of the solutions.
Since an increase in pH results
in less HOC1, and therefore
poorer disinfection, the ability
to control pH when using the
hypochlorite forms of chlorine is
important.
Establishing a Chlorine Residual
Hypochlorous acid is one of the
most powerful oxidizing agents
known. That means it will react
with many substances in addition
to the target organisms. In
order to achieve a concentration
of chlorine sufficient to do the
job of disinfection, it is neces-
sary to add enough chlorine to
react with all the reactive
substances which are likely to be
present. These reactions consume
chlorine and are collectively
called the "chlorine demand".
Thus, the chlorine demand of a
water must be satisfied before an
III-7
-------
Source: Water Chlorination Principles and Practices, AWWA No. M20
(1973), p. 12.
Figure 7. Distribution of Hypochlorous Acid and Hypochlorite Ions
in Water at Different pH Values and Temperatures
III-8
-------
adequate job of disinfection can
be expected. This essential
operation is tricky because the
consumption of chlorine (really
of hypochlorous acid) by the
chlorine-demanding materials is a
function of time. For a given
water, it is virtually certain
that the chlorine demand measured
after five minutes of contact
with chlorine will be greater
than the chlorine demand measured
after ten minutes of contact.
The concentration of chlorine
determined by an analytical
procedure is called the "avail-
able chlorine residual", and it
means only that amount of chlorine
which remains available for the
disinfecting operation. The
residual may be either a free
available residual or a combined
available residual. Free avail-
able chlorine is essentially the
sum of HOC1 and (OC1) concentra-
tions. Combined available chlorine
is the sum of the concentrations
of mono- and di- chlqramines (see
later discussion of chloramines).
Intuitively, one would expect
that each mg/L of chlorine added
to water would be measurable as
hypochlorous acid or hypochlorite
ion. This is not the case,
because the chlorine reacts with
many substances present in the
water in a complex way.
To understand the complex reac-
tions of chlorine better, refer
to Figure 8 (13), which shows
what is called typically a
"breakpoint curve". The amount
of chlorine added is on the
horizontal scale and the amount
of available chlorine determined
by an analytical procedure is on
the vertical scale. Assume that
chlorine is added slowly and that
the water contains small amounts
of reduced substances such as
sulfides and ferrous iron, some
organic materials, and some
ammonia, all of which exert a
chlorine demand. The initial
amount of chlorine added will be
taken up by the reduced substances
and the analysis for free avail-
able chlorine (HOC1 and OC1 )
will show that none is present.
After the chlorine demands of the
reduced substances are satisfied,
then the HOC1 will react with
ammonia and some of the organics
present to yield chloramines and
chloro-organic compounds.
When all of the ammonia and
chlorine-demanding organics
present have reacted with chlorine,
the addition of more chlorine
results in the HOC1 oxidizing the
same materials it just helped
create. The strange phenomenon
observed is that the addition of
more chlorine results in a decrease
in the amount of residual (at
this point a combined residual)
indicated by the analytical
procedure. When this oxidation
is complete (called the breakpoint),
then the addition of still more
chlorine results in an increase
in the amount of available chlorine
measured. Note that the breakpoint
must be passed before a free
residual can accumulate and
persist.
It is important to be aware that
the above illustration is consid-
erably more complex than as
described because the reactions
taking place are time-dependent.
For this reason, a breakpoint
curve is difficult to recreate.
Factors Affecting Disinfection
Efficiency of Chlorine
Chlorine in the free state (HOC1
+ OC1~) is a highly effective
disinfectant. Figure 9 (14)
III-9
-------
6 8 10
CHLORINE APPLIED, mg/L
12
14
Immediate
Demand
H2S,Fe*+,etc.
Chlorine and
Ammonia
or similar compounds
Free Residuals
Figure 8. Graphical Representation of the Breakpoint Chlorination
Reaction. The straight line at the left shows that
chlorine residual is proportional to dosage in pure
water. When impurities are present, they exert an
initial chlorine demand (14).
Ill-10
-------
o
o
X
o
«-
o
O.OI
I 10
Contact time for 99 percent kill, minutes
40
Figure 9. Concentration of Chlorine as HOC1 Required for 99 Percent
Kill of _E. Coli and Three Enteric Viruses at 0 to 6°C.
Note: mg/L = g/m (15).
III-l1
-------
shows that 1 mg/L HOC1 caused a
99 percent kill of the test
bacteria and viruses in six
minutes or less under the condi-
tions of exposure used in this
study.
Effective disinfection using
chlorine requires careful atten-
tion to:
o concentration of free avail-
able chlorine high enough
in the plant so that it
never drops to less than
0.2 mg/L at the farthest
(time basis) point in the
distribution system;
o pH as close to 7.0 as is
practical or consistent with
other water quality aspects,
so as to maintain as much of
the chlorine residual in the
HOC1 form (see Figures 7
and 10);
o time of contact long enough
to achieve microbe inactiva-
tion baffle the chlorine
contactor well to eliminate
the possibility of short
circuiting of flow.
Other factors also influence the
chlorine disinfection process.
Temperature_will affect the ratio
of HOC1:OC1~ (see Figure 7) and
the disinfection rate this
being faster at warmer tempera-
tures. However, usually there is
no means available to the operator
to control temperature. Perhaps
the most important factor for the
operator to be aware of is that
there are some organisms which
are extraordinarily resistant to
chlorine disinfection, and that
following the rules of good
practice does not guarantee their
destruction. These organisms
include the spores of tetanus and
botulism, for example, and the
cysts of protozoans such as
amoeba and Giardia. Fortunately,
these are not generally present
in groundwaters, the major source
of supply for small systems.
Surface water supplies should be
treated by coagulation and sedi-
mentation, plus filtration, in
addition to disinfection, in
order to control cysts.
Potentially Harmful By-Products
of Chlorination
Chlorine, whether in the form of
hypochlorous acid, hypochlorite
ion in solution or the gaseous
element, not only is a powerful
oxidizing agent, but also is a
chlorinating agent. When chlorine
comes in contact with certain
types of organic materials (such
as humic and fulvic acids),
chlorinated organic compounds are
formed. Some of these by-products
of the chlorine disinfection
process may be potentially damaging
to human health. One particular
group of halogenated organics,
the trihalomethanes (THMs), has
been identified as potential
human carcinogens substances
which encourage the growth of
cancer cells.
Humic or fulvic acids are produced
during the decay of vegetation.
Slow moving rivers or lakes which
drain heavily vegetated areas are
likely to contain significant
concentrations of humic and
fulvic acids, which can be termed
"trihalomethane precursors".
The term "trihalomethane" is used
rather than "trichloromethane"
because some of the compounds
isolated after chlorination have
been shown to contain bromine, as
well as chlorine. It has been
III-12
-------
I I I till, 1 I 11II
Monochloromine
10 100
Minutes
99% destruction of E.coli at 2to6°C
1000
Figure 10. Comparison of the Germicidal Efficiency of Hypochlorous
Acid, riypochlorite Ion and Monochloramine for 99 Percent.
Destruction of E. Coli at 2 to 6°C (15).
111-13
-------
demonstrated that when waters
being chlorinated also contain
bromide ions, these can be oxi-
dized by chlorine (or hypochlorite)
-to an oxidation state at which
the organic contaminants become
brominated as well as chlorinated.
Generically, the trihalomethanes
have the chemical formula:
X
I
H - C - X
X
where: H - a hydrogen atom
C = a carbon atom
X - chlorine and/or
bromine atoms
There are four THMs for which an
MCL of 0.10 mg/L has been estab-
lished for large water supply
systems. This 0.1 mg/L MCL is
the total of all four compounds:
bromodichloromethane, HCC1 Br
chlorodibromomethane, HCBr Cl
tribromomethane (bromoforra),
HCBr3
trich loromethane (chloroform),
HCC1 .
The summation of the concentra-
tions of these four compounds is
referred to as "total trihalometh-
anes" (TTHMs).
Other trihalomethanes are known
which contain iodine, but these
are not currently regulated by
the EPA.
Several techniques are known for
reducing the levels of TTHMs in
drinking water supplies; these
can be generalized as follows:
1) reduce the level of THM
precursors (organic materials
which produce THMs upon
chlorination) before
chlorination;
2) replace chlorine with a
disinfectant which does not
produce THMs;
3) remove THMs after they have
been formed.
4) move the point of chlorine
application until after the
majority of organic materials
has been removed.
All evidence available to date
indicates that, once formed, THMs
are difficult and costly to
remove. Aeration will physically
strip the lighter di- and tri-
chloro-THMs from solution, but
the heavier di- and tribromo-THMs
require more intensive (and
energy-consuming) aeration for
significant removal.
Granular Activated Carbon (GAG)
can remove some THMs from water
supplies. However, the useful
lifetime of the GAG before reac-
tivation is required is rather
short. Both capital costs of
installing GAG and regeneration
costs are high.
Changing to a disinfectant which
does not produce THMs appears to
be the simplest solution, and the
subject is discussed in detail in
this chapter. However, it is
generally recognized that removal
of THM precursors before chlori-
nation is the best technological
(although not necessarily the
most cost-effective) approach to
lowering concentrations of TTHMs.
For small water supply systems,
the following approaches to
111-14
-------
lowering THM precursor levels are
suggested:
1) Consider alternative raw
water supplies containing
lower amounts of THM
precursors.
2) Reevaluate the amount of
chlorine currently being
employed. Can the same
degree of disinfection be
attained with lower chlorine
dosages?
3) If chlorine currently is
added before pretreatment
(chemical addition, coag-
ulation, sedimentation,
filtration), consider moving
the point of chlorination.
Rather than adding chlorine
with the chemicals, consider
adding it after the filtra-
tion step. If this is not
practical, consider adding
the chlorine just before the
filter, but after chemical
pretreatment.
4) Optimize the efficiency of
the pretreatment steps.
Remember that the function
of pretreatment is to remove
turbidity and dissolved
organic chemicals. Can
improvements be made in the
way chemicals are being
mixed and/or in coagulating,
settling and filtering?
5) The use of a stronger oxidant
(ozone, chlorine dioxide)
added with chemical treatment
(replacing prechlorination)
is practiced for removal of
tastes and odors, colors,
iron and manganese, and
other purposes at some water
treatment plants. In such
cases, these oxldants have
been shown to improve the
flocculation process and in
some cases to lower the
concentrations of THM pre-
cursors. However, in many
other cases, it has been
shown that ozonation, while
effective in lowering tur-
bidity levels, increases the
THM formation potential.
6) The alternative disinfectants
chloramine, pure chlorine
dioxide, ozone or ultraviolet
light do not produce THMs
even in waters which contain
high levels of THM precursors.
Each of these disinfectants
is discussed later in this
section and should be con-
sidered in systems having a
trihalomethane problem.
Disinfection With Chlorine Gas
Chlorine is a poisonous, yellow-
green gas at ordinary temperatures
and pressures. It is supplied in
high strength steel cylinders,
under sufficient pressure to
liquefy the chlorine. When
chlorine is required, simply
opening the valve allows rapid
vaporization of the liquid.
There are two basic types of gas
chlorinators: direct feed and
solution feed. The former allows
chlorine gas, under pressure, to
be fed directly into the water to
be disinfected. Solution feed
units mix the gas with a side-
stream of water to form a solution
of hypochlorite, which then is
mixed with the main stream.
Disinfection With Sodium Hypo-
chlorite Solutions
Liquid chlorinators meter a
previously prepared hypochlorite
III-15
-------
solution directly into the water
to be disinfected. If the water
supply system cannot afford the
capital costs and potential risks
associated with storing and
handling chlorine gas, solutions
of sodium hypochlorite can be
purchased. It must be remembered
that sodium hypochlorite solutions
do not contain the concentrations
of chlorine available in cylinders
of chlorine gas. Additionally,
hypochlorite solutions decompose
if stored for prolonged periods.
As a result, a small water system
should plan to store no more than
a one-month supply.
In recent years, methods for
on-site electrolytic generation
of aqueous solutions of hypochlor-
ite have been developed. In a
two-cell unit, a brine solution
(salt in water) is electrolyzed,
producing a solution of hypo-
chlorous acid in one cell and a
solution of caustic (sodium
hydroxide) in the other:
Na+ + Cl~ +
sodium
chloride
2H 0 + e
NaOH
HOC1 +
hypochlorous
acid
H
sodium hydrogen
hydroxide
The advantages of this procedure
are that purchasing and storing
of gaseous chlorine and hypochlor-
ite solutions are avoided. The
primary disadvantages are the
generation of hydrogen (which
poses fire and explosion hazards)
and the need to dispose of the
caustic generated. In addition,
the cost per pound, on a chlorine
basis, typically is more than
double for on-site electrolytic
generation of hypochlorite (30 to
35c/lb) versus the cost of gaseous
chlorine (8 to 15£/lb). However,
site-specific considerations may
make on-site hypochlorite genera-
tion the process of choice.
Disinfection With Solid Calcium
Hypochlorite
Solid calcium hypochlorite is
stable when properly packaged and
sealed. Thus, a water supply
system can purchase its annual
requirements in a single procure-
ment. Simply mixing the proper
amount of solid with the appro-
priate volume of water to allow
metering without clogging of
pumps or metering valves is all
that is required for use. Nor-
mally, an entire drum of calcium
hypochlorite is made into solution.
This avoids the partial use of a
container, with attendant uncer-
tainties of proper resealing and
loss of strength.
Disinfection With Chloramines
Chloramines are formed when water
containing ammonia is chlorinated,
or when ammonia is added to water
containing chlorine (hypochlorite
or hypochlorous acid). This can
be accomplished by adding gaseous
ammonia (purchased as the anhydrous
liquid, NH , in 150 Ib cylinders)
directly to the water, or by
adding a solution of ammonium
sulfate, (NH ) SO , (purchased in
100 Ib bags, 98% pure; 25%
available NH ).
Chemistry of Chloramination
Three chloramine compounds can be
produced, depending upon the
111-16
-------
ratios of chlorine and ammonia
which are utilized:
NH + HOC1
) + NH,,C1 monochloramine
NH Cl + HOCl-"-
>-H 0 + NHC1 dichloramine
NHCl + HOC1
H_0
NCI,
nitrogen
trichloride
The distribution of the chemical
species of chloramines is a
function of pH and of the amount
of chlorine added. For example,
in the pH range of 7 to 8 and a
chlorine to ammonia weight ratio
of 3:1, monochloramine is the
principal product. At higher
chlorine:ammonia ratios or at
lower pH values (5 to 7), some
dichloramine will be formed. If
the pH drops below 5, some nitro-
gen trichloride (often erroneously
called "trichloramine") may be
formed. This compound should be
avoided because it imparts unde-
sirable taste and odor to the
water.
Figure 11 (16) shows the relative
percentages of monochloramine and
dichloramine produced as the pH
changes, for different weight
ratios of chlorine to ammonia.
At a pH value of about 5.7,
approximately equal amounts of
mono- and dichloramines are
present in solution.
Care also should be taken not to
exceed chlorine:ammonia ratios
of 5:1. This is the ratio existing
at the peak of the breakpoint
curve, above which all of the
ammonia will have been removed,
chloramines will be absent, and
free residual chlorine will be
present.
Establishing A Chloramine Residual
Generation of chloramines is
conducted on-site, in solution,
as required, simply by adding the
appropriate amount of chlorine to
waters already containing ammonia,
or by adding ammonia to waters
already containing chlorine, then
allowing a short holding time to
be certain that the chemicals
have had time to react with each
other to form chloramines.
Usually, chloramine-forming
reactions are at least 99% complete
within several minutes.
Factors Affecting the Disinfection
Effectiveness of Chloramine
Mono- and dichloramines (C1NH
and Cl NH, respectively) are '
effective bactericides, but are
much less effective against
viruses than is free chlorine.
Although dichloramine is about
35 times more powerful a bacteri-
cide than is monochloramine (17),
both chloramines are less effec-
tive bactericides than is free
chlorine. For example, at 4°C,
100% inactivation of bacteria
required 1.5 mg/L of monochlora-
mine at pH 7.0, and 1.8 mg/L at
pH 8.5, after 60 minutes of
exposure. By comparison, only
0.03 to 0.6 mg/L of free chlorine
was needed at pH ranges of 7.0 to
8.5 at either 4°C or 22°C to
achieve 100% bacterial activation
in 20 minutes (18).
Laboratory studies have demonstrated
that there is limited virus
inactivation after the added
111-17
-------
M
r
i'
oo
H-
OQ
C
l-J
(D
300
O H-"O
CDN5 O
3 ^ M
rt rt
PERCENT OF ACTIVE CHLORINE IN NHCI2
g
g
rt O
(D H>
H
O H* fl)
H- P3 A.
3 rt
n> H- a
o H.
(B 3 O
3 CT*
P.
r
H- O
rt H
P* Pi
W
3
a>
iU (J.
9 /
/^s o
S\ PJN3
I I I I
PERCENT OF ACTIVE CHLORINE IN NH2CI
-------
chlorine has reacted with any
ammonia that is in the water
(having produced chloramines).
Most inactivation probably occurs
in the first few seconds before
the chlorine has completed its
reaction with ammonia (19), when
chlorine is added to the water
before ammonia.
Changes in pH values cause dif-
ferences in the ratios of mono-
and dichloramines present. The
stronger disinfectant (dichlora-
mine) will be formed in higher
yield at pH values above 5.7 (see
Figure 11). Although different
studies show mixed results when
comparing dichloramine and mono-
chloramine with indicator organisms
and other types of organisms, the
important observation remains
that these differences are more
of a scientific curiosity than of
any engineering treatment value
at this time. However, the
observation that chloramines are
more stable than free chlorine is
important, particularly to small
systems which are not as likely
to be under 24-hour surveillance.
Chloramines will persist in
distribution systems where their
protection is very much needed.
Effective disinfection using
chloramine treatment is even more
complex than when using free
chlorine, because virtually all
of the factors that pertain to
free chlorine treatment apply,
plus additional considerations:
o the raw water quality must
be superior in terms of the
absence of pathogenic viruses
and cysts. The presence of
either of these virtually
requires the use of free
chlorine and perhaps addi-
tional treatment by chemicals
and filtration prior to
chlorination;
o the time of contact must be
long, being measured in
terms of hours rather than
minutes;
o organic chloramines will
form if proteinaceous mate-
rials are present, which
will give a combined resid-
ual reading by an analytical
test; however, these are not
as effective bactericidal
agents as are monochloramine
and dichloramine. Hence the
actual concentration of
mono- and dichloramines will
be less than indicated bv
the analytical test.
Chloramine treatment best follows
the principles of use of free
chlorine. Such treatment has
been used effectively by many
water supply systems for many
years, primarily to reduce levels
of chlorinous tastes. In recent
years it has become apparent that
the use of free chlorine may
result in the production of
undesirable trihalomethane com-
pounds, if their required pre-
cursors are present in the water.
Therefore, those small water
supply systems wishing to utilize
chloramines, but planning to add
chlorine prior to addition of
ammonia should plan to check the
formation of THMs under this mode
of chloramine generation, before
adopting this procedure.
By-Products of Chloramination
No detrimental reaction products
of chloramine use are known,
except for nitrogen trichloride,
which imparts disagreeable taste
and odor to the water, and may be
toxic to humans as well. The use
of the proper amounts of each
chemical reactant will avoid its
production.
111-19
-------
Chloramines do not produce THMs,
unless in the presence of free
chlorine. Therefore, one advantage
of adding chlorine to an ammonia-
containing water is that a free
residual can be avoided and no
trihalomethanes created. If this
technique provides the necessary
level of disinfection, it will be
a low cost method of meeting TTHM
limitations.
An advantage of chlorinating to a
free residual, and then adding
ammonia to convert the free
residual to a combined chloramine
residual is that the full advan-
tages of free chlorine disinfec-
tion can be attained in the
treatment plant prior to forming
the weaker combined residual. If
the levels of TTHMs thus produced
in the treatment plant are suffi-
ciently low, then converting to a
combined residual by adding
ammonia first prior to the distri-
bution system will insure that
higher TTHM levels will not
result.
Disinfection With Chlorine Dioxide
Chlorine dioxide (CIO ), an
unstable, greenish-yellow gas is
explosive in air at concentrations
above 11%. Because of its insta-
bility, it is generated in solution,
on-site, and is used immediately.
As long as care is taken to keep
chlorine dioxide in solution and
storage of solutions is avoided,
there are no potential explosion
hazards. Chlorine dioxide is
readily soluble in water and is
decomposed by sunlight.
Like chloramine, chlorine dioxide
has enjoyed increased usage in
treating water supplies in recent
years for several reasons.
First, it is a more effective
biocidal agent than is chlorine
or hypochlorous acid. When
prepared in the absence of excess
free residual chlorine, applica-
tion of chlorine dioxide will not
produce THMs. Additionally,
chlorine dioxide can be used in
pretreatment to oxidize phenolic
compounds and to separate iron
and manganese from organic com-
plexes, some of which are stable
to chlorination. Similar to
chlorine and chloramines, chlorine
dioxide provides a protective
residual in distribution systems.
This residual is longer lasting
than that of chlorine, because
chlorine dioxide does not react
with ammonia. It is not known to
impart tastes and odors, as does
chlorine.
Chemistry of Chlorine Dioxide
For drinking water treatment,
chlorine dioxide is generated
from sodium chlorite, NaCIO
This material, purchased as a
solid (80% NaCIO ) or in 28 to
30% aqueous solution, is treated
with aqueous solutions of chlorine
or hypochlorous acid, sometimes
in the presence of an added
strong mineral acid, such as
sulfuric or hydrochloric acid.
Three processes used in water
treatment plants for the synthesis
of CIO from sodium chlorite
employ (a) gaseous chlorine,
(b) sodium hypochlorite solution
and mineral acid, and (c) mineral
acid. Each process is summarized
below:
Gaseous Chlorine This is a
two-step procedure, beginning
with the formation of hypochlorous
acid by dissolution of chlorine
into water:
IH-20
-------
ci2
chlorine
-* HOC1
water
+ HC1
hypochlorous
acid
hydrochloric
acid
These intermediate products then
react with sodium chlorite to
form chlorine dioxide:
HOC1 + HC1 +
^IMCtVjJ.l-'^ '
sodium
chlorite
r* i.\jj_«j_ T
chlorine
dioxide
2NaCl + H20
sodium
chloride
The end result of these reactions
is summarized by the equation:
Cl,
chlorine
2NaC10,
sodium chlorite
basis, 1.57 parts of chlorine gas
are added per part of NaClO^
(calculated on a 100% solids
basis when solutions of sodium
chlorite or 80% solids materials
are employed).
Under these conditions of excess
chlorine gas being added, the
product CIO solution also will
contain an amount of hypochlorous
acid/hypochlorite ions. These
can react with THM precursor
materials to produce THMs.
Sodium Hypochlorite and Mineral
Acid This also is a two-step
reaction, in which sodium hypo-
chlorite reacts with hydrochloric
acid to form hypochlorous acid,
which then reacts with sodium
chlorite to form chlorine dioxide:
NaOCl +
sodium
hypochlorite
NaCl
sodium
chloride
HC1
hydrochloric
acid
HOC1
hypochlorous
acid
2C102
chlorine
dioxide
2NaCl
sodium
chloride
According to this equation, one
mole of chlorine reacts with two
moles of NaCIO to produce two
moles of chlorine dioxide. In
water supply practice, excess
chlorine is employed, so as to
insure conversion of the maximum
amount of chlorite ion to chlorine
dioxide. Therefore, the recom-
mended ratios of reactants is two
moles of chlorine to one mole of
sodium chlorite. On a weight
HOC1 +
hypochlorous
acid
HC1 +
hydrochloric
acid
2NaC10
sodium
chlorite
*- 2C10 +
chlorine
dioxide
2NaCl
sodium
chloride
water
III-21
-------
In this procedure as in the
gaseous chlorine and sodium
chlorite procedure, excess chlorine
is utilized to insure conversion
of the maximum amount of chlorite
ion to chlorine dioxide. The
CIO solution also will be able
to produce some THMs.
Mineral .Acid This process
involves mixing a solution of
acid with a solution of NaCIO .
The reaction of sodium chloride
with hydrochloric acid can be
depicted by the equation:
SNaCIO +
sodium chlorite
4HC1
4C10,
hydrochloric chlorine
acid dioxide
SNaCl
sodium
chloride
water
The reaction of sodium chlorite
with sulfuric acid solution can
be depicted by the equation:
10NaC102
sodium
chlorite
8C102
chlorine
dioxide
4H2°
water
5H2S°4~
sulfuric
acid
5Na SO, +
2 4
sodium
sulfate
2HC1
hydrochloric
acid
The exact ratios of reactants
will depend upon which mineral
acid is employed for the produc-
tion of CIO
When generated from either mineral
acid, excess chlorine is not
required. Therefore, solutions
of chlorine dioxide prepared in
this manner do not contain free
residual chlorine.
In all three cases, the appropri-
ate aqueous solutions of reactants
are metered into a chlorine
dioxide reactor (a cylinder
containing Raschig rings or glass
beads) where intimate mixing of
the reacting solutions occurs
(see Figures 15 and 16 in Sec-
tion 4). The size of the reactor
and the residence time of the
reacting solutions are such that
after a few seconds the solution
exiting from the reactor shows
the strongly yellow color of
dissolved chlorine dioxide. This
solution is pumped directly into
the water to be treated.
In this manner, solutions of
chlorine dioxide are generated as
the material is required and used
immediately, without storage.
Appropriate metering and control
instrumentation can be installed
with the CIO reactor so that the
generation and addition of chlorine
dioxide is paced by the flow rate
of the water to be treated. As a
result, the unit operates without
the need of constant attention.
Oxidation-Reduction Reactions of
Chlorine Dioxide Chlorine
dioxide does not react with water
itself, as does chlorine. On the
other hand, when performing its
function of a chemical oxidant,
chlorine dioxide is reduced. One
of the reduction products that is
produced is reformation of the
111-22
-------
chlorite ion from which the CIO,
was formed initially:
chlorine
dioxide
cio2
chlorite
ion
It also can disproportionate
(undergo self-oxidation and
reduction) to form chlorite and
chlorate anions:
2C102 +
chlorine dioxide
C1CK
water
cio3
chlorate
ion
chlorite
ion
2H
hydrogen
ion
Disproportionation reactions of
chlorine dioxide normally occur
rapidly at low and/or high pH
ranges (pH below 2 and above 11).
Thus, in normal water supply
systems, where these pH ranges
are not encountered, dispropor-
tionation products should not be
observed.
Establishing a Chlorine Dioxide
Residual
Because the cost of chlorine
dioxide is higher than that of
chlorine, and because of the
potential toxicity of chlorite
ion to humans (see below) , only
small dosages of chlorine dioxide
(maximum of 1 mg/L) currently are
recommended by EPA for drinking
water treatment (11). However, a
primary advantage of chlorine
dioxide is that it does not react
with ammonia, as does chlorine.
