Technology Transfer
EPA/625/5-90/025
Environmental Pollution
Control Alternatives:
Drinking Water Treatment
for Small Communities
April 1990
Panted on Recycled Paper
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This document has been reviewed by the U.S. Environmental
Protection Agency and approved for publication. Mention of
trade names or commercial products does not constitute
endorsement or recommendation of their use.
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Acknowledgements
Appreciation is expressed to those
individuals who assisted in providing
technical direction and resource
materials and reviewing drafts of this
publication:
John R. Trax, National Rural Water
Association, Washington, DC
Fred Reiff, Pan American Health
Organization, Washington, DC
Deborah Brink and Elizabeth
Kawczynski, American Water Works
Association Research Foundation,
Denver, CO
John Dyksen, Department of Water
Supply, Ridgewood, New Jersey
U.S. Environmental Protection Agency
Office of Drinking Water, Washington,
DC:
Steven Clark
Peter L. Cook
Jane Ephremides
Ken Hay
A.W. Marx
Marc J. Parrotta
Peter Shanaghan
U.S. Environmental Protection Agency
Risk Reduction Engineering
Laboratory, Cincinnati, OH:
Jon Bender
Walter Feige
Kim Fox
Benjamin Lykins, Jr.
Donald J. Reasoner
Thomas Sorg
Alan A. Stevens
James Westrick
U.S. Environmental Protection Agency
Office of Technology Transfer and
Regulatory Support, Washington, DC:
Ronnie Levin
Management of the preparation of this
document was provided by James E.
Smith, Jr. of EPA's Center for Environ-
mental Research Information. Techni-
cal writing, editorial work, production,
and design was provided by Jennifer
Helmick, Lynn Knight, Susan
Richmond, and Karen Ellzey of
Eastern Research Group, Inc.,
Arlington, MA.
iii
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Contents
Introduction 1
Chapter 1 Drinking Water Treatment: An Overview 3
Why Do We Need Drinking Water Treatment? 3
How Is Drinking Water Treated? 5
Chapter 2 New and Proposed Drinking Water
Treatment Regulations: An Overview 9
Compliance Schedules 10
Maximum Contaminant Levels 10
Monitoring 13
Surface Water Treatment Requirements 17
Chapter 3 Solutions to Drinking Water Treatment
Problems: An Overview 19
Questions to Consider in
Choosing Treatment Technologies 19
Special Issues for Small Systems 23
Chapter 4 Filtration Technologies for Small Systems 29
Processes Preceding Filtration 29
Choosing a Filtration Technology 30
Slow Sand Filtration 30
Diatomaceous Earth Filtration 33
Package Plants 34
Membrane Filtration (Ultrafiltration) 34
Cartridge Filtration 35
Innovative Filtration Technologies 36
Chapter 5 Disinfection 37
Chlorination 37
Ozonation 41
Ultraviolet (UV) Radiation 43
Obtaining Effective Disinfection: CT Values 44
Disinfection By-Products and Strategies for Their Control 44
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Chapter 6 Treating Organic Contaminants In
Drinking Water 47
Granular Activated Carbon (GAG) 47
Aeration 49
Emerging Technologies for Organics Removal 51
Chapter 7 Control and Removal of
Inorganic Contaminants 53
Corrosion 53
Treatment Technologies for
Removing Inorganic Contaminants 55
Chapter 8 Resources 61
Appendix A How to Take Bacteriological Samples 69
Appendix B Checklist: Some Factors Affecting
Water Treatment System Performance 71
Appendix C Selecting a Consulting Engineer 73
Appendix D Chlorine Residual Monitoring 77
Appendix E CT Values ; 79
Appendix F Sample CT Calculation 81
vi
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Introduction
Small drinking water systems face a
difficult challenge: to provide a safe,
sufficient supply of water at a
reasonable cost. Our growing aware-
ness of the biological and chemical
contaminants that can affect the safety
of drinking water has ted to the need
for more frequent monitoring and
reporting and, in some cases, addition-
al or upgraded treatment by water sup-
pliers.
This document provides information
for small system owners, operators,
managers, and local decision makers,
such as town officials, regarding drink-
ing water treatment requirements and
the treatment technologies suitable for
small systems. It is not intended to be
a comprehensive manual for water
treatment and protection of public
water supplies from sources of con-
tamination. Rather, it is designed to
give an overview of the problems a
small system may face, treatment op-
tions that are available to solve
specific problems, and resources that
can provide further information and
assistance.
Chapter 1 discusses why we need
drinking water treatment and gives an
overview of drinking water treatment
processes.
Chapter 2 provides a summary of ex-
isting and new federal drinking water
regulations and explains how these
regulations affect small systems.
Chapter 3 provides an overview of
how to select drinking water treatment
technologies and discusses special
management issues for small systems.
Chapters 4 through 7 describe tech-
nologies that can enable small sys-
tems to meet federal drinking water
regulations covering filtration, disinfec-
tion, removal of organic and inorganic
contaminants, and corrosion control.
These chapters describe established
technologies, which are commonly
used in the water treatment industry.
They also describe several emerging
technologies suitable for small sys-
tems. These technologies have not
been widely used, but have proven
effective on the pilot scale and are
emerging as viable full-scale options
for treating water supplies.
Chapter 8 lists organizations, publica-
tions, and other resources that can as-
sist small systems in their efforts to
provide safe drinking water to con-
sumers.
For the purpose of this document,
small systems are defined as systems
that serve 25 to 1,000 people, or that
have a flow of 9,500 to 380,000 liters
(2,500 to 100,000 gallons) per day.
They include small community sys-
tems as well as noncommunity sys-
tems, such as campgrounds and
restaurants.
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Chapter One
Drinking Water
Treatment:
An Overview
Why Do We Need Drinking Water
Treatment?
For thousands of years, people have
treated water intended for drinking to
remove particles of solid matter, re-
duce health risks, and improve aes-
thetic qualities such as appearance,
odor, color, and taste. As early as
2000 B.C., medical lore of India ad-
vised, "Impure water should be puri-
fied by being boiled over a fire, or
being heated in the sun, or by dip-
ping a heated iron into it, or it may
be purified by filtration through sand
and coarse gravel and then allowed
to cool."
Early in the nineteenth century, scien-
tists began to recognize that specific
diseases could be transmitted by
water. Since that discovery, treatment
to eliminate disease-causing microor-
ganisms has dramatically reduced the
incidence of waterborne diseases
(diseases transmitted through water)
such as typhoid, cholera, and hepa-
titis in the United States. For example,
in 1900, 36 out of every 100,000
people died each year from typhoid
fever; today there are almost no
cases of waterborne typhoid fever in
the United States.
Ancient medical lore of India ad-
vised that impure water should be
purified by heating or filtering
through sand and coarse gravel.
Although water treatment processes
have greatly improved the quality and
safety of drinking water in the United
States, there are still over 89,000
cases each year of waterborne
diseases caused by microorganisms—
bacteria, viruses, protozoa, helminths,
and fungi (Figure 1-1).1 Water can be-
come contaminated with these or-
ganisms through surface runoff (water
FUNGI
PROTOZOA
(microscopic one-
celled animals)
VIRUSES
HELMINTHS
(parasitic worms)
BACTERIA
Figure 1-1. Disease-causing microorganisms that might be found in
water supplies.
1Source: EPA estimate. Federal Register, June 19,1989 (54 FR 27522).
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that travels over the ground during
storms), which often contains animal
wastes; failures in septic or sewer
systems; and sewage treatment plant
effluents (outflow). Microbiological con-
tamination occurs most often in sur-
face water, but it can also occur in
ground water, usually due to improp-
erly placed or sealed wells. Contamina-
tion can also occur after water leaves
the treatment plant, through cross con-
nection (connection between safe
drinking water and a source of con-
tamination), backflow in a water supply
line, or regrowth of microorganisms in
the distribution system.
Table 1-1 lists some of the diseases
caused by microorganisms found in
v/ater supplies. The protozoan Giardia
Ismblia is now the most commonly
identified organism associated with
waterborne disease in this country.
This organism causes giardiasis,
which usually involves diarrhea,
nausea, and dehydration that can be
severe and can in some cases last for
months. Over 20,000 water-related
cases of this disease have been
reported in the last 20 years,2 with
probably many more cases going un-
reported. Another protozoan disease,
cryptosporidiosis. is caused by Cryp-
tosporidium, a cyst-forming organism
similar to Giardia. Other common
waterborne diseases include viral
hepatitis, gastroenteritis, and legionel-
tosts (Legionnaires' Disease).
Chemical contaminants, both natural
and synthetic, might also be present in
water supplies. Contamination
problems in ground water (used by 85
percent of small systems) are frequent-
ly chemical in nature. Common sour-
ces of chemical contamination include
minerals dissolved from the rocks that
form the earth's crust; pesticides and
herbicides used in agriculture; leaking
underground storage tanks; industrial
effluents; seepage from septic tanks,
sewage treatment plants, and landfills;
and any other improper disposal of
chemicals in or on the ground. In
some systems, the water quality can
Table 1-1. Waterborne Diseases
Waterborne
Disease
Causative
Organism
Source of
Organism
In Water
Symptom
Gastroenteritis
Rotavirus
Salmonella
(bacterium)
Human feces
Animal or
human feces
Enteropathogenic Human feces
£ Co//
Typhoid
Dysentery
Cholera
Salmonella
typhosa
(bacterium)
Shigella
(bacterium)
Vibrio comma
(bacterium)
Infectious hepatitis Hepatitis A
(virus)
Amoebic dysentery Entamoeba
histolytica
(protozoan)
Giardiasis
Giardia lamblia
(protozoan)
Human feceis
Human fece«
Human fecest
Human fecesi,
shellfish grown
in polluted
waters
Human feces.
Animal or
human feces
Cryptosporidiosis Cryptosporidium Animal or
(protozoan) human feces
Acute diarrhea
or vomiting
Acute diarrhea
and vomiting
Acute diarrhea
or vomiting
Inflamed intes-
tine, enlarged
spleen, high
temperature—
sometimes fatal
Diarrhea — rarely
fatal
Vomiting, severe
diarrhea, rapid
dehydration,
mineral loss—
high mortality
Yellowed skin,
enlarged liver,
abdominal pain —
low mortality, lasts
up to 4 months
Mild diarrhea,
chronic dysentery
Diarrhea, cramps,
nausea, and
general
weakness—not
fatal, lasts 1 week
to 30 weeks
Diarrhea, stomach
pain—lasts an
average of 5 days
Source: Adapted from American Water Works Association, Introduction to
Water Treatment: Principles and Practices of Water Supply Operations,
Denver, CO, 1984.
promote corrosion of materials in the
distribution system, possibly introduc-
ing lead and other materials into the
drinking water. The water treatment
process might also introduce
trihalomethanes— chemicals formed
when chlorine reacts with natural
organic materials and other chemical
contaminants—into the drinking water.
(It should be noted, however, that
while the potential for chlorination
by-product formation cannot be
• Source: Dava Ryan, "Water Treatment to Combat Illness," EPA Journal, December 1987.
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neglected, adequate disinfection is of
paramount importance to protect the
public from microbiological contamina-
tion of drinking water.)
Drinking water can be treated for
reasons other than to reduce health
risks from microorganisms and chemi-
cals. A system might treat water to im-
prove its color, odor, or taste even if it
is safe to drink. For example, some
systems remove iron and mangan-
ese, which can stain laundry and
plumbing fixtures. Some com-
munities add fluoride to drinking water
to improve dental health.
To protect the public from the health
risks of drinking water contaminants,
the U.S. Environmental Protection
Agency (EPA) has issued regulations
covering the quality and treatment of
drinking water. These regulations are
discussed in Chapter 2.
EPA has also issued guidance for
protecting public drinking water from
sources of contamination. Protecting
ground-water supplies from con-
taminants reduces the extent of treat-
ment needed to protect public health.
The Wellhead Protection (WHP)
Program for public water supplies is
an example of a protection program.
Publications on the WHP Program are
listed in Chapter 8, Resources.
How Is Drinking Water Treated?
Table 1 -2 shows the types and goals
of water treatment processes typically
used by small systems (including
preliminary treatment and main water
Process/Step
Table 1-2. Water Treatment Processes
Purpose
Preliminary Treatment Processes3
Screening
Chemical pretreatment
Presedimentation
Microstraining
Main Treatment Processes
Chemical feed and rapid mix
Coagulation/flocculation
Sedimentation
Softening
Filtration
Disinfection
Adsorption using granular
activated carbon (GAG)
Aeration
Corrosion control
Reverse osmosis, electrodialysis
Ion exchange
Activated alumina
Oxidation filtration
Removes large debris (leaves, sticks, fish) that can foul or damage
plant equipment
Conditions the water for removal of algae and other aquatic nuisances
Removes gravel, sand, silt, and other gritty material
Removes algae, aquatic plants, and small debris
Adds chemicals (coagulants, pH adjusters, etc.) to water
Converts nonsettleable to settleable particles
Removes settleable particles
Removes hardness-causing chemicals from water
Removes particles of solid matter which can include biological
contamination and turbidity
Kills disease-causing microorganisms
Removes radon and many organic chemicals such
as pesticides, solvents, and trihalomethanes.
Removes volatile organic chemicals (VOCs), radon, HaS, and other
dissolved gases; oxidizes iron and manganese
Prevents scaling and corrosion
Removes nearly all inorganic contaminants
Removes some inorganic contaminants, including hardness-causing chemicals
Removes some inorganic contaminants
Removes some inorganic contaminants (e.g., iron, manganese, radium)
"Generally used for treating surface water supplies.
Source: Adapted from American Water Works Association, Introduction to Water Treatment, Vol. 2, 1984.
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Chemicals from leaking under-
ground storage tanks might
migrate to ground water and/or
surface water.
treatment processes). This document
discusses the water treatment proces-
ses designed to protect the consumer
from waterborne disease. Chapters
discusses how to select appropriate
processes and technologies for a par-
ticular water system, and Chapters 4
through 7 discuss treatment tech-
nologies In more detail.
Filtration
Filtration is the process of removing
particles of solid matter from water,
usually by passing the water through
sand or other porous materials. Filtra-
tion helps to control biological con-
tamination and turbidity. (Turbidity is a
measure of the cloudiness of water
caused by the presence of suspended
matter. Turbidity can shelter harmful
microorganisms and reduce disinfec-
tion effectiveness.) Filtration tech-
nologies commonly used in small
systems include slow sand filtration,
diatomaceous earth filtration, and
package filtration systems. Filtration is
discussed in Chapter 4.
Disinfection
Disinfection is a chemical and/or physi-
cal process that kills disease-causing
organisms. For the past several
decades, chlorine (as a solid, liquid, or
gas) has been the disinfectant of
choice in the United States because it
is effective and inexpensive and can
provide a disinfectant residual in the
distribution system. However, under
certain circumstances, chlorination
Runoff from agricultural areas can introduce mlcrooioiogicai con-
taminants, pesticides, and nitrates into drinking water sources.
might produce potentially harmful by-
products, such as trihalomethanes.
Small systems can successfully use
ozone and ultraviolet radiation as
primary disinfectants, but chlorine or
an appropriate substitute must also be
used as a secondary disinfectant to
prevent regrowth of microorganisms in
the distribution system. Disinfection is
discussed in Chapter 5.
Treatment of Organic Contaminants
Many synthetic organic chemicals
(SOCs), manmade compounds that
contain carbon, have been detected in
water supplies in the United States.
Some of these, such as the solvent
trichloroethylene, are volatile organic
chemicals (VOCs). VOCs easily be-
come gases and can be inhaled in
showers or baths or while washing
dishes. They can also be absorbed
through the skin.
Water supplies become contaminated
by organic compounds from sources
such as improperly disposed wastes,
leaking gasoline storage tanks, pes-
ticide use, and industrial effluents.
Technologies that can be used effec-
tively by small systems to remove
these contaminants include activated
carbon and aeration. These tech-
nologies are discussed in Chapter 6.
Treatment of Inorganic
Contaminants
The inorganic contaminants in water
supplies consist mainly of naturally oc-
curring elements in the ground, such
as arsenic, barium, fluoride, sulfate,
radon, radium, and selenium. In-
dustrial sources can contribute metal-
lic substances to surface waters.
Nitrate, an inorganic substance fre-
quently found in ground-water sup-
plies, is found predominantly in
agricultural areas due to the applica-
tion of fertilizers. High levels of total
dissolved solids (TDS) might, in some
instances, require removal to produce
a potable supply.
Inorganic chemicals might also be
present in drinking water due to cor-
rosion. Corrosion is the deterioration
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or destruction of components of the
water distribution and plumbing sys-
tems by chemical or physical action,
resulting in the release of metal and
nonmetal substances into the water.
The metals of greatest health concern
are lead and cadmium; zinc, copper,
and iron are also by-products of cor-
rosion. Asbestos can be released by
corrosion of asbestos-cement pipe.
Corrosion reduces the useful life of the
water distribution and plumbing sys-
tems. It can also promote microor-
ganism growth, resulting in dis-
agreeable tastes, odors, and slimes.
Treatment alternatives for inorganic
contaminants include removal tech-
niques and corrosion controls.
Removal technologies — coagulation/
filtration, reverse osmosis, ion ex-
change, and activated alumina — treat
source water that is contaminated with
metals or radioactive substances
(such as radium). Aeration effectively
strips radon gas from source waters.
Corrosion controls reduce the
presence of corrosion by-products
such as lead at the point of use (such
as the consumer's tap). Treatment
technologies for inorganic con-
taminants are discussed in Chapter 7.
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Chapter Two
New and
Proposed
Drinking Water
Regulations:
An Overview
In 1974, Congress passed the Safe
Drinking Water Act (SDWA), setting up
a regulatory program among local,
state, and federal agencies to help en-
sure the provision of safe drinking
water in the United States.
Under the SDWA, the federal govern-
ment develops national drinking water
regulations to protect public health
and welfare. The states are expected
to administer and enforce these regula-
tions for public water systems (sys-
tems that either have 15 or more
service connections or regularly serve
an average of 25 or more people daily
for at least 60 days each year). Public
water systems must provide water
treatment, ensure proper drinking
water quality through monitoring, and
provide public notification of con-
tamination problems.
Congress significantly expanded and
strengthened the SDWA in 1986. The
1986 amendments include provisions
on the following:
• Maximum Contaminant Levels.
The Safe Drinking Water Act re-
quired EPA to set numerical stan-
dards, referred to as Maximum
Contaminant Levels (MCLs), or
treatment technique requirements
for contaminants in public water
supplies. The 1986 amendments
established a strict schedule for
EPA to set MCLs or treatment re-
quirements for previously unregu-
lated contaminants.
• Monitoring. EPA must issue
regulations requiring monitoring of
all regulated and certain unregu-
lated contaminants, depending on
the number of people served by the
system, the source of the water
supply, and the contaminants likely
to be found.
• Filtration. EPA must set criteria
under which systems are obligated
to filter water from surface water
sources. It must also devebp pro-
cedures for states to determine
which systems have to filter.
• Disinfection. EPA must develop
rules requiring all public water sup-
plies to disinfect their water.
• Use of lead materials. The use of
solder or flux containing more than
0.2 percent lead, or pipes and pipe
fittings containing more than 8 per-
cent lead, is prohibited in public
water supply systems. Public
notification is required where there
is lead in construction materials of
the public water supply system, or
where the water is sufficiently cor-
rosive to cause leaching of lead
from the distribution system/lines.
• Wellhead protection. The 1986
SDWA amendments require all
states to develop Wellhead Protec-
tion Programs. These programs are
designed to protect public water
supplies from sources of con-
tamination.
The impact of these new regulations
on small systems will generally con-
cern some fundamental aspects of
water treatment. Many systems will be
required to improve treatment for
removal of microorganisms (through
the addition of filtration and/or disinfec-
tion processes). Most small systems
do not face contamination by organic
and inorganic chemicals at levels ex-
ceeding the MCLs, and therefore will
not need to install treatment for
removal of these chemicals.3 Small
systems will be required to conduct
periodic monitoring, however, to docu-
ment whether chemical contaminants
are present in their water supplies.
Future regulations covering radioac-
tive substances (particularly radon)
and disinfection by-products could
also have a significant impact.
3 G. Wade Miller, John E. Cromwell, III, Frederick A. Marrocco. "The Role of the
States in Solving the Small System Dilemma," JAWWA, August 1988, pp 31-37.
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The rast of this chapter explains the
major provisions of EPA's new and
proposed drinking water regulations as
they apply to small systems. In addi-
tion to the federal regulations dis-
cussed here, the water supplier should
check with the state agency respon-
sible for drinking water (see Chapters,
Resources) to find out about state
regulations that apply to drinking water
treatment facilities.
Compliance Schedules
Most of the regulations contain com-
pliance schedules that affect large sys-
tems Initially and small water systems
2 to 4 years later. This means that
small systems have additional time to
plan for their specific compliance
requirements.
The SDWA recognizes that meeting
drinking water standards might place a
large burden on small systems. The
law therefore provides for variances,
allowing small systems to meet a less
stringent standard if an organic or inor-
ganic contaminant cannot be removed
due to the quality of the raw water or
other good reasons, as long as the
less stringent standard poses no un-
reasonable health risk. A small system
may also be granted a temporary ex-
emption if economic conditions
prevent the system from making
necessary corrections, provided no un-
reasonable risk to public health
results. No exemptions are allowed for
disinfection of surface supplies or the
coliform rule for all public water
supplies. Monitoring requirements may
also be reduced in some cases if the
public water supply has a program
under an EPA-approved state
Wellhead Protection Program.
Maximum Contaminant Levels
A Maximum Contaminant Level, or
MCL, is the highest allowable con-
centration of a contaminant in drinking
water. In developing drinking water
regulations, EPA establishes Maxi-
mum Contaminant Level Goals
Community, Nontransient Noncommunity,
and Transient NoncorrtmuhitV Systems
The drinking water regulations distinguish between community water
systems (CWS), nontransient noncommunity water systems (NNWS),
and transient noncommunity water systems (TNWS).
• ; A community system is a public water system that serves at least
15 service connections used by year-round residents, or regularly
'serves at least 25 year-round residents. Community systems include
mobile home courts and homeowner associations.
« A nontransient noncommunity system regularly serves at least 25
of the same people over six months of the year. Examples are
schools and factories.
• Transient noncommunity systems, such as restaurants, gas sta-
tions, and campgrounds, serve intermittent users.
The regulations governing each of these systems are slightly different.
This is because certain contaminants cause health problems only when
consumed on a regular basis over a long period of time, and are there-
fore of greater concern in systems that regularly serve the same people
than in those that serve transient users.
Only the MCLs for turbidity, nitrate, and bacteria apply to transient non-
community systems. (The new surface water treatment requirements, ex-
plained below in this chapter, will replace the currently MCL for turbidity
for TNWS). Most MCLs are set at levels designed to prevent health ef-
fects caused by long-term consumption of drinking water from a system.
However, the presence of nitrate, bacteria, and turbidity indicate the
potential of the water to cause illness even from short-term consump-
tion, so MCLS for these contaminants apply to transient noncommunity
as well as other systems.
(MCLGs), which are the maximum
levels of contaminants at which no
known or anticipated adverse health ef-
fects will occur. MCLs are set as close
to the MCLG as is feasible. In setting
an MCL, EPA takes into account the
technical feasibility of control systems
for the contaminant, the analytical
detection limits, and the economic im-
pact of regulating the contaminant. An
MCL is usually expressed in mil-
ligrams per liter (mg/L), which is
equivalent to parts per million (ppm)
for water quality analysis.