This means that if water has been
pretreated to remove most of the
oxidant-demanding consituents (or
does not contain them initially),
the 1 mg/L or less dosage of
chlorine dioxide can be utilized
almost totally for providing
disinfection. Stable residual
concentrations of chlorine dioxide
can be maintained in distribution
systems under such conditions.
For these same reasons of cost
and possible toxicity, its use as
a predisinfectant should not be
considered if it is also to be
used as a post-disinfectant.
This is because if chlorine
dioxide is used for both purposes,
the recommended maximum dosage of
1 mg/L will have to be exceeded,
in all likelihood.
Factors Affecting the Efficiency
of Disinfection With Chlorine
Dioxide
Chlorine dioxide is more effective
than chlorine or hypochlorous
acid as a disinfectant. Because
it does not react with water,,
ammonia or most organic nitro-
genous compounds, it is not
"wasted" in extraneous reactions
of this type. It is less sensi-
tive to changes in pH (except for
very low and very high values),
maintaining its capabilities to
disinfect over the pH range of 6
to 10.
On the other hand, because it is
a more powerful oxidizing agent
than chlorine, hypochlorous acid
or chloramines, chlorine dioxide
can and will react with oxidizable
impurities contained in a raw
water. Thus, it is important to
111-23
-------
ensure that oxidant-demanding
components of the water have been
removed to as low a level as is
feasible, consistent with the
costs involved.
By-Products of Chlorine Dioxide
Use
When chlorine dioxide is generated
free of excess chlorine (mineral
acid procedure), and used as a
disinfectant, it will not produce
THMs, even if the water being
treated has unsatisfied THM
formation potential (THMFP). On
the other hand, CIO can give
rise to oxygen-containing organic
oxidation products. Many of the
organic oxidation products of
chlorine dioxide have been identi-
fied, but others may form which
have not yet been identified.
The prudent water treatment plant
operator will recognize the
uncertainties involved and design
for addition of CIO at the point
in his treatment process where
concentrations of oxidant-demanding
materials are lowest, and where
he will derive the maximum benefit
from the small dosage (1.0 mg/L)
of chlorine dioxide currently
recommended by EPA.
Toxicity of Chlorine Dioxide
The gaseous material has a strong,
disagreeable odor, similar to
that of chlorine gas, and is
toxic to humans when inhaled. It
is detectable by the human nose
at concentrations between 1.4
and 1.7%. When present at 4.5%,
it irritates respiratory mucous
membranes and may cause severe
headaches. At concentrations
below 6% in air, it may be com-
pared to chlorine, with respect
to its toxicity (20). Eventual
intoxications appear by local
irritations of the nervous system,
ocular and respiratory mucous
membranes, without substantial
resorption or systemic poison-
ing (21). There are no cumula-
tive effects in cases of repeated
exposure (22).
Disinfection With Ozone
Ozone (0 ) is a very strong
chemical oxidizing agent, second
in oxidizing power only to ele-
mental fluorine among the readily
available chemicals. Because of
its oxidizing ability, ozone also
is a powerful disinfecting agent.
Ozone is an unstable gas at
ordinary temperatures, and decom-
poses rapidly at temperatures
above 35°C. For this reason, it
cannot be manufactured and packaged
at a central manufacturing plant,
as can chlorine. Therefore, like
chlorine dioxide, ozone must be
generated on-site and used
immediately.
For the on-site generation of
ozone, an oxygen-containing gas
(air, oxygen-enriched air or pure
oxygen) is dried and cooled, then
passed between two electrodes
separated by a discharge gap and
a dielectric material across
which high voltage potentials are
passed. In recent years, some
ozone generation equipment has
been modified to operate at high
frequencies rather than at high
voltages. Figure 12 is a schematic
diagram of the essential components
of a corona discharge ozone
generator, the type available
commercially which produces
sufficient quantities of ozone
for use in water and wastewater
treatment plants.
For small water treatment plants,
dried air will be the source gas
111-24
-------
1
HEAT
Ill
ELECTRODE
DIELECTRIC
02 *
DISCHARGE
GAP
ELECTRODE
HEAT
Figure 12. Typical Corona Cell Ozone Generator Configuration (23)
111-25
-------
fed to the ozone generator.
Under such conditions, the output
from an ozone generator will be
dried, cooled air containing 1 to
2% of ozone, which is partially
soluble in water (about 20 times
as soluble as oxygen). This
mixture of ozone in air then must
be mixed (by a process called
contacting) with the water to be
treated. This is accomplished by
means of porous diffusers placed
at the bottom of a contact chamber,
or by means of turbines, injectors,
or high speed agitators. In some
cases, the water to be treated is
sprayed through a small orifice
into an ozone-containing atmosphere.
Ozone has a characteristic odor
which can be detected by most
humans at low concentrations
(0.01 to 0.05 ppm), far below the
levels of acute toxicity. Ol-
factory fatigue has been noted in
some instances. This means that
as the length of exposure to an
ozone-containing atmosphere
increases, the odor of ozone
becomes less noticed by smell.
In distilled water, ozone has a
half-life (the time for 50% of it
to disappear by decomposition) of
about 160 minutes at 20°C.
However, in colder water, the
half-life of ozone is longer.
Chemistry of Ozone
When an oxygen-containing gas is
passed through an ozone generator,
part of the oxygen dissociates as
a result of being exposed to the
high energy electrical field of
the corona discharge:
-*-2[0] "fragments"
These oxygen "fragments" are
highly reactive, and they combine
rapidly with molecular oxygen,
forming the triatomic molecule,
ozone:
oxygen oxygen
fragments
ozone
The overall reaction to produce
oznne is the sum of the above
reactions:
oxygen
energy ozone
oxygen
The reaction to produce ozone is
reversible, meaning that once
formed, ozone decomposes back to
oxygen. This reverse reaction
occurs quite rapidly above 35°C.
Therefore, because reactions
involving high energy electrical
discharges also are accompanied
by generation of considerable
heat, ozone generators are designed
to provide a high degree of
cooling, in order to minimize
ozone losses by decomposition.
Uses of Ozone in Water Treatment
Because ozone is such a powerful
chemical oxidant, it is used for
a number of applications in the
treatment of drinking water.
This short-lived oxidant reacts
with a wide variety of organic
and inorganic pollutants in
water, as well as being a very
fast acting and effective disin-
fectant. It has been in use as a
water treatment chemical since
1906, primarily in Europe in more
than 1,000 water treatment plants,
although at least 15 U.S. water
treatment plants currently are
employing ozone. Some of the
111-26
-------
applications of ozone in drinking
water treatment are: disinfection;
pretreatment for oxidation of
organics; as a flocculant aid;
for taste, odor and color removal;
and for oxidation of a range of
organic and inorganic materials
(iron, manganese, sulfides,
cyanides, etc.).
Ozone provides almost instantan-
eous bacterial disinfection and
viral inactivation after only a
few minutes of continuous contact
with the water being treated.
Factors Affecting the Disinfecting
Efficiency of Ozone
It should be recognized that
because ozone is such a powerful
oxidizing agent, it is not particu-
larly selective. In other words,
if ozone is used early in the
water treatment process, for
example, to oxidize iron and
manganese, a high degree of
disinfection also will be obtained.
Conversely, if ozone is used at
the end of the water treatment
process for disinfection, it also
will oxidize any easily oxidizable
materials still present. The
same can be said of chlorine
dioxide and chlorine. Thus when
employing any strong chemical
oxidizing agent as a disinfectant,
the better job the pretreatment
process can do to lower the
"oxidant demand" of the water,
the less disinfectant will be
required and the fewer disinfec-
tant by-products will be formed.
Ozone is affected little by
changes in water temperatures or
pH, and it does not react with
water as does chlorine. Also,
ozone does not react rapidly with
ammonia except above pH 9.
However, ozone does have a short
half-life in water. This means
that ozonized waters will not
have a lasting residual in the
distribution system. Although
there are a number of European,
Canadian, and even two U.S.
plants which do use ozone as the
terminal disinfectant, these are
the exception rather than the
rule. In those cases in which
ozone is the last treatment step,
a combination of factors must
occur simultaneously (24):
o cool water temperature;
o clean and short distribution
system;
o short residence time (less
than 12 hours);
o low levels of organics;
o no ammonia present.
In all other cases, a disinfectant
which provides a stable residual
is added after ozone has been
utilized as the primary disinfec-
tant. The advantage of employing
ozone as the primary disinfectant
is that much smaller dosages of
chlorine, chlorine dioxide or
chloramines then must be added,
usually less than 0.5 mg/L to
provide a stable residual for the
distribution system.
In applying ozone as a disinfectant,
the customary European practice
is to utilize a two-chamber
contacting apparatus. In the
first chamber, the ozone demand
of the water is satisfied and the
dissolved residual ozone level is
brought to a level of 0.4 mg/L.
In the second contact stage, the
0.4 mg/L level is maintained over
a minimum period of four minutes.
These conditions have been shown
by Coin £t aL. (25,26) to provide
at least 99.99% inactivation of
Polioviruses Types I, II and III,
and to kill bacteria as well.
111-27
-------
The use of two contact chambers
allows economy in the amounts of
ozone to be added. About two-
thirds of the total ozone required
is added to the first stage
(which contains water having the
highest ozone demand). Once the
ozone demand has been satisfied,
however, much less ozone is
required to maintain the 0.4 mg/L
residual over the four minutes
subsequent contact time.
Establishing an Ozone Residual
Although a residual level of
ozone can be established in the
contact chambers, which is suf-
ficiently stable to allow measure-
ment to conform with the four
minutes/0.4 mg/L criteria for
disinfection, this residual
rapidly dissipates and, generally,
can not be maintained in the
distribution system. During
ozonation, considerable oxygen is
added and many of the dissolved
organic impurities present in
trace or higher concentrations
will be rendered more readily
biodegradable. This occurs
because during ozone oxidation,
oxygen atoms become chemically
bound into the organic contami-
nants. The partially oxidized
organic materials are now more
readily assimilated by aerobic
microorganisms present in the
water.
As a result of ozonation, there-
fore, biological aftergrowths can
occur more readily in distribution
systems. For this reason, most
water treatment plants using
ozone for disinfection also add
small quantities of chlorine
dioxide, chlorine, or chloramine.
As indicated earlier however,
considerably smaller dosages of
these residual-forming disinfec-
tants need be employed. In
European water treatment plants,
large or small, the dosages of
residual chemicals rarely exceed
0.5 mg/L.
Oxidation By-Products of Ozonation
Although ozone is chemically
incapable of producing chlorinated
organic by-products, nevertheless
there is the potential for gener-
ating other organic materials,
some of which may pose hazards to
the public health. This is all
the more recognizable when it is
realized that the small quantities
of ozone used in drinking water
treatment processes rarely are
sufficient to oxidize organic
materials completely to carbon
dioxide and water.
As a general principle, those
organic compounds which can be
oxidized by ozone will be oxidized
to materials which contain more
oxygen in their structures. This
makes the oxidized products more
easily flocculated and coagulated.
In addition, oxygen incorporated
into organic structures generally
increases the biodegradability of
organic compounds. Thus, ozona-
tion also produces food for
microorganisms which may find
their way into the treated water
after the ozone residual has
dissipated.
Some organic compounds may be
oxidized by ozone to produce new
compounds which are more toxic
than are their predecessors. For
example, oxidation of the pesticides
heptachlor, malathion, and parathion
with ozone produces, respectively,
heptachlorepoxide, malaoxon and
paraoxon as the first oxidation
products. All three of these
materials are of higher toxicity
111-28
-------
than their precursors. Although
malaoxon and paraoxon then con-
tinue to be oxidatively destroyed
upon continued ozonation, hepta-
chlorepoxide is quite stable to
continued ozonation.
It is important to recognize that
the production of these specific
intermediate oxidation products
may not be caused solely by the
use of ozone. It is possible
that chlorine dioxide and chlorine
may produce the same intermediates.
Thus the discerning water treat-
ment official should attempt to
know what contaminants are present
in his water supply, as well as
the chemistries of the disinfec-
tant/oxidant options available to
him. Armed with this informa-
tion, he then will be better able
to determine the most cost-
effective method for dealing with
his specific problem.
Toxicity of Ozone
In aqueous solution, ozone is a
powerful oxidizing agent which
will react with human tissues.
Therefore, the lack of a stable
residual in water is a benefit,
in that by the time ozonized
water reaches a consumer's tap,
there should be no dissolved
residual of ozone. Therefore,
from the standpoints of toxicity
and cost, it is important for
plant operators using ozone not
to add excessive amounts of ozone
in an attempt to maintain an
ozone residual in the distribu-
tion system (see case history on
Strasburg, PA).
In the ambient plant air, ozone
can cause temporary discomfort
for plant operators. Therefore,
precautions should be taken to
detect any leakages of ozone from
the generating units or from the
contacting chambers. This can be
accomplished conveniently by
installing an ambient air ozone
monitor in the ozone generating/
contacting room. This monitor-
can be coupled electronically
with the ozone generator, and an
alarm, so that in the event ozone
is detected in the plant ambient
air, electrical power to the
ozone generator will be cut off,
thus ceasing the generation of
ozone, and sounding an alarm.
This subject is treated in more
detail in Section V.
Disinfection With Ultraviolet
Radiation
Ultraviolet radiation is an
effective disinfecting agent
against bacteria and viruses, but
it is not effective against
spores and cysts. It has been
used commercially for many years
in pharmaceutical houses, cosmetics
manufacturing plants, beverage
production, aquaculture, and the
semiconductor industry to disinfect
large volumes of better-than-potable
quality waters. In addition, XJV
radiation has the additional
advantage of not being a chemical
oxidant. ; Therefore, microorganisms
can be killed without generating
by-products of chemical oxidation
or halogenation.
In practice, however, UV-generating
units also generate small quantities
of ozone, which can produce trace
amounts of organic oxidation
products.
Two drawbacks have been cited
against the use of UV radiation
for disinfecting potable water
supplies on a large scale, neither
of which is entirely correct.
The first is that UV radiation
111-29
-------
provides no stable residual in
the distribution system. This is
of little consequence, since
small amounts of chlorine, chlor-
ine dioxide or chloramine can be
added for that purpose. For
example, UV radiation is allowed
for disinfection aboard ships,
but new shipboard regulations
require the use of chlorine as
well.
The second objection is the
erroneous belief that only thin
films of water can be disinfected
effectively by UV radiation, thus
posing difficult engineering
design problems for treating
larger quantities of water.
Modern UV radiation units contain
multiple tubes which are arranged
around the periphery of the
units. Water to be disinfected
flows through these units follow-
ing baffled paths, thus allowing
adequate contact times and repeated
exposure to the UV radiation.
Figure 13 is a schematic diagram
of a typical assemblage of ultra-
violet radiation equipment for
treatment of water and wastewater.
As with the use of any other
disinfectant, the better the
pretreatment of the water, the
more efficient will be the disin-
fection efficiency of UV radiation.
Factors Affecting Disinfection
Efficiency of UV Radiation
In order for any radiation to
kill or inactivate a microorganism,
it is essential for the radiation
to reach the microorganism.
Thus, anything which prevents
radiation from striking the
microorganism, alters the wave-
length of the radiation, or
decreases the quantity of radia-
tion striking the microorganism,
will interfere with the disinfec-
tion process. Examples include:
o films or coatings which
develop on the surfaces of
UV lamps;
o agglomerations of organisms
in which the inner organisms
are protected from the
radiation;
o suspended materials in the
water (turbidity);
o colored water that can
attenuate the radiation;
o dissolved organics that
absorb the radiation;
o decrease in time of exposure
to radiation by short-
circuiting of water flowing
through the exposure chamber.
There also is a phenomenon associ-
ated with UV-damaged cells called
photo-reactivation. Upon exposure
to sunlight, some damaged cells
can repair damage they may have
sustained, and then continue
normal metabolism (e.g., living).
By-Products of UV Radiation
From the point of view of disin-
fection of drinking water, there
are no chemical byproducts of UV
radiation, other than those trace
quantities of organic oxidation
products which may be produced by
the small quantities of ozone
formed as a by-product of UV
radiation.
Hazards of UV Radiation
Damage to human eyes is the major
hazard from the use of UV radiation.
All reputable suppliers of UV
generating equipment have taken
this factor into account in
designing their equipment. Thus,
during operation, no "leaks" of
light should be observable by the
water treatment plant operator.
111-30
-------
GERMIC1DAL LAMP
IN QUARTZ SLEEVE
DUAL ACTION
WIPER SEGMENT
CHAMBER
TRANSFORMER HOUSING
AND JUNCTION BOX
PRINCIPLE OF OPERATION
1 The water enters the purifier and flows into the annular space
between the quartz sleeve and the outside chamber wall.
2 The internal baffle and wiper segments induce turbulence in the
flowing liquid to insure uniform exposure of suspended micro-
organisms to the lethal ultraviolet rays.
3 The sight port enables visual observation of lamp operation.
4 The wiper assembly facilitates periodic cleaning of the quartz
sleeve without any disassembly or interruption of purifier operation.
5 Water leaving the purifier is instantly ready for use.
Figure 13. Schematic Diagram of Ultraviolet Radiation Disinfection
Systems. (Courtesy of Pure Water Systems)
111-31
-------
-------
IV. DISINFECTION SYSTEM DESIGN
INTRODUCTION
Water utilities normally require
the services of an experienced
consulting engineer or equipment
vendor for design of disinfection
systems and other portions of a
water treatment system to obtain
the necessary approval of the
state agency having primary
enforcement responsibility for
safe drinking water. The scope
of services of the consultant or
the vendor's professional staff
can be tailored to fit the needs
of the particular water utility,
but may include some or all of
the following services:
o Preliminary Study
o Preliminary Design
o Detailed Design
o Construction Supervision
o Startup Assistance
A high level of rapport must be
established between representa-
tives of the utility and the
engineer. The engineer must be
familiar with the unique features
and requirements of the utility
as well as responsiveness of the
regional chemical suppliers and
equipment vendors prior to proceed-
ing to the detailed design stage
of the work.
This section presents discussions
of the factors important from the
design viewpoint in selection of
a disinfectant, the specific
design features of each of the
disinfectants in use today, then
a discussion of the provisions
necessary for the safe use of
these disinfectants.
OPTIMAL SYSTEM DESIGN
The designer of a water treatment
plant can ease the job of the
operator and also help lessen the
probability of error by following
some simple rules:
o Conduct sufficient laboratory
and pilot plant studies and
observations of the source
waters to fully characterize
them. Raw water quality in
many areas is declining due
to more extensive use, and
this must be anticipated in
the design. New facilities
should be adequate to handle
the full range of expected
water conditions, which
includes foreseeable water
quality deterioration.
o Initiate the design process
with a thorough review of
all possible non-treatment
or minimal treatment approaches.
Include consideration for
ease of maintenance, adequate
space and light, and simplici-
ty in the design and equipment.
Avoid overly elaborate
control systems and include
appropriate redundance
(i.e., never only one
chlorinator).
o Avoid dead ends in the
distribution system. Provide
equipment for flushing and
sampling, for storage, and
for emergency chlorination
of the distribution system.
Clearly identify such emer-
gency equipment, for example,
by the use of color-coded
paints.
IV-1
-------
SELECTION OF A DISINFECTANT
The selection of a disinfectant
and/or oxidant depends upon a
wide range of factors which
include the following:
o raw water characteristics;
o facility design flow - peak,
average, minimum;
o overall treatment system
requirements and complexity;
o distribution system
characteristics;
o consumer needs and prefer-
ences;
o cost-effective analyses;
o equipment supplier
representation;
o chemical supplier reliability;
o regulatory agency acceptance;
and
o site-specific problems,
which include
a. sludge disposal
b. power availability
c. facility access
d. safety
Raw water quality, design flow,
and finished water requirements
are key factors in the selection
of the disinfectant(s) and/or
oxidant(s) to be used in the
treatment process. A highly
complex treatment system may be
required to produce drinking
water from a low quality raw
water source. This finished
water must conform to regulatory
agency standards and be acceptable
to the consumer. This type of
system likely would require the
ability to operate a sophisticated
disinfection/oxidation system or
systems. In the same manner,
larger plants normally may justify
more complete disinfection systems
while small ones may not. Once
regulatory agency requirements
have been satisfied, finished
water parameters such as those
for taste, odor, color, and
dissolved organics become a
matter of consumer acceptance.
In specific cases, such as in
Strasburg, Pennsylvania (see
Section 8, CASE HISTORIES) and
Whiting, Indiana (27), consumer
demands forced the installation
of ozone rather than chlorine,
while consumer demand in Hamilton,
Ohio, caused the adoption of
chlorine dioxide in place of
chlorine (28).
Factors unique to the specific
treatment plant may dictate
disinfectant selection. Facilities
which have a sludge disposal
problem might seek to reduce the
problem by testing the benefit of
adding ozone early in the process
as a coagulant aid as well as an
oxidant. Limited availability of
power at the point of disinfection
could eliminate ozonation as a
disinfection alternative. Limited
site access during all or parts
of the year might favor the use
of disinfectants/oxidants generated
on-site. The use of bottled
chlorine as a disinfectant has
been precluded in certain areas
due to safety concerns.
The quantity of disinfectant/oxi-
dant to be used is governed by
the oxidant demand of the water
to be disinfected and by the
characteristics of the water
distribution system. Maintenance
of a required residual level of
disinfectant in the extremities
of a sprawling water distribution
system with long water retention
times requires large post-
treatment disinfectant dosages
for finished waters having high
oxidant demands.
IV-2
-------
Cost-effectiveness considerations,
operator acceptance, and equipment
vendor representation are three
remaining factors in the selection
process. In varying degrees, all
systems are sensitive to the
disinfectant/oxidant dosage
required, both in terms of initial
capital investment and of continu-
ing operation and maintenance
costs. Provision of a disinfec-
tion (or even treatment) system
which the utility staff will not
accept or which is beyond its
capabilities to operate and
maintain is of questionable
benefit to the waterworks.
Difficult to quantify, but fre-
quently of great importance to
the operator, is the posture of
the local representation of
various system vendors and chemi-
cal suppliers.
CHLORINATION SYSTEM DESIGN
Choice of the form of chlorination
system to be used; whether gaseous
chlorine (Cl ) , dry calcium
hypochlorite^[Ca(OCl)2], or
sodium hypochlorite solution
(NaOCl) depends upon a number of
factors which include the
following:
o availability of chlorine
source chemical;
o capital cost of the facility;
o operation and maintenance
costs for the equipment;
o chemical costs;
o location of the facility;
o operator skills available;
o safety.
Each of the methods of chlorina-
tion will provide the same disin-
fecting power on a pound for
pound basis of available chlorine
when utilized at the same pH.
However, each of the systems must
be approached differently in
terms of basic design and safety.
Sufficient chlorine must be
provided to satisfy the chlorine
demand of the water at the point
of chlorine addition, plus an
additional amount to maintain the
required residual after a specified
period of time. The relative
dosages of the various chemical
sources of hypochlorite ion
(OC1 ) in solution can be deter-
mined; these frequently will
depend upon the point of chlorine
application in the process. The
chlorine demand of raw water
usually is far higher than that
of finished water. In any case,
a minimum of 20 minutes contact
time at the peak water demand
rate must be provided between the
point of addition of the chlorine
to the water and the first customer
service in the distribution
system. If this contact time is
not provided in the distribution
system, a baffled holding tank
located at the plant or in the
system should be provided after
chlorination.
Chlorination With Gaseous Chlorine
Chlorine is supplied in high
strength steel cylinders with
chlorine capacities of 100 and
150 pounds (45.4 and 68.1 kilo-
grams), under sufficient pressure
to liquefy the chlorine. Major
manufacturers of gaseous chlorine
are shown in Table VI. However,
the quantity consumed by small
treatment facilities normally
would be purchased from local
suppliers which are listed in the
local telephone directory yellow
pages under "chemical suppliers"
or "swimming pool suppliers".
IV-3
-------
TABLE VI
MAJOR MANUFACTURERS OF GASEOUS CHLORINE
Name
Allied Chemical Corporation
Ashland Chemical Company
Pennwalt Corporation
PPG Industries, Inc.
Dixie Chemical Company
Address
P.O. Box 1139R, Morristown, NJ 07960
P.O. Box 2219, Columbus, Ohio 43216
Organic Chemicals Division, Three
Parkway, Philadelphia, PA 19101
Chemical Division, One Gateway
Center, Pittsburgh, PA 15222
3635 W. Dallas Street,
Houston, TX 77019
Direct feed chlorinators add gas
under pressure directly into the
water to be disinfected. This
type of unit normally is used
only when electrical power is
unavailable to operate a solution
feed unit. This is an extremely
site-specific application which
will not be discussed further.
Solution feed units mix chlorine
gas with a side stream of water
to form a chlorine (hypochlorous
acid) solution, which then is
injected into the main stream.
Solution feed chlorinators operate
on a vacuum controlled basis,
automatically shutting off if the
side stream flow is interrupted.
This type of unit, shown in
Figure 14, is preferable for
safety reasons over direct feed
units.
The basic solution feed gas
chlorinator includes the following
components:
o isolating valve to interrupt
gas flow;
o pressure regulating valve;
o gas flow indicator;
o adjustable gas flow controller;
o check valve;
o venturi type gas injector.
The market for supply of gas
chlorinators is extremely competi-
tive, as illustrated by Table VII
which provides a partial list of
suppliers of these types of
units.
Well established standards for
design of gas chlorination systems
exist in standard waterworks
industry literature (29,30). The
following points are provided to
highlight possible design questions:
o Under normal conditions, the
maximum withdrawal rate of
chlorine gas (40 Ibs/day -
18.16 kg/day) from a single
150 Ib (68.1 kg) liquid
IV-4
-------
TO VENT
CHLORINE
CYLINDER
VALVE
YOKE
CLAMP
LEAD
GASKET
RATE
VALVE
VACUUM SEAL
"0" RING
-«== CHLORINE LIQUID
OUTLET CONNECTION
VENT VALVE
RATE INDICATOR
REGULATING
DIAPHRAGM
ASSEMBLY
VACUUM LINE
EJECTOR AND
CHECK VALVE
ASSEMBLY
WATER SUPPLY "~
CHLORINE
~" SOLUTION
CHLORINE CYLINDER
Figure 14. Solution Feed Gas Chlorination System
-------
TABLE VII
SOME GAS CHLORINATOR MANUFACTURERS
Name
Air-0-Lator Corporation
BIF
Capital Controls Co.
Chlorinators, Inc.
Diamond Shamrock Corp.
Fischer & Porter, Co.
Force Flow Equipment
Ionics, Inc.
ProMinent Fluid Controls
Tait-Andritz Inc.
Wallace & Tiernan
Address
8100-04 Paseo, Kansas City, MO 64131
Unit of General Signal Corp., 1600
Division Road, West Warwick,
RI 02893
Advance Lane, Box 211,
Colmar, PA 18915
733 Northeast Dixie Highway,
Jensen Beach, FL 33457
351 Phelps Court, Irving,
TX 75062
Environmental Division, County
Line Road, Warminster, PA 18974
3567 Golden Gate Way, Lafayette,
CA 94549
65 Grove Street, Watertown, MA 02172
503 Parkway View Drive, Pittsburgh,
PA 15205
4601 Locust Street, Lubbock,
TX 79404
Division of Pennwalt Corporation,
25 Main Street, Belleville,
NJ 07109
chlorine container is more
than adequate to satisfy the
chlorine demand of the water
processed for 5,000 persons
(5,000 persons x 100 gal/
capita/day = 500,000 gal/day
= 1893 m /day) as illustrated
by the following calculation:
40 lbs/day/8.34 Ibs/gal x
0.5 mgd =9.6 mg/L. However,
weighing scales to provide a
positive measure of chlorine
usage should be provided. A
device for automatic switch-
over from empty cylinder to
full cylinder reduces manpower
IV-6
-------
requirements and increases
chlorination reliability.
Chlorine cylinders are heavy
and bulky, even when empty.
Provision should be made for
easy removal of gas cylinders
from the delivery truck and
their movement to the chlorine
storage room. A special
cart should be assigned to
the chlorination facility
for cylinder transport.
Stairways, narrow doorways
and passages should not be
part of the route from
delivery to storage. Any
cylinders stored upright
should be securely fastened
to the walls to prevent
their falling, which can
shear the neck and cause a
rapid discharge of the gas -
resulting in two hazards -
exposure to high concentra-
tions of chlorine and the
danger of physical injury
from the cylinder, which can
become a fast-moving
projectile.
Chlorinators should be
located as close as possible
to the point of application.
Provision should be made for
regular inspection of chlor-
ine gas and solution lines.
The 150-lb (68.1 kg) cylinders
should be operated so that
chlorine is used at a rate
no greater than 40 Ibs
(18.2 kg) per day per cylinder.
If chlorine is removed at a
greater rate, evaporation of
the liquid chlorine will
cool the chlorine, and
chlorine lines and valves
may freeze and impede flow.
Multiple cylinders should be
used for higher daily flow
rates.
The following calculation illus-
trates sizing of a gas chlorina-
tion system:
Preliminary Design Calculations
For A Gas Chlorination System;
Problem; Determine the capacity
of a gas chlorination system to
treat an average waterworks-flow
of 500,000 gal/day (1,893 m /day),
peak flow of 1 million gal/day
(3,786 m /day), and minimum flow
of 250,000 gal/day (947 m /day).
Given; The water to be chlori-
nated has been determined to have
a chlorine demand of 0.6 mg/L and
State public health standards
require 0.2 mg/L residual chlorine
after chlorination.
A. total chlorine dosage =
chlorine demand of water
plus required chlorine
residual = 0.6 mg/L + 0.2 mg/L
=0.8 mg/L.
B. average chlorine requirements
=0.5 mgd x 8.34 Ib/gal x
0.8 mg/L = 2.34 Ib (1.06 kg)
chlorine/day.
C. maximum chlorine requirement
= 1.0 mgd x 8.34 Ib/gal x
0.8 mg/L = 6.67 Ib (3.03 kg)
chlorine/day.
D. minimum chlorine requirement
= 0.25 mgd x 8.34 Ib/gal x
0.8 mg/L = 1.67 Ib (0.76 kg)
chlorine/day.
Chlorination With Calcium
Hypochlorite
Calcium hypochlorite is supplied
as a white solid which is highly
corrosive and gives off a strong
IV-7
-------
chlorinous odor. It contains
approximately 70% available
chlorine, is readily soluble in
water, and is available in gran-
ular, powdered, or tablet form.
It is provided in 0.91, 2.27,
3.63, and 15.9 kg (2, 5, 8,
35 Ib) cans and in 45.4, 136 and
363 kg (100, 300, and 800 Ib)
drums. The containers generally
are resealable.
Calcium hypochlorite is hygro-
scopic (readily absorbs moisture),
and reacts slowly with atmospheric
moisture to form chlorine gas.
Therefore, the shipping containers
must be emptied completely or
carefully resealed. It is not
feasible to handle this material
in bulk handling systems.
The contents of a calcium hypo-
chlorite container are emptied
into a mixing tank where it is
readily and completely dissolved
in water. The resulting highly
corrosive solution is stored in
and fed from a stock solution
vessel constructed of corrosion-
resistant materials such as
plastic, ceramic glass, wood, or
rubber-lined steel. Dosage of
the solution at 1 or 2% available
chlorine content is by diaphragm
type, chemical feed/metering
pumps.
The following calculations illus-
trate the sizing of a calcium
hypochlorite system:
Preliminary Design Calculations
For A Calcium Hypochlorite System:
Problem; How many pounds of 70%
available calcium hypochlorite
will be required to equal the
output of the gas chlorination
system previously described?
A. calcium hypochlorite required =
pounds chlorine required/day _
0.70 Ib Cl2/lb Ca(OCl)2
Ibs Ca(OCl) /day
B. average Ca(OCl) required =
2.34 Ib chlorine required/day
0.70 Ib Cl /Ib Ca(OCl)=
£. £
3.34 Ib (1.52 kg)/day
C. maximum Ca(OCl) required =
6.67/0.70 = 9.5 Ib (4.31 kg)/day
D. minimum Ca(OCl) required =
1.67/0.70 = 2.38 Ib (1.08 kg)/day
Problem; How many pounds of dry
calcium hypochlorite (70% available
chlorine) are to be dissolved in
55 gallons of water to make up a
2% solution of available chlorine?
Ib water x (% solution)/100% _
(% available Cl )/100%
Ibs Ca(OCl) required
55 gal x 8.34 Ibs/gal x (2%/100%)
(70%/100%)
13 Ibs (5.90 kg) Ca(OCl)
Calcium hypochlorite should be
stored in its original, sealed
shipping containers in a room
specifically designed for chlorine
chemicals, but separate from the
chlorine handling and dissolving
room. Provisions should be made
for the rapid removal of the
calcium hypochlorite from the
storage room in case of fire.
However, automatic sprinklers
should not be provided, because
of the evolution of chlorine gas
which occurs when the solid
calcium hypochlorite becomes wet.
IV-8
-------
Chlorination With Sodium
Hypochlorite
Sodium hypochlorite, usually
supplied in concentrations of 5
and 15% available chlorine, is
commercially available only in
liquid form. Supplied in this
form, it is easier to handle than
gaseous chlorine or calcium
hypochlorite. However, sodium
hypochlorite solutions will lose
oxidizing (disinfecting) power
during storage and should be
stored in a cool, dark, dry area.
The material is supplied in glass
or plastic bottles, carboys, or
in lined drums ranging in size
from 1.9 to 208 L (0.5 to 55 gal).
Bulk shipment by tank truck also
is a common form of transport.
No more than a one-month supply
of the chemical should be pur-
chased to prevent loss of avail-
able chlorine.
The following calculations illus-
trate the sizing of a sodium
hypochlorite solution system:
Preliminary Design Of Sodium
Hypochlorite Solution System
Problem; How many gallons of 15%
NaOCl solution will be required
to equal the output of the gas
chlorination system previously
described?
A. Amount of available chlorine
in sodium hypochlorite
% available chlorine
Ibs available ! per gal
1 5 10 15
0.083 0.42 0.83 1.25
B. Amount of NaOCl required =
Ibs chlorine required/day _
Ibs/gal available C12
gal NaOCI/day
C. Average amount of NaOCl
required =
2.34 Ib chlorine required/day _
1.25 Ibs available Cl /gal
1.87 gal (7.08 L)/day
D. Maximum NaOCl solution
required =
6.67 Ibs chlorine required/day _
1.25 Ibs available Cl2/gal
5.34 gal (20.33 L)/day
E. Minimum NaOCl solution
required =
1.67 Ibs chlorine required/day _
1.25 Ibs available Cl2/gal
1.34 gal (3.79 L)/day
Problem: How many gallons of 15%
NaOCl solution is to be mixed
with water to make 55 gallons
(208.33 L) of a 2% NaOCl solution?
gal diluted solution x
% diluted solution
% concentrated solution
gal concentrated solution
55 gal x 2% _ 7.3 gal (27.65 L)
15% gal concentrated
NaOCl solution
Sodium hypochlorite storage teinks
are either plastic or rubber, or
plastic lined. Storage tanks
IV-9
-------
normally are located outdoors in
temperate climates, but indoors
in northern climates. Chemical
feed pumps are used to add the
chemical at its as-received
strength.
CHLORINE DIOXIDE SYSTEMS DESIGN
This chemical is generated on-site,
as a dilute aqueous solution, and
in quantities as needed at the
moment, to avoid storage of
excesses. This aqueous solution
then is metered at a rate paced
and controlled hy the flow rate
of the water to be treated, so
that a constant dosage of CIO is
added at all times, irrespective
of the process water flow rate.
Table VIII provides a partial
listing of chlorine dioxide
equipment suppliers. Several
different types of generation
equipment are available which
vary depending upon the supplier,
but also upon the generation
process chosen (gaseous chlorine
versus sodium hypochlorite plus
acid, or acid plus sodium chlorite
solution, for example). Pertinent
aspects of each type of chlorine
dioxide generation equipment will
be discussed in this sub-section.
All three of the chlorine dioxide
generation procedures described
in Section 3 are in general use
in the United States at this time
for application in small water
treatment facilities. The three
generation procedures are:
#1) chlorine gas + sodium chlorite
solution
#2) sodium hypochlorite + sodium
chlorite + acid
#3) sodium chlorite + mineral
acid.
Chlorine plus sodium chlorite is
the most commonly used chlorine
dioxide production technique in
the U.S. A. schematic diagram of
equipment marketed by Olin Water
Services, which is designed to
produce chlorine dioxide by this
method is illustrated in Figure 15.
However, the principles of opera-
tion are similar for equipment
marketed by the other suppliers,
except for CIFEC, whose equipment
will be described later in this
sub-section.
The gaseous chlorine procedure is
particularly applicable when a
gaseous chlorination system
already exists at the water
treatment plant. The reaction by
which chlorine dioxide is generated
is as follows:
Cl,
chlorine
2C102
chlorine
dioxide
2NaC10
sodium
chlorite
2NaCl
sodium
chloride
This equation indicates that
71 Ibs (26.48 kg) of chlorine
mixed with a solution containing
181 Ibs (67.5 kg) of 100% NaCIO
will produce 135 Ibs (50.36 kg)2
of chlorine dioxide. However,
the ratio of reagents recommended
by most suppliers of chlorine
dioxide generating equipment and
chemicals is 1:1 by weight. This
means that more than double the
stoichiometric amount of chlorine
required by the equation above is
utilized. This excess of chlorine
over that required results in a
faster reaction rate and insures
a more complete reaction of
IV-10
-------
Water flow meter
f
Pneumatic
chlorine
orifice
positioner
6-Gage
Air regulator and filter
Chlorine dioxide
generating tower
Point of
application
Source: From HANDBOOK OF CHLORINATION, by George C. White (c) 1972 by Litton Educational
Publishing, Inc. Reprinted by permission of Van Nostrand Reinhold Company.
Figure 15. Automatic Flow-Proportional Chlorine Dioxide System;
Generation from Chlorine and Sodium Chlorite (31)
-------
TABLE VIII
PARTIAL LISTING OF CHLORINE DIOXIDE EQUIPMENT SUPPLIERS
Name
CIFEC
Fischer & Porter Co.
International Dioxcide, Inc.
Olin Water Services Co.
ProMinent Fluid Controls
Rio Linda Chemical Co., Inc.
Sherman Machine & Iron Works
Wallace & Tiernan
Division of Pennwalt Corp.
Address
10 Ave de la Porte Molitor,
F 7500, Paris, France
Environmental Division,
County Line Road
Warminster, PA 18974
136 Central Avenue,
Clark, NJ 07066
120 Long Ridge Road
Stamford, CT 06904
503 Parkway View Drive,
Pittsburgh, PA 15205
2444 Elkhorn Blvd.,
Rio Linda, CA 95673
26 E. Main Street,
Oklahoma City, OK 73104
25 Main Street,
Belleville, NJ 07109
chlorine with the chlorite ion.
Because a large excess of chlor-
ine is employed, chlorine dioxide
solution prepared by this tech-
nique also will contain some free
available chlorine, mostly as
hypochlorous acid.
The production of chlorine dioxide
using sodium hypochorite solution
with sodium chlorite and sulfuric
acid, as illustrated by Figure 16,
is well suited to small systems.
Dosage of each chemical can be
derived from the following
equation:
2NaC10 + NaOCl +
sodium
chlorate
H2S°4 ~
sulfuric
acid
NaCl
sodium
hypochlorite
2C10
chlorine
dioxide
sodium sodium
chloride sulfate
water
IV-12
-------
CIO,
3
c c
c c
c c
c c
c
e
c
c
Chlorine dioxide
generating tower
Point of
application
Sulfuric
acid
Source: From HANDBOOK OF CHLORIMTION, by George C. White (c) 1972 by Litton Educational
Publishing, Inc. Reprinted by permission of Van Nostrand Reinhold Company.
Figure 16. Equipment Arrangement for Generating Chlorine Dioxide from Hypochlorite and Acid (32)
-------
In this system, all three reac-
tants are in solution. Utiliza-
tion of acid increases the conver-
sion of chlorite ion to chlorine
dioxide. Solution feed pumps of
equal capacities can be used by
adjusting the solution strength
of each of the reactants. Thus,
the chlorine dioxide production
and addition rates can be paced
by the flow rate of the product
water and/or by its disinfectant
demand.
Sodium chlorite is available in
55 gallon (208.33 L) drums,
either as a solid (80% active
NaCIO ) or as a solution contain-
ing 2§ to 30% NaCIO (about
33% solids). If not used direct-
ly from the drum, sodium chlorite
solution is stored in polyvinyl-
chloride (PVC) or fiberglass
tanks and transferred by means of
PVC, rubber, or Tygon piping
systems. Diaphragm pumps incorpor-
ating PVC as the material in
contact with the solutions are
used for pumping sodium chlorite
solutions. Provision must be
made for immediate washdown of
any spills of the chemical. This
precaution is generic to all
chlorine dioxide generating
systems.
Acid handling systems are designed
and operated similarly to those
of the sodium chlorite system
described above.
The CIFEC System For Generating
Chlorine Dioxide
A schematic diagram of this newer
system is illustrated schemati-
cally in Figure 17. The equipment
was developed in France, but has
recently been installed at several
U.S. water treatment plants.
Because of its unique design
features, this system is able to
produce chlorine dioxide from
gaseous chlorine, in high yield
and containing little excess free
chlorine.
Gaseous chlorine is passed into
water which is circulated contin-
uously in what is referred to as
an "enrichment loop". Under
these conditions, dissolved
chlorine (hypochlorous acid)
concentrations become higher than
can be achieved in a single pass.
As a result, the pH of the hypo-
chlorous acid solution is lowered
to below 4. This solution then
is pumped into the CIO reactor
along with a solution of sodium
chlorite. When the pH of the
hypochlorous acid solution is
below 4, conversion of chlorite
ion to chlorine dioxide is claimed
to be significantly higher than
the single pass method employing
elemental chlorine gas. Therefore,
chlorine dioxide is produced
which is free of significant
quantities of free chlorine.
Rio Linda Chemical Chlorine
Dioxide Generator
Figure 18 shows a schematic
diagram of a newer acid/chlorite
CIO generator marketed by Rio
Linaa Chemical Co., Inc. Chlorine
dioxide is generated by addition
of dilute hydrochloric acid to
sodium chlorite solution. The
novel principle of this generator
is the mixing of acid with concen-
trated sodium chlorite solution
before the two solutions reach
the reactor. The two solutions
are brought together in an eductor
by means of vacuum created by
water flow through the eductor.
Such a system eliminates a pump
and allows the system to occupy a
smaller space.
IV-14
-------
C102 EXIT
Ui
VACUUM LINE OF CHLORINE
CHLORINATOR
EJECTOR WITH CHECK VALVE ASSEMBLY
SODIUM CHLORITE METERING PUMP
i_CHLORINE CYLINDER
RECIRCULAriNQ PUMP.
FLOW METER ©
ELECTRIC VALVE
Figure 17. CIFEC Chlorine Dioxide System
(Courtesy CIFEC, Paris, France)
-------
WALL MOUNT MODEL
FLOW DIAGRAM
REACTION
COLUMN
WATER
/" FLOW
EDUCTOR
SODIUM
CHLORITE
SUPPLY
Figure 18. Rio Linda Chemical Company, Inc. Acid/NaCIO CIO Generator
IV-16
-------
Miscellaneous Comments
CHLORAMINATION SYSTEM DESIGN
Because several types of chlorine
dioxide generation equipment are
available, as well as three
processes for its production, it
is considered inappropriate to
attempt to provide detailed
instructions in this document for
preparation of chemical solutions
and feed rates of solutions.
However, the small utility choosing
to install chlorine dioxide
generating equipment can have
confidence that each equipment
vendor will provide detailed
recipes for preparing and metering
the appropriate solutions to his
chlorine dioxide reactor so as to
produce an aqueous solution of
chlorine dioxide of known and
constant concentration for addi-
tion to the plant process water.
A final point to be noted is that
the currently recommended maximum
dosage level of 1 mg/L of chlorine
dioxide means that a water supply
system processing 0.5 mgd
(1,893 m /day) would require a
maximum CIO production rate of
only 4 Ibs fl.82 kg)/day. Smaller
systems would require even less
CIO . At such low dosage levels,
two of the three vendors of
chlorine dioxide generating
equipment contacted recommend
that their units be operated
intermittently, collecting C10?
solution in an enclosed holding
tank for metering into the water
being processed. This is because
at the low flow rates of reactant
solutions, mixing is less efficient
in the ClO^ reactor. As a conse-
quence, conversion of chlorite
ion to chlorine dioxide is less
efficient.
Ammonia is available as a gas
(NH ), as a 29% water solution
(aqua ammonia), or in powdered
form as ammonium sulfate,
(NH.) SO,. Gaseous ammonia is
supplied in 150-pound (68.1 kg)
cylinders, similar to gaseous
chlorine. Aqua ammonia is sup-
plied in 55 gallon (208.33 L)
drums. Ammonium sulfate is
provided in 100-pound (45.4 kg)
bags (98% pure, 25% available
ammonia).
Gaseous ammonia normally is added
to the treated water using systems
and equipment, similar to those
used for handling gaseous chlorine.
Aqua ammonia and ammonium sulfate
solutions are handled using
systems and equipment similar to
those for sodium hypochlorite and
calcium hypochlorite solutions,
respectively. Aqua ammonia is
basic, but is non-corrosive.
Sizing of the treatment facility
would take into consideration the
intended 3:1 chlorine:ammonia
ratio.
A 25 to 30% solution of ammonium
sulfate in water is prepared in a
plastic or fiberglass container
and added to the water by means
of a chemical metering pump.
Solutions of ammonium sulfate are
stable, but are acidic, and
therefore can be corrosive to
some metals. Materials which
will withstand dilute sulfuric
acid also will easily resist any
possible corrosion effects of
dilute ammonium sulfate solutions.
OZONE DISINFECTION SYSTEM DESIGN
Ozone also is generated on-site,
on an as-needed basis, and must
IV-17
-------
be applied to the liquid stream
as it is generated. Although
ozone is generated from oxygen or
air by custom designed units in
major water and wastewater treat-
ment plants throughout the world,
units for small water treatment
plants of the size discussed in
this document normally are sup-
plied in the form of pre-engineered,
skid-mounted units. Such a unit
is illustrated by Figures 19
and 20, and employs air as the
sole feed gas because of the
lower costs at small volumes of
ozone required.
Components Of Ozone Generation
Systems
Figure 21 illustrates the four
basic components of an ozonation
system which employs ambient air
as the generator feed gas. The
essential components include air
preparation, electrical power
supply, the ozone generator, and
the ozone contacting apparatus
(including destruction of excess
ozone).
Air Preparation
Ambient air must be dried to a
maximum -60°G dew point (a unit
of moisture content of air).
Even drier gas is preferable
(lower than -60°C). Figure 22
illustrates the common type of
air preparation system used for
skid mounted units. This sub-
process must be designed conserva-
tively, especially for warm humid
climates. Use of air having a
dew point higher than -60°C will
lower ozone production, foul the
ozone production (dielectric)
tubes, and increase corrosion
problems in the generator unit
and downstream as well.
Electrical Power Supply
Supply line voltage (220/440 V),
or frequency in some cases, is
varied to control the amount of
ozone being generated and its
rate of generation. Because
these two parameters are varied
in many ozone generating systems,
the electrical power subunit can
represent a proprietary product
of the ozonation system supplier.
As a result, the electrical power
system must be specified as an
integral power supply system
specifically designed for the
ozone generator to be supplied.
In other words, the power system
should be designed for and pur-
chased from the ozone generating
system supplier.
Ozone Generator
The most common commercially
available ozone generators can be
classified as follows:
o horizontal tube; one electrode
water-cooledj
o vertical tube; one electrode
water-cooled;
o vertical tube; both electrodes
cooled;
o plate; water- or air-cooled.
The operating conditions of these
ozone generators can be subdivided
as follows:
o low frequency (60 Hz), high
voltage ( >20,OOOV);
o medium frequency (600 Hz),
medium voltage (<20,OOOV);
o high frequency (>1,000 Hz),
low voltage ( <10,OOOV).
Currently, low frequency, high
voltage units are most common,
but recent developments in electron-
ic circuitry are resulting in
IV-18
-------
Figure 19. Preengineered, Skid-Mounted Ozone Generation System
(Courtesy, Welsback Corporation, Palo, Alto, CA)
IV-19
-------
Figure 20. Different View of Skid-Mounted Ozone Generation System
(Courtesy Welsback, Corporation, Palo Alto, CA)
IV-20
-------
to
I-1
THE FOUR BASIC
COMPONENTS
OF THE
OZONATION PROCESS
GAS
PREPARATION
ELECTRICAL
POWER SUPPLY
\
2
S.
*
i N
UNOZONATED
WATER
OZONE
GENERATOR
3
OZONE-
RICH
CONTACTOR
4
>P$li$lj
X
OZONATED
WATER
Figure 21. The Four Basic Components of an Ozonation System (33)
-------
COOLING
WATER
MOIST OXYGEN BEARING (AIR)
FILTER
GAS PRESSURIZATION
(COMPRESSOR)
AFTERCOOLER
OIL COALESCER
DESICCANT DRIER
PRESSURE REDUCING
VALVE
FILTER
OZONE GENERATOR
TO CONTACTORS
Figure 22. Air Preparation Unit for Ozone Generation (33)
IV-22
-------
higher frequency units (and lower
voltages) being used.
Ozone Contacting (or Diffusion
Ozone is a gas, at ordinary
temperatures and pressures, which
is generated in concentrations of
about 1% ozone plus 99% dried air
by most available generators at
the most efficient expenditure of
electrical energy. It is not
highly soluble in water (about
10 times more than oxygen as a
rule of thumb), and must be
brought rapidly into intimate
contact with the water flow to
make most efficient use of this
disinfectant.
The following types of ozone
contactors may be used for trans-
ferring ozone gas into the water
to be treated. Each of these has
advantages and disadvantages
which have been discussed at
length by Masschelein (34):
o spray towers
o packed beds
o turbine mixers
o injectors
o porous diffusers
The required contact time will
depend upon whether the specific
application of ozone is dependent
on the rate at which gaseous
ozone dissolves in the water
(ozone mass transfer dependent)
or on the chemical reaction rate.
Disinfection is a mass transfer
dependent process, whereas oxida-
tion of organic chemicals can be
limited by the mass transfer rate
or by the chemical reaction rate.
The most commonly used contactor
for ozone disinfection in the
production of drinking water is
the multiple stage chamber using
porous plate or porous tube
diffusers, as illustrated by
Figure 23.
Destruction Of Excess Ozone
At least 90% transfer of ozone
from the gas exiting the generator
into the water being treated is
reasonable to expect by proper
contactor design. However, the
gases vented from the contactor
(called contactor off-gases)
still contain sufficient ozone to
present possible hazards to plant
personnel, nearby residents, and
the immediate environment.
Therefore, treatment of off-gas
from the ozone contactor must be
provided for in the design to
reduce the ozone concentration to
less than 0.1 ppm (by volume).
This is the time-weighted average
(over 8 hours) maximum allowable
exposure limit currently set by
the Occupational Safety and
Health Administration for exposure
of workers. This can be achieved
by a number of methods which
include the following:
o dilution by prevailing winds
or supplemental air;
o passage through wet granular
activated carbon;
o thermal (heating);
o catalytic thermal destruction;
o recycling to other process
stages.
The most favored procedure currently
is passing the heated off-gases
through a chamber containing a
proprietary catalyst which recon-
verts the ozone to oxygen. The
so-treated off-gas then may be
vented safely to the atmosphere.
Ozone contactor off-gases are
treated in this manner, rather
than drying and recirculating
through the ozone generator
IV-23
-------
UN020NA.TED
WATER
CONTACT
CHAMBER
OFF-GAS
ro
OZONE-RICH
' AIR
FLOW METER (TYPICAL)
VALVE (TYPICAL)
Figure 23. Two-Compartment Ozone Contactor Using Porous Diffusers
(Reference 24, p. 120)
-------
because of economics. It is more
cost-effective to dry ambient air
than to dry the wet air exiting
the ozone contactor.
Other Ozone Design Considerations
Materials Of Construction
Care must be taken in selecting
materials of construction for
those portions of the ozonation
system in direct contact with
either "dry" (before the contac-
tor) or "wet" (after the contactor)
ozone-containing gas. While
reinforced concrete is an appropri-
ate material for ozone contactors,
the ozone-containing gas piping
system should be 304 L and 316 L
stainless steel for dry and wet
services, respectively.
Monitoring Of The Ozonation System
Equipment should be provided to
monitor the operation of the
components of the system. The
minimum degree of instrumentation,
all of which can be provided by
the ozone equipment supplier as
part of the package units, is as
follows:
o Gas pressure and temperature
devices at key points in the
air preparation system.
Simple pressure gauges and
mercury thermometers will
suffice.
o Continuous monitoring of the
dew point measuring device
to determine the moisture
content of the dried air
feed gas to the generator.