The SDWA amendments direct EPA to
establish MCLs for 83 specific contami-
nants and to develop a list of contami-
nants every 3 years to be considered
for regulation. The Agency must prom-
ulgate at least 25 MCLs from each of
these lists sitarting in 1991. EPA may
set treatment technology requirements
instead of MCLs when it is difficult or
expensive for water suppliers to test
for specific contaminants.
Whenever EPA establishes an MCL
for a particular contaminant, the
Agency must also identify the Best
Available Technology (BAT)4 for
4 EPA determines the BAT based on high removal efficiency of contaminant concentration; general geographic applicability; service
life; compatibility with other water treatment processes; and ability to achieve compliance at a reasonable cost.
10
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removing that contaminant. To comply
with the MCL, public water systems
are required to use the BAT or an alter-
native treatment technology deter-
mined by the state to be at least as
effective as the BAT.
MCLs for Volatile Organic
Compounds
EPA has issued final MCLs for 8
volatile organic compounds. These
are shown in Table 2-1. Nontransient
noncommunity water systems as well
as community systems must meet
these MCLs.
MCLs for Inorganic and Synthetic
Organic Compounds
The final MCL for fluoride has been
set at 4.0 mg/L (see Federal Register
April 2,1986 - 41 FR 11396).5 EPA
has proposed MCLs for lead and cop-
per (Table 2-2), and for 8 other inor-
ganic compounds and 30 synthetic
organic chemicals (Table 2-3). Table
2-3 shows proposed MCLs along with
maximum allowable levels under
regulations currently in effect.
MCLs for the inorganic chemicals and
synthetic organic chemicals in Table
2-4 will be proposed in the near future.
MCLs for Microbiological
Contaminants
EPA has set final MCLs for total
coliforms (Table 2-5). Coliforms are
usually present in water contaminated
with human and animal feces and are
often associated with disease out-
breaks. Although total coliforms in-
clude microorganisms that do not
usually cause disease themselves,
their presence in drinking water might
mean that disease-causing organisms
are also present. All public water sys-
tems must meet the MCL for total
coliforms; monitoring requirements are
discussed below.
fable 2-lV Volatile Organic Chemicals:
Chemical
Trichloroethylene
Carbon tetrachloride
Vinyl chloride
1 ,2-Dichloroethane
Benzene
para-Dichlorobenzene
1 ,1-Dichloroethylene
1,1,1 -Trichloroethane
Source: Federal Register, July 8, 1987 (52
Final MCLs (in mg/L> ; i
Final MCL
0.005
0.005
0.002
0.005
0.005
0.075
0.007
0.2
FR 25690).
For surface water (or ground water
under the direct influence of surface
water)6 EPA has set treatment require-
ments instead of MCLs for Giardia,
viruses, heterotrophic bacteria,
Legionella, and turbidity. These re-
quirements are explained below under
Surface Water Treatment Require-
ments. EPA intends to issue disinfec-
tion regulations for ground water,
including regulations to control the
level of viruses, Legionella, and
heterotrophic bacteria, at a later date.
MCLs for Radionuclide
Contaminants
New MCLs for radionuclides (radioac-
tive elements) will be proposed in the
future. The anticipated MCL for radon,
a naturally occurring radionuclide,
might affect many small public water
supplies. Table 2-6 shows the current
MCLs for radiological contaminants.
Note that only systems serving popula-
tions greater than 100,000 people are
required to meet MCLs for manmade
radionuclides.
MCLs for Disinfectants and
Disinfection By-Products
In 1979, EPA established an MCL for
total trihalomethanes—chloroform,
bromoform, bromodichloromethane,
and dibromochloromethane—of 0.1
milligram per liter. This MCL applies
only to systems serving populations
Table 2-2. Lead and Copper: Proposed jMCLs
(Measured as water leaves the treatment plant or enters the distribution
system)
Lead
Copper
0.005 mg/L
1.3 mg/L
Source: Federal Register, August 18, 1988 (53 FR 31571).
5 See Chapter 8, Resources, for information about the Federal Register.
6 Any water beneath the surface of the ground with (i) significant occurrence of insects or other microorganisms, algae, or large-
diameter pathogens such as Giardia lamblia, or (ii) significant and relatively rapid shifts in water characteristics such as turbidity,
temperature, conductivity, or pH which closely correlate to climatological or surface water conditions. Direct influence must be deter-
mined for individual sources in accordance with criteria established by the state.
11
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Table 2-3.-Proposed MCLs for Synthetic Organic Chemicals and Inorganic Chemica s
Contaminant
Existing
NPDWRa(mg/L)
Proposed
MCL (mg/L)
Acrylamide
Alachlor
Aldicarb
Aldicarb sulfoxide
Aldicarb sulfone
Atrazine
Carbofuran
Chlordane
cis-1,2-Dichloroethylene
Dibromochloropropane (DBCP)
1,2-Dichloropropane
o-Dichlorobenzene
2.4-D
Ethylenedibromide (EDB)
Epichlorphydrin
Ethylbenzene
Heptachlor
Heptachlor epoxide
Lindano
Methoxychlor
Monochlorobenzene
PCBs (as decachlorobjphenyl)
Pentachlorophenol
Styrene0
Telrachloroethylene
Toluene
2,4,5-TP (Silvex)
Toxaphane
trans-1,2-Dichloroethylene
Xylenes (total)
Asbestos
Barium
Cadmium
Chromium
Mercury
Nitrate (as nitrogen)
Nitrite (as nitrogen)
Selenium
0.1
0.004
0.1
0.01
0.005
1.0
0.010
0.05
0.002
10.0
0.01
IT"
0.002
O.OI
0.01
0.04
0.003
0.04
0.002
0.07
0.0002
0.005
0.6
0.07
0.00005
IT"
0.7
0.0004
0.0002
0.0002
0.4
0.1
0.005
0.2
0.005/0.1
0.005
2.0
0.05
0.005
0.1
10.0
7F/Ld
5.0
0.005
0.1
0.002
10.0
1.0
0.05
"NPDWR - National Primary Drinking Water Regulations.
bTT * Treatment Technique.
CEPA proposes MCLs of 0.1 mg/L based on a group C carcinogen classification and 0.005 mg/L based on a B2
classification.
d7 million fibers/liter (only fibers longer than 10 m).
Source: Federal Register, May 22.1989 (54 FR 22064).
12
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greater than 10,000 people. EPA
plans to propose new rules for ground-
water disinfection and for disinfection
by-products; small systems might be
included in these new requirements.
Disinfectants and disinfection by-
products that might be included in
these rules are shown in Table 2-7.
Monitoring
New monitoring requirements for
chemical contaminants under the
1986 SDWA amendments could have
a major impact on small systems.
These new requirements are ex-
plained below.
Volatile Organic Chemicals
All systems must monitor for the regu-
lated VOCs in Table 2-1 and the un-
regulated VOCs in Table 2-8. The
required monitoring is shown in Table
2-9. Small systems serving fewer than
3,300 people must complete initial
monitoring for these VOCs by Decem-
ber 31, 1991. Nontransient noncom-
munity systems, as well as community
systems, must meet the requirements
for VOCs.
Fluoride
Monitoring requirements for fluoride
are shown in Table 2-10.
Other Inorganic and Synthetic
Organic Chemicals
EPA has proposed monitoring require-
ments for 38 regulated chemicals and
111 unregulated contaminants (inor-
ganic and synthetic organic chemicals).
In addition, EPA will propose monitor-
ing requirements for chemicals in
Table 2-4.
Radionuclldes
Currently, community systems must
monitor for natural radiological chemi-
cals every 4 years. EPA will be propos-
ing new monitoring requirements for
radionuclides, including radium-226,
radium-228, uranium (natural), and
radon.
Microbiological Contaminants
• Total coliforms. In June 1989,
EPA issued new monitoring require-
Table 2-4. Inorganic and Synthetic Organic Chemicals
to be Regulated
Arsenic3
Methylene chloride
Antimony
Endrinb
Dalapon
Diquat
Endothall
Glyphosate
Andipates
2,3,7,8-TCDD (Dioxin)
Trichlorobenzene
Sulfate
Hexachlorocyclopentadiene
Nickel
Thallium
Beryllium
Cyanide
1,1,2-Trichloroethane
Vydate
Simazine
PAHs
Atrazine
"Current MCL is 0.05 mg/L.
bCurrent MCL is 0.0002 mg/L.
Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water
Regulations under 1986 Amendments to SDWA," February 1989.
Table 2-5. Maximum Contaminant Level for Total Coliforms
• Compliance is based on presence/absence of total coliforms in sample, rather
than on an estimate of coliform density.
• MCL for systems analyzing at least 40 samples/month: no more than 5.0 per-
cent of the monthly samples may be total coliform-positive.
• MCL for systems analyzing fewer than 40 samples/month: no more than 1
sample/month may be total coliform-positive.
• A public water system must demonstrate compliance with the MCL for total
coliforms each month it is required to monitor.
• MCL violations must be reported to the state no later than the end of the next
business day after the system learns of the violation.
Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water
Regulations under 1986 Amendments to SDWA," February 1989.
ments for total coliforms, effective
December 31,1990. Tables 2-11
and 2-12, respectively, show the
minimum number of routine and
repeat samples required.
Fecal coliforms/£sc/ie/7c/7/a coll.
The presence of fecal coliforms in
drinking water is strong evidence of
recent sewage contamination, and
indicates that an urgent public
health problem probably exists.
Therefore, EPA requires that public
water systems analyze each
sample that is positive for total
coliforms to determine if it contains
fecal coliforms. Alternatively, the
system may test for the bacterium
Escherichia coli instead of fecal
coliforms. The requirements for
monitoring fecal coliforms and E.
coli are effective December 31,
1990.
• Heterotrophic bacteria. Hetero-
trophic bacteria can interfere with
total coliform analysis. Effective
December 31,1990, public water
systems must follow specific proce-
dures to minimize this interference.
13
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Table 2-6. Maximum Contaminant Levels for Radiological Chemicals
Natural Radionuclides
Manmade Radionuclides
Gross
Alpha
Combined
Radium
226 &
228
Gross
Beta
Tritium
Strontium
90
Community
Systems
Noncommunity
Systems
15 pCi/L
State
option
5 pCi/L
State
option
50 pCi/Lb
State
option
20,000 pCi/Lb 8 pCi/Lb
State
option
State
option
•Pieocuries per liter (pCi/L) is a measure of. the concentration of a radioactive substance. A level of 1 pCi/L means that
approximately 2 atoms of the radionuclide per minute are disintegrating in every liter of water.
Applies only to surface water systems serving populations greater than 100,000 people.
Source: Adapted from National Rural Water Association, Water System Decision Makers: An Introduction to Water System
Operation and Maintenance, Duncan, OK, 1988.
liable 2-7. Disinfectants arftl DisinfectatitJBy-products
Disinfectants and Residuals
Chlorine, hypochlorous acid, and hypochlorite ion
Chlorine dioxide, chlorite, and chlorate
Chloramlnes and ammonia
Ozone
Disinfectant By-Products
Trihalomethanes: chloroform, bromoform, bromodichloromethane, dibromochloromethane
Haloacetonitriles: bromochloroacetonitrile, dibromochloroacetonitrile, dichlorobromoacetonitrile, trichloroacetonitrile
Haloacetic acids: mono-, di-, and tri-chloroacetic acids; mono- and dibromoacetic acids
Haloketones: 1,1-dichloropropanone and 1,1,1-tri-chloropropanone
Other: chloral hydrate, chloropicrin
Cyanogen chloride
Chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol)
N-organochloraminos
MXI3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone)]
Ozone by-products
Source: U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water Regulations under 1986 Amendments to
SDWA," February 1989.
14
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Table 2-8. Monitoring for Unregulated VOCs
Required for All Systems:
Chloroform
Bromodichloromethane
Chlorodibromomethane
Bromoform
trans-1,2-Dichloroethylene
Chlorobenzene
m-Dichlorobenzene
Dichloromethane
cis-1,2-Dichloroethylene
o-Dichlorobenzene
Dibromomethane
1,1-Dichloropropane
Tetrachloroethylene
Toluene
p-Xylene
o-Xylene
m-Xylene
1,1-Dichloroethane
1,2-Dichloropropane
1,1,2,2-Tetrachloroethane
Ethylbenzene
1,3-Dichloropropane
Styrene
Chloromethane
Bromomethane
1,2,3-Trichloropropane
1,1,1,2-Tetrachloroethane
Chloroethane
1,1,2-Trichloroethane
2,2-Dichloropropane
o-Chlorotoluene
p-Chlorotoluene
Bromobenzene
1,3-Dichloropropane
Ethylene dibromide
1,2-Dibromo-3-chloropropane
Required for Vulnerable Systems* Only:
1,2-Dibromo-3-chIoropropane (DBCP)
Ethylenedibromide (EDB)
At Each State's Discretion:
1,2,4-Trimethylbenzene
1,2,4-Trichlorobenzene
1,2,3-Trichlorobenzene
n-Propylbenzene
n-Butylbenzene
Naphthalene
Hexachlorobutadiene
Bromochloromethane
1,3,5-Trimethylbenzene
p-lsopropyltoluene
Isopropylbenzene
tert-Butylbenzene
sec-Butylbenzene
Fluorotrichloromethane
Dichlorodifluoromethane
*A system's vulnerability to contamination is assessed by evaluating factors such as geological conditions, use patterns
(e.g., pesticides), type of source, location of waste disposal facilities, historical monitoring record, and nature of the dis-
tribution system.
Source: Adapted from U.S. Environmental Protection Agency, Fact Sheet.
Amendments to SDWA," February 1989.
"Drinking Water Regulations under 1986
15
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Table 2jj$ Compliance Monitoring for Recjulated and!Unregulated Volatile Organic,Chemicals
Initial monitoring: All community and nontransient noncommunity systems must monitor each source at least
once within 4 years.
• Surface waters: four quarterly samples.
• Ground water: four quarterly samples; state can exempt systems from subsequent monitoring if no
VOCs are detected in the first sample.
• Composite samples of up to five sources are allowed.
Repeat monitoring: varies from quarterly to once every 5 years. The frequency is based on whether VOCs
are detected in the first round of monitoring and whether the system is vulnerable to contamination.
Source: Adapted from U.S. Environmental Protection Agency, Fact Sheet. "Drinking Water Regulations under 1986 Amend-
ments to SDWA," February 1989.
• Sanitary surveys. Periodic
sanitary surveys are required for all
systems that collect fewer than five
coliform samples per month. (A
sanitary survey is a comprehensive
review of a system's operations, in-
cluding watershed control, the disin-
fection system, raw water quality,
and monitoring, to determine
whether operational requirements
are being met.) The schedule for
conducting sanitary surveys is
shown in Table 2-13.
Laboratory Analysis and Sampling
Requirements
To meet the monitoring requirements
for some contaminants, small systems
will need the services of a commercial
laboratory. For compliance monitoring
purposes, analyses must be per-
formed in an EPA or state-approved
laboratory. Contact the Safe Drinking
Water Hotline (see Chapter 8, Resour-
ces) for assistance in locating a cer-
tified drinking water laboratory in your
area. (These laboratories must suc-
cessfully analyze performance evalua-
tion samples within limits set by EPA.)
To ensure proper sampling and
analysis7:
• Samples must be collected in
proper containers and preserved as
necessary. Discuss sample collec-
tion procedures for the contaminant
with the laboratory in advance.
(See Appendix A for bacteriological
sample collection procedures.)
• Sample chain of custody must be
maintained (to ensure that some-
one is always accountable for the
sample).
• Analysis must be performed within
specified holding times (the period
of time between sample collection
and analysis).
• Approved analytical procedures
must be used.
• Adequate quality assurance data
must be generated within the
laboratory.
A water system manager should ob-
tain the following information from a
laboratory he or she plans to use:
• References of similar work
• Copy of applicable accreditations
or certifications
• Information about availability and
cost of sample containers, preser-
vatives, and shipping containers
• Commitment or estimate of project
turnaround
• Definition of analytical methods,
detection limits, and cost of analysis
• Type of quality assurance data that
will be reported
• State-approved reporting forms, if
applicable
• Fees
Tablej2-1p, Monitoring Requirements fpr f lubr dfi
Surface waters:
Ground waters:
Minimum repeat:
1 sample each year
1 sample every 3 years
1 sample every 10 years
Source: Federal Register, April 2, 1986 (41 FR 11396).
7 From Metcalf and Eddy, A Guide to Water Supply Management in the 1990s, Wakefield, MA, November 1989.
16
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Table 2-11. Total Coliform Sampling Requirements According to
Population Served
Population Served
Minimum Number
of Routine Samples
Per Month*
25 to 1,000°
1,001 to 2,500
2,501 to 3,300
aln lieu of the frequency specified in this table, a noncommunity water system
using only ground water (except ground water under the direct influence of sur-
face water) and serving 1,000 persons or fewer may monitor at a lesser fre-
quency specified by the state (in writing) until a sanitary survey is conducted
and the state reviews the results. Thereafter, such systems must monitor in
each calendar quarter during which the system provides water to the public, un-
less the state determines (in writing) that some other frequency is more ap-
propriate. Beginning June 29, 1994, such systems must monitor at least once
every year.
A noncommunity water system using surface water, or ground water under the
direct influence of surface water, regardless of the number of persons served,
must monitor at the same frequency as a like-sized community water system,
i.e., the frequency specified in the table. A noncommunity water system using
ground water (which is not under the direct influence of surface water) and serv-
ing more than 1,000 persons during any month must monitor at the same fre-
quency as a like-sized community water system, i.e., the frequency specified in
the table, except that the state may reduce the monitoring frequency (in writing)
for any month the system serves 1,000 persons or fewer. However, in no case
may the state reduce the sampling frequency to less than once every year.
blncludes public water systems that have at least 15 service connections, but
serve fewer than 25 persons.
Source: Federal Register, June 29, 1989 (54 FR 27545).
Table 2-12. Monitoring Requirements Following a Total Coliform-
Positive Routine Sample
Number of Routine
Samples/Month
Number of Repeat
Samples"
Number of Routine
Samples Next Monthb
1/month or fewer
2/month
3/month
5/month
5/month
5/month
a Number of repeat samples in the same month for each total coliform-positive
routine sample.
b Except where state has invalidated the original routine sample, or where the
state substitutes an onsite evaluation of the problem, or where the state waives
the requirement on a case-by-case basis. See 40 CFR 141.21 a (b) (5) for more
details.
Source: Federal Register, June 29, 1989 (54 FR 27546).
Typical costs of laboratory analyses
are shown in Table 2-14.
Contact your state drinking water
agency for additional information
about requirements for sample collec-
tion and analysis and reporting.
Surface Water Treatment
Requirements
EPA has set treatment requirements to
control microbiological contaminants
in public water systems using surface
water sources (and ground-water sour-
ces under the direct influence of sur-
face water). These requirements,
effective December 31, 1990, include
the following:
• Treatment must remove or inac-
tivate at least 99.9 percent of
Giardia lamblia cysts and 99.99 per-
cent of viruses.
• All systems must disinfect, and also
might be required to filter if certain
source water quality criteria and site-
specific criteria are not met.
• The regulations set criteria for
determining if treatment, including
turbidity removal and disinfection
requirements, is adequate for fil-
tered systems.
• All systems must be operated by
qualified operators as determined
by the states.
Systems using surface water must
make certain reports to the state
documenting compliance with treat-
ment and monitoring requirements.
Detailed guidance on surface water
treatment requirements is provided in
EPA's Guidance Manual for Com-
pliance with the Filtration and Disinfec-
tion Requirements for Public Water
Systems Using Surface Water
Sources.
17
-------
liable 2p3, Sahltarjf Survey Frequency for; Riibjic Water Systems Collecting Fewer than! Five Samples/Month3
System Type
Initial Survey
Completed by
Frequency of
Subsequent
Surveys
Community water system
Noncommunity water system
June 29, 1994
June 29, 1999
Every 5 years
Every 5 years'3
aAnnuaI onsite inspection of the system's watershed control program and reliability of disinfection practice is also required by
40 CFR 141.71(b) for systems using unfiltered surface water or ground water under the direct influence of surface water.
The annual onsite inspection, however, is not equivalent to the sanitary survey. Thus, compliance with 40 CFR 141.71(b)
alone does not constitute compliance with the sanitary survey requirements of this coliform rule (141.21a(d)), but a sanitary
survey during a year can substitute for the annual onsite inspection for that year.
For a noncommunity water system that uses only protected and disinfected ground water, the sanitary survey may be
repeated every 10 years, instead of every 5 years.
Source: Fadoral Register, June 29, 1989 (54 FR 27546).
fable 2-14;|A|proxJmate Commer;-
clal Laboratory Costs Per Sample'
Analysis ($1989)
Turbidity $ 20
Coliform Bacteria $ 20
Copper $ 20
Lead $ 20
Radium 226/228 $120
8 VOCS (Table 2-10) $200
Table 2-8 Contaminants $500
Source: Adapted from Metcalf and
Eddy. A Guide to Water Supply
Management in the 1990s,
Wakefiold, MA, November 1989.
ri'fss£!fZ'"i *r:WWffirXJ5*r *«i„*«*.-•%-. v*r^-'V*T
Systems using surface water are required to filter unless stringent
criteria are met.
18
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Chapter Three
Solutions to
Drinking Water
Treatment
Problems:
An Overview
This chapter presents an overview of
the technologies that a small system
should consider for meeting its treat-
ment needs. In addition, it discusses
administration and other issues that
can be important for small systems,
including financial and capital improve-
ments, cooperative arrangements,
operator capabilities, and selection of
a consulting engineer or equipment
vendor. Appendix B presents a check-
list of factors that can affect water
treatment system performance. While
this list is not all-inclusive, it may help
a water system operator or manager
in determining improvements that may
be needed.
The treatment needs of a water sys-
tem are likely to differ depending on
whether the system uses aground-
water or surface water source. Com-
mon surface water contaminants
include turbidity, microbiological con-
taminants (Giardia, viruses, and bac-
teria), and low levels of a large
number of organic chemicals. Ground-
water contaminants include naturally
occurring inorganic contaminants
(e.g., arsenic, fluoride, radium, radon)
and nitrate, and a number of specific
organic chemicals (e.g., trichloro-
ethylene) that sometimes occur in rela-
tively high concentrations.8 Bacteria
and viruses can also contaminate rela-
tively shallow ground water (for ex-
ample, from sewage overflow or
seepage into wells and springs, or
from surface runoff). Giardia cysts are
less likely to be found in ground water,
but they have contaminated ground-
water supplies where sewage or con-
taminated surface water entered
improperly constructed or located
wells. Corrosion control is a concern
for systems using both surface and
ground-water supplies.
Rgure 3-1 presents an overview of
steps that a small system can follow to
determine treatment needs. Tables 3-1
and 3-2 present the contaminants like-
ly to be found in surface water and
ground water, and the most suitable
treatment technologies for each.
The treatment options available to
small systems for filtration, disinfec-
tion, organic and inorganic con-
taminant removal, and corrosion
control are also listed in Table 3-3.
This table presents the major ad-
vantages and disadvantages of each
technology. Costs are shown in Table
3-4. Chapters 4 through 7 contain
more detailed information about each
of these technologies, including their
effectiveness in removing specific con-
taminants in water.
Questions to Consider in
Choosing Treatment Technologies
When selecting among the different
treatment options, the water system
manager must consider a number of
factors: regulatory requirements, char-
acteristics-of the raw water, configura-
tion of any existing system, cost,
operating requirements, availability of
nontreatment alternatives, com-
patibility of the processes currently
being used or to be used, waste
management, and future needs of the
service area. Each of these factors is
discussed below.
8 Thomas J. Sorg, "Process Selection for Small Drinking Water Supplies,"Proceec/;/7£(s
of the Twenty-Third Annual Public Water Supply Engineers Conference: New Direc-
tions for Water Supply Design and Operation, University of Illinois, April 21 -23, 1981.
9 Gunther F. Craun, "Review of the Causes of Waterborne Disease Outbreaks,"
Surveillance and Investigation of Waterborne Disease Outbreaks, Health Effects
Research Laboratory, U.S. Environmental Protection Agency, November 1989.
19
-------
Step^to Determine Treatment Neefcls
f f, •j.iwy ,_ '•»*•'• '•• <. ^,. •(? "s
Collect sample of raw water (see Chapter 2, Laboratory
Analysis and Sampling Requirements)
Send sample to laboratory for analysis (microbiological, organic, and
inorganic contaminants)
Compare contaminants and their levels to applicable standards
(see Chapter 2, Maximum Contaminant Levels)
No Standards
Exceeded
Systems using surface water sour-
ces must disinfect, and must filter
unless stringent requirements are
met; systems using ground-water
sources will have to meet future
ground-water disinfection rules
(see Chapter 2)
Compile list of
"contaminants of concern"
(those that exceed maximum
concentration allowed by
regulations)
I
If filtrationjand/or
'disinfection must
beadde'dor
: upgraded
Identify and evaluate
treatment technologies avail-
able to control contaminants
of concern (see Tables 3-1
through 3-4 and Chapters 4
through 7)
Contact vendors or consulting engineer for information about
treatment technology selection, costs, and design (see Appendix C)
and/or contact organizations that assist small systems
(see Chapter 8, Resources)
Figure 3-1. Steps to determine treatment needs.
20
-------
Table 3-1. Common Problems and Suitable Treatment Technologies: Ground Water21
Micro-
biological
Fluoride Barium Nitrate Radium Radon Arsenic Selenium Organics
Chlorination
Ozonation
Ultraviolet
radiation
Aeration
Ion exchange
Activated alumina
Coagulation/Filtration
Membranes
(reverse osmosis
and electrodialysis)
Granular activated
carbon (GAG)
Point-of-use/
Point-of-entry systems Might be suitable for some very small systems to remove organic or inorganic contaminants.
Package Plants
Package plants might be available to solve specific inorganic or organic contamination problems.
aln general, "•" indicates the principal function of the treatment technology listed. Many of these technologies,
however, have secondary effects in addition to those shown here. (For example, ozone can remove some organic chemicals
as well as provide disinfection.)
What Are the Requirements for
Drinking Water Supplied by the
System?
Federal and state drinking water
regulations are the most important fac-
tors to consider in developing a water
system's treatment goals. The supplier
may also choose to consider con-
sumer preferences and nonmandatory
guidelines developed by regulatory
agencies and professional organiza-
tions, such as EPA's Secondary Maxi-
mum Contaminant Levels (federally
nonenforceable goals for controlling
contaminants that affect the aesthetic
qualities of drinking water), Health Ad-
visories (guidance values developed
by EPA to address immediate or emer-
gency concerns associated with acci-
dents, spills, or newly detected
drinking water contamination situa-
tions), and American Waterworks As-
sociation water quality goals.
Are Nontreatment Alternatives
Available?
Small water systems might not always
have the resources to install a com-
plete treatment system to solve a con-
tamination problem. In such situations,
however, a small system might be
able to find a new water source. For
example, a well can be located in an
area distant from the source of
contamination.
The development of a new well,
however, is only part of the solution.
The area around the well must be
managed to protect it from future con-
tamination. Establishing a wellhead
protection is an appropriate nontreat-
ment alternative.
As another option, a small system can
consider cooperating with other sys-
tems, such as by buying treated water
from a larger utility (see Multicom-
munity Cooperative Arrangements
below).
What Are the Characteristics of the
Raw Water?
To determine treatment needs, the sys-
tem manager must know the quality of
the source water—what biological and
chemical contaminants are in the
water and at what concentrations they
are present. Knowledge of other water
characteristics, such as pH, tempera-
ture, alkalinity, and calcium and mag-
nesium content is useful because of
21
-------
Table 3-2. Common Problems and Suitable treatment Technologies: Surface Watte.
Turbidity
Microbiological Control
Corrosion Control Organics
Chlorination
Ozonation
Ultraviolet radiation
Package plants
Slow sand filtration
Diatomaceous
earth filtration
Ultrafiltration
(membrane filtration)0
Cartridge filtration0
Aeration
Granular activated carbon (GAG)
pH control
Corrosion inhibitors
Point-of-use/
Point-of-entry systems'1
"In general, "•" indicates the principal function of the treatment technology listed. Many of these technologies, however,
have secondary effects in addition to those shown here. (For example, ozone can remove some organic chemicals as
well as provide disinfection.)
While package plants are most widely used to remove turbidity, color, and microbiological contaminants, package plants
are also available that can remove organic and/or inorganic contaminants.
°Emerging technology.
dMight be suitable for some very small systems that cannot install central treatment. Point-of-use/Point-of-entry systems
use a variety of treatment processes, including reverse osmosis, ion exchange, and activated carbon.
their impact on aesthetics and the ef-
ficiency of treatment processes.
What Is the Configuration of the
Existing System?
The configuration of the existing sys-
tem can be an important consideration
in selecting a treatment option. For ex-
ample, if a supplier is considering add-
ing a new treatment technology, he or
she must know if the existing system
is compatible with or adaptable to the
new technology. In addition, an exist-
ing system's ability to blend treated
water with raw water can be important.
A system might be able to economize
with an expensive technology by treat-
ing only part of the total flow, and still
meet regulatory requirements that limit
the concentration of a contaminant in
finished water.
The method of water distribution and
its composition (e.g., asbestos-cement
pipe, copper, polyvinyl chloride, gal-
vanized, lead) can also be an impor-
tant factor in selecting a treatment
option. For example, corrosion would
not be a great concern in systems
using polyvinyl chloride (PVC) pipes.
The length of the distribution system
and how quickly water moves through
it can affect requirements for secon-
dary disinfection (to prevent regrowth
of microorganisms in the distribution
system).
22
-------
What Are the Costs of the
Treatment Options?
The total costs of treatment include one-
time capital costs and annual operating
and maintenance costs. Each treatment
technology has a different mix of capi-
tal and operating and maintenance
costs. Technologies with high capital
costs often have lower operating and
maintenance costs (and those with tower
capital costs often have higher operating
and maintenance costs). Thus, small sys-
, terns that cannot afford appropriate capi-
tal equipment can become saddled with
higher operating and maintenance costs.
What Are the Treatment
Technology's Operating
Requirements?
The most important operational con-
sideration is the consistency of the raw
water. The less consistent the raw water
quality, the greater the need for monitor-
ing, and the greater the operating com-
plexity of most systems. Thus, a less
consistent influent requires a higher
level of operator training and attention,
and might require greater instrumenta-
tion, controls, and automation.
Other important operating considera-
tions include:
• Energy requirements
• Chemical availability, consumption
rate, and storage
• Instrumentation and automation
• Preventive maintenance
• Noise
• Aesthetics
• Backup/redundant systems
• Requirements for a startup phase
before full removal capacity is
achieved
« Cleaning and backwashing require-
ments
• Distribution system
• Staffing needs
• Operator training requirements
• Process monitoring requirements
How Compatible Are the Processes
Used?
To achieve overall treatment goals, all
the treatment processes must be com-
patible. For example, a lower pH is
desirable for efficient chlorine disinfec-
tion; however, lower pH increases cor-
rosion in the water distribution system.
Therefore, a system might maintain a
lower pH but use a corrosion inhibitor
(described in Chapter 7) to minimize
corrosion (or the system might elevate
the pH before distribution). All the ele-
ments of treatment should be chosen
so that they interact as efficiently and
effectively as possible.
In addition, using one treatment tech-
nology to meet more than one
regulatory requirement reduces costs
and operating complexity. For ex-
ample, a system might use reverse os-
mosis (described in Chapter 7) when
both organic and inorganic con-
taminants are present in raw water.
Ozone (described in Chapter 5) can
remove organic chemicals-as well as
provide primary disinfection. Packed
tower aeration (described in Chapter
6) can remove both volatile organic
chemicals and radon in ground water.
It also removes carbon dioxide, there-
by raising the pH to a more desirable
level for corrosion control. (Aeration,
however, can increase dissolved
oxygen levels, which can contribute to
corrosion.)
What Waste Management Issues
Are Involved?
Waste management can be a significant
issue for water treatment systems. Most
treatment processes concentrate con-
taminants into a residual stream (brine
or sludge) that requires proper manage-
ment. For example, removal of radon
with granular activated carbon can
produce a low-level radioactive waste.
Water treatment systems must follow
federal and state regulations covering
the management of wastes. In some
cases, this can significantly increase dis-
posal costs for the treatment system.
What Are the Future Needs of the
Service Area?
The future of the service and supply area
is another important factor in selecting a
treatment technology. The supplier can
evaluate future demands using popula-
tion and economic forecasts of the ser-
vice area. Present and potential water
supplies should also be examined to
determine their vulnerability to natural
and manmade contamination.
Special Issues for Small Systems
Financial/Capital Improvement
Financing water system improvements
can be an obstacle for a small system.
User charges must be high enough to
cover the actual costs of water treat-
ment, analytical work, and distribution.
Because costs are spread over fewer
people, rate increases have a greater
impact on the individual customer than
those for large systems.
Most small systems are also at a dis-
advantage when they attempt to raise
funds in the local and national capital
markets, since their credit base,
market recognition, and financing ex-
pertise are usually limited. They might
be able to obtain financial assistance
through state and federal loan and
grant programs. Many states currently
have drinking water financial assis-
tance programs. Some states assist
small systems in gaining access to
capital through low-interest loans from
state revolving loan funds, state bond
pools, and state-funded bond in-
surance.
Sources of federal grants and loans
for small systems include the Farmers
Home Administration (FmHA) and a
proposed federal grants program that
blends federal grant money with state
bond money to provide low-interest
loans to small water systems.
Other financing options for small sys-
tems include federal revenue sharing
and revenue bonds (for municipal sys-
tems), loans through the United States
Small Business Administration (SBA),
and use of tax exempt industrial
23
-------
Table 3-3. Overview of Water Treatment Technologies:
Treatment
Requirements
Technological
Options to Meet
Regulatory
Requirements
Stage of
Acceptability
Comments
Filtration of surface
wator supplies to
control turbidity
and microbial
contamination
Disinfection
Organic contamination
control
Slow sand filtration
Package plant filtration
Ultrafiltration
(Membrane filtration)
Cartridge filtration
Chlorine
Ozone
Ultraviolet radiation
Granular activated carbon
Packed column aeration
Diffused aeration
Multiple tray aeration
Higee aeration
Mechanical aeration
Catenary grid
Established
Established
Emerging
Emerging
Established
Established
Established
Best Available
Technology (BAT)
Best Available
Technology (BAT)
Established
Established
Experimental
Experimental
Experimental
Operationally simple; low
operating cost; requires
relatively low turbidity source
water
Compact; variety of process
combinations available
Experimental, expensive
Experimental, expensive
Most widely used method;
concerns about health effects
of by-products
Very effective but requires a
secondary disinfectant, usually
some form of chlorine
Simple, no established harmful
by-products, but requires
secondary disinfectant,
usually some form of chlorine
Highly effective; potential waste
disposal issues; expensive
Highly effective for volatile com-
pounds; potential air emissions
issues
Variable removal effectiveness
Variable removal effectiveness
Compact, high energy require-
ments; potential air emissions
issues
Mostly for wastewater treatment;
high energy requirements,
easy to operate
Performance data scarce;
potential air emissions issues
(continued on next page)
revenue bonds by a private contractor
supplying servfce to a municipality.
Multlcommunlty Cooperative
Arrangements (Reglonallzatlon)
In some cases, a small community
can share resources with other small
communities or a larger community
through a cooperative or a regional
water supply authority. Multicommunity
cooperative arrangements can im-
prove cost effectiveness, upgrade
water quality, and result in more effi-
cient operation and management.
A wide range of cooperative ap-
proaches is available to the small sys-
tem, including:
• Centralizing functions. A group of
small systems working together
can centralize functions such as
purchasing, maintenance,
laboratory services, engineering
services, and billing. Several small
systems together might be able to
afford resources, such as highly
24
-------
Table 3-3. Overview of Water Treatment Technologies3 (continued)
Treatment
Requirements
Technological
Options to Meet
Regulatory
Requirements
Stage of
Acceptability
Comments
Inorganic contam-
ination control
Corrosion
controls
Membranes
(Reverse osmosis
and electrodialysis)
Ion exchange
Activated alumina
Coagulation/Filtration
Aeration
Granular Activated Carbon
pH control
Corrosion inhibitors
Established
Established
Established
Established
Established
Established
Established
Established
and emerging
Highly effective; expensive;
potential waste disposal issues
Highly effective; expensive;
potential waste disposal issues
Highly effective; expensive;
potential waste disposal issues
May be difficult for very
small systems
Preferred technology for radon
removal
Highly effective for radon
removal; potential waste
disposal issues
Potential to conflict with other
treatments
Variable effectiveness
depending on type of inhibitor
aA variety of package plants are available that can perform one or several treatment functions (i.e., filtration, organic con-
taminant control, etc.).
Source: U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research Information,
Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.
skilled personnel, on a part-time
basis.
• Physically interconnecting exist-
ing systems. Two or more small
systems can be connected, or a
small system can join a larger sys-
tem, to achieve the economies of
scale available to large systems.
This approach might not be
feasible in some situations,
however, such as in locations
where supplies are isolated from
each other by long distances or
rugged terrain. It is also important
to weigh potential disadvantages
such as loss of local autonomy,
complexities of ensuring equity in
each community, and loss of cost
effectiveness when distribution
lines become too long.
• Creating a satellite utility. A satel-
lite utility taps into the resources of
an existing larger facility without
being physically connected to, or
owned by, the larger facility.
Resources provided by the larger
utility can include technical, opera-
tional, or managerial assistance;
wholesale treated water; or opera-
tion and maintenance responsibility.
• Creating water districts. Water
districts are formed by county offi-
cials and provide for the public
ownership of the utilities. The
utilities in a district combine resour-
ces and/or physically connect sys-
tems, so that one or two facilities
supply water for the entire district.
By forming a water district, privately
owned systems become eligible for
public,grants and loans.
• Creating county or state utilities.
A county or state, government can
create a board to construct, main-
tain, and operate a water supply
within its district. Construction
and/or upgrading of facilities may
be financed through bonds or
property assessments.
Operator Capabilities
The level of understanding and techni-
cal ability of small systems operators
25
-------
liable 3-4. Estimated Costs of Drinking Water Treatment Technologies for a 100,00^ GPD Plant3 ($1989) j [
i, , , , :l .... ]. . • I i j . ! i : ~L ' . I 1 H . i . I .... ' I,;,: -i 'Ji
Technology
Package Plant Filtration
Coagulation/Filtration with tube settlers
Pressure depth clarifier/Pressure filter
Pressure depth clarifior/
Pressure filter with GAC adsorber
Other Filtration
Diatomaceous earth vacuum filter
Diatomacoous earth pressure filter
Slow sand filter: covered
Slow sand filter: uncovered
Inorganic Contaminant Control
High pressure reverse osmosis
Low pressure reverse osmosis
Cation exchange
Anion exchange
Activated alumina
Organic Contaminant Control
GAC in pressure
vessel
Packed tower aerator
Capital
Cost
$176,000
$206,000
$246,000
$103,000
$106,000
$580,000
$335,000
$275,000
$275,000
$151,000
$115,000
$104,000
$175,000
$45,100
(continued on next page)
Annual O&M
$11,000
$10,400
$16,300
$11,100
$10,600
$ 7,700
$7.100
$41,300
$29,800
$ 8,500
$10,300
$14,600
$14,400
( 6-mo carbon
$ 9,800
(12-mo carbon
$ 2,900
•IH»IMHHH i«™m™iii™™ii.ii.i.i«ii™mi»u™ii™m™m»iim™».«™»iiii— iiiimiiiimn in
Total Cost" Per
1,000 Gallons
$1.73
$1.90
$2.47
$1.27
$1.26
$4.15
$2.55
$4.03
$3.40
$1.44
$1.46
$1.47
$1.92
replacement)
$1.67
replacement)
$0.45
la crucial to the success of the Safe
Drinking Water Act (SDWA). The
operator's basic knowledge, skills, and
training might include the following10:
• Sufficient training to protect public
health
• Knowledge of all aspects of the dis-
tribution system (including main-
tenance)
• Knowledge of the source water
supply (including pump operation)
Skill to maintain drinking water
quality (including water treatment
where necessary, plus state and
federally required sampling
routines)
10 From National Rural Water Association, Water System Decision Makers: An Introduction to Water System Operation and Main-
tenance, Duncan, OK, 1988.
26
-------
Table 3-4. Estimated Costs of Drinking Water Treatment Technologies for a 100,000 GPD Plant3 (continued)
Technology
Capital
Cost
Annual O&M
Total Cost" Per
1,000 Gallons
Disinfection
Gas feed chlorination
Hypochlorite solution
Pellet feed chlorinators
Ultraviolet light0 (57,600 GPD)
Ozonation-high pressure0
$ 10,465
$ 4,080
$ 1,670
$ 25,990
$ 39,270
$ 3,520
$ 5,558
$4,010
$ 2,090
$ 5,074
$0.26
$0.33
$0.23
$0.49
$0.53
Gallons x 3.785 = liters.
Sources: G.S. Logsdon, T.J. Sorg, and R.M. Clark, Cost and Capability of Technologies for Small Systems, Drinking Water
Research Division, Risk Reduction Engineering Laboratory, EPA, Cincinnati, OH, May 1989.
R.C. Gumerman et al., Estimation of Small System Water Treatment Costs, Final Report, Culp/Wesner/Culp, Santa Ana,
CA, November 1984.
U.S. Environmental Protection Agency, Office of Drinking Water, Microorganism Removal for Small Water Systems,
Washington, DC, June 1983. EPA 570/9-83-012.
Construction costs generally include manufactured equipment, concrete, steel, labor, pipes and valves, electrical equipment
and instrumentation, housing, site evacuation, some other site work, general contractor's overhead and profit, engineering
costs, financial and administrative costs, and interest costs during construction. Construction costs do not include land
costs, legal fees, interface piping, roads, and certain other site work. O&M costs generally include annual energy, labor, and
chemical costs. Construction costs can vary depending on specific data characteristics. O&M costs can vary, up to plus or
minus 100 percent for some technologies, depending on such variables as feed water characteristics, flow rate, and chemi-
cal dosage requirements.
bCosts include capital costs annualized at 10 percent interest over 20 years plus annual O&M costs. Average flow assumed
at 50 percent of design flow.
°Costs for ultraviolet and ozone disinfection reflect those for primary disinfection only. A secondary disinfectant is necessary
to maintain a residual in the distribution system. The costs of secondary disinfection are not included in the table.
• Knowledge of sources of con-
tamination and methods used to
manage these sources.
• Knowledge and understanding of
energy sources
• Understanding of emergency proce-
dures
• Knowledge of state and federal
regulations
• Recordkeeping skills
• A willingness to participate in con-
tinuing education programs
Without a properly trained operator,
system operation and water quality will
suffer. The small system might have
difficulty attracting skilled staff be-
cause of economic constraints. In addi-
tion, many small system operators
have multiple duties, such as maintain-
ing the grounds or performing other re-
lated public works duties, and might
not have the opportunity to specialize
and develop expertise in drinking
water treatment.
Operator capability can also limit the
technology options available to a
small system: a technology that works
well in a large city might require more
operator training than the small sys-
tem can obtain.
Small systems might be able to obtain
qualified plant operators by contract-
ing the services of personnel from a
larger neighboring utility, government
agency, service company, or consult-
ing firm. Small systems can also use
the National Rural Water Association
for technical assistance (see Chapter
8, Resources).
A "circuit rider" approach, in which ser-
vice is provided to several systems
that cannot individually afford a trained
operator, can also be used. The circuit
rider attends to a number of treatment
systems, and his or her salary is
shared among them. The circuit rider
can directly operate the plants or
provide technical assistance to in-
dividual plant operators through on-
the-job training and supervision.
Another source of training is the treat-
ment equipment manufacturer. When
treatment equipment is purchased,
vendors should supply startup assis-
27
-------
tance and training, as well as detailed
operation and maintenance manuals.
Additional training resources for small
systems are listed in Chapter 8.
Selecting a Consulting Engineer/
Equipment Vendor
In some cases, a small community
might need to use the services of a
consulting engineer or equipment ven-
dor to design a treatment system.
Consultants should have proven ex-
perience in solving problems for small
systems. Appendix B provides some
guidelines for selecting a consultant.
Using a Polnt-of-Use/Polnt-of-Entry
(POU/POE) System
A number of point-of-use (POD) and
point-of-entty (POE) systems are avail-
able from a large number of manufac-
turers. Types of systems include those
using reverse osmosis, activated
alumina, and ton exchange. In certain
situations, POU/POE devices can be a
cost-effective solution when a very
small community cannot afford central
treatment for a contaminant, such as
an organic chemical or fluoride. For ex-
ample, with state approval, several
small communities (25 to 200 people)
in Arizona installed home systems
using activated alumina to remove
fluoride. A manufacturing/engineering
company on contract with one com-
munity provides and maintains all the
systems.
office to determine whether POU/POE
devices are appropriate.
11
In addition to home devices, some
very small systems (such as trailer
parks) might be able to install a treat-
ment system at the point of entry and
blend resulting treated waters with
water not treated with the POE device.
A public water supplier must monitor
and ensure the quality of water treat-
ment, whether it provides central treat-
ment or decentralized treatment
through POU/POE devices. The sup-
plier should check with the state drink-
ing water agency or regional EPA
11 Thomas Sorg, "Process Selection for Small Drinking Water Supplies," Proceedings of the Twenty-Third Annual Public Water
Supply Engineers' Conference: New Directions for Supply Design and Operation, University of Illinois, April 21-23, 1981.
28
-------
Chapter Four
Filtration
Technologies
for Small
Systems
Filtration is the process of removing
suspended solids from water as the
water passes through a porous bed of
materials. Natural filtration removes
most suspended matter from ground
water as the water passes through
porous layers of soil into aquifers
(water-bearing layers under the
ground). Surface waters, however, are
subject to runoff and other sources of
contamination, so these waters must
be filtered by a constructed treatment
system.
The solids removed during filtration in-
clude soil and other participate matter
from the raw water, oxidized metals,
and microorganisms. Filtration can be
used to remove many microorgan-
isms, some of which might be resis-
tant to disinfection. Filtration also
prevents suspended material
(measured as turbidity) from interfer-
ing with later treatment processes,
including disinfection. Filtration com-
bined with disinfection provides a
"double barrier" against waterborne
disease caused by microorganisms.
The filtration process usually works by
a combination of physical and chemi-
cal processes. Mechanical straining
removes some particles by trapping
them between the grains of the filter
medium (such as sand). A more impor-
tant process is adhesion, by which
suspended particles stick to the sur-
face of filter grains or previously
deposited material. Figure 4-1
illustrates these two removal
mechanisms. Biological processes are
also important in slow sand filters.
These filters form a filter skin contain-
ing microorganisms that trap and
break down algae, bacteria, and other
organic matter before the water
reaches the filter medium itself.
Processes Preceding Filtration
Even when treating low turbidity water,
filtration is preceded by some form of
pretreatment. Several processes may
precede filtration (Figure 4-2):
• Chemical feed and rapid mix.
Chemicals may be added to the
water to improve the treatment
processes that occur later. These
chemicals may include pH ad-
justers and coagulants. (Coag-
ulants are chemicals, such as
alum, that neutralize positive or
negative charges on small par-
ticles, allowing them to stick
together and form larger, more easi-
ly removed particles.) A variety of
A. Mechanical
RAW WATER
Large particles become lodged and cannot
continue downward through the media.