High dewpoint indications
should be designed to sound
an alarm and shut down the
generator. Equipment for
calibration of the dew point
monitor should be provided
as well.
o Means of measuring inlet and
discharge temperatures of
the ozone generator coolant
medium (water and/or oil) is
required, as is a means of
determining whether the
coolant is actually flowing
through the generator. An
automatic system shutdown
should be provided if coolant
flow is interrupted or if
its discharge pressure
exceeds specified limits.
o A means of measuring flow
rate, temperature, pressure,
and ozone concentration of
the ozone-containing gas
discharged from the ozone
generator is required to
determine the ozone produc-
tion rate.
o A means of measuring the
power input to the ozone
generator is required.
Supplier's Obligations
The purchase order should stipu-
late that the supplier of the
ozonation system is responsible
for the supply, installation,
initial checkover, startup, and
operator training.
Maintenance Service Contract
The utility should consider
entering into a maintenance
service contract for the first
two years of operation of the
ozonation system. At the end of
this period, the need for the
service contract should be re-
evaluated versus the capability
IV-25
-------
of plant personnel to provide the
same services.
Table IX contains a listing of
the major suppliers of ozone
generation equipment in the
United States. Each of these
supplies the total ozone genera-
tion system, including electrical
power supply, air preparation
equipment, contacting apparatus,
and contactor off-gas destruction
device.
ULTRAVIOLET RADIATION SYSTEMS
DESIGN
Utraviolet (UV) radiation is
generated by means of special
lamps which emit radiation at
specific wavelengths. The major-
ity of available UV generators
are designed to operate using UV
lamps which emit light at 254
nanometers (nm). At this wave-
length, small amounts of ozone
also are produced in the air
surrounding the lamp itself.
Generation systems are enclosed
systems which contain a varying
number of UV bulbs, depending
upon the size of the equipment.
In turn, the size of the equipment
required depends upon the volume
of water to be disinfected. UV
disinfection can be effective
with equipment operating in
ambient air and in water at
temperatures in the range of 40
to 110°F. Therefore, UV gener-
ating units can be housed in
small metal utility buildings.
Should either the ambient air or
water temperature be substan-
tially outside this temperature
range, heating or cooling packages
are available from UV equipment
suppliers to maintain the proper
system operation.
Figure 13 (Section 3) is a schematic
diagram of ultraviolet disinfection
equipment as it is used for the
disinfection of water.
UV generating units designed to
disinfect 500,000 gpd (1,893 m /day)
of water will occupy a floor
space of about 40 square feet.
Since UV systems are completely
electrical, and operate satisfac-
torily with a 110V power supply,
no special safety systems are
required, except to remember not
to open the UV unit during opera-
tion because of the hazards of
eye exposure.
Water to be disinfected is piped
into the UV generating unit where
it flows past and/or around the
UV lamps. The exact configuration
of the lamps depends upon the
design of the specific commercial
unit. In any case, it should be
realized that the UV generating
lamps are submerged in the water
being disinfected. Because of
this, films of dissolved or
suspended materials contained in
the water can build up on the
surface of the lamps. These
films should be wiped off from
time to time. Many units can be
supplied with 0-rings mounted
around the lamp; these can be
moved over the surface of the
lamp from time to time to clean
it.
The frequency with which the UV
generating lamp bulbs require
cleaning depends upon the quality
of the water at the time it
enters the UV disinfection unit.
As stated earlier in this document,
it is desirable to provide water
that is as clean as practicable
to receive any disinfectant, and
this holds true for disinfection
via ultraviolet radiation.
IV-26
-------
TABLE IX
U.S. OZONATION SYSTEMS SUPPLIERS
Name
Envirotech
Eimco Process Machinery
Emery Industries, Inc.
Griffin Technics Corporation
Howe Baker Engineers, Inc.
Lotepro Corporation
Ozone Research & Equipment
Corporation
PCI Ozone Corp.
U.S. Ozonair Corp.
Welsbach Ozone Systems Corp.
(Polymetrics Corp.)
Address
P.O. Box 300,
Salt Lake City, UT 84110
4900 Este Avenue,
Cincinnati, OH 45232
66 Route 46, Lodi, NJ 07644
3102 E. 5th St., Box 956,
Tyler, TX 75710
1140 Avenue of the Americas,
New York, NY 10036
3840 North 40th Avenue,
Phoenix, AZ 85019
One Fairfield Crescent,
West Caldwell, NJ 07006
464 Cabot Rd.,
South San Francisco, CA 94080
1005 Timothy Drive,
San Jose, CA 95133
During use, the ceramic housing
of the bulbs through which UV
radiation passes solarizes (i.e.,
crystalline forces in the ceramic
change, and the material becomes
cloudy), and the intensity of
radiation passed into the water
gradually decreases. The average
lifetime of continuously operating
UV lamps is only six to 12 months.
However, changing lamps is no
more difficult than changing a
fluorescent light bulb.
UV generating units are easy to
install, requiring only two
plumbing connections (water in
and water out) and one electrical
connection (110V). In addition,
maintenance requirements are low.
Table X contains a partial listing
of suppliers of UV generating
equipment.
SAFETY PROVISIONS FOR WORKING
WITH DISINFECTANTS
Safety considerations must be
paramount when designing disinfec-
tion systems. The chemicals
discussed in this document can be
hazardous if provisions for
17-27
-------
TABLE X
MAJOR SUPPLIERS OF ULTRAVIOLET RADIATION EQUIPMENT
Name
Aquafine Corporation
Atlantic Ultraviolet Corp.
Jamlar Management Corp.
Katadyn-USA, Inc.
Koala Manufacturing Co.
Port Star Industries, Inc.
Pure Water Systems
Refco Purification Systems, Inc.
Trojan Environmental Products
Ultra Dynamics Corp.
Ultraviolet Technology Inc.
UV Purification Systems
Address
25230 Stanford Avenue West
Valencia, CA 91355
24-10 40th Avenue
Long Island City, NY 11101
172 Riverside Drive
N. Vancouver V7H 1T9, Canada
12219 St. James Road
Potomac, MD 20854
312 Roma Jean Parkway
Streamwood, IL 60103
375 N. Broadway, Suite 201
Jericho, NY 11753
4 Edison Place
Fairfield, NJ 07006
P.O. Box 2356, Dept. H.
San Leandro, CA 94577
845 Consortium Court
London, Ontario N6E 2S8$ Canada
1636 10th Street
Santa Monica, CA 90404
1355 Descanso Avenue
San Marcos, CA 92069
111 Business Park Drive
Armonk, NY 10504
IV-28
-------
emergency situations are not
provided in the initial system
designs. Such provisions must
include:
o monitoring equipment;
o emergency breathing apparatus
(preferably self-contained);
o protective clothing;
o eye protection:
o safety shower and eye wash;
o room ventilation;
o access doors;
o repair kits.
In addition, the following measures
should be designed into the
disinfection facility:
o All doors should open outward
and be equipped with panic
hardware which will eliminate
the need for operation of a
door knob or latch to open
the door;
o A minimum of two self-
contained breathing apparatus
units suitable for chlorine
service, certified by the
National Institute of Occupa-
tional Safety and Health
(NIOSH) and the Mine Safety
and Health Administration
(MSHA), should be provided
in the vicinity of the
disinfection facility, but
not in the equipment or
storage rooms.
o Activation of emergency
ventilator systems of the
disinfection facility should
actuate visual and audible
alarms to alert all employees
when emergency situations
develop.
o Continuous gas monitoring is
recommended in enclosed
spaces where gaseous chemicals
(chlorine, ammonia, and
ozone) are generated or are
used. Table XI lists the
physiological effects of
these gases. Each gas has a
characteristic sharp and
pungent odor, which normally
would be readily detected at
lower than toxic levels by
operating personnel. However,
olfactory fatigue could
reduce the sensitivity of
workers to the chemicals,
and therefore, monitoring
equipment should be supplied
and maintained.
The gas monitoring equipment
should be wired to initiate
an alarm sequence, which may
include horns, lights, and
telephone signals. In the
case of an ozonation facility,
the monitor would sound an ,
alarm at levels of 0.1 mg/m
(0.05 ppm), and shut down
the generator and start up
room purge blowers if the ~
ozone level reaches 0.2 mg/m
(0.1 ppm).
o Emergency showers and eye
washes should be provided
immediately adjacent to, but
outside of, the disinfection
facility. Showers and eye
washes should not be provided
in calcium hypochlorite
storage rooms, since this
chemical generates chlorine
gas when mixed with water.
o Emergency room ventilation.
should be provided for the
gases involved in disinfec-
tion. Air exhausts should
be provided at floor level
for chlorine and ozone and
at ceiling level for ammonia.
The emergency ventilation
systems should be wired for
initiation by monitors of
gas levels, as well as by
IV-29
-------
TABLE XI
PHYSIOLOGICAL EFFECTS OF CHLORINE, AMMONIA AND OZONE
Physiological
Effect
Parts of Gas per Million Parts of Air
(by volume)
Detectable Odor
Throat Irritation
Coughing
Dangerous in
30 to 60 minutes
Lethal
Chlorine
3.5
15.1
30.2
40 to 60
1,000
Ammonia
50
400
1,720
2,500-
4,500
?
Ozone*
0.01
1
?
50
2,000-3,000
* for 10 minute exposure times
emergency switches installed
inside and outside of the
rooms.
o Emergency repair tools,
equipment, and materials
should be maintained immedi-
ately adjacent to the disin-
fection facility. For
example, a Chlorine Institute
Emergency Kit A for 150-lb
(68.1 kg) chlorine cylinders
should be provided if gaseous
chlorine or ammonia is to be
used.
o Hose bibbs, hoses, and floor
drains should be provided
throughout the facility,
with the exception of the
calcium hypochlorite storage
room.
Further guidance in ensuring
safety provisions in disinfection
facilities is provided by standard
design guides and reference
materials (29,30, 35-38).
ASSOCIATED DESIGN CONSIDERATIONS
Bid Documents
The bid documents (plans and
specifications) for the disinfec-
tion facility must clearly estab-
lish the utility's intent.
Construction materials and construc-
tion quality must be established
clearly in order to minimize
conflicts which may arise during
the construction period. The
utility may wish a general con-
tractor to handle all aspects of
the work, or may serve as its own
general contractor by dealing
directly with individual trade
(electrical, mechanical, masonry)
contractors. In any case, the
appropriate review agencies
normally require the bid documents
to bear the seal of a professional
engineer licensed to practice in
the utility's state.
IV-30
-------
Since the plans of the facility
are the sole record of the project
that normally is retained, every
effort should be made to have the
original design criteria recorded
on the plans. This record should
include:
o design flows;
o disinfectant dosages;
o roof loadings;
o heating and ventilating
provisions.
There may be equipment incorpor-
ated into the disinfection system
with which the utility personnel
is unsure of its ability to
service and maintain. For this
equipment, the bid documents
should require that the equipment
vendor provide regular service
and maintenance by the vendor's
service technicians for a specific
period of time. This approach
would be particularly appropriate
for unfamiliar controls or moni-
toring equipment and unfamiliar
processes such as disinfection
with chlorine dioxide, ozone or
ultraviolet radiation.
Operation & Maintenance Manuals
The utility should require that
operation and maintenance (O&M)
manuals be prepared by the con-
sultant or equipment vendor. The
O&M manual should include the
following information:
o
o
o
o
the original design concepts;
description of the facility
as constructed, including
construction photographs of
buried components;
normal operational procedures;
emergency operational
procedures;
organized collection of
vendors' literature;
o safety considerations and
requirements;
o schematics with all valves
numbered to correspond to
detailed operational
procedures;
o maintenance procedures.
A number of copies of the manual,
which may consist of more than
one volume, should be provided to
assure that working and record
copies remain available throughout
the operational life of the
facility. The components of the
O&M manual should be keyed to a
facility component numbering
system, as illustrated by
Table XII.
Startup Assistance and Training
These services should be required
of both the consultant and the
various equipment vendors.
Frequently, this assistance and
training is a joint effort between
the engineer and vendor personnel.
In any event, the original contract
must ensure that these services
are provided. The engineer
normally is held responsible to
coordinate the startup and train-
ing services, but it is the
utility's ultimate responsibility
to determine whether its needs
have been adequately satisfied.
Followup Engineering Services
Representatives of the engineer
and key process equipment vendors
should be required to provide a
specific amount of followup
services during the first year of
facility operation. This should
constitute a minimum of one day
of effort at the site by specific
personnel classifications every
three months for the first nine
IV-31
-------
TABLE XII
EXAMPLE OF A PARTIAL FUNCTIONAL NUMBERING SYSTEM
FOR A WATER TREATMENT PLANT
Numbering
Code
100
101
102
103
104
105
200
201
202
203
204
205
300
301
302
303
304
305
306
307
308
400
401
402
403
404
405
500
501
502
503
504
505
506
507
508
Equipment
Well Pump Station
Pump No. 1
Pump No. 2
Pump No. 3
Pump Station Ventilation Fan
Pump Station Unit Heater
Chemical Clarification
Clarfier Drive Motors
Sludge Pump
Lime Silo
Lime Slaker
Motor Control Center No. MCC 2
Filter Building
Pressure Filter No. 1
Pressure Filter No. 2
Pressure Filter No. 3
Pressure Filter No. 4
Backwash Pump
Backwash Pump
Motor Control Center No. MCC 3
Filter Building Unit Heater
High Head Pump Station
Pump No. 1
Pump No. 2
Pump No. 3
Motor Control Center No. MCC 4
Pump Station Unit Heater
Disinfection Building
Chlorinator No. 1
Chlorinator No. 2
Chlorinator Scale No. 1
Chlorinator Scale No. 2
Chlorine Storage Room Ventilator Fan
Chlorine Feed Room Ventilator Fan
Chlorine Storage Room Unit Heater
Chlorine Feed Room Unit Heater
IV-32
-------
months and the two days immediately
prior to expiration of the warranty
period.
The engineering services contract
and the bid documents should
ensure the following equipment,
material, and information is
provided prior to facility
startup:
o safety equipment;
o special tools;
o process testing equipment;
o instrument calibration
equipment;
o contract documents;
o vendors' literature;
o draft O&M manual.
The engineer should be required
to provide the following informa-
tion within three months of
facility startup:
o record (as-built) drawings;
o final O&M manual;
o technical library on disinfec-
tion, such as AWWA manuals;
o copies of the project file,
including correspondence,
shop drawings, and payment
records.
IV-33
-------
-------
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
water treatment facility con-
struction project, and outlines a
procedure to estimate costs
associated with treatment for
microorganism destruction. It
also summarizes (in association
with Appendix A) some estimated
construction and operating cost
projections which have been made
for disinfection systems, ex-
plains how to update cost esti-
mates, and provides an overview
of potential funding sources for
small water utilities.
COST ESTIMATING PROCEDURES
The total cost estimate for a
water treatment facility gener-
ally is the sum of the costs
associated with two major
categories:
o construction costs
o operation and maintenance
costs
Each of these major cost cate-
gories 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 of water 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
generally are most useful for
comparing relative costs of the.
treatment alternatives and for
approximating the general cost
level to be expected for a pro-
posed water treatment system.
Construction Costs
Whenever treatment costs are
determined, whether from a pub-
lished report or from a vendor's
estimate, it is critically impor-
tant to establish exactly what
components and processes the cost
estimate includes. Different
cost estimates based on different
basic assumptions (such as water
quality) and different components
(such as housing) have resulted
in many misunderstandings in the
past. In addition, if cost data
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 four-volume series of reports
entitled: Estimating Water Treat-
ment Costs (EPA-600/2-79-162a,b,c,
and d)] can be used. Volume 3 of
this four-volume set (39) presents
cost data and curves applicable
to small water supply systems
(2,500 gpd to 1 mgd) for 99 unit
processes useful for removing
contaminants covered by the
NIPDWR. Some of these unit
processes involve the use of
disinfectants.
V-l
-------
In this regard, other EPA-sponsored
projects currently are in progress
to refine and improve the accuracy
of the cost data base. As these
projects are completed, they
should be consulted to obtain
more accurate cost estimates.
The construction cost curves in
Reference 39 were developed by
using equipment cost data supplied
by manufacturers, cost data from
actual plant construction, pub-
lished data, and using estimating
techniques described in Richardson
Engineering Services Process
Plant Construction Estimating
Standards, Mean's Building Con-
struction Cost Data, and the
Dodge Guide for Estimating Public
Works Construction Costs. The
construction cost curves then
were checked and verified by an
independent engineering consulting
firm.
Although the cost data in Refer-
ence 39 are somewhat outdated and
do not include cost curves for
some of the most common disinfec-
tion processes, the method used
to generate costs provides an
outline of the items to consider
when developing cost estimates.
These include:
o Excavation and Site Work
This category includes work
related only to the applicable
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 con-
crete 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.
V-2
-------
o Housing
In lieu of segregating
building costs into several
components, this category
represents all material and
labor costs associated with
the building, including
equipment for heating,
ventilating, air conditioning,
lighting, normal convenience
outlets, and the slab and
foundation.
To the subtotal for construction
costs normally is added 15 percent
for contingencies.
The total construction cost is
obtained by adding to the above
costs the cost of the following
items:
Special sitework;
General contractor overhead and
profit;
Engineering;
Interest;
Land;
Legal, fiscal, and administrative
services.
These costs are not directly
applicable to the costs for
specific disinfection processes,
but typically, will average
between 30% and 35% of the total
construction cost. The cost
curves of Reference 39 do not
include these items; they must be
added on to arrive at a total
cost estimate.
The costs given in Reference 39
are based on October 1978 dollars,
and can be updated by using the
Engineering News Record (ENR)*
* Engineering News Record is a
weekly McGraw-Hill publication
which periodically summarizes
updated Construction Cost (and
other) Indices.
Construction Cost Index (CGI) or
Building Cost Index (BCI).
The following formula can be used
to update construction costs:
Updated Cost = Cost from Curve x
(current ENR-CCI)
(ENR-CCI when costs were determined)
The cost curves used in Reference 39
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 39 cost estimates to
June 1982, 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 and that there is a wide
variation between data of individ-
ual 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
overestimate or underestimate
costs, depending upon construction
costs in the locality of interest.
More sophisticated cost estimating
techniques are available, and are
described in Reference 39.
Annualizing Construction Costs
To determine the true total
yearly cost of owning, maintaining,
and operating a disinfection
system, all costs must be stated
on an annualized basis. As shown
later herein, O&M costs normally
are stated on this basis. Capital
costs can be annualized as a
series of equal payments needed
to recover the initial expenditure
V-3
-------
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 of the system in
years (n)(40):
CRF
.n,
Many finance handbooks provide
tables of CRF values corresponding
to various combinations of interest
and financing period. Table XIII
is an abbreviated example of this
type of table, taken from Refer-
ence 40. The illustrative cost
calculation example given below
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.
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 requirements generally are
provided in kilowatts per year,
and labor in hours per year.
Cost curves are developed by
multiplying these requirements by
the costs of power and labor,
respectively. To update such
curves, the cost per year is
multiplied by the ratio of cur-
rent energy or labor costs divided
by the respective unit cost used
to develop the original curve.
For example, assume an available
energy cost curve was 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 ratio
of 0.05/0.03.
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 PPI
at the time the graph was prepared.
O&M Cost Basis And Assumptions
O&M costs also must be determined
based on site-specific considera-
tions, such as volume of water
treated, energy costs, labor
costs, and building heating
requirements. O&M costs do not
include the cost of chemicals;
these must be added to the sum of
annualized construction costs and
O&M costs to arrive at total
annual costs.
V-4
-------
TABLE XIII
CAPITAL RECOVERY FACTORS FOR SOME COMBINATIONS
OF INTEREST (i) AND FINANCING PERIOND (n)
n Years
5
10
15
20
25
0.
0.
0.
0.
0.
6%
237396
135868
102963
087185
078227
0.
0.
0.
0.
0.
7%
243891
142378
109795
094393
085811
0.
0.
0.
0.
0.
8%
240456
149029
116830
101852
093679
0.
0.
0.
0.
0.
9%
257092
155820
124059
109546
101806
0.
0.
0.
0.
0.
10%
263797
162745
131474
117460
110168
12%
0.277410
0.176984
0. 146824
0.133879
0.127500
The procedures outlined on the previous pages were used to develop the
following illustrative cost example:
Example for Approximating Total Annual Costs for a Small Solution-Feed
Chlorination System Using Chlorine Gas (Feed Capacity = 100 Ibs/day)
Step 1: Calculate Cost Adjustment Factors as of the desired date
(assume June 1982, for example).
A. Construction Cost Escalation Factor (CCEF)
CCEF = Current ENR-CCI
Base ENR-CCI
The cost curves of Reference 39 are based on October 1978 cost data
when the ENR-CCI was 265.38. The June 1982 ENR-CCI was 352.92.
Therefore:
CCEF = 352.92
1.33
265.38
B. Maintenance Material Cost Escalation Factor (MMCEF)
MMCEF = Current PPI
Base Year PPI
The October 1978 U.S. Department of Commerce Producer Price Index
(PPI) was 199.7. The June 1982 PPI was 299.4.
Thereto re:
MMCEF
299.4
199.7
1.50
V-5
-------
Step 2; Determine Construction Costs
The Reference 39 construction cost for gaseous chlorine was $4,310,
which included manufactured equipment, labor, pipe and valves, electri-
cal housing (25 ft ) and 15% of the total estimate for contingencies.
June 1982 construction cost x CCEF = $4,310 x 1.33 = $5,272
SteP 3i A<1<1 30% ($1,720) for special site work, general contractor
overhead and profit, engineering, land, legal, fiscal and
administrative services.
TOTAL CONSTRUCTION COSTS = $5,272 + $1,720 = $7,092
Step 4; Annualize Total Construction Costs
A. Assume loan conditions are:
interest @ 12%
loan period - 20 years
B. Determine CRF (see Table XIII)
CRF @ 12% for 20 years = 0.133879
C. Determine annual construction cost =
total construction costs x CRF:
$7,092 x 0.133879 = $949.47
Step 5; Determine Operation and Maintenance Costs
Reference 39 estimates that process energy (booster pump) requires
1,630 kWh/yr. At an energy cost of $0.07/kWh, the annual cost is:
1,630 kWh x $0.07/kWh = $114.10
Building energy (note that this is extremely site-specific)
requires 2,560 kWh/yr. Thus the annual building cost =
2,560 kWh/yr x $0.07/kWh = $179.20
Maintenance material is estimated at $40/yr (1978 costs). Thus
1982 costs =
$40 x MMCEF = $40 x 1.5 = $60. 00/yr
Labor requirements are estimated at 183 hrs/yr. Assuming labor
rates at $10.00/hr, then labor costs =
183 hrs/yr x $10.00/hr = $l,830/yr
V-6
-------
Total O&M Costs = the sum of the above = $ 114.10
179.20
60.00
1,830.00
Total $2.183.30
Step 6; Determine Chemical Costs
Chemical costs are discretely related to both the volume of water
flow treated and to the dosage of chemical disinfectant applied.
A small plant treating 250,000 gal/day (946,324 L/day) at an
average applied chlorine dosage of 5 mg/L would use:
946,324 L/day x 5 mg/L = 4,731,620 mg chlorine/day
4,731,620 tag/day x 1 g/1,000 mg = 4,731.62 g chlorine/day
4,731.62 g/day x 1 lb/435.59 g = 10.43 Ibs chlorine/day
10.43 Ibs/day x 365 days/yr = 3,807 Ibs of chlorine/yr
At an estimated cost of $0.47/lb (Washington, DC area price in
early 1983), the annual cost for chlorine gas would be:
3,807 Ibs/yr x $0.47/lb = $1.789/yr
Step 7: Determine Total Annual Cost
Total annual construction cost
Annual operation & maintenance costs
Annual chemical costs
TOTAL ANNUAL COSTS
$ 949.47
2,183.30
1.789.00
$4,921.77
Step 8; Determine Cost per 1,000 Gallons of Water Treated
Cost per thousand gallons treated can be determined by dividing
the total annual cost by the total annual water production:
if 250,000 gallons of water are produced daily, then
250,000 gal/day x 365 days/yr =
91,250,000 gallons produced annually
Total annual cost per gallon =
$4,921.77/91,250,000 gal = $0.000053937/gal
$0.000053937/gal x 1,000 gal = $0.053937/1,000 gal, or
5.4£/1,000 gallons of water treated
V-7
-------
Because costs of equipment,
labor, energy, and chemicals are
subject to rapid change, the
authors have determined more
recent costs for the various
methods of disinfecting drinking
water supplies for small water
treatment systems by obtaining
vendor estimates (in mid-1982),
rather than by relying upon ENR's
Construction Cost Indices and
attempting to update data de-
veloped from EPA's October 1978
values. This information,
augmented by information in the
earlier EPA report (Reference 39),
where considered appropriate, is
provided in Appendix A. Additional
cost information obtained at
several operating plants is
provided in Section 7, CASE
HISTORIES.
FUNDING SOURCES
The principal financing options
open to small water systems for
treatment process improvement can
be categorized as follows:
o Self Financing
o Grant Programs
o Direct Loan Programs
o Loan Guarantee Programs
o Other Assistance Programs
- Bond Banks
- Research and Development
- State Loan Programs
- Shared Operator Costs
With Other Utilities
These are discussed below.
Self-Financing
Water utilities process, deliver
and charge consumers for potable
water. In providing this service,
they bear close resemblance to
other businesses that provide
products and services. Most
larger utilities, publicly or
privately owned, normally do not
have problems in financing needed
capital improvements, achieved
either through increases in user
fees or by floating bond issues (41),
However, the financing needs for
constructing and operating suffi-
ciently sophisticated disinfection
systems may strain the financial
capabilities of small community
water systems, either by requiring
capital expenditures beyond their
ability to finance, or by causing
relatively large incremental
increases in user charges. The
latter course may incur substan-
tial consumer resistance to the
improvement program, a major
impediment in the case of publicly
owned systems. Very small
systems may be particularly
vulnerable to problems of this
type.
The prime considerations for
self-financing include the
following (41):
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 typical residential
water bill to the community's
median family income.
In competing for funds in the
private capital markets, the larger
utility is expected to have a
debt service ratio (ratio of
income less operating expenses to
interest costs) of 1.3 and income
at least twice that of interest
charges. Private utilities must
be showing a net profit, after
V-8
-------
taxes, of 10 to 13 percent. User
fees should amount to less than
1.5 to 2.0 percent of median
family income (41).
Smaller utilities may not be able
to compete in the capital markets,
but still may have the ability to
raise money locally. Utility
customers may be willing and able
to put up the needed capital.
Even so, the utility should have
a debt service ratio of at
least 1.0 so that interest and
bond repayment schedules can be
met.
Grant Programs
The principal financial assistance
program available to small community
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
of community water systems that
serve fewer than 10,000 people.
The emphasis of this program, as
its name implies, is on farmers
and other rural residents.
Program aid priorities are as
follows:
public bodies and towns with
emphasis to those serving
5,500 people or less;
assistance in complying with
the Safe Drinking Water Act;
low income communities;
systems proposing to merge
and/or regionalize;
state recommended projects;
projects promoting water
energy conservation.
o
o
o
o
FmHA can be contacted for further
information at any one of 340
offices nationwide.
Direct Loan Programs
The Farmers Home Administration
has a direct loan program with
criteria similar to those used in
their grant program. The loan
can be for 100 percent of the
project cost.
Loan Guarantee Programs
The Farmers Home Administration
(FmHA) can provide backing for
privately placed loans through
its Business and Industry Loan
Program. This is available to
public or private organizations,
particularly those located in
rural areas and serving fewer
than 50,000 persons. Loan guaran-
tees range up to 90 percent of
face value.
Other Forms of Assistance
Other methods of reducing financing
and/or operating costs include
the following:
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 placement
enhanced,
Research and Development
The U.S. Environmental Protection
Agency (EPA) has funded pilot
plant demonstration projects for
water and wastewater systems
using uncommon technologies.
Pilot plant studies at McFarland,
California, were carried out as
part of an EPA research project.
V-9
-------
State Loan Programs
Several states provide direct
loans for construction of public
water and sewer projects. States
with either loan programs or
cost-sharing programs include
Pennsylvania, New Jersey, Massa-
chusetts, and Washington.
Shared Operator Costs With Other
Utilities'
Operation and maintenance of a
single small water system does
not require a full-time person;
hence, operator costs could be
divided up between two or more
nearby utilities where travel
distance permits. Regionali-
zation is one approach to shared
operating expenses.
V-10
-------
VI. OPERATION AND MA.INTENA.NCE
INTRODUCTION
Ultimately, on a day to day
basis, the operator is responsi-
ble for providing clean, safe
drinking water in a cost-effective
manner. Proper operation and
maintenance of disinfection
facilities is essential to protect
the health of water utility
consumers. Adequate personnel,
training, equipment, tools, and
material must be provided to
operate and maintain the disinfec-
tion system. Regardless of the
quality of the physical plant, a
water treatment facility is only
as good as the people who run it.
Inadequately skilled or trained
operators can cost the utility
many times their annual salaries
in equipment damage and excessive
O&M costs. Points to remember
when starting and staffing new
plants include the following:
o Hire and expect to pay
skilled operators. The
provision of safe drinking
water is a highly responsible
profession. Senior operators/-
managers should have appropri-
ate training in sanitation,
process control and management.
o Hire the plant staff suffi-
ciently in advance of initiating
operation so that a startup
training program can be
carried out. Include training
of the staff in equipment
purchase contracts, and
request the services of
factory experts for equip-
ment break-in and shakedown.
Have engineers give the
operators specific training
in process operation and
control. Enlist the aid of
local and state sanitarians
to train the staff in the
health aspects of plant
operation, including mandated
sampling, monitoring, and
reporting.
o Support a program of continu-
ing education for the staff.
Include in the utility
budget the costs of membership
of the utility as well as
of the operators in
professional organizations.
Provide funding and time off
for staff participation in
continuing education seminars
at local/state universities
and health departments.
Subscribe to trade journals
and publications to foster a
high-quality professionalism
and esprit in the staff.
OPERATION AND MAINTENANCE PRACTICES
Good O&M practices include the
following items:
o Encouragement of good opera-
tor attitudes and skills,
o Provision of up to date
manuals, equipment, and
safety devices,
o Appropriate monitoring
programs,
o An effective preventive
maintenance program,
o An understanding of emergency
procedures,
o Routine use of good sanitary
practices,
o Routine use of effective
safety procedures,
o Compliance with the require-
ments of the NIPDWR.
VI-1
-------
Encouragement of Good Operator
Attitudes and Skills
Operation of small disinfection
systems does not require unusual
operator skills. However, the
operator must have a high level
of awareness of the importance of
drinking water disinfection and
must be dedicated to continuous
proper operation of the equipment.
Assigned personnel should have
sufficient comprehension levels
to enable them to read and
understand:
- basic literature on drinking
water disinfection;
- equipment vendor manuals;
- process diagrams;
- electrical diagrams; and
- other literature associated
with the process.
Operators should be reasonably
expert in performing simple
plumbing, electrical, and ana-
lytical tasks and should under-
stand the operation and repair of
valves, water meters, pumps, and
controls. Disinfection personnel
must be capable of carrying out
regular sampling and monitoring
programs and be able to calibrate
and use residual disinfectant
analyzers.
The skills of the utility staff
may have to be supplemented by
means of service contracts with
disinfection equipment vendors.
These may be required for work
which requires equipment and
skills beyond those maintained by
the utility. Examples of such
work include cleaning and adjustment
of chlorinators, ozone generators,
and instruments. Availability of
such services will have been a
major factor in the initial
selection and specification of
the disinfection system components.
Operating personnel should be
given the opportunity to partici-
pate in design decisions and to
observe construction progress.
Within the constraints of project
protocol and harmony, personnel
should observe the installation
activities of the equipment
vendors' technicians. Appropriate
utility personnel must take the
maximum benefit from the vendors'
training required (and paid for)
as part of the construction
contract. The construction
contractor should not be released
from his training obligation
until the utility personnel have
certified that they have been
adequately trained in the use of
disinfection facilities and
associated equipment. It may be
possible to maintain a permanent
record of the vendor training
program by means of tape recordings
or video recording equipment.
The design engineer has a contrac-
tual or implied obligation to
familiarize the utility's operation
and maintenance personnel with
the features of the disinfection
system. These efforts by the
engineer may include formal
classroom training or may be
limited to "hands-on" training in
the field. In either case, all
appropriate utility personnel
should be required to attend such
training programs.
Start-up of the disinfection
system requires the participation
of representatives of the contractor,
equipment supplier, engineer, and
utility operation and maintenance
personnel. The utility personnel
must take full advantage of this
activity as operational modes are
developed based on the advice of
field representatives of the
parties involved. These may be
VI-2
-------
continued throughout the operational
life of the facility.
Operating and maintenance personnel
should be given sufficient time
to review the various literature
made available to them by vendors
and the engineer. Information
that is not readily understandable
by utility personnel should be
rejected immediately by the
utility for resubmission and
acceptance before the party
responsible for the deficient
material is released from his
contractual obligation.
Additional efforts will be required
to train replacement personnel
and to refresh the skills and
knowledge of current personnel.
Although some training is provided
at the facility on a "free" basis
as part of promotional efforts by
vendors or engineers, funds
should be budgeted for the cost
of attendance by appropriate
utility personnel at local,
state, or regional training
sessions and technical seminars.
Continual training is required on
an in-house basis to maintain
safety awareness as well as to
maintain necessary operator
skills.
A 'self-teaching' operator training
program is being developed by the
California State University,
Sacramento, under contract to the
Environmental Protection Agency.
Dr. Kenneth D. Kerri is the
Project Director. The complete
program, with manual, is to be
available in 1984 (42).
MANUALS, EQUIPMENT, AND SUPPLIES
REQUIRED
The documents resulting from the
construction of the disinfection
facilities should be reviewed,
inventoried, and filed. Two or
more complete sets of the documents
should be maintained by the
utility as shown in Table XIV.
The documents for use by operation
and maintenance personnel should
be maintained in filing cabinets
at a point or points readily
accessible to them. Proper
filing facilities are essential
to enable the personnel to perform
their tasks in an organized
manner.
Tools, materials, and safety
equipment, including those specific
to the disinfection system,
should be identified, inventoried
and stored in the vicinity of the
disinfection process. They
should be designated and main-
tained as specific to the disinfec-
tion process so that they are
readily available for regular and
emergency use.
MONITORING
Monitoring of the disinfection
process and its equipment covers
four activities, which are as
follows:
(1) evaluation of condition of
process equipment;
(2) process quality control;
(3) distribution system quality
control;
(4) regulatory agency monitoring
and reporting requirements.
The process equipment and conditions
must be monitored daily to assure
the safe, continuous operation of
the disinfection process. This
activity may be as simple as
VI-3
-------
TABLE XIV
AVAILABILITY OF DISINFECTION SYSTEM DOCUMENTS
Description of
Document
Readily
Available
to O&M
Personnel
Utility
Headquarters
Emergency File
(Bank Vault)
As-built
construction and
specifications
Contractor's
shop drawing
submissions
Equipment
Vendors manuals
Engineer's O&M
manual
Training manuals
Proj ect cons true-
One copy
One set
One set
One set
One copy
One copy
Reproducible
copy
One set
One set
One set
One copy
One copy
Microfilm copy
Microfilm copy
Microfilm copy
Microfilm copy
Microfilm copy
tion file One copy
Project adminis-
tration file
One copy
One copy
Microfilm copy
Microfilm copy
recording the weight of chlorine
in the gas cylinder currently in
use to the more complex recording
of temperature - pressure - flow
measurements of an ozonation
system. Operational condition
monitoring serves the dual purpose
of requiring that the operator
physically inspect the installa-
tion on a regular basis, as well
as providing "trend" information
that may be helpful in future
trouble-shooting activities.
Operational monitoring for all
modes of the disinfection equipment
is beyond the scope of this
document. Details will be pro-
vided in the Operation and Mainte-
nance manual to be provided by
the design engineer and/or the
system vendor. Additional informa-
tion will be available in
Reference 42.
Process control monitoring basi-
cally should focus on the quality
of the water receiving the disin-
fectant, the effective dosage
being applied, and the resulting
concentration of disinfectant.
Effective dosage of a disinfec-
tant/oxidant may be measured by
residual for the chlorine compounds,
but other site-specific, surrogate
measurements must be obtained for
VI-4
-------
UV or ozone disinfection. The
dosage of disinfectant/oxidant
must be sufficient to achieve the
desired level of disinfection.
However, overdosing unnecessarily
increases water treatment costs,
and, with the exception of ozone
and ultraviolet radiation, actually
will reduce water quality, in
terms of increasing levels of
dissolved solids and trihalo-
me thanes.
Monitoring of process parameters
must be performed daily, or even
more frequently, if the water
quality is highly variable. The
raw data should be processed to
establish relationships, such as
chemical requirements compared to
turbidity level. These relation-
ships are valuable tools in
process troubleshooting or as a
manual control guide if the
automatic control systems fail or
are suspect.
The utility should carry out
frequent inspections, sampling,
and analyses throughout the
system to assure the bacteriolog-
ical safety of the water being
provided to the system's consumers.
Sampling points for chlorine
residual measurement and bacter-
iological sampling should include
the following:
o treatment plant product;
o flow from reservoir or
storage tank;
o key points in the distribu-
tion system;
o consumer taps on dead end
lines.
Conditions in the water distribu-
tion system are changing constantly,
due to the many demands placed
upon it. For example, an existing
cross-connection may have no
effect on the system until a
heavy demand is placed on it,
such as the prolonged use of a
fire hydrant, which significantly
reduces the system pressure.
Reduced system pressure could
allow a contaminant to enter the
system through the cross-
connection.
Regulatory agency reporting
requirements were discussed in
Section 2. Water samples must be
tested periodically for coliforms
by a state or EPA approved labora-
tory using either the membrane
filter or multiple tube fermenta-
tion techniques. The frequency
of bacteriological testing is the
minimum required by law. The
water utility likely will choose
to have sampling and analytical
tests performed more frequently
by a local laboratory. This
"in-house" data can be used to
identify problems which may
include:
- sampling and sample handling;
- distribution system operation;
and
- treatment plant operation.
It should be clearly understood
that the process quality control
and distribution system quality
control are the key factors in
maintaining compliance with the
regulatory agency monitoring and
reporting requirements. A positive
coliform test report to the
regulatory agencies is the final
indication that the waterworks
has failed in its responsibility
to provide the public with a
safe, pathogen-free drinking
water.
Appendix B includes sample forms
for the recording of data from
coliform sampling and analysis.
VI-5
-------
PREVENTIVE MAINTENANCE
Preventive maintenance (PM) is
the key to reliable service and
long equipment life. Setting up
a good PM program requires a
strong planning effort but, once
established, it pays for itself
throughout the life of the facility.
Close attention to the scheduled
PM activities will reduce annual
operating costs and minimize
failures.
A PM program is specific to the
utility and the facility. However,
the following guidelines can be
provided for utility personnel
setting up and working with a PM
program for a disinfection system:
o Gain a thorough knowledge of
the facility through documents
listed under MANUALS, EQUIP-
MENT, AND SUPPLIES REQUIRED;
o Maintain a file for each
process unit component;
o Maintain a system which will
provide a reminder of work
to be performed weekly,
monthly, seasonally, and
annually;
o Provide sufficient funds for
rigorous application of the
PM program.
Several proprietary PM programs
exist which provide the user with
the material to develop a proven
PM system. One such system is
the Envirotech Operating Services
Simplified Automatic Maintenance
(SAM) system which has been
successfully applied in a number
of wastewater treatment plants (43).
The utility may consider entering
into maintenance and service
contracts for certain process
components such as ozone genera-
tors, electronic controls, and
flow metering. The need for this
type of assistance may decrease
as utility personnel become more
familiar with the equipment.
Services quite frequently are
provided by the vendors' local
representative, but could be
provided by any firm with the
prerequisite skills and equipment.
The necessary personnel, tools,
equipment and materials must be
readily available to perform PM
work to assure that it gets done.
EMERGENCY PROCEDURES
It is imperative that a written
Emergency Procedures Manual be
available to enable continuous
operation of the disinfection
process. Possible causes of
interruption of disinfection must
be identified and their solutions
found and prepared for. Documen-
tation of emergency procedures
should clearly establish the
hazards to utility personnel,
utility facilities, the consumers,
and the general public of various
emergency situations. Restorative
actions should be identified as
well as those people responsible
for taking that action. The
emergency procedures should be
practiced on a routine basis by
utility personnel.
Every practicable means must be
taken to continue to maintain the
disinfection equipment in operation.
These methods include:
- use of stand-by equipment
maintained by the utility;
- use of stand-by equipment
maintained by another utility;
- use of equipment available
from a vendor.
The most practicable short-term
solution for disinfection system
VI-6
-------
emergency shutdowns would appear
to be having available sodium
hypochlorite solution fed by a
manually controlled, positive
displacement chemical feed pump
operating on its own emergency
backup power source. Sodium
hypochlorite stored for emergency
use should be tested periodically
and replaced, if it is determined
to have lost strength.
Possible emergency conditions
include the following:
- failure of a key piece of
equipment;
- interrupted chemical delivery;
- power failure;
- strikes;
- fire, flood, tornado, or
other natural disasters.
For each problem, a check list of
procedures to be followed should
be available. Depending upon the
type of emergency, one or more
groups of interested parties will
be contacted. These parties
include the following:
- utility personnel;
- rescue, fire, police or
emergency management agencies;
elected officials;
- regulatory agency personnel;
- consumers;
- chemicals suppliers;
- equipment vendors;
- local maintenance contractors;
- local construction contractors;
- equipment sales and rental
firms;
- the media (radio, television,
newspapers).
Updated lists of names, addresses,
and telephone numbers should be
maintained as part of the Emergency
Procedures Manual.
Utility personnel must be briefed
and trained in emergency proce-
dures for a variety of potential
emergency situations. Key situa-
tions such as a faulty chlorine
cylinder should be identified and
response procedures rehearsed to
assure that personnel understand
their roles and that the necessary
response equipment is readily
available and its use understood.
GOOD SANITARY PRACTICES
Flush the distribution system,
particularly dead ends, on at
least an annual basis to remove
accumulated sediment. Clean a:nd
disinfect reservoirs and storage
tanks annually, and repaint with
commercial paints developed for
clear water reservoirs.* Period-
ically clean and flush settling
tanks, filters and other treatment
equipment. Keep plant buildings
clean and free from insect infesta-
tions and small animals (e.g.,
mice).
Maintain Close Liasion With Your
Local Health Service And Medical
Societies. Ask to be notified of
any increase in patient load
which might be attributable to
waterborne infectious agents.
Conduct Periodic Sanitary Surveys
Of The Watershed, Treatment
Plant, And Distribution System
* Information on commercial
reservoir paints is available
from the American Water Works
Association, 6666 W. Quincy
Avenue, Denver, Colorado,
80235, and from the Office of
Drinking Water, U.S. EPA, 401 M
Street, S.W., Washington, D.C.
20460.
VI-7
-------
All elements of the system, from
source to distribution, and the
surroundings, can be examined in
a walking inspection. Faulty
septic systems, leaking sewers,
and high local concentrations of
domestic animals or wildlife are
particular sources of contamination.
Some of these elements are:
For Groundwater Sources
1) character of local geology;
2) slope of water table;
3) extent of drainage;
4) methods used to protect the
supply against pollution
from sewage or waste disposal;
5) various well construction
features;
6) protection of supply wells
at the top;
7) availability of a backup
water supply;
8) treatment methods;
9) storage methods; and
10) distribution practices.
For Surface Water Sources
1) nature of surface geology;
2) population and sewered
population per square mile;
3) character and efficiency of
sewage treatment plants on
watershed;
4) proximity of sources of
fecal pollution to water
supply intakes;
5) sources and proximity of
industrial wastes;
6) character and quality of raw
water;
7) measures used to protect
watershed and reservoir
against pollution;
8) adequacy of water treatment
process to cope with specific
contaminants in the specific
raw waters;
9) adequacy and efficiency of
pumping facilities; and
10) distribution practices.
Persons trained and skilled in
either sanitary or public health
engineering, (e.g., registered
professional sanitary engineers)
and having knowledge of both good
engineering practices and the
health aspects of waterborne
diseases should conduct the
sanitary surveys.
Protect Water Sources
Poorly enclosed well houses can
allow small animals to pollute
the source with droppings. A
groundwater well can be contami-
nated by seepage around the well
head if it is not properly grouted
at the surface.
Check For Leaks In The Distribution
System
Leaks in the distribution system
not only lose water (hence revenues)
and increase pumping costs, but
also may allow pathogens a point
of entry into the system.
Maintain Plant Operating Records
It is essential that good plant
operating records be maintained.
Such records also will help in
operation for example, if
chlorine usage increases it may
be necessary to order the next
shipment sooner. Operating
records should contain checks of
the various metering systems such
as pressure recorders.
VI-8
-------
SAFETY PROCEDURES
The safety hazards associated
with specific disinfection pro-
cesses must be clearly identified
by the utility personnel with the
assistance of the engineer,
equipment vendors, and chemical
suppliers. Strong oxidizing
agents can kill or injure. An
initial step to provide protec-
tion against such disinfectants
is to restrict access to the
disinfection facilities. Access
can be restricted by means of
warning signs, fences, lock
doors, and should be noted in
utility procedural manuals.
Personnel authorized to operate
and maintain the disinfection
facility should be kept continu-
ally aware of the hazards of the
disinfectants/oxidants in use.
This familiarization should be
achieved by formal training and
retraining, signs, paint coding
and practices in emergency proce-
dures. Generalized guidance
associated with the various
disinfectants follows:
Gaseous Chlorine
1. Heat should not be applied
to chlorine cylinders. If a
higher gas rate is required
additional cylinders should
be manifolded together.
2. The fusible plug of the
cylinder should not be
tampered with.
3. The cylinder hood should be
kept in place except when
the cylinder is in use.
4. The cylinder should not be
lifted by its hood.
5. A cylinder should not be
dropped or knocked over.
6. The chlorination system
should be checked periodically
for leaks. This is done
using a rag dipped in strong
ammonia solution (28% ammonia
in water). Household ammonia
is not strong enough for
this activity.
7. Chlorine gas is heavier than
air. Therefore, plant
personnel should stay upwind
of and uphill from a chlorine
gas leak, unless protective
breathing apparatus is being
utilized.
Sodium and Calcium Hypochlorites
1. Store and handle using clean
(both) and dry (calcium
hypochlorite) implements,
free of oils, grease, and
other organic impurities.
2. Store in areas separate from
all other chemicals with
which they might react.
3. Immediately remove a leaking
or defective container from
the storage area.
4. Mix calcium hypochlorite
solid only with water.
5. Protective equipment (face
protection, gloves, aprons)
must be worn when preparing
and handling hypochlorite
solut ions.
Chlorine Dioxide
1. All safety precautions
described for handling
gaseous chlorine or sodium
VI-9
-------
hypochlorite (depending upon
the method of generation of
chlorine dioxide) should be
practiced.
2. The chlorine dioxide generator
room should be kept free of
all organic materials.
3. Do not allow spills of
sodium chlorite solution to
dry. In the dry state,
sodium chlorite is spontane-
ously combustible. Flush
all spills, however small,
with water promptly and
thoroughly. Never allow
organic materials (cloths,
brooms, mops, etc.) to come
in contact with concentrated
solutions of sodium chlorite.
They may ignite.
4. When strong mineral acid is
used for the generation of
chlorine dioxide, observe
all safety precautions
concerning spills and leaks
of such materials.
5. Do not allow chlorine dioxide
gas to escape from solution
into the ambient plant
atmosphere. Not only is
chlorine dioxide gas toxic,
but in certain concentrations
in air, it can be explosive.
Chloramines
1. Observe the safety precautions
described for chlorine gas
or hypochlorite solutions.
2. Observe the same precautions
for handling cylinders of
liquid ammonia as for gaseous
chlorine, although ammonia
cylinders normally are not
equipped with fusible plugs.
3. Note that ammonia gas is
lighter than air and will
rise.
Ozone
1. Avoid breathing ozone.
Although it has a character-
istic odor, personnel exposed
to ozone for prolonged
periods of time at threshold
levels may become insensitive
to it, and thereby fail to
detect ozone at higher
levels which can be hazardous.
2. Equipment for monitoring
ozone levels in the ambient
atmosphere of work areas
should be tested weekly and
recalibrated when necessary.
3. In the event of an ozone
leak, ventilate work areas
completely.
4. Ozone generators and associ-
ated ozone/air gas handling
systems should be purged for
a minimum of 30 minutes with
dried air (with power to the
generator turned off) before
opening the generator or
breaking any piping systems.
This will prevent ozone from
escaping to the plant
atmosphere.
5. When ozone diffuser contactors
are to be emptied and entered
by plant personnel, the
contactors should be pressure
ventilated for a minimum of
12 hours. Personnel entering
purged ozone contactors
should wear self-contained
breathing apparatus.
VI-10
-------
Ultraviolet Radiation
1. UV radiation can damage eye
tissues. Personnel should
never look directly into a
UV unit which is operating.
To change UV bulbs, the
electrical power to the unit
should first be shut off.
Safety procedures which are
established for plant personnel
should be enforced rigorously.
Enforcement is necessary not only
for the protection of employees,
but also to reduce potential
liability of the utility.
NIPDWR COMPLIANCE
A complete program for delivery
of safe and sanitary water must
include a conscientious effort to
comply with NIPDWR monitoring,
analytical, and reporting require-
ments. These regulations, largely
based on normal water utility
practices, provide a framework
for assuring sanitary water
supplies at reasonable cost.
VI-11
-------
-------
VII. CASE HISTORIES
Three case histories are presented
in this section which illustrate
the successful use of chlorine,
chlorine dioxide and ozone technol-
ogies for disinfection of drinking
water. These case histories are
the following:
o White Haven, PA - Chlorination
o Hamilton, OH - Chlorine
Dioxide
o Strasburg, PA - Ozone
White Haven and Strasburg are
small systems. Hamilton, OH,
with an average daily production
of about 15 mgd (56,781 m ), is
not a small system. On the other
hand, Hamilton represents the
most successful use of chlorine
dioxide by a U.S. water supply
system for terminal disinfection,
as of mid-1982.
Although chlorine dioxide now is
used for some purpose by more
than 100 water supply systems in
the U.S., only a few apply it as
the sole disinfectant (24).
Vendors contacted were unable to
identify a small water supply
system (flow of le^s than
0.5 mgd 1,853 m /day) which
uses chlorine dioxide as the
terminal disinfectant. As has
been clearly pointed out earlier
in this document, there is no
reason why CIO cannot be applied
successfully for disinfection in
small water systems.
Fifteen U.S. water treatment
facilities currently use ozone
for some purpose (44), and thir-
teen of these plants have installed
ozonation facilities since 1977.
One of the most successful of-^
these is an 18 mgd (68,137 m day)
plant at Monroe, MI, which uses
ozone for oxidation of organics,
taste and odor removal, and
reduction in levels of TTHMs (45).
Three systems which use ozone as
the terminal disinfectant are
Newport, DE, Strasburg, PA, and
Casper, WY. The story of ozone
treatment at Strasburg perhaps is
the better known (46), and it has
been selected for inclusion.
The authors were unable to identify
a small water treatment system
employing chloramine for disinfection.
As a result, there is no case
history available to illustrate
this method of disinfection.
These case histories are presented
to illustrate how these water
supply systems undertook to
evaluate and install the disinfec-
tion technologies selected. It
should be recognized, however,
that all three case histories
involve the use of groundwater
sources, and not surface waters.
Good sanitary engineering practice
dictates that surface water
supplies use conventional treat-
ment (coagulation, sedimentation
and filtration) before the disin-
fection step.
WHITE HAVEN, PA
White Haven Borough, located in
the Pocono mountains of north-
eastern Pennsylvania, has a
population of about 1,000. Its
water supply is located in the
nearby mountains, approximately
one mile from the Borough.
Access is by a dirt road to the
open reservoir, which is fed by
springs and supplemented by a
VI I-1
-------
well. Daily flows are approxi-
mately 110,000 gpd (416.4 m /day),
and vary between a low of 20 gpm
(75.8 L/min) to a normal maximum
of 200 gpm (758 L/min). Fire
flows of 750 gpm (2,839 L/min) to
1,000 gpm (3,785 L/min) are
possible. Chlorine contact is
conducted in the 8-inch (20.3 cm)
transmission line of approximately
5,000 feet (1,524 m) providing
about an 18-min detention time at
750 gpm (2,839 L/min).
In 1979, the White Haven Borough
Municipal Authority, the system
owner, was faced with the problem
of replacing an old hydraulically-
driven hypochlorinator that was
worn beyond repair. The remote
location of the plant in the
surrounding mountains made daily
attention during wintertime
time-consuming and costly. The
hypochlorinator was not designed
to allow flow-pacing, problems
had been experienced with freezing
pipes, and proper mixing of the
hypochlorite solution was a
continual problem. However, the
old stone building which housed
the hypochlorinator was subject
to considerable leakage.