B. Adsorption
RAW WATER
Particles stick to the media and cannot
continue downward through the media.
Figure 4-1. Filtration primarily depends on physical and chemical
mechanisms to remove particles from water. (Reprinted from Introduction
to Water Treatment, Vol. 2, by permission. Copyright 1984, American Water
Works Association.)
29
-------
Pump Intake
Figure 4-2. Several processes can precede filtration to Improve treatment processes that occur later.
devices, such as baffles, hydraulic
jumps, static mixers, impellers, and
in-line jet sprays can be used to
mix the water and distribute the
chemicals evenly.
Flocculation. In this process,
which follows rapid mixing, the
chemically treated water is sent into
a basin where the suspended par-
ticles can collide and form heavier
particles called floe. Gentle agita-
tion and appropriate detention
times (the length of time water
remains in the basin) facilitate this
process-
Sedimentation. Following floccula-
tfon, a sedimentation step may be
used. During sedimentation, the
velocity of the water is decreased
so that the suspended material (in-
cluding flocculated particles) can
settle out of the water stream by
gravity. Once settled, the particles
combine to form a sludge that is
later removed from the clarified su-
pernatant water.
Filtration processes can include only
one of these pretreatment procedures
or all of them.
Choosing a Filtration Technology
Conventional filtration, which includes
coagulation with the addition of chemi-
cals, rapid mixing, floccuiation and
sedimentation, and granular media
filtration, is the most versatile system
for treating raw water that is variable in
quality. However, a conventional filtra-
tion plant is usually neither appropriate
nor economically feasible for very
small systems. Package plants are
one available cost-effective alternative
when automatic chemical feed control
systems simplify operation.
Other filtration technologies that can
be more suitable for small systems are
slow sand filtration and diatomaceous
earth filtration. Membrane filtration and
cartridge filtration are two emerging
technologies that are suitable for small
systems. Table 4-1 presents the ad-
vantages and disadvantages of these
technologies. Table 4-2 shows the
removal capacities (percentages that
are effectively removed) of Giardia
cysts and viruses for these four tech-
nologies. Filtration technologies for
small systems are described in more
detail below.
Slow Sand Filtration
Slow sand filtration, first used in the
United States in 1872, is the oldest
type of municipal water filtration. A
slow sand filter consists of a layer of
fine sand supported by a layer of
graded gravel. Slow sand filtration
does not require extensive active con-
trol by an operator. This can be impor-
tant for a small system in which an
operator has several responsibilities.
Slow sand filters require a very low ap-
plication or filtration rate (.022 cubic
meters per hour per square centimeter
[0.015 to 0.15 gallons per minute per
square foot of bed area], depending
on the gradation of the filter media and
the quality of the raw water). The
removal action includes a biological
process in addition to physical and
30
-------
Table 4-1. Advantages and Disadvantages of Filtration Technologies
Filtration Technology
Advantages
Disadvantages
Slow sand
Diatomaceous earth
Membrane
Operational simplicity and reliability
Low cost
Ability to achieve greater than 99.9
percent Giardia cyst removal
Compact size
Simplicity of operation
Excellent cyst and turbidity removal
Extremely compact
Automated
Not suitable for water with high turbidity
Maintenance needs of filter surfaces
Most suitable for raw water with low
bacterial counts and low turbidity
(less than 10 NTU)
Requires coagulant and filter aids
for effective virus removal
Potential difficulty in maintaining
complete and uniform thickness of
diatomaceous earth on filter septum
Little information available to
establish design criteria or
operating parameters
Most suitable for raw water with
less than 1 NTU; usually must be
preceded by high levels of
pre treatment
Easily clogged with colloids and
algae
Short filter runs
Concerns about membrane failure
Complex repairs of automated
controls
High percent of water lost in
backflushing
Cartridge
Easy to operate and maintain
Little information available to
establish design criteria and
operating parameters
Can be quickly clogged by algae and
colloids
Requires low turbidity influent
Can require relatively large
operating budget
31
-------
Table 4-2. Removal Capacities of Four Filter Options
Filtration Options
Achievable
Giardia Cyst
Levels
(percent Removal)
Achievable
Virus
Levels
Slow sand
Diatomaceous earth
Membrane
Cartridge
99.99
99.99a
100
>99
99.9399
99.95b
Very low
Little data available
"Aided by coagulation.
''With filter aid.
Source: U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research Information,
Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.
chemical ones. A sticky mat of
suspended biological matter, called a
"schmutzdecke," forms on the sand
surface, where particles are trapped
and organic matter is biologically
degraded. Water applied to slow sand
filters is usually not prechlorinated,
since the chlorine destroys the
organisms in the schmutzdecke that
he!p remove microbiological, organic,
and other contaminants. (Sometimes
Water is prechlorinated and then
dechlorinated before slow sand
filtration.)
Water with high turbidity can quickly
clog the fine sand in these filters.
Water is generally applied to slow
sand filters without any pretreatment
when it has turbidity levels lower than
10 NTU (nephelometric turbidity units).
The upper turbidity limit for slow sand
filters is between 20 and 50 NTU.
When slow sand filters are used with
surface waters having widely varying
turbidity levels, they can be preceded
by infiltration galleries or roughing fil-
ters, such as upflow gravel filters, to
reduce turbidity.
RAW
WATER
INLET
TO DRAIN -
FILTERBOX -fl
D
- SCUM OUTLET
1 TO DRAIN
FILTERED _ ^J^^^esES^pesEsraaa]
WATER SUPPLY
FOR BACKFILLING
FILTER BOTTOM
VENTILATION
I FILTERED
^ZZ WATER
OUTLET
TO DRAIN
TO DRAIN
Figure 4-3. Slow sand filter. (Source: International Reference Centre for
Community Water Supply and Sanitation, Technology of Small Water Supply
Systems in Developing Countries, WHO Collaborating Centre, The Hague,
The Netherlands, 1982.)
Because of the absence of coagulation,
slow sand filtration is limited to certain
types of raw water quality. Slow sand fil-
ters do not provide very good removal of
organic chemicals, dissolved inorganic
substances such as heavy metals, and
trihalomethane precursors (chemical
compounds, formed when natural or-
ganic substances dissolve in water, that
might form THMs when mixed with
chlorine). Also, waters with very fine
clays are not easily treated using sand
filters. High algae blooms will result in
short filter runs.
A slow sand filter must be cleaned
when the fine sand becomes clogged
(as measured by the head loss). The
length of time between cleanings can
range from several weeks to a year,
depending on the raw water quality.
Cleaning is performed by scraping off
the top layer of the filter bed. A "ripen-
ing period" of 1 to 2 days is required
for scraped sand to produce a function-
ing biological filter. The filtered water
quality is poor during this time, and the
filtered water must be wasted. Ex-
tended cleaning periods require redun-
dant or standby systems. In some
small slow sand filters, geotextile filter
material is placed in layers over the
surface. A layer of filter cloth can be
removed periodically so that the upper
sand layer requires less frequent re-
placement.
32
-------
In climates subject to below-freezing
temperatures, slow sand systems
usually must be housed. Unhoused fil-
ters in harsh climates develop an ice
layer that prevents cleaning. Thus,
uncovered slow sand filters will
operate effectively only if turbidity
levels of the influent (water flowing in)
are low enough for the filter to operate
through the winter months without
cleaning. In warm climates, a cover
over the slow sand filter may be
needed to reduce algae growth within
the filter. Figure 4-3 shows a typical
slow sand system.
In addition to maintenance, slow sand
filters require:
• Daily inspection
• Control valve adjustment
• Daily turbidity monitoring
Slow sand filters can achieve 91 to
99.99 percent removal of viruses and
greater than 99.9 percent removal of
Giardia cysts.
Package slow sand filters, constructed
from lightweight materials and
transported for local installation, have
been used successfully in small rural
communities in developing
countries.12 These might be ap-
propriate where community size is
less than 1,000 people and conven-
tional construction of a slow sand filter
would be too slow or inconvenient.
Diatomaceous Earth Filtration
Diatomaceous earth (DE) filtration,
widely used for filtering swimming pool
waters, has also been used success-
fully to remove turbidity and Giardia
cysts from drinking water. Advantages
of DE filters include compact size,
simplicity of operation, and excellent
turbidity removal. They are most
suited for water systems with low tur-
bidity (less than 10 NTU) and low bac-
terial counts.
Filtrate
Clear liquid line
q
Precoat
tank
I
Cj
Body
teed
tank
_ /n
i
Backwash
line .
Filter
Body feed
o
Backwash J1
drain line
To drain
Figure 4-4. Typical pressure diatomaceous earth filtration system.
DE filters (Figure 4-4) use a very thin
layer of diatomaceous earth as a filter
material (3.2 to 6.4 mm [1/8 to 1/4 in.])
which is coated on a porous septum or
filter element. An appropriate grade of
diatomaceous earth should be used.
(Grades vary from fine to coarse, with
fine grades removing smaller particle
sizes but producing shorter filter runs).
The septum is placed in a pressure
vessel or operated under a vacuum in
an open vessel. Additional diatoma-
ceous earth ("body feed") is also
added to the influent water during the
filtration process to prolong the filter
run. Higher body feed doses are
needed for higher concentrations of
suspended solids in the raw water.
When the filter becomes plugged, it is
backwashed and agitated so that the
diatomaceous earth falls off the sep-
tum and is flushed from the filter tank.
Operation and maintenance of
diatomaceous earth filters require:
• Preparing slurries of filter body feed
and precoat diatomaceous earth.
• Adjusting body feed dosages for ef-
fective turbidity removal.
• Periodic backwashing, every 1 to 4
days, depending on raw water
quality.
• Disposing of spent filter cake.
• Periodically inspecting the filter sep-
tum for cleanliness and damage.
• Verifying the effluent quality.
• Maintaining pumps, mixers,
feeders, valves, and piping needed
for precoat and body feed opera-
tions.
DE filters can effectively remove
Giardia cysts, algae, and asbestos,
and the fine grades of diatomaceous
earth can remove bacteria. These fil-
ters require, however, that the water
be pretreated with coagulating chemi-
cals and special filter aids to effective-
ly remove viruses.
Plain diatomaceous earth treatment
(without the use of a coagulant) does
not provide good removal of very fine
particles. DE filters also are not
capable of removing dissolved sub-
stances, including color-causing
materials. Excessive suspended mat-
ter and algae in the raw water can
cause short filter runs.
12 B.J. Lloyd, M. Pardon, D. Wheeler, Rural Water Treatment Package Plant: Final Report for the U.K. Overseas Development
Administration, July 1986. DelAgua, P.O. Box 92, Guildford, GU2STQ, England.
33
-------
Figure 4-5. A package filtration system in Meredith, New Hampshire.
Package Plants
Package plants (Figure 4-5) are treat-
ment units that are assembled in a fac-
tory, skid mounted, and transported to
the treatment site or that are trans-
ported as component units to the site
and then assembled. They are most
widely used to treat surface water
supplies for removal of turbidity, color,
and coliform organisms with filtration
processes, but package plants that
can remove inorganic and/or organic
contaminants are also available. Pack-
age plants are often used to treat
small community water supplies, as
well as supplies in recreational areas,
state parks, construction sites, ski
areas, military installations, and other
areas not served by municipal supplies.
Package plants can vary widely in
their design criteria and operating and
maintenance requirements. The most
Important factor to consider in select-
Ing a package plant is the nature of
the influent, including characteristics
such as temperature, turbidity, and
color levels. Pilot tests (tests that
evaluate treatment processes and
operations on a small scale to obtain
performance criteria) might be neces-
sary before a final system can be
selected. The package treatment
equipment manufacturer can often per-
form these tests.
Package plants can be (and usually
are) designed to minimize the amount
of day-to-day attention required to
operate the equipment. Their opera-
tion and maintenance are simplified by
automated devices such as effluent tur-
bidimeters connected to chemical feed
controls and other operating para-
meters, such as backwashing. Chemi-
cal feed controls are especially
important for plants without full-time
operators or with variable influent char-
acteristics. Even with these automated
devices, however, the operator needs
to be properly trained and well ac-
quainted with the process and control
system.
Figure 4-6 depicts a package plant.
The three basic types of package
water treatment systems are:
• Conventional package plants.
These contain the conventional
processes of coagulation, floccula-
tion, sedimentation, and filtration.
• Tube-type clarifier package
plants. These use tube settlers to
reduce settling detention time (the
average length of time water
remains in the tank or chamber).
• Adsorption clarifier package
plants. Theise use a contact "bed"
with plastic bead media (an adsorp-
tion clarifier) to replace the floccula-
tion and sedimentation basin,
thereby combining these two steps
into one. A mixed media filter (a fil-
ter with a coarse-to-fine gradation
of filter media or several types of fil-
ter media) completes the treatment.
Package plants can effectively remove
turbidity and bacteria from surface
water of fairly consistent quality,
provided that they are run by com-
petent operators and are properly
maintained. Package plants also can
be designed to remove dissolved sub-
stances from the raw water, including
color-causing substances and
trihalomethane precursors. However,
when the turbidity of the raw water
varies a great deal, these plants re-
quire a high level of operational skill
and operator attention.
Membrane Filtration (Ultrafiltratlon)
Membrane filtration, also known as
ultrafiltration, uses hollow fiber
membranes to remove solids from
water. It can be an attractive option for
small systems because of its small
size and automated operation, and it
does not require coagulation as a
pretreatment stop.
Many membrane systems are
designed as skid-mounted units.
Figure 4-7 shows an example of this
type of membrane system.
Membrane filtration systems can
remove bacteria, Giardia, and some
viruses. They are most suitable for
polishing water'that has already been
treated by other methods, or for drink-
ing water supplies with turbidity of less
than 1 NTU. Fouling of the fibers is the
major problem preventing widespread
application of this technology.
Traditional membrane filters work by
feeding water to the inside of the fiber
membrane, with the filtrate (filtered
water) emerging on the outside of the
membrane. State-of-the-art membrane
34
-------
SERVICE ACCESS PLATFORM
WITH HANDRAIL AND 4" KICKPLATE
TYPICAL STANDARD
AXIAL FLOW TYPE
VARIABLE SPEED
FLOCCULATORS TWO
STAGE EACH TRAIN
TUBE SETTLERS 60°
PVC TYPICAL STANDARD
EACH TRAIN
DIE FORMED TANK
STRUCTURALS
SLUDGE DRAW OFF TO
WASTE EACH TRAIN
SETTLED SOLIDS TROUGHS
WITH COLLECTORS AND
MANIFOLDS
ROTARY SURFACE
AGITATOR EACH FILTER
NON-CORRODING FILTER
UNDERDRAIN SYSTEM
LAUNDER WITH ADJUSTABLE
WEIRS EACH TRAIN
WASHWATER COLLECTION TROUGH
WITH ADJUSTABLE WEIRS
EACH TRAIN
SURFACE AGITATOR INLET
CONNECTION EACH TRAIN
WASHWATER OUTLET TO WASTE
EACH TRAIN
FILTERED .WATER OUTLET AND
BACKWASH WATER INLET
FILTER MEDIA
EACH TRAIN
Figure 4-6. Package plant system for surface water treatment. (Courtesy of Smith and Loveless, Inc.)
filters pass influent to either the inside
or outside of the membrane. The hol-
low fiber membranes are contained in
a pressure vessel or cartridge. The
contaminants collect on the end of the
hollow fiber and are discharged to
waste by a reversal of water flow.
Uitrafiltration membranes exclude par-
ticles larger than 0.2 microns.
The membrane filter system must be
cleaned to clear the hollow fibers. This
is done by backflushing and chemical
cleaning or by air pressure. Some
manufacturers have developed self-
cleaning systems to extend the time
between chemical cleanings.
One major concern about membrane
filters is the potential for membrane
failure. The failure of a membrane
should trigger an operational shut-
down or an alarm to the operator.
A diagram of a sample membrane sys-
tem is shown in Figure 4-8.
Cartridge Filtration
Cartridge filters consist of ceramic or
polypropylene filter elements that are
packed into pressurized housings.
They use a physical process for
filtration—straining the water through
porous media. Cartridge filtration sys-
tems require raw water with low
turbidity.
Cartridge filters are easy to operate
and maintain, making them suitable
for small systems with low turbidity in-
fluent. Skilled personnel are not
needed; personnel are needed only
for daily operation and general main-
tenance (cleaning and cartridge re-
Non-Corrosive Piping
System
Chemical Resistant Membranes
Microprocessor
Controls for Radial
Pulse, CIP System,
and Membrane
Integrity Check
Stainless Steel
Centrifugal Pumps
Prefiltration and Pretreatment System
When Required
Figure 4-7. Typical skid-mounted membrane filtration assembly.
35
-------
placement). Ceramic filters may be
cleaned and used for repeated filter
cycles. Polypropylene cartridges be-
come fouled relatively quickly and
must be replaced with new units. Al-
though these filter systems are opera-
tionally simple, they are not automated
and can require relatively large operat-
ing budgets.
Cartridge filtration systems sometimes
use "roughing filters" as pretre'atment
to remove large solids. Prechlorination
Is recommended to prevent the growth
of microorganisms on the filters.
(However, this should be avoided if the
raw water contains organic substan-
ces that can contribute to formation of
trihalomethanes.) Except for a disinfec-
tant, no other chemicals need to be
added.
Little information is available concern-
ing the effectiveness of cartridge filters
for virus removal.
Innovative Filtration Technologies
Several other simple low-cost filtration
methods might be appropriate for
some small systems. For example, a
system developed by 3M Company
using disposable filter bags made of
polypropylene fibers (Figure 4-9) can
remove G/a/tf/a cysts from drinking
water supplies. Small systems in
several states have successfully used
these filters with disim'ection for treat-
ment of water from surface sources.
FILTERED
HOLLOW FIBER
MEMBRANES
RAW 'WATER
CLARIFIED
RECYCLE
DISCHARGE
MEMBRANE CLEANING
SOLUTION TO SEWET
AIR INLET FOR
BACKWASHING
—BACKFLUSH
WASTEWATER
BACK1-LUSH CLARIFIER
Figure 4-8. Flow sheet of membrane filtration system.
Figure 4-9.1 Simple filter bag system removes partii
to 4 microns. (Courtesy of 3M Filtration Products)
36
-------
Chapter Five
Disinfection
Disinfection is the treatment process
used to destroy disease-causing or-
ganisms in a water supply. Primary
disinfection refers to the part of the
treatment process that provides the
necessary inactivation of Giardia
cysts, bacteria, and viruses in source
water. Secondary disinfection refers to
maintenance of a disinfectant residual
which prevents the regrowth of
microorganisms in the water distribu-
tion system. Systems must disinfect
surface water according to the require-
ments of the Surface Water Treat-
ment Rule (see Chapter 2).
Chlorination (the addition of chlorine)
is the most common method of disin-
fecting drinking water. Other disinfec-
tants that small systems might want to
consider are ozone and ultraviolet
(UV) radiation. Table 5-1 summarizes
the advantages and disadvantages of
these three disinfectants. The
preferred application point for each dis-
infectant is shown in Table 5-2.
Chlorination
When Chlorination is performed proper-
ly, it is a safe, effective, and practical
way to destroy disease-causing or-
ganisms. It also provides a stable
residual (disinfectant remaining in the
water) to prevent regrowth in the dis-
tribution system. However, under cer-
tain conditions, chlorine can combine
with remaining organic materials in the
water to produce potentially harmful
by-products such as trihalomethanes.
(See Disinfection By-Products and
Strategies for Their Control below.)
Complex chemical reactions occur
when chlorine is added to water, but
these reactions are not always ob-
vious. For example, a chlorine taste or
odor in finished water is sometimes
the result of too little chlorine rather
than too much, ft is important for
operators to understand basic chlorina-
tion chemistry and the factors affecting
Chlorination efficiency. These topics
are covered thoroughly in many water
supply textbooks. (See Chapter 8,
Resources.)
Disinfection Terminology
When chlorine is fed into water, it
reacts with any substances that exert
a "chlorine demand." Chlorine
demand is a measure of the amount of
chlorine that will combine with im-
purities and therefore will not be avail-
able to act as a disinfectant. Impurities
that increase chlorine demand include
natural organic materials, sulfides, fer-
rous iron, and nitrites.
Chlorine can also combine with am-
monia or other nitrogen compounds to
form chlorine compounds that have
some disinfectant properties. These
compounds are called combined avail-
able chlorine residual. ("Available"
means available to act as a disinfec-
tant.)
The uncombined chlorine that remains
in the water after any combined
residual is formed is called free avail-
able chlorine residual. Free chlorine is
a much more effective disinfectant
than combined chlorine.
Free chlorine is not available for disin-
fection unless the chlorine demand of
the raw water is satisfied. When
chlorine dosage exceeds the "break-
point"—4he point at which chlorine
demand is satisfied—additional
chlorine will result in a free available
chlorine residual. The chlorine dosage
needed to produce a free residual
varies with the quality of the water
source.
Factors Affecting Chlorination
Efficiency
Five factors are important to success-
ful Chlorination: concentration of free
chlorine, contact time, temperature,
pH, and turbidity levels.
The effectiveness of Chlorination is
directly related to the concentration of
free available chlorine and the contact
time. Contact time is the length of time
37
-------
Table 5-1. Advantages and Disadvantages of Three 'Disinfectants
Disinfectant
Advantages
Disadvantages
Chlorine
Ozone
Ultraviolet
radiation
Very effective; has a proven history
of protection against waterborne
disease. Widely used. Variety of
possible application points.
Inexpensive. Appropriate as both
primary and secondary disinfectant.
Operators can easily test for chlorine
residual throughout the water system.
Very effective. Minimal harmful
by-products identified to date.
Very effective for viruses and
bacteria. Readily available.
No known harmful residuals.
Simple operation and maintenance
for high quality waters.
Potential for harmful
by-products under
certain conditions
Relatively high cost. More complex
operations because it must be
generated on site.
Requires a secondary disinfectant.
Inappropriate for surface water
Requires a secondary disinfectant.
Source: Adapted from U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research
Information, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990.
EPA 625/4-89-023.
the organisms are in physical contact
with the chlorine. If the chlorine con-
centration is decreased, then the con-
tact time must be increased.
The tower the pH, the more effective
the disinfection. The pH also affects
corrosh/'rty and formation of disinfec-
tion by-products. The effects of pH
should be considered along with disin-
fection effectiveness.
The higher the temperature, the faster
the disinfection rate. The treatment
system operator usually cannot control
the temperature, but then must in-
crease the contact time or dose at
tower temperatures.
Chlorine (or any disinfectant) is effec-
tive only if it comes into contact with
the organisms to be killed. High tur-
bidity levels can prevent good contact
and protect the organisms. Turbidity
should be reduced where necessary
through coagulation, sedimentation
and filtration, or other treatment
methods.
Chlorination Chemicals
Chlorine is available as a liquid
(sodium hypbchlorite), a solid (calcium
hypochlorite), or a gas. Small systems
most commonly use sodium
hypochlorite or calcium hypochlorite,
because they are simpler to use and
have less extensive safety require-
ments than gaseous chlorine. The
choice of a chlorination system—liq-
uid, solid, or gas—depends on a num-
ber of site-specific factors, including:
• Availability and cost of the chlorine
source chemical
• Capital cost of the chlorination sys-
tem !
• Operation and maintenance costs
of the equipment
• Location of the facility
• Availability of electricity at the treat-
ment site
• Operator skills
• Safety considerations
Disinfection with Sodium
Hypochlorite Solution
Sodium hypochlorite (chlorine in liquid
form) is available through chemical
and swimming pool equipment sup-
pliers, usually in concentrations of 5 to
15 percent chlorine. It is easier to
handle than gaseous chlorine or cal-
cium hypochlorite. Sodium
hypochlorite is very corrosive,
however, and should be handled and
stored with care and kept away from
equipment that can be damaged by
corrosion.