The Authority's objective was to
install a disinfection system
that could be flow-paced to
maintain residual control and be
capable of extended periods of
wintertime operation with little
or no attention. Additionally,
the municipality did not want
another hypochlorination system
because of the considerable
maintenance problems which had
been experienced, the problem of
maintaining a uniform solution,
and the need for frequent
attention.
Therefore, the goal became to
select a system that would be
responsive both to low flows and
to the high flows required by
fire demands. The system has no
storage of disinfected water, so
that disinfection also must be
conducted during fire flows.
The White Haven Gas Chlorination
System
In conjunction with their consulting
engineers, White Haven officials
decided upon a new gas chlorination
system, which consists of the
components listed below. A
schematic diagram of the treatment
process is presented in Figure 24.
o Wallace & Tiernan V-500 Gas
Chlorinator
o Wallace & Tiernan 50-345
Dual Cylinder Scale
o Sta-Rite 3/4 HP JGD Booster
Pump
o Mine Safety Appliance 457083
Gas Mask
o Ramapo Mark V Flow Meter
with Transmitter
o Badger Model 2061 Recorder-
Indicator-Totalizer
o Fiberglass Building
The treatment system achieves the
objectives of the owner. Enough
chlorine cylinders can be stored
to last through winter periods of
heavy snows. Two 150 Ib (68.1 kg)
chlorine cylinders with an automatic
changeover valve are an integral
part of the system. One cylinder
lasts for about one month. In
addition, larger quantities of
chlorine can be ordered at each
purchase, thus resulting in
savings due to lower unit cost.
The new gas chlorination system
was installed in early 1980.
After startup and debugging, it
has been operating in a satisfac-
tory manner, with chlorine residuals
VI1-2
-------
Open
Raw Water
Reservoir
Chlorination
Distribution
System
Figure 24. Schematic of Treatment Process at White Haven, PA
VI1-3
-------
of 0.5 to 1.0 mg/L being maintained
throughout the system.
Costs
The installed cost (January 1980)
of the gas chlorination system,
including pouring of a concrete
pad for the building and installa-
tion by a local contractor,
amounted to $15,749. Engineering
fees of about 7%, or another $1,000,
brought the total installed costs
to $16,749.
HAMILTON, OH (29)
3
The 15 mgd (56,781 m /day) plant
at Hamilton uses chlorine dioxide
as the only disinfectant, although
excess chlorine is present in
solution because of the method of
CIO generation (excess chlorine
gas is added to sodium chlorite
solution). This lime softening
plant obtains its raw water
supply from deep wells (200 feet -
61 m). Chlorine was used as the
disinfectant when the plant
started operation in 1956, but
because of customer complaints
about chlorine tastes in the
finished water, the plant switched
to chlorine dioxide in 1972.
Subsequently, the complaints have
ceased. The groundwater contains
trace amounts of iron and manganese,
which are removed prior to CKL
treatment.
The Hamilton Water Treatment
Process
A schematic flow diagram of the
water treatment process used at
the Hamilton plant is shown in
Figure 25. The individual pro-
cess steps include the following:
o aeration
o chemical addition (lime/alum)
o flash mix
o sedimentation
o recarbonation
o filtration
o chemical addition - sodium
silicofluoride; CIO
o clearwell - distribution
system
The Hamilton Chlorine Dioxide
System
Chlorine dioxide is generated by
mixing aqueous solutions of
NaCIO (37%) and chlorine in a
1:1 weight ratio. This involves
20 Ibs (9.08 kg) per day of
sodium chlorite (dry basis) and
20 Ibs (9.08 kg) per day of
chlorine. Gaseous chlorine is
delivered to the site in 150 Ib
(68.1 kg) cylinders. Sodium
chlorite is shipped to the site
by an area distributor in drums
containing 200 Ibs (90.8 kg) of
37% aqueous solution.
The chlorine dioxide generation
system consists of a single
plant-fabricated reactor vessel
for CIO production, one BIF
peristaltic pump for sodium
chlorite solution, and two Fisher
& Porter chlorinators, one of
which serves as a standby. The
CIO reactor vessel appears to be
schedule 80 PVC (polyvinyl chlor-
ide) pipe material, 18 inches
(45.7 cm) high and approximately
6 inches (15.2 cm) in diameter.
The vessel is filled with 1-inch
(2.54 cm) diameter PVC rings.
The chamber is opaque and a sight
glass is mounted "in-line" on the
discharge piping. A white card
is placed behind the sight glass
to allow observation of the CIO
color. ^
VI1-4
-------
Aeration
S ed imentat ion
Lime/Alum
Addition
Flash Mix
Recarbonat ion
Filtration
C102
Disinfection
Sodium
Silicofluoride
Add it ion
Clearwell
Storage
Distribution
System
Figure 25. Schematic of Treatment Process at Hamilton, OH
VI1-5
-------
Two 150-pound chlorine cylinders
are positioned next to the chlor-
inators. The weight of chlorine
in the cylinders is measured by a
scale. Switchover from one tank
to the other is made manually.
Fischer & Porter specifies schedule
80 PVC tubing for the line between
the chlorinator and the reactor
vessel. Heavy Tygon tubing is
used for transporting the liquid
NaCIO solution from the drum to
a small plastic day tank and to
the reactor vessel. After about
one month of service, the Tygon
tubing loses its rigidity and
must be replaced. The semi-
transparent day tank allows
visual inspection of the level of
NaCIO solution. Keeping the
proper level in this tank thereby
enables the operator to maintain
an acceptable suction head on the
peristaltic pump.
The chlorine dioxide generation
equipment is housed in a room
which does not have direct access
to the outside. A corridor
connects the room to the outside
where chlorine cylinders are
stored, but are protected from
exposure to direct sunlight.
There is an exhaust fan system in
the CIO room, but no chlorine
leak detector. Both entrance
doors to the chlorine dioxide
room have glass panels for visual
inspection of the room interior
from outside of the room.
Production of C10_ is monitored
visually (by the sight glass) by
the characteristic golden-yellow
color that appears inside the
reactor vessel when the proper
amounts of NaCIO and Cl are
mixed. Both the color of solution
exiting the reactor and chemical
feed rates are checked hourly, to
ensure that the proper mix of
chemicals for CIO production is
being maintained.
Effectiveness and Analysis of
Chlorine Dioxide at Hamilton
Effectiveness of CIO is deter-
mined by means of bacteriological
tests and the absence of taste
and odor problems in the finished
water. Plant water is analyzed
three times daily, while water in
the distribution system is analyzed
once per day. Levels of CIO in
the finished water are measured
spectrophotometrically by plant
laboratory personnel to concentra-
tions of less than 0.2 mg/L as
CIO . The H-acid method (10) is
usea for this analysis, which is
reported by plant laboratory
personnel to require a higher
level of skill than other analytical
test methods, such as OTA or DPD.
The concentration of CIO added
to the plant water is 0. z mg/L as
CIO ; this concentration generally
is constant year-round. The CIO
residual leaving the plant is
0.15 mg/L, and the residual at
the extremities of the distribution
system is 0.10 mg/L.
Costs of Chlorine Dioxide Treatment
at Hamilton
An EPA-sponsored team of investiga-
tors visited the Hamilton plant
in late summer of 1977 (24). At
that time, the cost of chlorine
dioxide treatment at Hamilton was
about 3.6£ per capita per year.
Chlorine and NaCIO together cost
about $6,540 per year (1977 dollars),
The fraction of total plant costs
attributed to CIO was reported
to be negligible. Operating and
maintenance costs for CIO genera-
tion were estimated to be less
than $50 per year in 1977 dollars.
VI1-6
-------
The plant-fabricated CIO reactor,
piping, hardware, and installation
were estimated by the plant
supervisor to cost around $400,
and the BIF peristaltic pump for
NaCIO addition cost less than
$200. To this $600 must be added
the cost of the two chlorinators.
Installation was performed by
plant personnel.
Initial Consequences of Chlorine
Dioxide Use at Hamilton
It was reported to the 1977 EPA
survey team that the introduction
of CiOy abated the problems
caused by iron bacteria in the
Hamilton distribution system.
Consumers frequently had complained
about the staining effects from
tap water when chlorine was the
disinfectant. However, when the
plant switched from chlorine to
chlorine dioxide as the disinfec-
tant, brown slimes apparently
were loosened from the mains and
aggravated this situation even
more. Plant personnel then
flushed out the entire distribu-
tion system, and shortly thereafter,
the complaints stopped. Plant
personnel attributed the source
of the problem to crenothrix and
leptothrix bacteria (iron bacteria)
that had been present in the
extremeties of the distribution
system before introduction of
chlorine dioxide. This problem
has not reappeared since CIO,, was
incorporated as the disinfectant.
STRASBURG, PENNSYLVANIA
The Borough of Strasburg is
located in southeastern Pennsyl-
vania in the heart of Pennsylvania
Dutch country. With a population
of about 2,000, Strasburg owns
and operates its own water supply
system, which serves the Borough
and various farms between its
reservoir and the town itself.
It is the only small water system
in Pennsylvania utilizing ozone
as its primary disinfectant.
During EPA's National Organics
Reconnaissance Survey of 80 munici-
pal water supplies, conducted in
1974 and 1975 (47), less than
0.1 microgram of chloroform was
found per liter of Strasburg's
finished water supply. No traces
of the other three trihalomethanes
were found.
The water system, originally
constructed in 1896, utilized
13 springs as its source until
the mid-1970s, when additional
springs and a well were added,,
Prior to 1973, the system had no
disinfection capability until the
Commonwealth of Pennsylvania by
court order* ordered the Borough
to install a disinfection process.
Under significant pressure from
customers not to install chlorina-
tion, the Borough opted to install
an alternative (ozonation) disinfec-
tion system. This alternative
disinfection system was approved
by the Pennsylvania Department of
Environmental Resources after the
Borough agreed to install a
chlorinator as backup.
The Borough had constructed a
500,000 gallon covered storage
reservoir in the 1940s that is
gravity-fed by the springs; two
additional gravity-fed springs
* Under Title 25, Chapter 109 of
the Pennsylvania Clean Stream
Law, which requires disinfection
of all water sources.
VI1-7
-------
were added in 1977. Increases in
customer demand and extended dry
periods in 1980 resulted in water
rationing and ultimately in the
drilling of a well. This well is
capable of producing 75 gal/min
(284 L/min) and supplies 18.000 to
27,000 gal/day (60 to 102 m /day)
to the system. The distribution
system consists of 9,000 feet
(2,743 m) of 12-inch (30.48 cm)
and 12,000 feet (3,657 m) of
8-inch (20.32 cm) line. Present
water usage of the system (1982)
is approximately 140,000 gal/day
(520 m /day), with a higher
averagg of 180,000 gal/day
(681 m /day) during summer months.
No detailed tests have been made
on the well to determine its
ultimate capacity. Addition of
the well to the water supply has
relieved present water rationing,
but the plant operator is uncer-
tain if the system has adequate
future capacity to service cus-
tomers outside the Borough.
A schematic diagram of the Stras-
burg water treatment process is
illustrated in Figure 26. The
high quality groundwater requires
only disinfection (by ozonation)
and addition of soda ash for pH
adjustment.
The Strasburg Ozonation System
The Borough's ozonation system
consists of two tube-type, water-
cooled ozone generators which
were lease-purchased from the
Welsbach Ozone Systems Corpora-
tion. Ozonation equipment is
located in a 10 x 10 ft (3 x 3 m)
cinder block building adjacent to
the buried reservoir. The ozone
generators are operated on two-
month cycles; one is cleaned and
checked by the operator on a
rotating basis every two months.
(The authors consider this fre-
quent cleaning to be unusual.
Most ozone systems are maintained
on a six-month to one-year basis).
All maintenance is performed by
Borough personnel.
The system, originally installed
in 1973 for $23,182 (cash price,
not including lease-purchase
agreement), initially fed
3.7 Ibs/day (1.38 kg/day) of
ozone into a water flow of approxi-
mately 110,000 gal/day (416 m /day)
at an average dosage of 4 mg/L.
This rather high ozone addition
rate, dictated by Pennsylvania
standards to provide a residual
concentration of ozone equivalent
to that of residual chlorine were
it to have been used, resulted in
customer complaints of milky
water (caused by excessive amounts
of air being added to the water
along with the ozone). Subsequent-
ly, the State has allowed the
Borough to lower the amount of
ozone dosed to the water, and
present practice is to dose at a
rate of 0.67 mg/L of ozone
less than one Ib/day (464 g/day),
an amount believed by the plant
operator to be adequate for
disinfection. The operator can
measure the amount of ozone being
produced only by testing for
residual ozone in the treated
water. This test is performed
within the ozonation house using
colorimetry. The rate of ozone
generation is controlled manually
by a rheostat.
For ozone generation, atmospheric
air is pressurized by an air
compressor, then dried by passage
through a desiccant and fed to
the generator. The Borough has
spare parts for all units. Power
outages have occurred during the
past three years, the longest of
which lasted two hours. The
VI1-8
-------
Well Water
Ozonation
4
1
Standby
NaOCl
Generator
Elevated
Storage
Tank
Distribution
System
Figure 26. Schematic of Treatment Process at Strasburg, PA
VI1-9
-------
standby chlorinator has been used
only then and when the ozone
generators were being repaired.
Ozone contacting equipment con-
sists of a porous tube diffuser
placed at the bottom of an under-
ground concrete chamber. This is
a vertical, 32-foot (9.75 m)
underground pipe located within
20 feet (6.1 m) of the ozone
generation shelter. Ozone (1% by
weight in air) enters the dif-
fusers through a stainless steel
pipe.
The Strasburg ozonation system
does not have the capability of
destroying excess ozone present
in the contactor off-gases.
Atmospheric dispersion of the
excess ozone appears to be suffi-
cient for this rural plant.
Actual maintenance costs for the
first nine months of 1982 (through
September 30) were $830. The
operator spends an average of six
hours per week (at $10 per hour =
$3,120 per year) to keep the
ozonation system operable, and
for water testing.
The operator performs pH and
ozone residual tests three days
per week to maintain a pH of 6.8
to 6.9 and an ozone residual of
0.7 mg/L in the system. Samples
also are collected independently
at other points in the water
supply system by a local labora-
tory. Total water use in 1980
was 50 million gallons. The cost
of treatment in 1980 was $108 per
million gallons (per 3,785 m ) of
water, or about $0.11 per thousand
gallons (3,785 L).
Other Water Treatment At Strasburg
The only other treatment step at
Strasburg consists of addition of
soda ash (less than 5 Ibs/day
2.27 kg/day) to raise the pH from
6.5 to 6.8-6.9.
Costs Of Ozonation At Strasburg
Power costs of operating the
Strasburg ozonation system are
$1,100 per year. This includes
heating costs for the ozonation
shelter, the only building struc-
ture possessed by the water
system. Costs for soda ash are
estimated at $600 per year. In
the ozonation equipment, the
glass dielectric tubes require
unusually frequent replacement.
Each of the two ozone generators
has four tubes, and the Borough
purchases an average of three
replacement tubes per year.
Replacement tubes and spare parts
run about $600/yr at this plant.
Additional Operator Comments
According to its operator, the
Strasburg Water System has not
had any problems with regulatory
agencies regarding compliance
with the requirements of the Safe
Drinking Water Act. There is no
ozone residual in the system at
consumer taps; however there have
been no complaints about the
water, and no positive plate
counts have been found in samples
taken by the independent laboratory.
The operator describes the well
water quality as equal to that of
spring water.
VII-10
-------
REFERENCES
1. National Research Council, Prinking Water and Health (Washington,
DC: Natl. Acad. Sciences, 1977).
2. States' Compliance Lacking in Meeting Safe Prinking Water Regulations
(Washington, DC: U.S. Genl. Accounting Office, 3 March 1982),
Report No. CED-82-43.
3. Manual of Individual Water Supply Systems (Raleigh, NC: U.S. EPA
Report No. 430-9-74-007, 1974), p. 11.
4. "Natl. Interim Primary Drinking Water Regulations; Trihalomethanes",
Federal Register 47(44):9795-9799 (5 March 1982).
5. "Natl. Interim Primary Drinking Water Regulations", Federal Reg-
ister 40(248): 59565-59588 (1975).
6. G.F. Craun, "Waterborne Outbreaks in the United States, 1971-1978",
Proc. Ann. Conf. Am. Water Works Assoc. , Part I (Denver, CO: Am.
Water Works Assoc., 1980), pp. 99-120.
7. F.J.W. Miller and J.P. Anderson, "Two Cases of Primary Tuberculosis
After Immersion in Sewage-Contaminated Water", Arch. Disease in
Childhood 29:144, 152 (1954).
8. Pseudomonas aeruginosa; Ecological Aspects and Patient Colonization,
V.M. Young, Ed. (New York, NY: Raven Press, 1977), p. 31.
9. The Safe Drinking Water Act, Handbook For Water System Managers,
(Denver, CO: Am. Water Works Assoc.).
10. Standard Methods for the Examination of Water and Wastewater,
15th Edition (Washington, DC: Water Poll. Control Fed., 1980).
11. "National Interim Primary Drinking Water Regulations; Control of
Trihalomethanes in Drinking Water; Final Rule", Federal Regis-
ter 44(231):68637 (1979).
12. M. Pare, "Analytical Instrumentation for Control of Ozonation
Systems", in Handbook of Ozone Technology and Applications, R.G.
Rice & A. Netzer, Eds. (Ann Arbor, MI: Ann Arbor Science Pub-
lishers, Inc., 1982), pp. 285-306.
13. Reference 37, p. 12.
14. Anonymous, "Water and Wastewater Chemistry, Part Two", Public Works
(1978), September issue.
-------
15. Wastewater Engineering. 2nd Edition, G. Tchobanoglous, Ed. (New
York, NY: McGraw Hill Book Co., 1979).
16. Drinking Water and Health, Volume 2 (Washington, DC: National
Academy Press, 1980), p. 21.
17. P. Esposito, P.V. Scarpino, S.L. Chang and G. Berg, "Destruction by
Dichloramine of Viruses and Bacteria in Water", Abstr. No. G99.
Abstracts of the Annual Meeting, Am. Soc. Microbiology, Washington,
DC (1974). See also: P. Esposito, "The Inactivation of Viruses in
Water by Dichloramine", M.S. Thesis, Univ. of Cincinnati, Ohio
(1974).
18. Reference 16, p. 27.
19. V.P. Olivieri, T.K. Donovan and K. Kawata, "Inactivation of Virus
in Sewage", J. Sanit. Engrg. Div., Am. Soc. Civil Engrs. 97:661-673
(1971).
20. W.J. Masschelein, Chlorine Dioxide (Ann Arbor, MI: Ann Arbor
Science Publishers, Inc., 1979), p. 6.
21. H. Ehrlicher, Zentr. Arbeitsmed. Arbeitsschutz 14:260 (1964).
22. J.F. Haller and W.W. Northgraves, Tappi 38:199 (1955).
23. "Ozone Generation by Corona Discharge", in Handbook of Ozone Tech-
nology and Applications. R.G. Rice & A. Netzer, Eds. (Ann Arbor,
MI: Ann Arbor Science Publishers, Inc., 1982), p. 43.
24. G.W. Miller, R.G. Rice, C.M. Robson, R.L. Scullin, W. KHhn and H.
Wolf, "An Assessment of Ozone and Chlorine Dioxide Technologies for
Treatment of Municipal Water Supplies", U.S. EPA Report No. 600/2-
78-147 (1978). U.S. Environmental Protection Agency, Municipal
Environmental Research Laboratory, Drinking Water Research Division.
25. L. Coin, C. Hannoun and C. Gomella, "Inactivation of Poliomyelitis
Virus by Ozone in the Presence of Water", la Presse Medicale 72(37):-
2153-2156 (1964).
26. L. Coin, C. Gomella, C. Hannoun and J.C. Trimoreau, "Ozone Inacti-
vation of Poliomyelitis Virus in Water", la Presse M2dicale
75(38):1883-1884 (1967).
27. J.F. Bartuska, "Ozonation at Whiting (Indiana)", J. Am. Water Works
Assoc. 33(11):2035-2050 (1941); also, J.F. Bartuska, "Ozonation at
Whiting: 26 Years Later", Public Works, Aug. 1967.
28. H.W. Augenstein, "Use of Chlorine Dioxide to Disinfect Water
Supplies", J. Am. Water Works Assoc. 66:716-717 (1974).
-------
29. Great Lakes - Upper Mississippi River Board of State Board of
Sanitary Engineers, Recommended Standards For Water Works ^ 1976
Edition, (Albany, NY: Health Education Service, 1976).
30. Water Treatment Plant Design (Denver, CO: Am. Water Works Assoc.,
1969).
31. G.C. White, Handbook Of Chlorination (New York, NY: Van Nostrand
Reinhold Co., 1972), p. 618.
32. Reference 31, p. 622.
33. C.M. Robson, "Design Aspects of Ozonation Systems", in Handbook Of
Ozone Technology And Applications, R.G. Rice & A. Netzer, Eds. (Ann
Arbor, MI: Ann Arbor Science Publishers, Inc.,1982), pp. 307-340.
34. W.J. Masschelein, "Contacting of Ozone With Water and Contactor
Off-gas Treatment", in Handbook Of Ozone Technology And Applications,
R.G. Rice & A. Netzer, Eds. (Ann Arbor, MI: Ann Arbor Science
Publishers, Inc., 1982), pp. 143-226.
35. Great Lakes - Upper Mississippi River Board of State Board of State
Sanitary Engineers, Recommended Standards For Sewage Works ^ 1978
Edition (Albany, NY: Health Education Service, 1978).
36. Water Chlorination Principles and Practices - AWWA Manual M20
(Denver, CO: Am. Water Works Assoc., 1976).
37. Chlorination of_ Wastewater ^_ Manual of Practice No. _4_ (Washington,
DC: Water Poll. Control Fed., 1976).
38. Proceedings of_ the Seminar on "The Design and Operation of Drinking
Water FacilitTes Using Ozone o£ Chlorine Dioxide" ^ June 4-5, 1979,
R.G. Rice, Ed. (Dedham, MA: New England Water Works Assoc., 1979).
39. S.P. Hansen, R.C. Gumerman, and R.L. Gulp, "Estimating Water Treat-
ment Costs. Volume 3. Cost Curves Applicable to 2,500 gpd to
1 mgd Treatment Plants", U.S. EPA Report No. 600/2-79-162c (Cincin-
nati, OH: Municipal Environmental Research Lab., 1979).
40. Highway Engineering Handbook, First Edition (New York, NY: McGraw-
Hill Book Co., Inc., 1960).
41- Water Utility Financing Study, Prepared for U.S. EPA, Office of
Drinking Water by Temple, Barker & Sloane, 1981.
42. Water Treatment Plant Operation, K.D. Kerri. To be available from
K.D. Kerri, California State University, Sacramento, 6000 J Street,
Sacramento, CA 95819, in 1984.
43. O.K. Bpc, "Simple Automatic System, 'Icepick Computer' ", Presented
at Calif. Water Poll. Control Assoc. Annual Conference, April 1979.
-------
44. E.G. Rice, "Innovative Applications of Ozone in Water and Wastewater
Treatment", presented at A Seminar on Innovations in the Water &
Wastewater Fields, Univ. of Michigan, Ann Arbon, MI, Feb. 3, 1983.
45. W.L. LePage, "The Anatomy of an Ozone Plant: Monroe Waterworks",
in Proc. AWWA Seminar on Water Disinfection with Ozone, Chloramines
and Chlorine Dioxide. Atlanta, GA, June 15, 1980 (Denver, CO:AmT~
Water Works Assoc., 1980), pp. 71-86.
46. W.C. Harris, "Ozone For Water: What's The Story?", Water & Wastes
Engrg. 11:44 (1944).
47. J.H. Symons, "National Organics Reconnaissance Survey", in Interim
ReP°rt To_ Congress, Preliminary^ Assessment of_ Suspected Carcinogens
in Drinking Water (Appendices) (Washington, DC: U.S. EPA, 1975)
pp. 12-100.
-------
APPENDIX A
DETAILED COST DATA
In the following discussion, cost data are presented for the following
disinfection systems:
o solution-feed chlorination with chlorine gas;
o chlorination with sodium hypochlorite solution;
o chlorination with calcium hypochlorite solution;
o chlorine dioxide;
o chloramines;
o ozone;
o ultraviolet radiation.
Cost data presented are taken from Reference 39, where considered appro-
priate, and are supplemented by vendor quotes obtained for the various
disinfection systems. Vendor quotes were obtained during -the period
1980-1982.
Operating and maintenance costs presented do not include chemical costs.
These will vary depending upon the volume of water treated and the
dosage required. However, sample calculations are presented in this
Appendix for determining quantities of each disinfectant. The reader
then can calculate a total annual cost by employing the procedures
presented in Section 5.
COSTS FOR CHLORINATION SYSTEMS
Solution-Feed Chlorination With Gaseous Chlorine
Equipment Costs
Table XV shows a detailed cost breakdown obtained during May 1980 from
three prominent vendors of chlorination equipment. Data are presented
in terms of a basic gas chlorination system, as well as costs for five
increasingly complex systems. The basic system includes equipment to
handle two 150-Ib chlorine cylinders, two cylinder-mounted chlorine gas
regulators, automatic changeover valve, and chlorine gas flow and rate
valve ejector (with system backup). Alternate #1 adds two scales, a gas
mask and a diffuser corporation cock (to allow connection under water
line pressure). Alternate #2 adds a flow-pacing chlorine addition
system. Alternate #3 adds a flow meter. Alternate #4 adds a booster
pump and piping. Alternate #5 adds a chlorine leak detector.
-------
TABLE XV
CAPITAL COSTS GAS CHLORINATION*
EQUIPMENT COSTS
Basic System**
Alternate 1 - add scales,
mask diffuser, corp cock
Alternate 2 - add flow
pacing - existing signal
Alternate 3 - add flow
meter & signal, 8" or less
Alternate 4 - add booster
pump & piping
Alternate 5 - add Cl gas
detector
INSTALLATION
SAFETY ENCLOSURE
CONTRACTOR'S OVERHEAD & PROFIT (20%)
ENGINEERING FEES (10%)
TOTAL CAPITAL COST:
Basic System
Most Sophisticated
Avg.
High
Low
avg.
avg.
avg.
avg.
avg.
avg.
high
low
avg.
high
low
$1,873
$2,300
$1,320
770
1,694
2,068
792
1,382
1,167
1,500
1,000
3,500
6,000
2,000
1,869
934
$9,343
$16,049
(with Alternate 5)
* May 1980 quotes (three vendors)
** Basic system includes two 150-lb chlorine cylinders, two
cylinder-mounted regulators, automatic changeover valve, chlorine
gas flow and rate valve ejector (system with backup).
-------
The size of this basic gas chlorination system is such as to be appli-
cable to small water systems treating volumes of water at least up to
1 mgd. The larger systems will have to change chlorine cylinders more
frequently than will the smaller systems. For example, a 1 mgd water
treatment plant using an average chlorine dosage of 5 mg/L will use
nearly 42 Ibs of chlorine per day. Thus a 150-lb cylinder of chlorine
will last between three and four days at this size plant.
The cost comparisons present a basic-to-most-sophisticated comparison
between the various system configurations in which gaseous chlorination
systems can be purchased. Costs in Table XV are comprised of equipment,
installation, safety enclosure, contractor's overhead and profit, plus
10% engineering fee for the basic system estimates.
The basic (lowest cost) gaseous chlorination system costs about $9,350;
with all options added, the most sophisticated gaseous chlorination
system costs $16,050, in May 1980 dollars.
Operation and Maintenance Costs
Reference 39 states that in general, O&M costs for chlorination systems
treating 2,500 gpd to 1 mgd are independent of flow. Process energy
requirements are for the booster pump on^y and are about 1,630 kWh/yr.
Building energy requirements for a 25 ft building to house the system
would be 2,560 kWh/yr. Maintenance material requirements would be only
for miscellaneous repair of valving, electrical switches, and other
equipment, and would total about $40/yr. Labor requirements are for
periodic checking of equipment, with an average requirement of
0.5 hr/day, or 183 hr/yr.
O&M costs of $2,457/yr are summarized in Table XVI. Note that power
costs were estimated at $0.07/kWh and labor at $10.00/hr. These rates
were prevalent in 1982, and were used to update the corresponding energy
and labor estimates originally made in Reference 39.
Chemical Costs
The costs of chemicals must be added to these O&M costs. In 150-lb
cylinders, chlorine cost $0.47/lb in the Washington, DC area in
January 1983. Taking a chlorine dosage rate of 5 mg/L for a sample
calculation, gaseous chlorine chemical costs would be about $18/yr to
treat 2,500 gpd and about $7,150/yr to treat 1 mgd. These costs were
calculated as follows:
First, calculate the number of liters of water being treated per day.
For a 2,500 gpd plant:
2,500 gal/day x 3.785 L/gal = 9,462.5 liters of water to be
treated per day.
-------
TABLE XVI
OPERATION AND MAINTENANCE SUMMARY FOR SOLUTION
FEED GAS CHLORINATION
Item
Requirements*
Costs
Electrical Energy:
Process
Building
TOTAL
Maintenance Material
Labor
TOTAL ANNUAL O&M COST
1,630 kw-hr/yr x $0.07
2,560 kw-hr/yr x $0.07
4,190 kw-hr/yr x $0.07
183 hr/yr x $10/hr
$ 114.10
179.20
293.30
$ 40/yr
$1,830
$2,457
* estimates of energy, maintenance and labor made in Reference 39
-------
Next, determine the number of milligrams of chlorine required per day.
If the average chlorine dosage is 5 mg/L:
9,462.5 L x 5 mg/L = 47,312.5 ing/day
Then convert the number of mg required to pounds required per day:
47,312.5 mg x 1 g/1,000 mg = 47.31 g x 1 lb/454 g = 0.104 Ib of
chlorine required per day for a 2,500 gpd facility.
Finally, multiply the number of pounds of chlorine required per day by
365 (days per year), and that figure by the current cost of chlorine:
0.104 Ibs chlorine required/day x 365 = 37.96 Ibs x $0.47/lb =
$17.84/yr.
A 1 mgd facility operating at design capacity treats 400 times as much
water as does a 2,500 gpd plant (1,000,000/2,500 = 400). Therefore, a
1 mgd facility using a 5 mg/L chlorine dosage will require 400 times the
amount of chlorine annually:
37.96 Ibs Cl x 400 = 15,840 Ibs/yr x $0.47 = $7,445/yr.
To calculate costs for gaseous chlorine at lower or higher dosages, the
following formula can be used:
dosage (mg/L) x no. of L dosed/day x Cl cost/lb
= Cl cost/day
1000 (mg/g) x 454 (g/lb)
Sodium Hypochlorite Solution Feed
Equipment Costs
Table XVTI displays estimates obtained in May 1980 from two vendors of
sodium hypochlorite chlorination equipment. Data are presented for the
basic liquid hypochlorination system [which includes two metering pumps
(one to be standby), solution tank, diffuser and appropriate quantities
of tubing]. However, two types of basic systems are costed, one acti-
vated electrically and the other activated hydraulically. The basic
systems can be supplemented, and costs for four increasingly sophisti-
cated alternatives also are presented in this table. Alternate #1 adds
a diffuser corporation cock and anti-siphon backflow preventer, Alter-
nate #2 adds a safety housing enclosure, Alternate #3 adds a flow-pacing
system, and Alternate #4 adds a flow meter and signal.
The total capital costs for the basic and most sophisticated systems
are:
-------
TABLE XVII
CAPITAL COSTS LIQUID CHLORINATORS*
EQUIPMENT COST
(Basic System**)
INSTALLATION
SITE WORK
CONTRACTOR'S OVERHEAD & PROFIT (20%)
ENGINEERING FEES (10%)
Alternate JL: add dif fuser
corporation cork & anti-
siphon backflow preventer
Alternate 2i add safety
enclosure (housing)
Alternate 3: add flow pacing
existing signal
Alternate 4^ add flow meter &
signal, 8" or less
TOTAL CAPITAL COST:
Basic System (Equipment +
Installation + Site Work +
Overhead & Profit +
Engineering Fees)
Most Sophisticated
(with Alternate 2)
(with Alternate 4)
Electric Activated
avg. $ 1,800
high 2,300
low 1,300
500
250
729
364
165
6,930
$ 3,643
Hydraulic
Activated
$ 2,266
2,782
1,750
1,000
250
1,004
503
231
6,930
1,485
1,452
$ 5,023
10,738
15,121
* May 1980 quotes (two vendors)
** Basic system includes two metering pumps (one standby), tubing,
solution tank and diffuser.
-------
basic system
electrically activated
hydraulically act ivated
$ 3,643
$ 5,023
most
sophisticated
system
$10,738
$15,121
Operating and Maintenance Costs
As is the case with solution-feed gas chlorination, Reference 39 states
that O&M requirements are independent of flow for plants handling
2,500 gpd to 1 mgd. Process energy requirements are for the diaphragm
metering pump and amount to 570 kWh/yr. Building energy requirements
for a 25 ft building would be 2,560 kWh/yr. Maintenance material would
be required only for minor component repair; these costs are estimated
at $20/yr.
Labor is required for periodic mixing of the sodium hypochlorite solu-
tion, as well as for checking of the equipment. Based on a requirement
of 1 hr/day, the annual labor requirement would be 365 hr/yr.
Annual O&M costs of $4,108 are summarized in Table XVIII. Note again
that power costs are based on $0.07/kWh and labor costs of $10.00/hr.
Chemical Costs
Sodium hypochlorite is sold as a 1.5 to 15% (by weight) solution. In
January 1983, the cost of a 15% solution in 1,500 gal tanks in the
Washington, DC area was $0.93/gal.
How many gallons of 15% sodium hypochlorite (NaOCl) solution are required
to dose 2,500 gpd of water with 5 mg/L of chlorine?
In the preceeding example, it was determined that 2,500 gpd of water
using an assumed 5 mg/L dosage of chlorine requires 0. .104 Ib of chlorine
per day. One gallon of hypochlorite solution weighs approximately
8.34 Ibs and contains 15% by weight of NaOCl. Therefore, 1 gal of 15%
NaOCl solution contains 8.34 x 0.15 = 1.251 Ib of NaOCl. However, one
Ib of NaOCl contains 47.65% available chlorine. Therefore, one gal of
15% NaOCl solution contains 1.251 Ib of NaOCl x 0.4765 = 0.596 Ib of
ava ilable chlorine.
Since only 0.104 Ib of available chlorine is required per day, then
0.104/0.596 = 0.175 gal/day of 15% NaOCl solution is required to provide
a 5 mg/L dose of chlorine.
Over 365 days (one year), the amount of 15% NaOCl solution required is
0.175 x 365 = 63.7 gal. At $0.93/gal, the 2,500 gpd utility will spend
about $59.24/yr (at an average dosage of 5 mg/L of chlorine). A 1 mgd
facility will require 400 times more hypochlorite, and will spend
$23,696/yr for the 15% solution.
-------
TABLE XVIII
OPERATION AND MAINTENANCE SUMMARY FOR SODIUM
HYPOCHLORITE SOLUTION FEED
Item
Electrical Energy:
Process
Building
TOTAL
Maintenance Material
Labor
Requirements*
Cost
570 kw-hr/yr x $0.07
2,560 kw-hr/yr x 0.07
3,130 kw-hr/yr x 0.07
365 hr/yr
TOTAL ANNUAL O&M COST
$ 39.90
179.20
219.10
$ 20/yr
x $10/hr = 3,650
$4.108
* amounts estimated in Reference 39
-------
Calcium Hypochlorite Solution Feed
Equipment costs and operating and maintenance costs for this method of
disinfection should be very close to those for sodium hypochlorite feed
systems. Solutions of calcium hypochlorite are prepared in a day tank
(a tank which holds enough solution to last for one day), then injected
into the water stream using a diaphragm metering pump.
Chemical Costs
Solid calcium hypochlorite, Ca(OCl) , contains 65% available chlorine.
Therefore, one Ib contains 0.65 Ib of available chlorine. Since a
2,500 gpd water treatment plant requires 0.104 Ib of chlorine per day
(for an average dosage of 5 mg/L), 0.104/0.65 = 0.16 Ib of Ca(OCl) per
day is required with which to prepare a solution for metering into the
water to be treated.
During January 1983, calcium hypochlorite was selling for $1.40/lb in
100 Ib bags in the Washington, DC area. Over a one year period, the
2,500 gpd facility will require 0.16 Ib x 365 days = 58.4 Ibs of
Ca(OCl) , x $1.40/lb = $81.76/yr. The 1 mgd facility, which uses
400 times the amount of chlorine, therefore will spend $32,704/yr for
Ca(OCl)2.
Costs For Chloramination
Generation of chloramine requires the same equipment for chlorination
(gaseous or aqueous hypochlorination) plus equipment for the addition of
ammonia (gaseous or aqueous). Costs for chlorination equipment and for
its operation and maintenance have been discussed above; in this section,
costs for addition of ammonia are presented.
Ammonia is available in either of three forms:
- anhydrous ammonia (100% available ammonia);
- 28% solution in water, called aqua ammonia (28% available NH )5
- solid ammonium sulfate (25.76% available NH ).
For small water supply systems, anhydrous ammonia is purchased as a
pressurized liquid in 150-lb cylinders. It is fed as a gas to the point
of application. Aqua ammonia is purchased in 55-gallon drums, and food
grade ammonium sulfate is purchased as a solid in 100-Ib bags.
During January 1983, costs for liquid ammonia were $0.40/lb (in 150-Ib
cylinders), $0.70/lb of contained ammonia in 28% solution (purchased in
55-gal drums), and $0.51/lb for solid ammonium sulfate (purchased in
100-lb bags), in the Washington, DC area.
Cost calculations given below are based upon the following reaction of
chlorine gas and ammonia to produce monochloramine:
Cl,
C1NH
HC1
-------
In addition, the calculations assume a 5 mg/L dosage of disinfectant, in
this case 5 mg/L of monochloramine, which is obtained either by adding
the proper amount of chlorine to water, then adding the requisite amount
of ammonia, or vice-versa. It is also assumed that all chlorine added
will be free available chlorine, and will be utilized during reaction
with ammonia to produce monochloramine. This does not strictly reflect
actual water supply situations, because some chlorine demand is usually
present for producing trihalomethanes, if chlorine is added prior to
ammonia. Therefore, these calculations reflect the minimum amounts of
chlorine which will be required to produce a 5 mg/L dosage of monochlor-
amine.
Finally, cost calculations will be given based upon chlorine added as
the gas. By using previously described calculations involving solutions
of sodium hypochlorite or of calcium hypochlorite, the amounts of these
chlorinating agents required to produce monochloramine can be calculated
readily.
Costs For Monochloramine From Anhydrous Ammonia + Chlorine Gas
A 2,500 gpd water treatment plant will require 0.104 Ib/day (47.31 g/day)
of monochloramine at a dosage of 5 mg/L. According to the chemical
stoichiometry of the equation given above for the generation of monochlor-
amine from ammonia and chlorine, each gram-molecular weight (weight of
one mole of compound expressed in grams) of monochloramine produced will
require 1 gram-molecular weight each of ammonia and chlorine. Thus:
17 g NH3 + 71 g C12 »*51.5 g C1NH2 + 36. 5 g HC1
Since 47.31 g/day of monochloramine are required each day, the corres-
ponding amounts of ammonia and chlorine required are:
Ammonia: (47.31/51.5) x 17 - 15.62 g/day
Chlorine: (47.31/51.5) x 71 = 65.22 g/day
Dividing the grams of each reactant by 454 (the number of grams per
pound), gives a daily requirement of 0.034 Ib of ammonia and 0.143 Ib of
chlorine.
Multiplying each of these figures by 365 days yields the annual number
of pounds of ammonia and chlorine required. Finally, annual costs for
each are calculated by multiplying the annual requirements by the current
costs:
Ammonia; 0.034 Ib/day x 365 = 12.41 Ib/yr x $0.40/lb = $4.96/yr
Chlorine; 0.143 Ib/day x 365 = 52.20 Ib/yr x $0.47/lb = $24.53/yr.
The sum of these two numbers ($4.96 + $24.53) = $29.49, total annual
chemical costs for the 2,500 gpd facility.
-------
A 1 mgd facility will require 400 times the amounts of chemicals at the
same 5 mg/L dosage, therefore:
$29.49 x 400 = $ll,796/yr, annual chemical costs.
Costs For Monochloramine From Aqua Ammonia + Chlorine Gas
From the preceeding calculations, the 2,500 gpd facility will require
12.41 Ibs/yr of anhydrous (gaseous) ammonia. If the source of ammonia
is 28% aqueous ammonia, the calculation of the costs is as follows:
1 gal of 28% ammonia weighs 8.34 Ibs and contains 8.34 x 0. 28 =
2.34 Ibs of ammonia.
12.41 Ibs/yr ammonia requires 12.41/2.34 =5.3 gal/yr of aqua
ammonia.
At $0.70/lb of ammonia contained in aqua ammonia, the annual cost of
aqua ammonia is:
12.41 Ibs x $0.70/lb = $8. 69/yr.
The annual cost of gaseous chlorine is $24.53/yr, therefore the total
annual chemical costs are:
$8.69 + $24.53 = $33.22/yr.
The 1 mgd water treatment plant will require 400 times the amounts of
chemicals:
$33.22/yr at the 2,500 gpd plant x 400 = $13,288/yr at the 1 mgd
plant.
Costs For Monochloramine From Ammonium Sulfate + Chlorine Gas
One pound of ammonium sulfate contains 0.2576 Ib (28.76%) of available
ammonia. The 2,500 gpd plant using solid ammonium sulfate will require
12.41 Ibs/yr of anhydrous ammonia annually. To obtain this amount of
available ammonia requires 12.41/0.2576 = 48.18 Ibs/yr of ammonium
sulfate. At $0.51/lb current cost, the 2,500 gpd plant will require:
48.18 Ibs/yr x $0.51/lb = $24. 57/yr + $24.53 for chlorine =
$49.10/yr.
The 1 mgd facility will require 400 times as much chemicals, or:
$49.10 x 400 = $19.640/yr.
-------
TABLE XIX
COMPARATIVE ANNUAL O&M AND CHEMICAL COSTS FOR
CHLORINE AND MONOCHLORAMINE (ASSUMED 5 mg/L DOSAGE)
Disinfectant
Source
2,500 gpd plant costs
O&M Chemical Total
1 mgd plant costs
O&M
Chemical Total
Chlorine:
gaseous chlorine
NaOCl solution
$2,457 $17.84 $2,475
4,108 59.24 4,167
4,108 81.76 4,190
Chloramine (from gaseous chlorine):
Ca(OCl) solution
anhydrous NH
aqua ammonia
ammonium sulfate
2,457 29.49 2,486
2,457 33.22 2,490
2,457 49.10 2,505
$2,457 $ 7,445 $ 9,902
4,108 23,696 27,804
4,108 32,704 36,812
2,457 11,796 14,253
2,457 13,288 15,745
2,457 19,640 22,097
-------
Summary of Chlorination Costs
Table XIX summarizes the annual operation and maintenance and chemical
costs for the three types of chlorination (gaseous, hypochlorite solu-
tion, and calcium hypochlorite) plus chloramination (prepared from
anhydrous ammonia, aqua ammonia and ammonium sulfate) using gaseous
chlorine. Annual chemical costs are calculated for 2,500 gpd and 1 mgd
plants based on a 5 mg/L dosage of chlorine or of monochloramine. This
dosage was selected solely for convenience in calculating exemplary
costs for controlling microorganisms with chlorine, hypochlorite or
chloramines. It is not a recommended dosage.
O&M costs are the same at each size plant, since they are independent of
flow. O&M costs for solution feed of either sodium hypochlorite or
calcium hypochlorite are identical because the same equipment is used in
both cases. O&M costs shown for chloramine are identical because gaseous
chlorination has been assumed for these calculations. If monochloramine
is made using sodium hypochlorite or calcium hypochlorite solutions, O&M
costs will be higher ($4,108 versus $2,457) because O&M costs for feeding
solutions are higher.
It is apparent from the data of Table XIX that the annual chemicals
costs at the 2,500 gpd plants are only 1 to 2% of the annual O&M costs.
However, at the 1 mgd plants, annual chemical costs are 3 to 8 times the
annual O&M costs. Costs at intermediate sized plants will be increasing-
ly dependent upon chemical costs as plant sizes increase.
It should also be noted that the cost of chlorination using gaseous
chlorine is 36% of the cost of using sodium hypochlorite solution, and
27% of the cost of using calcium hypochlorite.
COSTS FOR CHLORINE DIOXIDE
Reference 39 summarizes costs for generation of chlorine dioxide from
equal parts of 2.4% sodium chlorite solution, 25% sulfuric acid solution
and 1% sodium hypochlorite solution. Suppliers contacted in 1982 have
designed their generation systems for small water supply systems to use
33% hydrochloric acid rather than 25% sulfuric acid.
The cost estimates of Reference 39 assume the use of a dual head dia-
phragm pump for simultaneous addition of the hypochlorite and acid
solutions, and a second single head pump for the addition of sodium
chlorite solution. Detention time in the chlorine dioxide reactor is
estimated at 12 seconds, and the costs of generating equipment are
assumed constant up to 50 Ibs/day of chlorine dioxide. The recommended
maximum dosage rate for chlorine dioxide is 1 mg/L. At this maximum
dosage rate, a 1 mgd water treatment plant would use about 8 Ibs/day and
a 2,500 gpd facility would use about 0.2 Ib/day of chlorine dioxide.
-------
Equipment Costs
Quotes were obtained from three suppliers of chlorine dioxide generation
equipment sized so as to prepare CIO at the rate of 8 Ibs/day. This
low production volume would be required by a 1 mgd plant, dosing chlorine
dioxide at a maximum rate of 1 mg/L, as is currently recommended by
EPA (11). These quotes (obtained in June 1982) are shown in Table XX.
The recirculating loop system made by a French manufacturer is the
highest in equipment price; their lowest cost unit is priced at $34,000.
This unit operates with a special recirculating pump designed to handle
hypochlorous acid solution at pH below 4, plus a sodium chlorite solu-
tion pump and all necessary instrumentation to allow automatic opera-
tion, with shutdown provisions in the event that water flow ceases.
Next lowest in price is the system from Supplier B, which generates
chlorine dioxide from 33% hydrochloric acid, 12% sodium hypochlorite
solution and 25% sodium chlorite solution. This unit costs $25,000
(installed), and includes three solution pumps, water flow rate detector
and switches to shut down the unit if the water flow stops. This unit
is wall-mounted and requires 3.5 ft x 4 ft of wall space, plus space for
drums of the three chemical solutions used to feed the generator. For
volumes of CIO sufficient to treat flows in communities of 5,000 and
2,500 population, this unit is said to be capable of continuous opera-
tion, with no loss in efficiency of conversion of chlorite ion to chlorine
dioxide. However, to supply the needs of systems serving as few as
25 people, the unit would have to be operated intermittently, with CIO
solution being stored in a holding tank for later metering into the
water.
Finally, Supplier C provides two types of generators for small water
supply systems: one uses acid/sodium chlorite; the other uses chlorine
gas and sodium chlorite. These units cost $3,600, if wall-mounted, and
$4,320 for a floor mounted cabinet. The single size unit currently
offered by this company will produce up to 140 Ibs/day. In order to
produce 8 Ibs/day or less on a continuous flow basis, this unit would
have to be operated at such low solution flow rates as to provide ineffi-
cient mixing, and, therefore, poor conversions of the reactants to
chlorine dioxide. Therefore small water supply systems considering the
use of this unit also will have to install a holding tank for the product
and operate the generator intermittently at design rates of solution
flows.
The chlorine gas/sodium chlorite CIO generator of Supplier C requires a
gas chlorinator in order to feed chlorine gas. Therefore, in new plants
considering use of this generator, the cost of a chlorinator must be
added to the cost of the CIO generator. In existing plants currently
using gas chlorination, the chlorinator already is in place and would
not represent an added equipment cost.
-------
TABLE XX
1982 VENDOR QUOTES CHLORINE DIOXIDE GENERATORS
Vendor
C102
production
capacity
(Ibs/day)
recircu-
lating
loop
Supplier A
(French)
1-10
Supplier B 4
Supplier C 14-140
Supplier C 14-140
space
required*
2'x3'x6'
high
Reactants Unit Cost
Cl gas + $34,000
NaCIO (1 rate,
solutxon adjust
manually)
$38,000
(2 rates,
adjust auto-
matically)
$41,700
(3 rates,
adjust auto-
matically)
prices delivered in New York
3.5'x4'x
1.5' deep
(wall-
mounted)
4'x3'x
1.5' deep
37.5"x 27"
6.5" deep
4'x3'x
1.5' deep
37.5"x27"
x 6. 5" deep
HC1,
NaOCl,
NaCIO
solut ions
Cl gas &
NaCIO
solution
same
, HC1 +
NaCIO
solution
same
$25,000
(installed)
$ 4,320**
(floor
mounted)
$3,600**
(wall mount)
$4,320
(floor
mounted)
$3,600
(wall
mounted)
* all units require additional space for solution tanks.
** this unit requires a chlorinator for operation, which is not
included in price estimates
-------
TABLE XXI
OPERATION AND MAINTENANCE SUMMARY FOR CHLORINE
DIOXIDE GENERATING AND FEED SYSTEMS
It an
Requirements*
Cost
Electrical Energy:
Process
Building
TOTAL
Maintenance Material
Labor
TOTAL ANNUAL O&M COST
1,240 kw-hr/yr x $0.07
4,100 kw-hr/yr x $0.07
5,340 kw-hr/yr x $0.07
365 hr/yr x $10.00
$ 86.8
$ 287.0
$ 373.8
$ 100/yr
$3,650
$4,124
* based on estimates made in Reference 39
-------
Because equipment quotes for generating chlorine dioxide vary so widely,
small water system personnel are advised not to try to apply indices to
update older cost estimates. Technology for generating and applying
chlorine dioxide is changing (as opposed to technologies for addition of
gaseous or aqueous chlorine) and new suppliers enter the market from
time to time. It is more advantageous to seek quotations from the
various suppliers as to the various methods of generating C10-. Select
the method most appropriate to the specific plant, then determine what
piping and wiring will be needed to install the equipment selected.
Operating and Maintenance Costs
Reference 39 states that, in general, O&M costs for generating CIO are
independent of the quantities generated. Process energy requirements,
which are for metering pumps and mixer for preparing chlorite solution
from solid sodium chlorite, are estimated at 1,240 kWh/yr. Energy
requirements for 40 ft of building space to house the equipment would
be 4,100 kWh/yr, resulting in total energy requirements of 5,340 kWh/yr.
Maintenance material requirements would be for minor equipment repair
only, amounting to about $100/yr. Labor is required for preparation of
solutions and periodic maintenance of the equipment. Annual labor
requirements are estimated to be 1 hr/day or 365 hr/yr.
Annual O&M costs of $4,124/yr (based on $0.07/kWh power cost and
$10.00/hr labor cost) are summarized in Table XXI.
Chemical Costs
At an annual CIO production rate of only 8 Ibs/day (maximum at a 1 mgd
plant), chemical costs are not as significant as pumping costs. Never-
theless, gaseous chlorine costs $0.47/lb, sodium chlorite costs $1.55 to
$1.65/lb (as solid or in solution), hydrochloric acid costs about
$0.10/lb, and sodium hypochlorite costs $0.93/gal for 15% solution. A
production rate of 8 Ibs/day equates to 2,920 Ibs/yr of chlorine dioxide.
If the chemicals cost of CIO is arbitrarily assumed to be $l/lb, a
1 mgd water treatment plant can expect to pay $2,920 in addition to the
annual O&M costs. Chemical costs at a 2,500 gpd plant would be
$2,920/400 = $7.30/yr for producing chlorine dioxide at $1.00/lb.
COSTS FOR OZONATION SYSTEMS
Equipment Costs
These will include estimates for ozone generation equipment and ozone
contacting systems, both of which are supplied by the ozone systems
manufacturer. Water supply systems treating 0.5 mgd and less will
require a daily ozone generation capacity of from three to 21 pounds,
and will be able to dose ozone at average levels of up to 3-5 mg/L. At
these production levels, ozone will be generated from dried air, not
oxygen, in order to avoid the costs of oxygen recovery and recycle
equipment.
-------
Ozonation equipment to be purchased includes the following:
- air preparation equipment (drying and chilling)
- ozone generator
ozone contactor
- ozone destruction unit
- instrumentation and controls
For the small production quantities of ozone required by small water
treatment plants (three to 21 pounds per day) items 1, 2, 4, and 5 can
be assembled into a single, skid-mounted unit. If the contactor selected
is a turbine type, even the ozone contactor is small enough to be included
in the skid-mounted assembly unit.
Diffuser contactors for small ozonation systems generally are constructed
of polyvinyl chloride (PVC) pipe standing on end, or of fiberglass
reinforced plastic (FRP) tanks. A contact chamber containing diffusers
should be approximately 18-ft high, providing a water depth of 16-ft and
a detention time of 10 to 15 minutes. These conditions will insure the
maximum transfer of ozone from gas phase to aqueous solution when em-
ploying diffuser contacting systems.
Equipment cost estimates were obtained from three of the major U.S.
ozonation systems suppliers in 1982. These are presented in
Tables XXII, XXIII, and XXIV for various daily ozone generation rates.