A basic liquid chlorination system or
hypochlorinator (Figure 5-1) includes
two metering pumps (one serving as a
standby), a solution tank, a diffuser (to
inject the solution into water), and
38
-------
Table 5-2. Desired Points of Disinfectant Application3
Disinfectant
Point of Application
Chlorine
Ozone
Ultraviolet radiation
Towards the end of the water treatment process so that water is as clarified
(organic free) as possible, thereby minimizing THM formation and providing
secondary disinfection.
Prior to the rapid mixing step in all treatment processes. In addition,
sufficient time for biodegradation of the oxidation products of the ozpnation
of organic compounds is recommended prior to secondary disinfection.
Towards the end of the water treatment process to minimize the presence of other
contaminants that interfere with this disinfectant and to minimize operating
problems.
aln general disinfectant dosages will be lessened by placing the point of application towards the end of the water treatment
process because of the lower levels of contaminants there to interfere with efficient disinfection. However, water plants with
short detention times in clear wells and with nearby first customers might be required to move their point of disinfection
upstream to attain the appropriate CT value (see page 44) under the Surface Water Treatment Rule.
Source- U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research Information,
Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990. EPA 625/4-89-023.
tubing. Hypochlorinators. used with
chlorine in either liquid or solid form,
are discussed in more detail under
Hypochlorination Equipment below.
Sodium hypochlorite solutions lose
their disinfecting power during
storage, and should be stored in a
cool, dry, dark area. No more than a
1-month supply should be purchased
at one time, to prevent loss of avail-
able chlorine.
Sodium hypochlorite solution is more
costly per pound of available chlorine
than chlorine gas. It also does not con-
tain the high concentration of chlorine
available from chlorine gas. However,
the handling and storage costs are
lower than for chlorine in its gaseous
form.
Disinfection with Solid Calcium
Hypochlorite
Calcium hypochlorite is a white solid
that can be purchased in granular,
, powdered, or tablet form. It contains
65 percent available chlorine and is
easily dissolved in water. The chemi-
cal is available in 1-, 2-, 4-, and 16-kg
(2-, 5-, 8-, and 35-pound) cans and
360-kg (800-pound) drums.
When packaged, calcium hypochlorite
is very stable, so that a year's supply
can be bought at one time. However, it
is hygroscopic (readily absorbs mois-
ture) and reacts slowly with moisture
in the air to form chlorine gas. There-
fore, shipping containers must be
emptied completely or carefully
resealed.
CONSTANT HEAD
DOSING DEVICE
Figure 5-1. Simple liquid chlorination disinfection system for ground-water
supplies. Source water is pumped to a service reservoir into which a
chlorine solution is dosed. (Source: International Reference Centre for Com-
munity Water Supply and Sanitation, Technology of Small Water Supply Systems
in Developing Countries, WHO Collaborating Centre, The Hague, The Nether-
lands, 1981.)
39
-------
Calcium hypochlorhe is dissolved in
water in a mixing tank. The resulting
solution is stored in and fed from a
stock solution vessel made of
corrosion-resistant materials, such as
plastic, ceramic, glass, or rubber-lined
steel.
The equipment used to mix the solu-
tion and inject it into the water is the
same as that for liquid chlorine. Solu-
tions of 1 or 2 percent available
chlorine can be delivered by a
diaphragm-type, chemical feed/meter-
ing pump.
Calcium hypochtorite is a corrosive
material with a strong odor, and re-
quires proper handling. It must be kept
away from organic materials such as
wood, cloth, and petroleum products.
Reactions between calcium hypo-
chtorite and organic material can
generate enough heat to cause a fire
or explosion.
Hypochlorlnatlon Equipment13
Hypochtorinators, used with chlorine in
either liquid or solid form, pump or in-
ject a chlorine solution into the water.
When they are properly maintained,
hypochlorinators provide a reliable
method for applying chlorine to disin-
fect water.
Types of hypochlorinators include posi-
tive displacement feeders, aspirator
feeds, suction feeders, and tablet
hypochlorinators.
Positive displacement feeders. A
common type of positive displacement
hypochtorinator uses a piston or
diaphragm pump to inject the solution.
This type of equipment, which is adjus-
table during operation, can be
designed to give reliable and accurate
feed rates. When electricity is avail-
able, the stopping and starting of the
hypochtorinator can be synchronized
with the pumping unit. A hypo-
chtorinator of this kind can be used
with any water system; however, it is
especially desirable in systems where
water pressure is low and fluctuating.
Aspirator feeders. The aspirator
feeder operates on a simple hydraulic
principle that uses the vacuum created
when water flows either through a ven-
turi tube or perpendicular to a nozzle.
The vacuum created draws the
chlorine solution from a container into
the chlorinator unit where it is mixed
with water passing through the unit,
and the solution is then injected into the
water system. In most cases, the water
inlet line to the chlorinator is connected
to receive water from the discharge side
of the water pump, with the chlorine solu-
tion being injected back into the suction
side of the ^ame pump. The chlorinator
operates only when the pump is operat-
ing. Solution flow rate is regulated by
means of a control valve, though pres-
sure variations may cause changes in
the feed rate.
Suction feeders. One type of suction
feeder consists of a single line that
runs from the chlorine solution con-
tainer through the chlorinator unit and
connects to the suction side of the
pump. The chlorine solution is pulled
from the container through suction
created by ithe operating water pump.
Another type of suction feeder operates
on the siphon principle, with the chlorine
solution beihg introduced directly into a
well. This type also consists of a single
line, but the: line terminates in the well
below the water surface instead of the in-
fluent side of the water pump. When the
pump is operating, the chlorinator is ac-
tivated so that a valve is opened and the
chlorine solution is passed into the well.
In each of these units, the solution
flow rate is regulated by means of a
control valve and the chlorinators
operate only when the pump is operat-
ing. The pump circuit should be con-
nected to a liquid level control so that
the water supply pump operation is in-
terrupted when the chlorine solution is
exhausted.
Tablet hypochlorinators. The tablet
hypochlorinating unit consists of a spe-
cial pot feeder containing calcium
hypochtorite tablets. Accurately con-
trolled by means of a flow meter, small
jets of feed water are injected into the
lower portion of the tablet bed. The
slow dissolution of the tablets provides
a continuous source of fresh hypo-
chtorite solution. The hypochlorinating
unit controls the chlorine solution. This
type of chlorinator is often used when
electricity is not available, but requires
adequate maintenance for efficient
operation. It can operate where the
water pressure is low.
Disinfection with Chlorine Gas
Chlorine is a toxic, yellow-green gas at
standard temperatures and pressures.
It is supplied as a liquid in high-
strength, high-pressure steel cylin-
ders, and immediately vaporizes when
released. Small water systems can
purchase the quantities they need
from chemical or swimming pool sup-
pliers.
Gas chlorinators used in small sys-
tems are often cylinder-mounted or
wall-mounted systems. Figure 5-2
shows a gas chlorinator. Daily opera-
tion of a gas chlorinator consists of
regulating the feed rate, starting and
stopping the chlorinator, and changing
the chlorine cylinders.
Chlorine gas, if accidentally released
into the air, irritates the eyes, nasal
membranes, and respiratory tract. It is
lethal at concentrations as low as 0.1
percent air by volume. Therefore,
systems using chlorine gas must have
several major pieces of safety
equipment:
• Chlorine gas detectors to provide
early warning of leaks
• Self-contained breathing apparatus
for the operator
Pr°tection Agency' Office of Drinkin9 Water- Manual of Individual Water Supply Systems, October 1982.
40
-------
• A power ventilation system for
rooms in which chlorine is housed
• Emergency repair kits
Chlorination Monitoring
Whenever chlorine is used for disinfec-
tion, the chlorine residual should be
monitored at least daily. Samples
should be taken at various locations
throughout the water distribution sys-
tem, including the farthest points of
the system. Most small systems use-a
quick and simple test called the DPD
colorimetric test, available as a kit
from companies specializing in water-
testing equipment and materials
(Figure 5-3). Table 5-3 lists some com-
panies that supply chlorine residual
test kits. Appendix D describes how to
take a sample for chlorine residual
analysis.
Ozonation
Ozone (Oa) is widely used as a
primary disinfectant in other parts of
the world, but is relatively new to the fectant, requiring shorter contact time
United States as a drinking water disin- than chlorine for disinfection.
fectant. A toxic gas formed when air
containing oxygen flows between two
electrodes, ozone is a powerful disin-
Ozone gas is unstable and must be
generated on site. In addition, it has a
Two-stage ozone system. (Courtesy of Carus Chemical Company)
:igure 5-2. Typical deep well gas Chlorination system. (Courtesy of Fischer & Porter, Inc.)
41
-------
liable 5-3. Some Suppliers of Chlorine Residual Test Kits
Capital Controls Co. Box 211, Colmar, PA 18195
(215) 822-2901 (800) 523-2553
Fischer and Porter Co., County Line Rd., Warminster, PA 18974
(215)674-6000 (800)421-3411 '
Hach Co., Box 389, Loveland, CO 80537
(303) 669-3050 (800) 227-4224
Hydro Instruments, Inc., Box 615, Quakertown,'PA
(215)538-1367
Wallace & Tiernan, 25 Main St., Belleville, NJ 07109
(201)759-8000
1 -r
Figure 5-3. Test kit analyzes free and total chlorine. (Courtesy of Hach
Company)
low solubility in water, so efficient con-
tact with the water is essential.
A secondary disinfectant, usually
chlorine, is required because ozone
does not maintain an adequate
residual in water.
Pure oxygen or ambient (freely circulat-
ing) air can be used in ozone produc-
tion. Pure oxygen delivers higher
concentrations of ozone. Packaged
ozone generator systems using
oxygen to produce the ozone are avail-
able for small systems.
Air feed systems used for ozonation
are classified by low, medium, or high
operating pressure. (High pressure
systems typically are used in small-to
medium-sized applications.) These
systems vary in their maintenance re-
quirements, bapital costs, and operat-
ing costs. The air feed systems are
necessary tq dry the air (lower its dew
point) to increase the amount of ozone
produced and to prevent fouling and
corrosion of equipment.
Ozone used for water treatment is
usually generated using a corona dis-
charge cell consisting of two
electrodes separated by a discharge
gap and a dielectric plate (Figure 5-4).
The dried air (or pure oxygen) flows
between the electrodes and is con-
verted to ozone. Several types of
ozone generators are commercially
available: horizontal tube, vertical
tube, and plate generators. These
systems are available with varying
operating frequencies and voltages.
An ozone contactor is used to dissolve
the ozone in water. Ozone can be
generated under positive or negative
pressure, depending on the needs of
the contactor to be used.
As with chlorine, the ozone demand of
the water must be satisfied before an
ozone residual is available for disinfec-
tion. This can be accomplished by
using two ozone contacting chambers
(Figure 5-5). The ozone delivered to
the first chamber satisfies the ozone
demand of the water, and the second
chamber maintains the disinfecting
residual.
Because ozone is toxic, the ozone in
exhaust gases from the contactor
must be recycled or removed and
destroyed before venting. Figure 5-6
depicts a complete treatment system
that includes ozone disinfection.
The capital costs of ozonation sys-
tems are relatively high and operation
and maintenance are relatively com-
plex. Electricity is a major part of
operating costs, representing 26 to 43
percent of total operating and main-
tenance costs for small plants. Opera-
tion and maintenance for ozonation
systems include periodic repair and
replacement of equipment parts, peri-
odic generator cleaning, annual main-
tenance of the contacting chambers,
maintenance of the air preparation
system, and day-to-day operation of
the generating equipment (averaging
1/2 hour per day).
42
-------
Monitoring the Ozonation System
Operation
Proper monitors should be supplied
with the ozonation system, including:
• Gas pressure and temperature
monitors in the air preparation
system
• Continuous monitors to determine
moisture content of the dried gas
fed to the ozone generator
• Generator coolant monitors
• Flow rate, temperature, and pres-
sure monitors, and ozone con-
centration monitor for the gas
discharged from the ozone gener-
ator to determine the ozone produc-
tion rate
• Power input monitor for the ozone
generator
• Ozone residual monitor
The ozone residual should be
measured at a minimum of two points
in the contactor(s). Ozone residual
monitoring can be performed using a
manual chemical analyzer (by a
trained laboratory technician) or an in-
line instrument that continuously
samples the water.
Ultraviolet Radiation (UV)
Ultraviolet radiation effectively kills
bacteria and viruses. As with ozone, a
secondary disinfectant must be used
in addition to ultraviolet radiation to
prevent regrowth of microorganisms in
the water distribution system. UV
radiation can be attractive as a
primary disinfectant for a small system
because:
• It is readily available.
• It produces no known toxic
residuals.
• Required contact times are short.
• The equipment is easy to operate
and maintain.
Ultraviolet radiation, however, does
not inactivate Giardia cysts, and can-
not be used to treat water containing
ELECTRODE
DIELECTRIC
Figure 5-4. Typical ozone generating configuration for a corona discharge
cell.
UNOZONATED
WATER |—
CONTACT
CHAMBER
OFF-GAS
•'/' z.'l j '':
« • yv Oj • p *
S ••o.vJ4"? 5 I /„•?
".«\-T*^ i/A-
"••.'o&ooo-vX-.
OZONE-RICH
AIR
020NATED
WATER
FLOW METER (TYPICAL)
VALVE (TYPICAL)
Figure 5-5. Two-compartment ozone contactor with porous diffusers.
those organisms. Therefore, it is
recommended only for ground water
not directly influenced by surface
water, in which there is no risk of
Giardia cyst contamination. (Future
ground-water disinfection rules will es-
tablish whether and how UV may be
used.) UV radiation is unsuitable for
water with high levels of suspended
solids, turbidity, color, or soluble or-
ganic matter. These materials can
react with or absorb the UV radiation,
reducing the disinfection performance.
UV radiation is generated by a special
lamp (Figure 5-7). When ultraviolet
radiation penetrates the cell wall of an
organism, it destroys the cell's genetic
material and the cell dies.
43
-------
The effectiveness of UV radiation disin-
fection depends on the energy dose
absorbed by the organism, measured
as the product of the lamp's intensity
(the rate at which photons are
delivered to the target) and the lime of
exposure. If the energy dosage is not
high enough, the organism's genetic
material might only be damaged in-
stead of destroyed. To provide a safety
factor, the dosage should be higher
than needed to meet disinfection re-
quirements. For example, if disinfec-
tion criteria require a 99.99 percent
reduction of viruses, the UV system
should be designed to provide a
99.999 percent reduction.
Substances in the raw water exert a
UV demand similar to chlorine
demand. The UV demand of the water
affacts the exposure time and intensity
of the radiation needed for proper
disinfection.
The most important operating factor
for ultraviolet radiation disinfection is
the cleanliness of surfaces through
which the radiation must travel.
Surface fouling can result in inade-
quate performance, so a strict main-
tenance schedule should be followed.
Another important operating factor is
the timely replacement of the UV
lamps, because they lose their output
intensity apd this loss is not readily ap-
parent. A sensor should be used at all
times to ensure the desired dose.
Obtaining [Effective Disinfection:
CT Values
To ensure proper disinfection, the disin-
fectant must be in contact with the tar-
get organisms for a sufficient amount
of time. CT values describe the
degree of disinfection that can be ob-
tained as a'product of the disinfectant
residual concentration, C, (in mg/L)
and the contact time, T (in minutes).
EPA's Guidance Manual for Com-
pliance with the Filtration and Disinfec-
tion Requirements for Public Water
Systems Using Surface Water Sour-
ces provides CT values for achieving
various levels of inactivation of Giardia
and viruses. Appendix E presents CT
values for chlorine and ozone at
several water temperatures and water
pH levels for inactivating Giardia and
viruses, and Appendix F provides an
example of a CT calculation for a
small system.
Disinfection By-Products and
Strategies for Their Control
Adding a disinfectant to water might
result in the production of harmful by-
products.
Chlorine, for example, can mix with
the natural organic compounds in
water to form trihalomethanes (THMs).
AIR PREPARATION OXIDATION
FLOCCULATION
FILTRATION
Mixed Bed Filler
SECONDARY DISINFECTION
l£j Filter Degassing
STORAGE
I
'].
fj
~
1
Trnatod :
Water '
i
i
ii
ii
if
If
ii
it
it
DISTRIBUTION
7%y, WELL
Figure 5-6. Schematic of system that provides primary disinfection with ozone, filtration, secondary disinfection
and axcess ozone gas destruction. (Courtesy of Cams Chemical Company) "
44
-------
TRANSFORMER HOUSING
AND JUNCTION BOX
Figure 5-7. Ultraviolet disinfection unit. (Courtesy of Atlantic Ultraviolet
Corporation)
used alone. For these reasons, it is im-
portant to know what compounds are
in the raw water before choosing
ozone as a disinfectant. Researchers
are continuing to study ozonation by-
products and their potential health
effects.
Ultraviolet radiation might produce
some by-products from organic com-
pounds, but by-products of UV radia-
tion have not yet been identified.
One THM—chloroform—is a
suspected carcinogen. Other common
trihalomethanes are similar to
chloroform and may cause cancer.
The formation of chlorination by-
products depends on several factors,
including:
• Temperature and pH of the water
• Chlorine dosage
• Concentration and types of organic
materials in the water
• Contact time for free chlorine
Several strategies for minimizing harm-
ful chlorination by-products can be
used by small systems:
• Reducing the concentration of or-
ganic materials before adding
chlorine. Common water clarifica-
tion techniques, such as coagula-
tion, sedimentation, and filtration,
can effectively remove many or-
ganic materials. Activated carbon
(described in Chapter 6) might be
needed to remove organic
materials at higher concentrations
or those not removed by other
techniques.
• Reevaluating the amount of
chlorine used. The same degree
of disinfection might be possible
with lower chlorine dosages.
• Changing the point in treatment
where chlorine is added. If
chlorine is presently added before
treatment (chemical feed, coagula-
tion, sedimentation, and filtration),
it can instead be added after filtra-
tion, or just before filtration and
after chemical treatment.
• Using alternative disinfection
methods. A system with a high con-
centration of chlorination by-
products in the treated water might
consider alternative disinfection
methods. However, ozonation and
ultraviolet radiation, the alternative
methods most practical for small
systems, cannot be used as disin-
fectants by themselves. Both re-
quire a secondary disinfectant
(usually chlorine) to maintain a
residual in the distribution system.
Ozonation might also result in the for-
mation of some harmful by-products.
Ozone can produce toxic by-products
from a few synthetic organic com-
pounds, such as the pesticide hep-
tachlor. If ozone is added to water
containing bromide ions, it can form
brominated organic compounds such
as bromine-containing trihalo-
methanes. Also, studies have shown
that the addition of ozone followed by
chlorine orchloramines can result in
higher levels of certain by-products
than when these disinfectants are
45
-------
-------
Chapter Six
Treating Organic
Contaminants
in Drinking
Water
Some small drinking water systems
face contamination of raw water by
natural or synthetic organic substan-
ces. Sources of these substances
include leaking underground
gasoline/storage tanks, runoff of
herbicides or pesticides, or improperly
disposed of chemical wastes. Natural
organic materials might also be
present in water.
The technologies most suitable for or-
ganic contaminant removal in small
systems are granular activated carbon
(GAG) and aeration. Several emerg-
ing technologies using aeration may
also be suitable for small systems.
Table 6-1 presents operational condi-
tions for the organics treatment tech-
nologies most suitable for small
systems. Table 6-2 presents removal
effectiveness data for organic con-
taminants by granular activated car-
bon, packed column aeration, and
diffused aeration. Information about
organics removal effectiveness is not
yet available for the other technologies
described in this chapter.
Granular Activated Carbon (GAC)
Granular activated carbon (GAC)
removes many organic contaminants
from water supplies. Congress has
designated GAC as the Best Available
Technology (BAT) for synthetic organic
chemical removal.
Activated carbon is carbon that has
been exposed to very high tempera-
ture, creating a vast network of inter-
nal pores (Figure 6-1). ft removes
contaminants through adsorption, a
process in which dissolved con-
taminants adhere to the porous sur-
face of the carbon particles. Because
activated carbon is very porous, it has
a large internal surface area; 1 gram.
of activated carbon has a surface area
equivalent to a football field. One
Table 6-1. Operational Conditions for Organic Treatments
Technology
Level of
Operational Level of
Skill Maintenance Energy
Required Required Requirements
Granular activated Medium Low Low
carbon (GAC)
Packed column Low Low Varies
aeration (PCA)
Diffused aeration Low Low Varies
Multiple tray Low Low Low
aeration
Mechanical aeration Low Low Low
Catenary grid Low Low High
Higee aeration Low Medium High
Source: U.S. Environmental Protection Agency, Office of Drinking Water and
Center for Environmental Research Information, Technologies for Upgrading
Existing or Designing New Drinking Water Treatment Facilities, March 1990.
EPA 625/4-89-023.
47
-------
Table? 6||j'|J|eatiTient Techno ogy"RemovaljEf||ctlven6ss Reported for Organic CbtSiminan^ (PerceLit)8
Contaminant
Granular Activated
Carbon (GAC)
Packed Column
Aeration (PCA)
Diffused
Aeration
Acryl amide
Alachlor
Aldicarb
Benzene
Carbofuran
Carbon tetrachloride
Chlordane
Chtorobenzene
2,4-D
1,2-Dichloroethane
1,2-Dichloropropane
Dibromoch loropropane
Dichloro benzene
o-Dichlorobenzene
p-Dichlorobenzene
1,1-Dichloroethylene
c/s-1,2-Dichtoroethylene
frans-1,2-Dichloroethylene
Epichlorohydrin
Ethylbenzene
Ethytene dibromide
Heptachlor
Heptachlor epoxide
High motecuiar weight
hydrocarbons (gasoline,
dyes, amines, humics)
Linda ne
Methoxychlor
Monochlorobenzene
Natural organic material
PCBs
Phenol and chlorophenols
Pentachlorophenol
Styrene
Tetrachloroethylene
Trichloroethylene
Tricholoroethane
1,1,1-Trichloroethane
Toluene
2,4.5-TP
Toxaphene
Vinyl chloride
Xylcnes
NA
0-49
NA
70^100
70-100
70^-100
70J-100
70^00
70-100
70J100
70-100
70r100
70T100
70-100
70-100
70-100
70-100
70-100
NA
70-100
70-100
70-100
NA
W
70-100
70-100
NA
P
70-100
W
70-100
NA
70-100
70-100
70-100
70-100
70-100
70-100
70-100
70-100
70-100
1-29
70-100
0-29
70-100
0-29
70-100
0-29
70-100
70-100
70-100
70-100
30-69
NA
70-100
70-100
, 70-100
70-100
70-100
0-29
70-100
70-100
70-100
NA
NA
0-29
NA
NA
NA
70-100
NA
0
NA
NA
70-100
NA
70-100
70-100
NA
70-100
70-100
70-100
NA
NA
NA
NA
11-20
NA
NA
NA
NA
42-77
12-79
NA
NA
14-72
NA
97
32-85
37-96
NA
24-89
NA
NA
NA
NA
NA
NA
14-85
NA
MA
MA
NA
NA
73-95
53-95
NA
58-90
22-89
NA
NA
NA
18-89
"Additional treatment information is available! in EPA Office of Drinking Water Health Advisories for specific contaminants.
W * well removed. p = :poorly removed. NA = not available.
Note: Little or no specific performance data Were available for:
1. Multiple Tray Aeration 3. Higee Aeration
2. Catenary Aeration 4. Mechanical Aeration
Source: U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research
Information, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities March 1990
EPA 625/4-89-023.
48
-------
pound of activated carbon can adsorb
over 1/2 pound of carbon tetrachloride.
GAG has an affinity for high molecular
weight compounds. It is not effective
in removing vinyl chloride, a highly
volatile substance, from water. Table
6-3 lists organics that are readily or
poorly adsorbed by activated carbon.
GAG can be used as a replacement
for existing media (such as sand) in a
conventional filter or it can be used in
a separate contactor (a vertical steel
pressure vessel used to hold the ac-
tivated carbon bed).
GAG contactors require monitoring to
ensure that they work effectively. A
GAG monitoring system should
include:
• Laboratory analysis of treated
water to ensure that the system is
removing organic contaminants
• Monitoring of headloss (the amount
of energy used by water in moving
from one point to another) through
the contactors to ensure that back-
flushing (reversing the flow to
remove trapped material) is per-
formed at appropriate times
• Bacteria monitoring of the
contactor's effluent (since bacteria
can grow rapidly within the ac-
tivated carbon bed)
• Turbidity monitoring of the
contactor's effluent (to determine if
suspended material is passing
through GAG bed)
After a period of a few months or a
few years, depending on the con-
centration of contaminants, the sur-
face of the pores in the GAG can no
longer adsorb contaminants. The
carbon must then be replaced.
Several operational and maintenance
factors affect the performance of GAG.
Contaminants in the water can occupy
GAG adsorption sites, whether they
are targeted for removal or not. Also,
adsorbed contaminants can be
replaced by other contaminants with
Figure 6-1. Representation of
internal carbon structure. (Reprinted
from Introduction to Water Treatment,
Vol. 2, by permission. Copyright 1984,
American Water Works Association.)
which GAG has a greater affinity.
Therefore, the presence of other con-
taminants might interfere with the
removal of the contaminants of
concern.
A significant drop in the contaminant
level in influent water will cause a
GAG filter to desorb, or slough off, ad-
sorbed contaminants, because GAG is
an equilibrium process. As a result,
raw water with frequently changing
contaminant levels can result in
treated water of unpredictable quality.
Bacterial growth on the carbon is
another potential problem. Excessive
bacterial growth may cause clogging
and higher bacterial counts in the
treated water. This means that bac-
terial levels in thci treated water must
be closely monitored and the final dis-
infection process must be carefully
controlled.
GAG is available in different grades of
effectiveness. Low-cost carbon re-
quires a lower initial capital outlay, but
must be replaced more often, resulting
in higher operating costs.
Aeration
Aeration, also known as air stripping,
mixes air with Wetter to volatilize
Table 6-3. Readily and Poorly Adsorbed Organic
Readily Adsorbed Organics
• Aromatic solvents (benzene, toluene, nitrobenzenes)
• Chlorinated aromatics (PCBs, chlorobenzenes, chloronaphthalene)
• Phenol and chlorophenols
• Polynuclear aromatics (acenapthene, benzopyrenes)
• Pesticides and herbicides (DDT, aldrin, chlordane, heptacr lor)
• Chlorinated aliphatics (carbon tetrachloride, chloroalkyl eth ers)
• High molecular weight hydrocarbons (dyes, gasoline, amir es, humics)
Poorly Adsorbed Organics
• Alcohols
• Low molecular weight ketones, acids, and aldehydes
• Sugars and starches
• Very high molecular weight or colloidal organics
• Low molecular weight aliphatics
Source: U.S. Environmental Protection Agency, Office of Drinking Water and
Center for Environmental Research Information, Technologies for Upgrading
Existing or Designing New Drinking Water Treatment Facilities, March 1990.
EPA 625/4-89-023.
49
-------
Finished Wator
to System
Figure 6-2, Packed tower aeration system.
AERATION BASIN
MIXING PATTERNS
COMPRESSED AIR PIPING
OOWNCOMER PIPE
DIFFUSERS
MANIFOLD
Figure 6-3. Diffuser aeration system. (Reprinted from Introduction to Water
Treatment, Vol. 2, by permission. Copyright 1984, American Water Works
Association.)
Aeration, also known as air stripping,
mixes air with water to volatilize
contaminants (turn them to vapor).
The volatilized contaminants are either
released directly to the atmosphere or
are treated and then released. Aera-
tion is used to remove volatile organic
chemicals and can also remove radon
(see Chapter 7).
A small system might be able to use a
simple aerator constructed from rela-
tively common materials instead of a
specially designed aerator system.
Examples of simple aerators include:
• A system that cascades the
water or passes it through a
slotted container
• A system that runs water over a
corrugated surface
• An airlift pump that introduces
oxygen as water is drawn from
a well
Other aeration systems that might be
suitable for small systems include
packed column aeration, diffused
aeration, arid multiple tray aeration.
Emerging technologies that use aera-
tion for organics removal include
mechanical aeration, catenary grid,
and Higee aeration.
Packed Column Aeration
Packed column aeration (PCA) or
packed tower aeration (PTA) is a
waterfall aeration process which drops
water over a medium within a tower to
mix the water with air. The medium is
designed to break the water into tiny
droplets, and maximize its contact with
tiny air bubbles for removal of the con-
taminant. Air is also blown in from un-
derneath the medium to enhance this
process. Figure 6-2 shows a PCA
system.
Systems using PCA may need
pretreatment to remove iron, solids,
and biological growth to prevent clog-
ging of the packing material. Posttreat-
ment (such as the use of a corrosion
inhibitor) may also be needed to
reduce corrosive properties in water
due to increased dissolved oxygen
from the aeration process.
Packed columns usually operate auto-
matically, and need only daily visits to
ensure that She equipment is running
satisfactorily. Maintenance require-
ments include servicing pump and
blower motors and replacing air filters
on the blower, if necessary.
PCA exhaust gas may require treat-
ment to meet air emissions regula-
tions, which can significantly
increase the costs of this technology.
Diffused Aeration
In a diffused aeration system, a dif-
fuser bubbles air through a contact
chamber for aeration (Figure 6-3).
The main advantage of diffused aera-
tion systems is that they can be
created from existing structures, such
as storage tanks. However, they are
less effective than packed column
aeration, and usually are used only in
systems with adaptable existing
structures.
SO
-------
Multiple Tray Aeration
Multiple tray aeration directs water
through a series of trays made of
slats, perforations, or wire mesh
(Figure 6-4). A blower introduces air
from underneath the trays.
Multiple tray aeration units have less
surface area than do PGA units. This
type of aeration is not as effective as
PCA, and can experience clogging
from iron and manganese, biological
growth, and corrosion problems.
Multiple tray aeration units are readily
available from package plant manufac-
turers.
Emerging Technologies for
Organics Removal
Mechanical Aeration
Mechanical aeration uses mechanical
stirring mechanisms to mix air with the
water (Figure 6-5). These systems
can effectively remove volatile organic
chemicals (VOCs).
Mechanical aeration units need large
amounts of space because they
demand long detention times for effec-
tive treatment. As a result, they often
require open-air designs, which can
freeze in cold climates. These units
also can have high energy require-
ments. However, mechanical aeration
systems are easy to operate, and are
less susceptible to clogging from
biological growth than PCA systems.
Catenary Grid
Catenary grid systems are a variation
of the packed column aeration
process. The catenary grid directs
water through a series of wire screens
mounted within the column. The
screens mix the air and water in the
same way as packing materials in
PCA systems. Figure 6-6 shows a
catenary grid unit.
These systems can effectively remove
volatile organic chemicals. There is lit-
tle information available about the ef-
fectiveness of catenary grid systems
for other organic compounds, but they
probably would not remove these com-
pounds effectively. They have higher
energy requirements than PCA sys-
tems, but their more compact design
lowers their capital cost relative to
PCA.
Higee Aeration
Higee aeration is another variation of
the PCA process. These systems
pump water into the center of a spin-
ning disc of packing material, where
the water mixes with air (Figure 6-7).
Higee units require less packing
material than PCA units to achieve the
same removal efficiencies. Because
of their compact size, they can be
used in limited spaces and heights.
Current Higee systems are best suited
for temporary applications of less than
1 year with capacities up to 380 liters
(100 gallons) per minute.
INLET
DISTRIBUTOR
•~-~.
AIR INLET -
\
/^
((Oj
>t
n
AIR S
A|R WATER
-j
"-•• -.-• •.". ;. L- '—i ^ BAFFLES
,Lr.L ..::.'-' — .-_m-^'^-^=r— ' t
J^l^S^cSoS^^S^SSSIa^?1!
js^iL^sssScM^^s?sssm^3 !
•. . j^^is^^^^^n^f i
_jCr^f;nr2ain- '•• '••. : ;
]! '•• [- ; TJ-. ^ 1 ; .' I, i
EAL V/ATEH""""^
OUTLET
Figure 6-4. Schematic of a
wood slat tray aerator
red-
Sur£ac« Aerator
-—) Compressor
T t^l
Turbine
Sparger
Sutea«r9»d Turbine A«r»to
Figure 6-5. Schematic of mechanical aeration process.
51
-------
Treated Waier /
to Drain —/
Figure 6-6. Catenary grid system.
EXHAUST AIR
AIR IN
O-o-
BLOWER
GROUND WATER
FILTER
HIGEE
ho
PRODUCT
WATER
PUMP
Figure 6-7. Schematic of Higee system.
52
-------
Chapter Seven
Control and
Removal of
Inorganic
Contaminants
Water systems control or remove inor-
ganic contaminants using two different
strategies:
1. Preventing Inorganic contamina-
tion of finished water. Corrosion
controls prevent or minimize the
presence of corrosion products
(such as lead and copper) at the
consumer's tap.
2. Removing inorganic
contaminants from raw water.
Removal technologies treat source
water that is contaminated with me-
tals or radioactive substances
(radionuclides).
Inorganic contaminants presently
regulated under the Safe Drinking
Water Act (SDWA) include lead,
radium, nitrate, arsenic, selenium,
barium, fluoride, cadmium, chromium,
mercury, and silver.
This chapter describes several tech-
nologies for inorganic contaminant
removal (reverse osmosis, ion ex-
change, activated alumina, aeration,
and granular activated carbon). Con-
ventional treatment (coagulation/
filtration) can also remove inorganic
contaminants and is discussed in this
chapter.
Corrosion
Corrosion is the deterioration of a sub-
stance by chemical action. Lead, cad-
mium, zinc, copper, and iron might be
found in water when metals in water
distribution systems corrode. Drinking
water contaminated with certain me-
tals (such as lead and cadmium) can
harm human health.
Corrosion also reduces the useful life
of water distribution systems, and can
promote microorganism growth, result-
ing in disagreeable tastes, odors,
slimes, and further corrosion. Often a
customer complaint is the first indica-
tion of a corrosion problem, and at this
stage corrosion may be extensive.
Table 7-1 shows typical customer com-
plaints and their causes..
Controlling Lead Levels In
Drinking Water
Because it is widespread and highly
toxic, lead is the corrosion product of
greatest concern. Table 7-2 shows the
risk factors that can indicate potential-
ly high lead levels at the tap. Lead
levels in drinking water are managed
indirectly through corrosion controls.
Lead is not typically found in source
water, but rather at the consumer's tap
as a result of the corrosion of the
plumbing or distribution system. The
1986 amendments to the Safe Drink-
ing Water Act ban the use of lead
solders, fluxes, and pipes in the instal-
lation or repair of any public water sys-
tem or in any plumbing system
providing water for human consump-
tion. In the past, solder used in plumb-
ing has been 50 percent tin and 50
percent lead. Using lead-free solders,
such as silver-tin and antimony-tin
solders is a key factor in lead cor-
rosion control. Replacement of lead
pipes can also be an effective strategy
for reducing lead in drinking water.
The current Maximum Contaminant
Level (MCL) for lead applies to water
delivered by the supplier. New lead
regulations might include an MCL for
water at the consumer's tap.
If tests for corrosion by-products find
unacceptably high levels of lead, im-
mediate steps should be taken to mini-
mize consumers' exposure until a
long-term corrosion control plan is im-
plemented. Some short-term
measures the consumer can take
include:
• Running the water for about 1
minute before each use
• Using home treatment processes in
extreme cases
• Using bottled water
53
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Table |-l| Typical Customer Water Quality Cbrnplainjts That Might Be DJue ta: CJorrofion
Customer Complaint
Red water or reddish-brown staining
of fixtures and laundry
Bluish stains on fixtures
Black water
Foul taste and/or odors
Loss of pressure
Lack of hot water
Short service life of household
plumbing
Possible Cause
Corrosion of iron pipes or presence of natural iron in raw water
Corrosion of copper lines
Sulfide corrosion of copper or iron lines or precipitations of natural
manganese
By-products from microbial activity
Excessive scaling, tubercle buildup from pitting corrosion, leak in system
from pitting or other type of corrosion
Buildup of mineral deposits in hot water system (can be reduced by setting
thermostats to under 60'C [140'F])
Rapid deterioration of pipes from
pitting or other types of corrosion
Source: U.S. Environmental Protection Agency, Office of Drinking Water, Corrosion Manual for Internal Corrosion of Water Dis-
tribution Systems, April 1984. EPA 570/9-84-001.
liable 7r2.' Risk Fabtors Indicating Potenffaliy High Lfead Levels at the Tap
• Components of the water distribution system or structure's plumbing are made of lead, or lead-containing
material such as brass, and/or the structure's plumbing has solder containing lead.
And one or more of the following apply:
• The structure is less than 5 years old.
• The tap water is soft and/or acidic.
• The water stays in the plumbing for 6 or more hours.
• The structure's electrical system is grounded to the plumbing system.
Source: Adapted from U.S. Environmental Protection Agency, Office of Drinking Water and Center for Environmental Research
Information, Technologies for Upgrading Existing or Designing New Drinking Water Treatment Facilities, March 1990 EPA
625/4-89-023.
Techniques for Controlling
Corrosion
Solutions to corrosion problems in-
clude modifying the water quality-
(especially pH and alkalinity), and add-
ing corrosion inhibitors to form protec-
tive coatings over metal. It should also
bo noted that corrosion in a
homeowner's plumbing can be related
to conditions In the home (such as
pipes that are too small or the use of
dissimilarmetals in joining pipes and
valves) rather than to the quality of
water from the distribution system.
Modifying water quality. Table 7-3
shows some of the characteristics of
water that affect its corrosivity. All
water is corrosive to some degree, but
water that is acidic (less than 7.0 pH)
is likely to corrode metal more quickly.
54
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table 7-3. Chemical Factors Influencing Corrosion and Corrosion Control
Factor
Effect
pH
Alkalinity
Dissolved oxygen (DO)
Chlorine residual
Total dissolved solids
(IDS)
Hardness (Ca and Mg)
Chloride, sulfate
Hydrogen sulfide
Silicate, phosphates
Natural color, organic matter
Iron, zinc, or manganese
Low pH may increase corrosion rate; high pH may protect pipes
and decrease corrosion rates
May help form protective calcium carbonate (CaCOs) coating,
helps control pH changes, reduces corrosion
Increases rate of many corrosion reactions
Increases metallic corrosion
High IDS increases conductivity and corrosion rate
Ca may precipitate as CaCOa and thus provide protection
and reduce corrosion rates
High levels increase corrosion of iron, copper, and galvanized steel
Increases corrosion rates
May form protective films
May decrease corrosion
May react with compounds on interior of asbestos-cement pipe
to form protective coating
Source: U.S. Environmental Protection Agency, Office of Drinking Water, Corrosion Manual for Internal Corrosion of Water Dis-
tribution Systems, April 1984. EPA 570/9-84-001.
Adjusting pH and alkalinity is the most
common corrosion control method, be-
cause it is simple and inexpensive.
(pH is a measure of the concentration
of hydrogen ions present in water;
alkalinity is a measure of water's
ability to neutralize acids.) Generally,
an increase in pH and alkalinity can
decrease corrosion rates and help
form a protective layer of scale on cor-
rodible pipe material. Chemicals com-
monly used for pH and alkalinity
adjustment are lime, caustic soda,
soda ash, and sodium bicarbonate. Ad-
justing pH to control corrosion,
however, might conflict with ideal pH
conditions for disinfection and control
of disinfection by-products. Drinking
water suppliers should carefully
choose the treatment methods so that
both disinfection and corrosion control
are effective.
Avoiding high dissolved oxygen levels
decreases water's corrosive activity.
Removing oxygen from water is not
practical because of cost. However,
treatment systems might be able to
minimize the dissolved oxygen levels
by minimizing air/water contact.
Corrosion inhibitors. Corrosion in-
hibitors reduce corrosion by forming
protective coatings on pipes. The most
common corrosion inhibitors are inor-
ganic phosphates, sodium silicates,
and mixtures of phosphates and sili-
cates. These chemicals have proven
successful in reducing corrosion in
many systems.
Treatment Technologies for
Removing Inorganic Contaminants
Inorganic contamination of raw water
supplies can come from a wide variety
of sources. Naturally occurring inor-
ganics, such as fluoride, arsenic,
selenium, and radium, are commonly
found in ground-water sources. Syn-
thetic contaminants are usually found
in surface water supplies. Nitrates and
nitrites are a problem in agricultural
areas and areas without sanitary
sewer systems, and have been found
at relatively high levels in both surface
water and ground water.
No single treatment is perfectly suited
for all inorganic contaminants. Table
7-4 shows the removal effectiveness
of six inorganic treatment processes
55
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Table 7-4, Most Probable Applications of Wajter Treatment Processes for Inorganic clntaminant Remdval
Treatment
Process
Principal Application for
Water Treatment
Inorganic Contaminant
Treatment Capability
Effectivenessa
High Moderate Low
Most Probable Application
for Inorganic Removal
Conventional
coagulation
Clarification of surface waters
Cation exchange
Anion exchange
Activated alumina
Granular activated
carbon
Reverse osmosis and
electrodialysis
Removal of hardness
from ground water
Removal of nitrate from
ground water
Removal of fluoride from
ground water
Removal of taste, odors,
and organics
Desalting of sea water
or brackish ground water
AsV
Ba
Cr
Pb
Cd
Se
Ag
F
Ra
Hg
As III
SelV
Hg(0)
Hg(l)
Cd
Crlll
CrVI
AsV
Ag
Pb
Ba
Ra
Cd
Pb
Crlll
NOs
CrVI
Se
F
As
Se
Hg(l) Cd
Hg(0)
NO3
As III
Ba
F
No3
Ra
SeVI
As
Se
N03
F
CrVI
Ba
Ra
Cd
Pb
Crlll
Ba
Ra
Cd
Ag
Ba
Ra
Crlll
F
NO3
Removal of Cd, Cr, As, Ag, or
Pb from surface waters
Removal of Ba or Ra from
ground water
Removal of NOs from
ground water
Removal of F, As, or Se from
ground water
Removal of Hg from surface or
ground water
Removal of all inorganics
from ground water
"High—greater than 80 percent; moderate—20 to 80 percent; low—less than 20 percent.
Ag
As
Ba
Cd
Cr
F
Silver
Arsenic
Barium
Cadmium
Chromium
Fluoride
Hg
N03
Pb
Ra
Se
Mercury
Nitrate
Lead
Radium
Selenium
Source: Adapted from Thomas J. Sorg and Gary S. Logsdon, "Treatment Technology to Meet the Interim Primary
Drinking Water Regulations for Inorganics: Part 5," Journal of the American Water Works Association, July 1980.
56
-------
and their most probable application for
inorganic removal. Processes suitable
for small systems include:
• Coagulation/filtration
• Membranes (reverse osmosis and
electrodialysis)
• Ion exchange
• Activated alumina
Table 7-5 presents advantages and
disadvantages of these processes.
Coagulation/filtration is generally too
operationally complex for very small
systems (serving 500 people or
fewer). Reverse osmosis, ion ex-
change, and activated alumina are
simpler operations and may be better
alternatives for these systems, unless
the contaminant of concern cannot be
removed by these processes, or un-
less the costs or maintenance require-
ments are prohibitive. Each of these
processes is described below. Aera-
tion and granular activated carbon,
commonly used to remove radon from
water supplies, are also discussed
below.
Coagulation/Filtration
Coagulation (described in Chapter 4)
is traditionally used to control turbidity,
hardness, taste, and odors, but is also
effective in removing some inorganic
contaminants.
Coagulation using aluminum or iron
salts is effective in removing most
metal ions or colloidally dispersed
compounds (finely divided substances
that do not settle out of water for a
very long period of time). It is ineffec-
tive in removing nitrate, nitrite, radium,
and barium. Table 7-6 presents poten-
tial removal efficiencies using
aluminum and iron salts as coag-
ulants. Coagulation to remove inor-
ganics is more expensive than
coagulation to remove turbidity be-
cause higher dosages of coagulant
are needed.
Table 7-5. Advantages and Disadvantages of Inorganic
Contaminant Removal Processes
Coagulation/Filtration
Advantages
* Low cost for high volume
• Reliable process well suited to automatic control
Disadvantages
• Not readily applied to small or intermittent flows
• High-water-content sludge disposal
• Very low contaminant levels may require two-stage precipitation
• Requires highly trained operators
Membranes (Reverse Osmosis and Electrodialysis)
Advantages
' Removes nearly all contaminant ions and most dissolved non-ions
• Relatively insensitive to flow and total dissolved solids level
• Low effluent concentration possible
• In reverse osmosis, bacteria and particles are also removed
• Automation allows for less operator attention
Disadvantages
' High capital and operating costs
• High level of pretreatment required in some cases
• Membranes are prone to fouling (RO). Electrodes require replace-
ment (ED).
Ion Exchange
Advantages
* Relatively insensitive to flow variations
• Essentially zero level of effluent contamination possible
• Large variety of specific resins available
Disadvantages
' Potential for unacceptable levels (peaks) of contamination in effluent
• Waste requires careful disposal
• Usually not feasible at high levels of total dissolved solids
• Pretreatment required for most surface waters
Activated Alumina
Advantages
• Insensitive to flow and total dissolved solids background
• Low effluent contaminant level possible
• Highly selective for fluoride and arsenic
Disadvantages
' Strong acid and base are required for regeneration
• Medium tends to dissolve, producing fine particles
• Adsorption is slow
• Waste requires careful disposal
Source: U.S. Environmental Protection Agency, Office of Drinking Water and
Center for Environmental Research Information, Technologies for Upgrading
Existing or Designing New Drinking Water Treatment Facilities, March 1990.
EPA 625/4-89-023.
57
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Table 7-6. Removal Efficiency Potential of Alum Versus Ferric
Chloride : t
Removal Efficiency
Inorganic
Contaminant
Alum
Coagulant
Iron
Coagulant
Ag (pH < 8.0)
Ag (pH = 8.0)
AsV
90%
70%
90%
AsV(pH< 7.5)
AsV(pH = 7.5)
Cd(pH>8.0)
90%
90%
Cd (pH 2 8.5)
Or (III)
Cr III (pH = 10.5)
CrVI (usingFell)
Hg
Pb
70%
90%
70%
90%
90%
90%
Ag
As
Cd
Cr
Hg
Pb
Silver
Arsenic
Cadmium
Chromium
Mercury
Lead
Source: U.S. Environmental Protection Agency, Office of Drinking Water
and Center for Environmental Research Information, Technologies for
Upgrading Existing or Designing New Drinking Water Treatment Facilities,
March 1990. EPA 625/4-89-023.
Reverse Osmosis and
Electrodlalysls
Reverse osmosis removes con-
taminants from water using a semiper-
meable membrane that permits only
water, and not dissolved ions (such as
sodium and chloride), to pass through
its pores (Figure 7-1). Contaminated
water is subjected to a high pressure
that forces pure water through the
membrane, leaving contaminants be-
hind in a brine solution. Membranes
are available with a variety of pore
sizes and characteristics.