Ozone Supplier A (Table XXII) provided estimates for ozone dosages of 3
and 5 mg/L at water flow rates of 500,000 gpd, 350,000 gpd and
180,000 gpd. This cost breakdown shows that equipment costs for air
pretreatment and ozone generation capacity available from this supplier
depend upon the dosage required at a particular water flow rate. In
addition, the size (and cost) of the ozone destruction units required
also varies, as does the power requirement to operate the total ozona-
tion system.
Ozone Supplier A can provide four monitors with his system (all are
optional, but all are recommended for optimal performance and minimal
downtime). These will monitor:
- the dew point in the air preparation unit;
- ozone output of the generator;
- ozone in the ambient plant air (in case of leaks);
- dissolved ozone residual in the water.
The cost of these four monitors is constant at $15,000, regardless of
system size in the range shown in Table XXII (5 to 21 pounds per day).
Table XXIII shows similar cost data for equipment of Ozone Supplier B.
In this case, equipment costs are presented for water flows of 100,000,
200,000, 300,000, 400,000 and 500,000 gpd. Average ozone dosages are
taken to be 3 mg/L, and the daily ozone output required varies from
3 Ibs/day for treating 100,000 gpd to 15 Ibs/day for treating
500,000 gpd.
-------
TABLE XXII
COSTS OF OZONATION EQUIPMENT FOR SMALL WATER SUPPLY SYSTEMS (Company A - May 1982)
Size of water supply
Maximum dosage of ozone (mg/L)
at peak flow
Daily ozone requirement (Ibs)
Contact chamber diameter (14 ft
high, 4 compartments, 4 dif-
fusers, Derakane fiberglass
reinforced plastic)
EQUIPMENT COSTS
Air preparation + ozone
generation unit
Contact chamber with diffusers
Monitoring Instrumentation
1) Ozone in generator product
2) Ozone in ambient plant air
3) Ozone dissolved in water
4) Dew point monitor in air
preparation unit
Ozone Destruction Unit
TOTAL EQUIPMENT COSTS
Power requirement kWh
6 ft
6 ft
$31,500 $25,000
$11,500 11,500
$15,000 15,000
$6,700 5,000
(10 cfm) (7 cfm)
$64,700 $56,500
13.3 10.1
350,000 gpd
5 ft
5 ft
$25,000 $22,000
10,200 10,200
15,000 15,000
5,000 4,200
(7 cfm) (3 cfm)
$55,200 $51,400
10,1 5.0
180,000 gpd
5
21
3
14
5
14
3
7
5
7
3
5
4 ft
4 ft
$22,000 $19,500
z 9,900 z 9,900
15,000 15,000
z 4,200 4,200
(3 cfm) (3 cfm)
$51,100 $48,600
5.0 3.65
-------
* 1-3 1 1 J
* * * o rt o- (~C>LD\
3r X» 3fr X" O !!> (D O\ OJ &J )
C/3 H 5! P" V J~»
CO- -CO- CO CO H PJ H> rt PJ H"TO
N> *>-S pi fD H- P COM >tf i 0 (D
PI B Hi i"i o ,O O &" O 0
ooofBH i-> a H-fogro
OOfD H-'US M 01-t l-(
OO PJ TO M {X O CO H X M.
0 0 .n IT1 01 PJ >zi 0-00
CO CO C <« rt i-l PJ rt PJO0
rt rt H- y. PJ H- H 0 *
l-t i-t i-i PJ CO "d fD H- l-t
CO CO PI l-t rt 01
B i"t rt -co-
P PJ gj pi pj H. p. OJOJ
O 0 H- rt 0 0 o Ui OJ
rt 0 H- {X 0 0 -
pi rt O h-» --J --J
PJ £ fD 0 PJ C OO
C rt 0 fX O O o
ft O PJ CO IX fl> N T
o a 0 <
H-CfDOOI-l »
N co co g pi o vo vo
fD >XJ 0 CO N O O
coi-igi-ti-tfDO oo
fD O (D *^3 0 T
S, 01 l-t CO PL. pi fD
fD (X fD CO l-t l-|
rt H- O v4 pi ex -co.
f5TO 0 i-i O CO to .p.
@H- i-i fD CO l-t to ts3
.. 9 S3 I-1 -C 00
H- 1 «"^ H. O O O
CO M < O rt T
rt H- CD O H-
H 0 H go
*< fD CO >O 0 <«.
* _ , H Ul ON
B Pi fD 01 vo r- *
O H- CO 0 «
0 H CO O. IO to
H- 0 00
rt PJ H CO O O
0 rt < .°°.0
*^0 rt *«*j ^j
O O
co oo o o
CO I-"
rt to
B id oo oo
co ON oo
rt H-
PI TO Ul Ul
P? 00
(D rt O 0
CO O I
(* pi
fD -co-
ca oo oo
ca OJ ui
** *t
Ul Ul
0 0
00
o
OJ 10 10
Ul IO O
00 0
0 O O
0
H
O O TO *-** ha i>
N SjNfDS^OOH-
O H-OPSSiNi-t
0 rt P fD P' CD 0
fD P4fDi-f---.i-!p13
_ 01 r-1 fD H
g (X O rt CT1 i-i fD
O H- O (D fD TO "O
0' Hi0afDpJ
H- hhrtv-'l-hcpi-i
rt C pi /-VH> fD PJ
O CO O lOV? l-t rt
H fD rt loo JO PJ H-
05 s s ^i s§
sa +
CO
P '
Maximum ozone dosage
(mg/L), at peak flov
Daily ozone requiren
(Ibs/day)
Equipment Costs
f1 fD
m 0
V. r-<-
Ul * "
-co- -co-
P- oo
" OJ OJ
O Ul
0 0
o o -co-
S
to - *
O Ul *
r
s?
rt
fD
O
*
§
(X
^^
CO-
H * OJ
0 00
*
( n K.1
f
-co- -co- o
OJ IO IO .p- |-» o
* * v *» fO ^-i i &
Ul to o
O O O
00 0
0
o
O CD
o o -co-
Or-1 OJ
oo o
^
w
Ul to
P
ho
£3
(X
0
-co-
r-1 00
O 00 f
tT-t
ui Ui
-co- -co- o
OJ tO IO
Ul IO O
p. |-a o
ON -^j (ij
=> » ^
O O O O O
O O O O O -CO-
o
Or-1 OJ
OJ Ul
Ui Ul
O
fi§
o
OJ
3
TO
fX
O
-CO-
O OJ
t-*
hrl
Ul O
-co- -co- o
OJ to to 4
t- tO C3 li
<»»!' io oj
Ui to O O
0 O 00 0
o o o <
o
i-i
<
OJ tO IO
«* <* » w
Ul 10 O C
3 O -CO-
Of-1 -P-
OJ O
hrt
Ui O
o
-P-
s
JQ
PJ
o
-co-
O VO
w
r^
Ul OO
0- -CO- O
^ to o H->
VO -P- oo
3
o o o o o
0 0 0 O O -CO-
Or-1 -P-
oj ON 1 pd
Ul 00
£~ }
*
Ul
3
xj
o
o
8
rt
en
§
o
o
E!
.
S
^H
M
j jj
2
H3
S
*"^
i
tr*
S
T)
iTl
rw
M
S
CO
, «.
r3
S
CO
-^
o
%
01
1
^
w
1
VQ
00
N>
-------
TABLE XXIV
COSTS OF OZONATION EQUIPMENT FOR SMALL SUPPLY SYSTEMS (Company C - February 1983)
Flow Rate
Maximum ozone dosage
(mg/L) at peak flow
Daily ozone requirement
(Ibs/day)
Equipment Costs*
Ozone Monitors**
Power Requirement
(kWh/lb 0 generated)
Estimated Room Size
(10 ft. high)
Total Equipment Costs
0. 1 mgd
3
2.5
$38,000
$15,875
16.2
10 x 14 ft
$53,875
0.2 mgd
3
5
$44,000
$15,975
14.6
10 x 15 ft
$59,875
0.3 mgd
3
7.5
$49,700
$15,875
13.6
10 x 16 ft
$65,575
0. 4 mgd
3
10
$61,800
$15,875
12.3
10 x 16 ft
$77,675
0.5 mgd
3
12.5
$68,700
$15,875
11.8
10 x 17 ft
$84,575
* Includes air preparation by desiccation, ozone generation, turbine contactor, ozone destruction,
and controls
** Includes monitoring of air dew point, ozone production, dissolved ozone residual in water, and
ozone in ambient plant air.
-------
Ozone Supplier B offers two types of air preparation equipment, however,
and estimates are presented for each. One type operates at high
pressures (80-120 psig), and the other at low pressures (8-12 psig).
The high pressure air treatment units are lower in capital cost, but
require more energy for their operation.
Ozone Supplier B does not normally provide a residual dissolved ozone
monitor, but offers two types of monitor for ozone output from the
generator. The automatic, in-line, continuous reading monitor costs
$4,000; the non-automatic monitor requires wet chemistry determinations
to develop data at some period of time after the sample has been taken,
and costs $2,000.
Therefore, cost data presented in Table XXIII vary by the differences
between costs for high and low pressure air preparation equipment, and
by the costs of the two ozone generator monitors.
Cost estimates provided by Ozone Supplier C are given in Table XXIV. In
contrast to the ozonation systems of Suppliers A and B, the system of
Supplier C operates at sub-atmospheric pressure. The submerged turbine
contactor provided by this supplier is the key to the difference in
system pressure operation. When activated, the turbine creates a vacuum
in the ozone generator, thereby drawing ambient air into the air prepara-
tion system, then through the ozone generator, and into the ozone
contactor.
In addition, the contactor tank housing the submerged turbine is much
smaller in size than the tank required for diffuser contacting. For
small water supply systems treating up to 500,000 gpd with ozone, the
turbine contactor tank of Ozone Supplier C is about two feet in diameter
and about 30 inches high. As a result, this contactor can be incorpor-
ated into the skid-mounted ozonation system. If desired, this contactor
can be installed out of doors as well.
Ozone Supplier C also provided cost estimates for water flows of 100,000,
200,000, 300,000, 400,000 and 500,000 gpd. Equipment costs for increa-
singly larger ozone generation volumes include costs for air preparation
by means of dual tower silica gel desiccant dryers, ozone generation,
ozone contacting (by submerged turbine), ozone destruction in contactor
off-gases, and control systems. Costs for the four recommended ozone
monitors are presented separately, and total $15,875. This cost is
constant for all five systems.
It should be appreciated that if the system of Ozone Supplier C is
installed in a southern U.S. location subject to high temperatures and
high humidities the year round, the desiccant air preparation unit
quoted in Table XXIV should be modified by addition of an air chiller
unit. This will add to the equipment cost, but will reduce the operating
costs. Without the chiller, the desiccant columns would have to be
regenerated (thermally) much more frequently when fed high relative
humidity air than when being fed low relative humidity air.
-------
Installation Costs
Costs for installation of the ozonation equipment include labor and
material costs for piping water to and from the ozone generators (if
they are water-cooled), for piping ozone-containing air to the contactor
chamber, for piping water to and from the contact chamber, and for
piping contactor off-gases to and from the ozone destruction unit.
Electrical wiring costs also must be considered in these costs. Ozona-
tion equipment suppliers contacted advise that for production of up to
about 30 Ibs/day of ozone, installation costs will be roughly the same,
and will average 15 to 25% of the equipment costs of the largest units
estimated in Tables XXII, XXIII, and XXIV. The actual figures for the
individual equipment suppliers then become:
Supplier
A
B
C
Housing Costs
Cost of Equipment
(500,000 gpd plant)
$64,700
$85,000
$84,575
Installation Cost
(15 to 25%)
$ 9,705 - $16,175
$12,750 - $21,250
$12,686 - $21,143
The power supply, air preparation equipment, ozone generation equipment,
and turbine contacting units can be installed in existing plants rela-
tively easily, in areas on the order of 10 x 17 feet. However, diffuser
contacting units are tall (18 feet) and bulky, and normally are in-
stalled outside existing buildings (above ground) or underground inside
buildings being constructed. Alternatively, a 170 sq ft Butler building
can house the ozonation system, except for above-ground diffuser unit.
Such a building costs about $6,000.
It should also be noted that if the small water supply system selects
ozone as its primary disinfectant, then wishes to add chlorine, chlorine
dioxide or chloramine for residual, equipment for addition of the desired
residual-forming chemical also will be required.
Operation and Maintenance Costs
Operating costs for ozonation systems vary, and depend upon a number of
factors:
- method of air preparation
- method of cooling the generator (air or water)
- if water cooled generators, the amount of refrigeration required
for cooling water
- method of contacting
dosage of ozone required
- pumping of generator coolant
- method of contactor off-gas destruction
-------
Air Preparation
High pressure versus low pressure systems, versus sub-atmospheric pressure
desiccant system with or without addition of air chiller.
Ozone Generator Cooling
Air versus water. If water, the amount of cooling required. In northern
climates, water produced at the plant generally is cold enough to serve
as the generator coolant the year round. In southern climates, generator
cooling water must be refrigerated most, if not all, of the year.
Method of Contacting
Diffuser contactors require no added energy. Ozone/air mixtures normally
are generated under a sufficient pressure to overcome the head of 16 feet
of water. On the other hand, turbine diffusers require energy for their
operation, but take up much less space than diffuser contactors.
Contactor Off-Gas Destruction
Atmospheric dispersion, versus thermal destruction, versus catalytic
destruction. Operating costs of each of these techniques differ.
Maintenance material requirements are for periodic equipment repair and
replacement of parts. Air preparation systems contain air prefilters
which must be replaced frequently. Ozone generators of the tubular type
normally are shut down once per year for cleaning of the tubes and other
general maintenance. This can require several man-days of time, depending
upon the number of ozone generators in the system. Spare parts normally
consist of replacement tubes, which can be broken during cleaning, or
which can deteriorate after years of operation at high voltages.
Labor requirements are for periodic cleaning of the ozone generation
apparatus, annual maintenance of the contacting basins, and day-to-day
operation of the generating equipment (average 0.5 hr/day).
Operating and maintenance costs for equipment of Ozone Suppliers A, B,
and C for various sizes of small water supply systems up to 500,000 gpd
are summarized in Table XXV. Also included are building heating costs
(which are taken to be the same up to 0.5 mgd) and costs for maintenance
materials and O&M labor. There are no chemicals costs related to ozone
generation, except for periodic changing of desiccant in air preparation
systems (usually after 10 years of use).
Electrical energy is a major component of operating costs, representing
26% to 43% of total O&M costs at small plants (0.1 mgd) increasing to
59% to 65% at the larger plants (0.1 mgd). Building energy costs (which
are shown to be the same for all small size systems up to 0.5 mgd)
include energy costs for heating, lighting, and ventilation. Labor
costs (which are independent of the plant sizes listed - 0.1 to 0.5 mgd)
account for 54% to 70% of total O&M costs at the small plants, but only
30% to 36% at the 0.5 mgd plant.
-------
TABLE XXV
OPERATING AND MAINTENANCE COSTS FOR SMALL OZONE SYSTEMS APPLYING 3 mg/L DOSAGE
Water Flow Electrical
Rate (mgd) Building*
Supplier A
0.18
0.35
0.50
Supplier B
0.10
0.20
0.30
0.40
0.50
Supplier C
0.10
0.20
0.30
0.40
0.50
6,570
6,570
6,570
(High Pressure
6,570
6,570
6,570
6,570
6,570
6,570
6,570
6,570
6,570
6,570
Energy
Process
6,661
12,775
51,611
(kWh/yr)
Total x
13,231
19,345
58,181
Air Preparation)
21,900 28,470
29,565
34,493
59,130
68,985
14,783
26,645
37,230
44,895
53,838
36,135
41,063
65,700
75,555
21,353
33,215
43,800
51,465
60,408
$0.07/kWh =
$ 926
$1,354
$4,073
$1,993
$2,529
$2,874
$4,599
$5,289
$1,495
$2,325
$3,066
$3,603
$4,229
= Maintenance Labor x $10/hr =
Material (hrs/yr)
$120
200
300
$120
120
200
250
300
120
120
200
250
300
250
250
250
250
250
250
250
250
250
250
250
250
250
$2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
2,500
Total Cost
($/yr)
$ 3,546
4,054
6,873
$ 4,613
5,149
5,574
7,349
8,089
$ 4,115
4,945
5,766
6,353
7,029
* Estimated from data of 'Reference 39
-------
Summary Statement Regarding Costs For Ozonation Systems
Because of the many differences in methods of air pretreatment, ozone
contacting, contactor off-gas destruction, monitoring, and other opera-
tional parameters, equipment costs given above should not be considered
as more than general guidelines. No attempt should be made to update
these costs in the future by applying Engineering News Record Indices.
Instead, at the time ozone is being considered by the small water supply
system, vendor quotes should be obtained at that time.
However, it also should be noted that vendor quotes obtained for esti-
mating purposes are likely to be higher than firm bids made to specifica-
tions. This is because the market for ozonation systems currently is
quite competitive, and suppliers usually bid their best prices when
responding to clear specifications.
COSTS FOR DISINFECTION WITH ULTRAVIOLET RADIATION
Construction Costs
Table XXVI summarizes costs developed in 1978 (39). The major change
which has occurred through 1982 is that the costs for UV generating
units (manufactured equipment) in the size ranges listed are about 15%
higher. Data presented in Table XXVI are for single and multiple UV
lamp disinfecting units ranging in capacity of water throughput from
14,400 gpm to 1,123,200 gpm.
All UV generating units are quitg compact, the 1,123,400 gpm unit occu-
pying an area of less than 24 ft . Costs listed in Table XXVI include
equipment costs of the UV units, and the related costs of piping, elec-
trical equipment, equipment installation, and a building to house the
equipment.
As was the case with disinfection by ozone, if the water system wishes
to disinfect with UV, then follow with a residual of chlorine, chlorine
dioxide, or chloramine, additional equipment will be required to provide
the residual disinfectant selected.
Operating and Maintenance Costs
These are shown in Table XXVII for the same size plants as in Table XXVI.
Process energy is required for the mercury lamps operating inside of the
UV generating units. Continuous 24-hr/day operation is assumed, with
only occasional shutdown to clean cells and replace ultraviolet lamps
which have become weakened by lengthy use. Building energy requirements
are for heating, lighting, and ventilation.
Maintenance materials are related to the replacement cost of the ultra-
violet lamps, which usually are replaced after operating continuously
for about 2,000 hours (about eight months).
-------
TABLE XXVI
CONSTRUCTION COSTS FOR ULTRAVIOLET LIGHT DISINFECTION
Plant Capacity (gpd)
Cost Category
Excavation and
Sitework*
Manufactured
Equipment
Concrete*
Labor*
Pipe and Valves*
Electrical and
Ins trumentation*
Housing*
SUBTOTAL
Miscellaneous and
Contingency*
14,400
$ 60
800
250
110
60
430
1,500
3,210
470
28,800
$ 60
1,125
250
170
150
430
1,500
3,885
560
187,200
$ 60
4,485
250
250
350
430
1,500
7,225
1,010
374,400
$ 60
8,685
250
300
450
430
1,500
11,675
1,580
748,800
z$ 80
17,365
280
400
750
480
1,800
21,155
2,830
1,123,200
$ 110
26,050
300
500
1,000
480
2,000
30,440
4,060
TOTAL
$3,680
$4,445
$8,335
$13,255
$24,085
$34,500
* Data from Reference 39
-------
Labor requirements are related to occasional cleaning of the quartz
sleeves which surround the mercury vapor lamps, and periodic replacement
of the weak UV bulbs.
It is noteworthy that replacement bulb costs at the smallest plant
(14,400 gpm) are only about 9% of the total O&M costs, whereas at the
largest plant size (1,123,200 gpm) replacement bulb costs are about 48%
of the total O&M costs. This reflects the fact that the larger UV
generating units contain a greater number of UV bulbs per unit volume of
water treated.
No chemical costs are associated with the use of UV radiation per se;
however, following UV with a residual disinfectant (chlorine, chlorine
dioxide, or chloramine) will add costs for these chemicals. The use of
UV radiation for primary disinfection will lower the amounts of chemicals
subsequently used for maintaining a disinfectant residual in the product
water.
-------
TABLE XXVII
OPERATION AND MAINTENANCE SUMMARY FOR ULTRAVIOLET LIGHT DISINFECTION
Plant Flow
Rate (gpm)
14,400
28,800
187,200
374,400
748,800
1,123,200
Energy (kWh/yr*
Building
10,260
10,260
10,260
10,260
12,310
13,340
Process
440
800
5,260
10,510
21,020
31,540
Total x
10,700
11,140
15,520
20,770
33,330
44,880
$0.07/kWh =
$ 749
780
1,086
1,454
2,333
3,142
Maintenance
Matl.*($/yr)
$ 100
140
600
1,120
2,250
3,300
Labor
(hr/yr) x $10 /hr =
24
24
24
30
36
42
$240
240
240
300
360
420
Total Cost
($/yr)
$ 1,089
1,160
1,926
2,874
4,943
6,862
* Data from Reference 39
-------
-------
APPENDIX B
HOW TO TAKE BACTERIOLOGICAL SAMPLES
Routine and special bacteriological samples must be taken in accordance
with established procedures to prevent accidental contamination, and
analyzed by an EPA- or state-certified laboratory. Usually the lab will
provide specially prepared sampling containers, properly sterilized and
containing sodium thiosulfate to destroy any remaining chlorine. If
water system personnel prepare containers, follow the procedures given
in Reference 5.
The following steps should be observed in coliform sampling:
1)
2)
3)
4)
5)
6)
use only containers which are provided by the bacteriological
laboratory and which have been prepared for coliform sampling.
Follow all instructions for sample container handling and
storage.
THE CONTAINERS ARE STERILE.
DO NOT RINSE THEM.
DO NOT OPEN THEM BEFORE USE AND
take samples at the consumer's faucet, but avoid:
faucets with aerators (unless removed) or swivel spouts;
taps inside homes served by home water treatment units
such as water softeners;
locations where the water enters separate storage tanks;
and
leaking faucets that permit water to run over the outside
of the faucet.
always allow the water to flow moderately from a faucet two or
three minutes before taking the sample;
hold the sample container at the base keeping hands away from
the container neck. Be sure the inside of the container cap
is protected and does not touch anything.
without adjusting the flow, fill the sample container, leaving
about 20% air space at the top. Replace the cap immediately.
If the sample is collected incorrectly, take another sample
container -^ do not reuse the original bottle:
take a second sample and measure the concentration of the
disinfectant and record relevant information (date, time,
concentration, place, sampler, etc.);
_
-------
7) package the bacteriological sample for delivery to the lab.
Record all pertinent field information on a form and on the
sample container label;
8) samples must be cool during shipment to the lab. Use insulated
boxes for shipping containers if needed, or refrigerate during
transit.
SHIP IMMEDIATELY VIA EXPRESS TRANSPORT. DO NOT ALLOW MORE
THAN 30 HOURS BETWEEN SAMPLING AND TEST TIMES.
Be sure the laboratory can process the samples immediately upon receipt.
-------
MONTHLY BACTERIOLOGICAL SUMMARY
Multiple-Tube Fermentation Method
Water System ID
Number of Samples Required
Water System
SAMPLING INFORMATION
LAB ANALYSIS INFORMATION
Date
Time
Location
Sampled
By
Type
Sample
ID*
Date
Routine Samples
No. of
Tubes
10
No. of
Positive
Tubes
11
No. of
Samples
with 3 or
more
Positive
Tubes
12
Samples
No. of
Positive
Tubes
13
TOTAL
Number of
Routine Samples
for the Month
TOTAL TOTAL TOTAL
Number of Number Number of
Tubes Used of Samples with
in Monthly Positive 3 or more
Tests Tubes Positive Tubes
MONTHLY CALCULATIONS
I. CALCULATE THE MONTHLY PERCENTAGE
% of Tubes Positive
TOTAL No. of Positive Tubes
TOTAL No. of Tubes Used in Monthly Tests
II. DETERMINE THE NUMBER OF TIMES 3 OR MORE PORTIONS WERE POSITIVE
For Systems Taking Fewer than 20 Samples Per Month:
Use the total box, "TOTAL Number of Samples with 3 or
more Positive Tubes", to determine compliance with the MCL.
For Systems Taking 20 or More Samples Per Month:
% of Samples
with 3 or More = TOTAL No. of Samples With 3 or More Positive Tubes
Positive Tubes TOTAL No. of Routine Samples for the Month
Person responsible for analysis
-------
MONTHLY BACTERIOLOGICAL SUMMARY
Membrane Filter
Water System ID
Number of Samples Required .
Water System
SAMPLING INFORMATION
LAB ANALYSIS INFORMATION
Date
Time
Location
Sampled
By
Type
Sample
ID*
Date
Routine
Samples
Colonies/
100ml
10
Samples
Exceeding
4/100 ml
11
Check
Sample:
Colonies/
100ml
TOTAL
Number of
Routine Samples
for the Month
TOTAL
Number of
Coliform
Colonies
For the
Month
TOTAL
Number of
Routine Samples
Exceeding
4/100 ml
MONTHLY CALCULATIONS
I. CALCULATE THE MONTHLY AVERAGE VALUE
Average Coliform Density _ Total No. of Coliform Colonies
for the Month Total No. of Routine Samples
II. DETERMINE THE NUMBER OF TIMES 4 COLONIES/100 ml WAS EXCEEDED -
For Systems Taking Fewer Than 20 Samples Per Month:
Use the total box "TOTAL Number of Routine Samples
Exceeding 4/100 ml"
For Systems Taking 20 or More Samples Per Month:
% of Samples
Exceeding _ TOTAL No. of Samples Exceeding 4/1QQ ml
4/100 ml TOTAL No. of Routine Samples Taken
Person responsible for analysis
-------
APPENDIX C
DISINFECTANT RESIDUAL SAMPLING
Chlorine is the disinfectant in most common use in the U.S. for sanitizing
drinking water. Its most active form is as the 'free residual', which
is stable only in the absence of agitation, sunlight, and certain inorganic
and organic materials with which it can react.
Reactions of free residual chlorine with chlorine-demanding substances
continue over long periods of time. Therefore, the sample taken for
disinfectant analysis must be analyzed immediately. Specially prepared
sampling containers, properly cleansed, sterilized, and not containing
sodium thiosulfate should be employed. In general, the same sampling
precautions described in Appendix B for taking coliform samples should
be observed, but in addition:
1)
2)
3)
draw the sample gently, avoiding agitation;
analyze immediately in the shade or subdued light.
store the sample;
Do not
do not use a bacteriological sampling container which may
contain a chemical to counteract or destroy the disinfecting
agent.
-------
------- |