Reverse osmosis can effectively
remove nearly all inorganic con-
taminants from water. It removes over
70 percent of arsenic(lil), arsenic(IV),
barium, cadmium, chromium(lll),
chromium(VI), fluoride, lead, mercury,
nitrite, selenium(IV), selenium(VI), and
silver. Properly operated units will at-
tain 96 percent removal rates.
Reverse osmosis can also effectively
remove radium, natural organic sub-
stances, pesticides, and microbiologi-
cal contaminants.
Reverse osmosis systems are com-
pact, simple to operate, and have mini-
mal labor requirements, making them
suitable for small systems. They are
also suitable for systems with a high
degree of seasonal fluctuation in water
demand.
One disadvantage of reverse osmosis
is its high capital and operating costs.
For systems; of less than 3.8 million
liters per day (1 million gallons per day
[MGD]), operating costs range from $3
to $6 per 3,800 liters (thousand gal-
lons) of treated water. Capital costs
range from $1 to $2 per 3.8 liters (gal-
lon) of capacity, depending on the
level of pretreatment required. Manag-
ing the wastewater (brine solution) is
also a potential problem for systems
using reverse o-;r,,osis.
Electrodialysis is a process that also
uses membranes. In this process,
however, direct electrical current is
used to attract ions to one side of the
treatment chamber. Electrodialysis sys-
tems include a source of pressurized
water, a direct current power supply,
and a pair of selective membranes.
Multistage units, in which membrane
pairs are "stacked" in the treatment
vessel, can Increase the removal ef-
ficiency. Electrodialysis is very effec-
tive in removing fluoride and nitrate,
and can also remove barium, cad-
mium, and selenium.
Ion Exchange
Ion exchange units (Figure 7-2) can be
used to remove any ionic (charged)
substance from water, but are usually
used to remove hardness and nitrate
from ground water. Inorganic substan-
ces are removed by adsorption onto
an exchange medium, usually a syn-
thetic resin. One ion is exchanged for
another on the surface of the medium,
which is regenerated with the ex-
changeable ion before treatment
operations. Ion exchange waste is
highly concentrated and requires
careful disposal.
The ion exchange process, like
reverse osmosis, can be used with
fluctuating flow rates. Pretreatment
58
-------
with filtration might be needed if the in-
fluent has a high level of suspended
solids. Ion exchange units are also
sensitive to the presence of competing
ions. For example, influent with high
levels of hardness will compete with
other cations (positive ions) for space
on the exchange medium, and the ex-
change medium must be regenerated
more frequently.
Ion exchangers often use sodium
chloride to regenerate the exchange
medium because of the chemical's low
cost. However, this might result in a
high sodium residual in the finished
water. High sodium residual might be
unacceptable for individuals with salt-
restricted diets. This problem can be
avoided by using other regenerant
materials, such as potassium chloride.
Ion exchange effectively removes
more than 90 percent of barium, cad-
mium, chromium (III), silver, radium,
nitrites, selenium, arsenic (V),
chromium (VI), and nitrate. Ion ex-
change is usually the best choice
for small systems to remove
radionuclides.
Activated Alumina
Activated alumina systems are il-
lustrated in Figure 7-3. Activated
alumina is a commercially available
ion exchange medium, primarily used
to remove fluoride from ground water.
The activated alumina medium is
regenerated using a strong sodium
hydroxide solution. Because this in-
creases the pH level of the water, sul-
furic acid must be added to the water
after it leaves the exchange unit.
Activated alumina removes over 90
percent of arsenic (V), fluoride, and
selenium (IV), and 70 percent of
selenium (VI). ft also effectively
removes iron. It is not effective in
removing barium, cadmium, and
radium.
While activated alumina effectively
removes several contaminants, it can
be hazardous because of the strongly
acidic and basic solutions used.
Another disadvantage of activated
F««d
(Raw Wal.r)
Courtesy of MiffiDOre Corporation
PROCESS FLOW THROUGH SPIRAL-WOUND REVERSE OSMOSIS UNIT
r
Hoilow Fiber
V— f^
HOUOW.FIBEP. REVERSE OSMOSIS UNIT
Figure 7-1. Two types of reverse osmosis membranes.
Figure 7-2. Ion exchange treatment system.
59
-------
Ac;a-
- Treated Watar-
TREATMENT AND
OCWNFLOW RINSE
BACKWASH AND
UPPLOW RINSE
Tr«alm«nt Unit
Trsalment Unit
UPFLOW
REGENErlATION
DOWNFUOW
REGENERATION
Figure 7-3. Activated alumina systems: Operating mode flow schematics.
alumina is the long contact time re-
quired (5 minutes, compared to 2 to 3
minutes for ion exchange). Finally, ac-
tivated alumina's costs are higher than
those for bn exchange. Waste
management might also increase
costs because of high concentrations
of aluminum and other contaminants
in the waste stream, as well as high
pH.
Technologies tor Radon Removal:
Aeration and Granular Activated
Carbon
Several tow-cost/low-technology aera-
tion techniques can effectively lower
the concentration of radon in drinking
water. (Radon is a naturally occurring
radioactive gas that contaminates
ground water in some geographical
areas.) These techniques include
open air storage with no mixing, a flow-
through 'reservoir system with influent
control devices, and a flow-through
reservoir with bubble aeration. Initial
studies found that minimal aeration
applied during 30 hours of storage can
achieve more than 95 percent radon
removal:14
Another relatively low-cost aeration
technique is a multistaged diffused
bubble aeration system manufactured
by Lowry Engineering, Inc. of Unity,
Maine. This process is applied in'a
box-shaped, low profile vessel made
of high density polyethylene. It is
designed to remove volatile organic
chemicals as well as radon. Packed
tower aeration also is commonly used
to remove radon. The size of the pack-
ed tower required for radon removal
generally is much less than for or-
ganics removal.
Granular activated carbon (GAG) can
also effectively remove radon from
water. There are, however, concerns
about worker safety and disposal of
carbon that is contaminated with
radon.15
Aeration and GAG are discussed in
greater detail in Chapter 6, Treating
Organic Contaminants in Drinking
Water.
1 N.E. Kinner. C.E. Lessard, G.S. Schell, and K.R. Fox. "Low-Cost/Low-Technology Aeration Techniques for Removing Radon from Drink-
ing Water," Environmental Research Brief, U.S. Environmental Protection Agency, Office of Research and Development, September 1987.
EPA/600/M-87/031.
15 N.E. Kinner. C.E. Lessard, and G.S. Schell, Radon Removal from Small Community Water Supplies Using Granular Activated Carbon
and Low Teclmology/LowCost Techniques, U.S. Environmental Protection Agency Cooperative Research Agreement CR-81-2602-01-0.
60
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Chapter Eight
Resources
Safe Drinking Water Hotline
1-800-426-4791
1-202-382-5533
This hotline, run by the U.S. Environ-
mental Protection Agency, provides
information on drinking water regula-
tions, policies, and documents to the
public, state and local government,
public water systems, and, consultants.
The Safe Drinking Water Hotline's
hours are 8:30 a.m. to 4:30 p.m. East-
ern Standard Time, Monday through
Friday excluding holidays.
U.S. Environmental Protection
Agency Regional Offices
Regional offices of the U.S. Environ-
mental Protection Agency are listed in
Table 8-1.
State Drinking Water Agencies
State agencies responsible for public
water supervision are listed in Table 8-2.
Organizations Assisting Small
Systems
American Water Works Association
(AWWA) Small Systems Program
This program provides information,
training, and technical assistance to
small systems, in coordination with
state regulatory agencies and other
organizations assisting small systems.
Contact the AWWA at 6666 W. Quincy
Avenue, Denver, CO 80235 (303-794-
7711) for the name of a contact for the
small systems program in your area.
National Rural Water Association
(NRWA)
This organization provides training
and technical assistance to small sys-
tems. Contact the NRWA office at P.O.
Box 1428, Duncan. OK 73534 (405-
252-0629) for national information and
the name of your local contact.
Rural Community Assistance
Program (RCAP)
This program consists of six regional
agencies formed to develop the
capacity of rural community officials to
solve local water problems, ft provides
onsite technical assistance, training,
and publications, and works to im-
prove federal and state government
responsiveness to the needs of rural
communities. Table 8-3 lists the six
RCAP regional agencies.
Farmers Home Administration
(FmHA)
The Farmers Home Administration
provides grants and loans for rural
water systems and communities with
populations less than 25,000. Contact
FmHA at USDA/FmHA, 14th and Inde-
pendence Avenue SW, Washington,
DC 20250 (202-447-4323).
Publications
General
American Water Works Association.
Basic Management Principles for
Small Water Systems. Denver, Co,
1982.
American Water Works Association.
Design and Construction of Small
Water.Systems—A Guide for
Managers. 1984.
American Water Works Association.
Introduction to Water Treatment. Den-
ver, CO, 1984.
Concern, Inc. Drinking Water: A Com-
munity Action Guide. Washington, DC
(1794 Columbia Road, NW, Washing-
ton, DC 20009), December 1986.
National Rural Water Association.
Water System Decision Makers: An
Introduction to Water System Opera-
tion and Maintenance. Duncan, OK,
1988.
Opltow. A monthly publication of the
American Water Works Association
focusing on the "nuts and bolts" con-
cerns of treatment plant operators.
61
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Table 8-1. EPA Regional Offices
EPA Headquarters
401 M Street, SW
Washington, DC 20460
202-382-5043
EPA Region 1
JFK Federal Building
Boston, MA 02203
617-565-3424
Connecticut, Massachusetts,
Maine, New Hampshire,
Rhode Island, Vermont
EPA Region 2
26 Federal Plaza
New York, NY 10278
212-264-2515
New Jersey, New York,
Puerto Rico, Virgin Islands
EPA Region 3
841 Chestnut Street
Philadelphia, PA 19107
215-597-9370
Delaware, Maryland, Pennsylvania,
Virginia, West Virginia,
District of Columbia
EPA Region 4
345 Courtland Street, NE
Atlanta, GA 30365
404-347-3004
Alabama, Florida, Georgia,
Kentucky, Mississippi,
North Carolina, South Carolina,
Tennessee
EPA Region 5
230 South Dearborn Street
Chicago, IL 60604
312-353-2000
Illinois, Indiana, Ohio, Michigan
Minnesota, Wisconsin
EPA Region 6
1445 Ross Avenue
Dallas, TX 75202
214-655-2200
Arkansas, Louisiana, New Mexico,
Oklahoma, Texas
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
913-236-2803
Iowa, Kansas, Missouri, Nebraska
EPA Region 8
One Denver Place
999 18th Street, Suite 1300
Denver, CO 80202
303-293-1692
Colorado, Montana, North Dakota,
South Dakota, Utah, Wyoming
EPA Region 9
215 Fremont Street
San Francisco, CA 94105
415-974-8083
Arizona, California, Hawaii, Nevada,
American Samoa, Guam,
Trust Territories of the Pacific
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
206-442-1465
Alaska, Idaho, Oregon, Washington
62
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Table 8-2. State Drinking Water Agencies
Region I
Connecticut Department of Health Services
Water Supplies Section
150 Washington Street
Hartford, CT 06106
203-566-1251
Division of Water Supply
Department of Environmental Protection
One Winter Street, 9th Floor
Boston, MA 02108
617-292-5529
Drinking Water Program
Division of Health Engineering
Maine Department of Human Services
State House (STA 10)
Augusta, ME 04333
207-289-3826
Water Supply Engineering Bureau
Department of Environmental Services
P.O. Box 95, Hazen Drive
Concord, NH 03302-0095
603-271-3503
Division of Drinking Water Quality
Rhode Island Department of Health
75 Davis Street, Cannon Building
Providence, Rl 02908
401-277-6867
Water Supply Program
Vermont Department of Health
60 Main Street
P.O. Box 70
Burlington, VT 05402
802-863-7220
Region II
Bureau of Safe Drinking Water
Division of Water Resources
New Jersey Department of
Environmental Protection
P.O. Box CN-029
Trenton, NJ 06825
609-984-7945
Bureau of Public Water Supply Protection
New York State Department of Health
2 University Place
Western Avenue, Room 406
Albany, NY 12203-3313
518-458-6731
Water Supply Supervision Program
Puerto Rico Department of Health
P.O. Box70184
San Juan, PR 00936
809-766-1616
Planning and Natural Resources
Government of Virgin Islands
Nifky Center, Suite 231
St. Thomas, Virgin Islands 00802
Region III
Office of Sanitary Engineering
Delaware Division of Public Health
Cooper Building
P. O. Box 637
Dover, DE 19903
302-736-4731
Water Supply Program
Maryland Department of the Environment
Point Breeze Building 40, Room 8L
2500 Broening Highway
Dundalk, MD 27224
301-631-3702
Water Hygiene Branch
Department of Consumer and Regulatory Affairs
5010 Overlook Avenue, SW
Washington, DC 20032
202-767-7370
Division of Water Supplies
Pennsylvania Department of Environmental
Resources
P.O. Box 2357
Harrisburg, PA 17105-2357
717-787-9035
(continued on next page)
63
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Table 8-2. State Drinking Water Agencies (continued)
Evironmental Engineering Division
Office of Environmental Health Services
State Department of Health
Capital Complex Building 3, Room 550
1900 Kanawha Blvd., East
Charleston, WV 25305
304-348-2981
Division of Water Supply Engineering
Virginia Department of Health
James Madison Building
109 Governor Street
Richmond, VA 23219
804-786-1766
Region IV
Water Supply Branch
Department of Environmental Management
1751 Congressional W.L Dickinson Drive
Montgomery, AL 36130
205-271-7773
Drinking Water Section
Department of Environmental Regulation
Twin Towers Office Building
2600 Blair Stone Road
Tallahassee, FL 32399-2400
904-487-1779
Drinking Water Program
Georgia Environmental Protection Division
Floyd Towers East, Room 1066
205 Butler Street, S.E.
Atlanta, GA 30334
404-656-5660
Drinking Water Branch
Division of Water
Department of Environmental Protection
18 Reilly Road, Frankfort Office Park
Frankfort, KY 40601
502-564-3410
Division of Water Supply
State Board of Health
P.O. Box 1700
Jackson, MS 39215-1700
601-354-6616/490-4211
Public Water Supply Section
Division of Environmental Health
Department of Environment, Health and
Natural Resources
P.O. Box 27687
Raleigh, NC 27611-7687
919-733-2321
Bureau of Drinking Water Protect
Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
803-734-5310
Division of Water Supply
Tennessee Department of Health
and Environment
150 Ninth Avenue, North
Terra Building, 1st Floor
Nashville, TN 37219-5404
615-741-6636
Region V
Division of Public Water Supplies
Illinois Environmental Protection Agency
2200 Churchill Road
P.O. Box19276
Springfield, IL 62794-9276
217-785-8653
Public Water Supply Section
Office of Water Management
Indiana Department of Environmental Manage-
ment
105 South Meridian
P.O. Box 6015
Indianapolis, IN 46206
317-633-0174
Division of Water Supply
Michigan Department of Public Health
P.O. Box30195
Lansing, Ml 48909
517-335-8318
Minnesota Department of Health
Section of Water Supply and Well Management
Division of Environmental Health
925 S.E. Delaware Street
P.O. Box 59040
Minneapolis, MN 55459-0040
612-627-5170
(continued on next page)
64
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Table 8-2. State Drinking Water Agencies (continued)
Division of Public Drinking Water
Ohio Environmental Protection Agency
1800 WaterMark Drive
P.O. Box 1049
Columbus, OH 43266-0149
614-644-2752
Bureau of Water Supply
Department of Natural Resources
P.O. Box 7921
Madison, Wl 53707
608-267-7651
Region VI
Division of Engineering
Arkansas Department of Health
4815 West Markham Street - Mail Slot 37
Little Rock, AR 72205-3867
501-661-2000
Office of Public Health
Louisiana Department of Health and Hospitals
P.O. Box 60630
New Orleans, LA 70160
504-568-5105
Drinking Water Section
New Mexico Health and Environment Department
1190 St. Francis Drive
Room South 2058
Santa Fe, NM 87503
505-827-2778
Water Quality Service
Oklahoma State Department of Health
P.O. Box 53551
Oklahoma City, OK 73152
405-271-5204
Bureau of Environmental Health
Texas Department of Health
1100 W. 49th Street
Austin, TX 78756-3199
512-458-7533
Region VII
Surface and Groundwater Protection Bureau
Environmental Protection Division
Iowa Department of Natural Resources
Wallace State Office Building
900 East Grand Street
Des Moines, IA 50319
515-281-8998
Public Water Supply Section
Bureau of Water
Kansas Department of Health and Environment
Forbes Field, Building 740
Topeka, KS 66620
913-296-1500
Public Drinking Water Program
Division of Environmental Quality
Missouri Department of Natural Resources
P.O. Box 176
Jefferson City, MO 65102
314-751-5331
Division of Drinking Water and Environmental
Sanitation
Nebraska Department of Health
301 Sentenial Mall South
P.O. Box 95007, 3rd Floor
Lincoln, NE 68509
402-471-2541
Region VIII
Drinking Water Program
Colorado Department of Health
4210 East 11th Avenue
Denver, CO 80220
303-320-8333
Water Quality Bureau
Department of Health and Environmental Scien-
ces
Cogswell Building, Room A206
Helena, MT 59620
406-444-2406
Division of Water Supply and Pollution Control
ND State Department of Health and Consolidated
Laboratories
1200 Missouri Avenue
R O. Box 5520
Bismark, ND 58502-5520
702-224-2370
Office of Drinking Water
Department of Water and Natural Resources
Joe Foss Building
523 East Capital Avenue
Pierre, SD 57501
605-773-3151
(continued on next page)
65
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Table 8-2. State Drinking Water Agencies (continued)
Bureau of Drinking Water/Sanitation
Utah Department of Health
P.O. Box 16690
Salt Lake City, UT 84116-0690
801-538-6159
DEQ - Water Quality
Herschler Building, 4 West
122 West 25th Street
Cheyenne, WY 82002
307-777-7781
Region IX
Field Services Section
Office of Water Quality
2655 East Magnolia Street
Phoenix, AR 85034
602-257-2305
Office of Drinking Water
California Department of Health Services
714 P Street. Room 692
Sacramento, CA 95814
916-323-6111
Safe Drinking Water Branch
Environmental Management Division
P.O. Box 3378
Honolulu, HI 96801-9984
808-548-4682
Public Health Engineering
Nevada Department of Human Resources
Consumer Health Protection Services
505 East King Street, Room 103
Carson City, NV 89710
702-885-4750
Guam Environmental Protection Agency
Government of Guam
Harmon Plaza Complex Unit D-107
130 Rojas Street
Harmon, Guam 96911
Division of Environmental Quality
Commonwealth of the Northern Mariana Islands
P.O. Box 1304
Saipan, CM 96950
670-322-9355
Marshall Islands Environmental Protection
Authority
P.O. Box 1322
Majuro, Marshall Islands 96960
Via Honolulu
Government of the Federated States of Micronesia
Department of Human Resources
Kolonia, Pohnpei 96941
Palau Environmental Quality Protection Board
Hospital
Koror, Palau 96940
Region X
Alaska Drinking'Water Program
Wastewater and Water Treatment Section
Department of Environmental Conservation
P.O. Box O
Juneau, AK 99811-1800
907-465-2653
Bureau of Water Quality,
Division of Environmental Quality
Idaho Department of Health
and Welfare
Statehouse Mail
Boise, ID 83720
208-334-5867
Drinking Water Program
Department of Human Resources
Health Division
1400 S.W. 5th Avenue, Room 608
Portland, OR 97201
503-229-6310
Drinking Water Section
Department of Health
Mail Stop LD-11, Building 3
Airdustrial Park
Olympia, WA 98504
206-753-5954
66
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Table 8-3. Rural Community Assistance Program (RCAP). Agencies
Community Resources Group, Inc.
2705 Chapman
Springdale, AR 72764
501-756-2900
Great Lakes Rural Network
109 South Front Street
Freemont, OH 43420
419-334-8911
Midwest Assistance Program, Inc.
P.O. Box 81
New Prague, MN 56071
612-758-4334
Rural Community Assistance Corporation
2125 19th Street, Suite 203
Sacramento, CA 95818
916-447-2854
Rural Housing improvement, Inc.
218 Central Street, Box 429
Winchendon, MA 01475-0429
617-297-1376
Virginia Water Project, Inc.
Southeastern Rural Community
Assistance Program
702 Shenandoah Avenue, NW
P.O. Box 2868
Roanoke, VA 24001
703-345-6781
Publications (continued)
Schautz, Jane W. The Self-Help
Handbook. This manual gives specific
guidelines and techniques for estab-
lishing self-help projects (projects
where the community does some of
the work itself to save money). Focus
is on improving or creating water and
wastewater systems in small rural
communities. For ordering information,
contact: Rensselaerville Institute,
Rensselaerville, NY 12147 (518-797-
3783).
U.S. Environmentai Protection
Agency, Office of Drinking Water.
Guidance Manual for Compliance with
the Filtration and Disinfection Require-
ments for Public Water Systems Using
Surface Water Sources. EPA 570/9-89-
018. October 1989.
U.S. Environmental Protection
Agency, Office of Drinking Water.
Manual of Individual Water Supply
Systems. EPA 570/9-82-004. October
1982.
Sampling
U.S. Environmental Protection Agen-
cy, Office of Research and Develop-
ment. Handbook for Sampling and
Sample Preservation of Water and
Wastewater. EPA 600/4-82-029. Sep-
tember 1982.
Filtration
American Waterworks Association
Research Foundation. Manual of
Design for Slow Sand Filtration. (To be
published Fall 1990.)
Huisman, L and Wood, WE. Slow
Sand Filtration. World Health Or-
ganization, Geneva. 1974.
Slezak, LA. and Sims, R.C. "The Ap-
plication and Effectiveness of Slow
Sand Filtration in the United States."
Journal AWWA, 76:1238-43.1984.
Visscher, J.T., Paramasivam, R.,
Raman, A., and Heijnen, H.A. Slow
Sand Filtration for Community Water
Supply. Technical Paper 24. Interna-
tional Reference Centre for Com-
munity Water Supply and Sanitation,
The Hague, The Netherlands. 1987.
Disinfection
American Waterworks Association.
Water Chlorination Principles and
Practices (M20). 1973.
SMC Martin, Inc. Microorganism
Removal for Small Water Systems.
EPA 570/9-83-012. Valley Forge, PA.
June 1983.
Corrosion Control
U.S. Environmental Protection Agen-
cy, Office of Drinking Water. Corrosion
Manual for Internal Corrosion of Water
Distribution Systems. EPA 570/9-84-
001. April 1984.
Economic and Engineering Services.
Lead Control Strategies. American
Water Works Association Research
Foundation. Denver, CO. 1989.
Radlonuclide Removal
Kinner, N.E., Lessar, C.E., Schell,
G.S., and Fox, K.R., "Low Cost/Low-
Technology Aeration Techniques for
Removing Radon from Drinking
Water." EPA/600/M-87-031. U.S.
Environmental Protection Agency,
Office of Research and Development.
September 1987.
67
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SMC Martin, Inc. Radionuclide
Removal for Small Public Water Sys-
tems. EPA 570/9-83-010. Valley
Forge, PA. June 1983.
Wellhead Protection
U.S. Environmental Protection Agency,
Office of Ground-Water Protection.
Wellhead Protection: A Decision
Maker's Guide. 1987.
U.S. Environmental Protection Agency,
Office of Ground-Water Protection.
Developing a State Wellhead Protec-
tion Program: A User's Guide to Assist
State Agencies Under the Safe Drink-
ing Water Act. 1988.
U.S. Environmental Protection Agency,
Office of Ground-Water Protection.
Ground-Water Protection Document
Request Form.
Costs/Financial Management
American Water Works Association.
Water Utility Capital Financing (M 29).
1988.
Gumerman, B.C., Burris, B.E., and
Hansen, S.P. Estimation of Small Sys-
tem Water Treatment Costs. Final
Report. CuIpAVesner/Culp. Municipal
Environmental Research Lab, Cincin-
nati, OH, 1984.
U.S. Environmental Protection Agency,
Office of Water. A Water and Waste-
water Manager's Guide for Stay ing
Financially Healthy. EPA 430/09-89-
004. July 1989.
U.S. Environmental Protection Agency,
Office of Ground-Water Protection.
Local Financing for Wellhead Protec-
tion. 1989.
Consultants
Directory—Professional Engineers in
Private Practice. Published by the
National Society of Professional
Engineers. Contact SPE Order Depart-
ment, 1420 King Street, Alexandria,
VA22314.
Who's Who in Environmental Engineer-
ing. Published by the American
Academy of Environmental Engineers.
Contact the American Academy of
Environmental Engineers, 132 Holiday
Court, Suite 206, Annapolis, MD
21401.
The Federal Register
The Federal Register is published
daily to [make available to the public
regulations and legal notices issued
by federal agencies. It is distributed by
the U.S. Government Printing Office,
Washington, DC 20402. To order
copies, call 1-202-783-3238.
A wide Variety of publications on
specific topics of concern to water sys-
tems is available from the American
Water Works Association and the Na-
tional Rural Water Association.
68
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Appendix A
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. The laboratory will usually
provide specially prepared sampling
containers, properly sterilized and con-
taining sodium thiosulfate to destroy
any remaining chlorine. The following
steps should be followed in coliform
sampling:
1. Use only containers that are
provided by the bacteriological
laboratory and that have been
prepared for coliform sampling. Fol-
low all instructions for sample con-
tainer handling and storage.
The containers are sterile. Do
not open them before use and do
not rinse them.
2. 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
• Leaking faucets that permit
water to run over the outside of
the faucet
3. Always allow the water to flow
moderately from a faucet 2 or 3
minutes before taking the sample.
4. Hold the sample container at the
base, keeping hands away from
the container neck. Be sure the in-
side of the container cap is
protected and does not touch
anything.
5. Without adjusting the flow, fill the
sample container, leaving about 20
percent air space at the top.
Replace the cap immediately. If the
sample is taken incorrectly, take
another sample container—do not
reuse the original bottle.
6. Take a second sample and
measure the concentration of the
disinfectant and record relevant in-
formation (date, time, concentra-
tion, place, sampler, etc.).
7. Package the bacteriological sample
for delivery to the laboratory.
Record all pertinent field informa-
tion on a form and on the sample
container label.
8. Samples must be cool during ship-
ment to the laboratory. Use insu-
lated boxes for shipping containers
if needed, or refrigerate during
transit.
Do not allow more than 30 hours be-
tween sampling and test times.
Be sure the laboratory can process
the samples immediately upon receipt.
Source: SMC Martin, Inc., Microorganism Removal for Small Water Systems, June 1983.
EPA 570/9-83-010.
69
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Checklist:
Some Factors
Affecting Water
Treatment
System
Performance
Administration
1. Does the manager have first-hand
knowledge of plant needs through
plant visits and discussions with
operators?
2. Are there long-range plans for
facility replacement, alternative
source waters, emergency
response, etc.?
3. Is there an adequate number of per-
sonnel to accomplish necessary
operational activities?
4. Are staff adequately trained and
able to make proper operation and
maintenance decisions?
5. Are adequate funds available for
spare parts, improvements or re-
placement of equipment, required
chemicals, etc.?
6. Are the plant unit processes ade-
quate to meet the demand for
finished water?
7. Is the staff aware of the potential
sources of contamination that might
affect the drinking water supply and
the available management
methods?
Maintenance
1. Is there an effective scheduling and
recording procedure to prevent
equipment failures, excessive
downtime, etc. resulting in plant per-
formance or reliability problems?
2. Is the spare parts inventory ade-
quate to prevent long delays in
equipment repairs?
3. Are procedures available to initiate
maintenance activities on equip-
ment operating irregularities? Are
emergency response procedures in
place to protect process needs if
critical equipment breaks down?
4. Are good housekeeping proce-
dures followed?
5. Are equipment reference sources
available (such as operation and
maintenance manuals, equipment
catalogs, etc.)?
6. Does the plant staff have neces-
sary expertise to keep equipment
operating and to make equipment
repairs when necessary?
7. Are technical resources (such as
equipment suppliers or contract ser-
vice) available to provide guidance
for repairing, maintaining, or install-
ing equipment?
8. Are old or outdated pieces of equip-
ment replaced as necessary to
prevent excessive equipment
downtime-or inefficient process per-
formance/reliability?
Design
1. Is the plant design adequate for
raw water quality (e.g., turbidity,
temperature, seasonal variation,
etc.)?
2. Do facilities exist to control raw
water quality entering the plant
(e.g., can intake levels be varied,
can chemicals be added to control
aquatic growth, do watershed
management practices adequately
protect raw water quality)?
3. Are the size of filters and type,
depth, and effective size of filtration
media adequate? Are the surface
wash and backwash facilities ade-
quate to maintain a clear filter bed?
4. Are design features of the disinfec-
tion system adequate (proper
mixing, detention time, feed rates,
proportional feed, etc.)?
5. Are sludge facilities and size of the
sludge disposal area adequate?
6. Do process control features provide
adequate measurement of plant
flow rate, backwash flow rate, filtra-
tion rate, and flocculation mixing in-
71
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puts? Do chemical feed facilities
provide adjustable feed ranges that
are easily set for operation at all re-
quired dosages? Are chemical
feed rates easily measured?
7. Are automatic monitoring or control
devices used where needed to
avoid excessive operator time for
process control and monitoring?
8. Are standby units for key equip-
ment available to maintain process
performance during breakdown or
during preventive maintenance ac-
tivities?
Operation
1. Are plant and distribution monitor-
ing tests representative of perfor-
mance?
2. Is the proper process control test-
ing performed to support opera-
tional control decisions?
3. Does the plant staff have sufficient
understanding of water treatment
process control testing and plant
needs to make proper process con-
trol adjustments?
4. Has the plant staff received ap-
propriate operational information
from technical resources (e.g.,
design engineer, equipment repre-
sentative, state trainer or inspector)
to enable them to make proper
operational decisions?
5. Does the operation and main-
tenance manual/procedure provide
appropriate guidance for operation-
al decisions? Do operators utilize
the manual?
6. Are distribution system operating
procedures adequate to protect the
integrity of finished water (e.g.,
flushing, reservoir management)?
Source: Adapted from U.S. Environmental Protection Agency, Office of Research and Development and Center for Environmental Re-
search Information, Summary Report: Optimizing Water Treatment Plant Performance with the Composite Correction Program March
1990.EPA625/8-90/017. '
72
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Appendix C
Selecting a
Consulting
Engineer
Selecting the right consultant involves
the following steps:
1. Identifying potential engineering
firms. Start by drawing up a list of
at least five firms that might be able
to meet your needs. Sources of
names include your own past ex-
perience or that of neighboring
towns, lists maintained by your
state drinking water agency, and
suggestions received from the local
Rural Community Assistance
Program. Local professional en-
gineering societies may be able to
provide lists of members who spe-
cialize in drinking water treatment
work. The National Society of
Professional Engineers and the
American Academy of Environmen-
tal Engineers have lists of their
members available (see Chapter 8,
Resources).
2. Issuing a Request for Proposals.
Notify engineering firms that you
are interested in their services. One
good way to do this is by preparing
a Request for Proposals (RFP). In
your RFP, briefly describe your
town's water treatment problem
and request proposals from consult-
ants on how they would solve it.
Depending on your community's
size and the nature of your
problem, the RFP may be a letter to
the engineering firms on your list or
it may be a longer, more formal
document. You may wish to adver-
tise your RFP. In any case, it
should include at least the following:
• A brief description of the problem
• A statement telling what it is you
want the consulting firm to do
• The deadline by which your
town must receive the proposal
• The person in your town to con-
tact for additional information
• Standards by which the
proposals will be judged
• The place and time the proposal
must be submitted
3. Interviewing candidate engineer-
ing firms. When you receive the
proposals, check to see if they
meet your judging standards, and
are within an acceptable cost
range. From those that meet the
standards, select three or four and
interview each firm individually.
The following criteria may be help-
ful in evaluating engineering firms:
• Small town experience. Does
the firm have experience with
communities like yours? Which
towns have they worked with in
the recent past?
• System design experience.
Does the firm have experience
in designing systems for small
communities? What types of
systems has the firm actually
recommended, designed, and in-
stalled? When were they in-
stalled? How are these systems
working? What were the es-
timated costs? What are the
present operation and main-
tenance needs and costs of
these systems? What systems
has the firm recommended for
communities that are most like
your own? Ask for the cost per
dwelling serviced, the up-front
assessments, and monthly char-
ges for the last few projects of a
size and technology comparable
to your situation.
Sources: Adapted from U.S. Environmental Protection Agency, Office of Municipal Pollution
Control, It's Your Choice: A Guidebook for Local Officials on Small Community Wastewater
Management Options, September 1987. EPA 430/9-87-006; SMC Martin, Inc., Microor-
ganism Removal for Small Water Systems, June 1983. EPA 570/9-83-012.
73
-------
• Experience with financial in-
stitutions and funding agen-
cies. What experience has the
firm had in helping communities
get financing from commercial
sources (banks, bond sales}?
What experience has the firm
had in dealing with state grant
or loan programs or Farmers
Home Administration grant and
loan programs? What ex-
perience has the firm had in
working with lending institutions
or financial consultants?
• Experience with state and
county agencies. What ex-
perience does the firm have in
working with the state and county
environmental agencies, the
health department, etc.?
• Willingness to work with the
community. If your community
came up with a range of accept-
able user costs, would the en-
gineer be willing to use these
estimates as guidelines to
design a drinking water treat-
ment system? How does the
firm plan to handle public par-
ticipation in this project?
• Willingness to work for the
community. Does the firm have
any experience in using tech-
nologies and maintenance
programs that are different from
what the state and county agen-
cies have traditionally ac-
cepted? Does the firm have the
willingness and capability to util-
ize innovative or alternative tech-
nology where appropriate?
(Some engineers have dealt
only with large centralized treat-
ment systems and might not be
familiar or experienced with
other alternatives.)
• Staff capabilities and
workload. What projects is the
firm now working on and what
new ones may be coming soon?
Which people on their staff will
be devoted to your project?
What time schedule does the
firm propose for completing your
work? Does the firm use sub-
contractors for certain work? If
so, which firms and for what
work?
• : Cost of engineering work. Be
i prepared to pay for good en-
gineering work. Do not choose
your engineer only on the basis
; of cost. It is well worth spending
a little extra to get an engineer
who will design a system that
; will provide service at lower cost
1 for years to come. Ask the en-
gineer to briefly explain the
firm's estimated fee. Make sure
you understand exactly what ser-
vices will be provided. Is there a
1 distinction between basic ser-
vices and additional services?
' What circumstances could sig-
nificantly change the estimate?
4. Checking references. Be sure to
check references for the firms you
thought were best. Talk to repre-
sentatives from communities the
firm has recently worked for. Ask
about the overall experience,
problems or special situations that
arose, delays, etc.
5. Selecting a firm and contracting
for its services. The final selection
of a firm involves evaluating all the
information you have gathered.
Once you have selected a firm, you
must negotiate and sign a contract
for their services. The form of this
coptract and the payment may be
governed by the method your town
will use to finance this part of your
project. Be sure to consider this
aspect in your evaluation. When
tha't is done, you are ready to begin
working with the engineer to
evaluate and solve your town's
drinking water treatment problems.
The consultant should do the following
to achieve the best system design and
to simplify the operator's job:
• Establish a high level of com-
munication with the community and
representatives of the drinking
water treatment facility, and be-
come familiar with the unique fea-
tures and requirements of the
utility, as well as the responsive-
ness of regional chemical suppliers
and equipment vendors.
• Conduct sufficient laboratory and
pilot plant studies and observations
of the source waters to fully charac-
terize 'them. New facilities should
be adequate to handle the full
range of expected water condi-
tions, including foreseeable water
quality deterioration.
• Initiate the design process with a
thorough review of all possible non-
treatment or minimal treatment ap-
proaches. Consider potential ease
of maintenance, adequate space
and light, and simplicity in the
design and equipment. Avoid over-
ly elaborate control systems, and in-
clude appropriate redundance (i.e.,
never only one chlorinator).
• Avoid dead ends in the distribution
system. Provide equipment for
flushing and sampling, for storage,
and for emergency chlorination of
the distribution system.
« Allow operating personnel to par-
ticipate in design decisions and ob-
serve construction progress.
* Prepare operation and main-
tenance manuals, which include
the following information:
— the original design concepts
— description and drawings of
tho facility as constructed
- normal operational procedures
— emergency operational proce-
dures
- organized collection of
vendors' literature
- safety considerations and re-
quirements
74
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— schematics with all valves num-
bered to correspond to
detailed operational procedures
- maintenance procedures
Provide startup assistance and
training and followup engineering
services.
75
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Appendix D
Chlorine
Residual
Monitoring
Chbrine in its most active form—as
"free residual chlorine"—is stable only
in the absence of agitation, sunlight,
and certain organic and inorganic
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 disin-
fectant analysis should be analyzed
immediately. Specially prepared sam-
pling containers, properly cleansed,
sterilized, and not containing sodium
thiosulfate should be used.
In general, the same sampling precau-
tions described in Appendix A for
taking coliform samples should be ob-
served, but in addition:
1. Draw the sample gently, avoiding
agitation.
2. Analyze immediately in the shade
or subdued light. Do not store the
sample.
3. Do not use a bacteriological sam-
pling container, which may contain
a chemical to counteract or destroy
the disinfecting agent.9
Demonstration of Maintaining a
Residual"
The Surface Water Treatment Rule
(SWTR) establishes two requirements
pertaining to the maintenance of a
residual. The first requirement is to
maintain a minimum residual of 0.2
mg/L entering the distribution system.
Also, a detectable residual must be
maintained throughout the distribution
system. These requirements are fur-
ther explained in the following sections.
Maintaining a Residual Entering
the System
The SWTR requires that a residual of
0.2 mg/L be maintained in the water
entering the distribution system at all
times. Continuous monitoring at the
entry point(s) to the distribution sys-
tem is required to ensure that a detec-
table residual is maintained. Any time
the residual drops below 0.2 mg/L, the
system must notify the Primacy Agen-
cy0 prior to the end of the next busi-
ness day. The system is in violation of
a treatment technique if the residual
level is not restored to 0.2 mg/L within
4 hours and filtration must be installed.
(If the Primacy Agency finds that the
exceedence was caused by an un-
usual and unpredictable circumstance,
it may choose not to require filtration.)
In cases where the continuous
monitoring equipment fails, grab
samples every 4 hours may be used
for a period of 5 working days while
the equipment is restored to operable
conditions.
The system must record, each day of
the month, the lowest disinfectant
residual entering the system and this
residual must not be less than 0.2
mg/L. Systems serving less than or
equal to 3,300 people may take grab
samples in lieu of continuous monitor-
ing at the frequencies shown in the
box below:
System Population Samples/day*
<500
501-1,000
1,001-2,500
>2,501-3,000
1
2
3
4
•Samples must be taken at dispersed
time intervals as approved by the
Primacy Agency.
a From SMC Martin, Inc., Microbiological Removal for Small Water Systems, June 1983.
EPA 570/9-83-010.
b Adapted from U.S. Environmental Protection Agency, Guidance for Compliance with the
Filtration and Disinfection Requirements for Public Water Systems Using Surface Water
Sources, October 1989.
0 The Primary Agency is a state with primary enforcement responsibility for public water sup-
plies, or EPA in the case of a state that has not obtained primacy.
77
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If the residual concentration falls
below 0.2 mg/L, another sample must
be taken within 4 hours and sampling
continued at least every 4 hours until
the disinfectant residual is a minimum
of 0.2 mg/L.
Maintaining a Residual within the
System
The SWTR also requires that a detec-
table disinfectant residual be main-
tained throughout the distribution
system, with measurements taken at a
minimum frequency equal to that re-
quired by the Total Coliform Rule (54
FR 27543-27568). The same sampling
locations as required for the coliform
regulation must be used for taking the
disinfectant residual or HPC (hetero-
trophic plate count) samples. How-
ever, for systems with both ground-
water and surface water sources (or
ground water under the direct in-
fluence of surface water) entering the
distribution system, residuals may be
measured at points other than coliform
sampling points if these points are
more representative of the disinfected
surface water and allowed by the
Primacy Agency. An HPC level of less
than 500/mL is considered equivalent
to a detectable residual for the pur-
pose of determining compliance with
this requirement, since the absence of
a disinfectant residual does not neces-
sarily indicate microbiological con-
tamination.
Disinfectant residual can be measured
as total chlorine, free chlorine, com-
bined chlorine, or chlorine dioxide (or
HPC level). The SWTR lists the ap-
proved analytical methods for these
analyses. For example, several test
methods can be used to test for
chlorine residual in the water, including
amperometric titration, DPD
colorimetric method, DPD ferrous
titrimetric method, and iodometric
method, as described in the 16th Edi-
tion of Standard Methods for the Ex-
amination of Water and Wastewater,
APHA, AWWA, and WPCF, Wash-
ington, DC, 1985.d
The SWTR requires that a detectable
disinfectant residual be present in 95
percent or more of the monthly distribu-
tion system samples. In systems that
do not filter, a violation of this require-
ment for 2 consecutive months caused
by a deficiency in treating the source
water will trigger a requirement for
filtration to be installed. Therefore, a
systefn that does not maintain a
residual in 95 percent of the samples
for 1 month because of treatment
deficiencies, but is maintaining a
residual in 95 percent of the samples
for the following month, will meet this
requirement.
The absence of a detectable disinfec-
tant residual in the distribution system
may be due to a number of factors,
including:
• Insufficient chlorine applied at the
treatment plant
• Interruption of chlorination
• A change in chlorine demand in
either the source water or the dis-
tribution system
• Long standing times and/or long
transmission distances
Available options for systems to cor-
rect trie problem of low disinfectant
residuals within their distribution sys-
tem include:
• Routine flushing
• Increasing disinfectant doses at the
plant
• Cleaning of the pipes (either
mechanically by pigging or by the
addition of chemicals to dissolve
the, deposits) in the distribution sys-
tem to remove accumulated debris
that may be exerting a disinfectant
demand
• Flushing and disinfection of the por-
tions of the distribution system in
which a residual is not maintained
• Installation of satellite disinfection
feed facilities with booster
chlorinators within the distribution
system
For systems unable to maintain a
residual, the Primacy Agency may
determine that it is not feasible for the
system to monitor HPCs and judge
that disinfection is adequate based on
site-specific conditions.
Additional information on maintaining
a residua! in the system is available in
the American Water Works Assoc-
iation's Manual of Water Supply Prac-
tices and Water Chlorination Principles
and Practices.
Also, portable test kits are available that can be used in the field to detect residual upon approval of the Primacy Agency. These kits may
employ titration or colorimetric test methods. The colorimetric kits employ either a visual detection of a residual through the use of a color
whool, or the detection of the residual through the use of a hand held spectrophotometer.
78
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Appendix E
CT Values
CT Values for Achieving Inactivation of Viruses at pH 6 through 9
(in mg/L-m)
Free
chlorine3
Ozone
aCT values
Los
Inac
vatc
2
3
4
2
3
4
include
II-
»n 0.5'C
6
9
12
0.9
1.4
1.8
Temperature
5'C
4
6
8
0.6
0.9
1.2
10'C
3
4
6
0.5
0.8
1.0
15'C
2
3
4
0.3
0.5
0.6
20'C
1
2
3
0.25
0.4
0.5
25'C
1
1
2
0.15
0.25
0.3
a safety factor of 3.
CT Values for Achieving 99.9 Percent Inactivation of
Giardia Lambliaa
Temperature
Disinfectant pH
0.5'C 5'C
10'C 15'C 20'C 25'C
Free
chtorineb
Ozone
6
7
8
9
6-9
165
236
346
500
2.9
116
165
243
353
1.9
87
124
182
265
1.4
58
83
122
177
44
62
91
132
29
41
61
88
0.95 0.72 0.48
aThese CT values for free chlorine, chlorine dioxide, and ozone will guaran-
tee greater than 99.99 percent inactivation of enteric viruses.
b CT values will vary depending on concentration of free chlorine. Values
indicated are for 2.0 mg/L of free chlorine. CT values for different free
chlorine concentrations are specified in tables in the EPA Guidance Manual
for Compliance with the Filtration and Disinfection Requirements for Public
Water Systems Using Surface Water Sources.
79
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CT Values for Achieving 90 Percent Inactivation of Giardia Lamblia
\ (in mg/L-m) j
Temperature
Disinfectant pH 0.5'C 5'C 10'C 15'C 20'C 25'C
Free
chlorine3
(2 mg/L)
Ozone
6
7
8
9
6-9
55
79
115
167
39
55
81
118
0.97 0.63
29
41
6.1
88
0.48
19
28
41
59
15
21
30
44
10
14
20
29
0.32 0.24 0.16
aCT values will vary depending on concentration of free chlorine. Values indi-
cated are for 2.0 mg/L of free chlorine. CT values for different free chlorine con-
centrations are specified in tables in the EPA Guidance Manual for Compliance
with the Filtration and Disinfection Requirements for Public Water Systems
Using Surface Water Sources.
80
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Appendix F
Sample CT
Calculation for
Achieving
1-log Giardia,
2-log Virus
Inactivation
with Chlorine
Disinfection
A 50,000 GPD slow sand filtration
plant supplies a community of 500
people with drinking water from a
reservoir in a protected watershed.
The raw water supply has the follow-
ing characteristics:
• Turbidity: 5to10NTU
• Total estimated Giardia cyst level:
less than 1 per 100 mL
• pH: 6.5 to 7.5
• Temperature: 5' to 15'C
An overall removal/inactivation of 3
logs for Giardia and 4 logs for viruses
is sufficient for this system. The
Primacy Agency credits the slow sand
filter, which produces water with tur-
bidity ranging from 0.6 to 0.8 NTU,
with a 2-log Giardia and virus removal.
Disinfection must achieve an addition-
al 1-log Giardia and 2-log virus
removal/inactivation to meet overall
treatment objectives.
To begin the calculations for determin-
ing the adequacy of the inactivations
achieved by the disinfection system,
the total contact time must be deter-
mined.
In this plant, chlorine for disinfection is
added prior to the clearwell, which has
a 2,000-gallon capacity. The distance
from the plant to the first customer is
bridged by a 1,000-foot 2-inch trans-
mission main. The contact time
provided in both the clearwell basin
and the distribution pipe up to the first
customer comprises the total contact
time for disinfection.
In the calculations, contact time is rep-
resented by T-io —the time needed for
10 percent of the water to pass
through the basin. In other words, Tio
describes the time, in minutes, that 90
percent of the water remains in the
basin. (For the distribution pipe, con-
tact time is 100 percent of the time
that water remains in the pipe.)
The contact time multiplied by the con-
centration (mg/L) of residual chlorine
in the water is the calculated CT value
for the system. Proved inactivation of
Giardia and viruses are correlated to
calculated CT values in EPA's
Guidance Manual for Compliance with
the Filtration and Disinfection Require-
ments for Public Water Systems Using
Surface Water Sources. (Appendix E
contains excerpts from the CT tables
in the manual.)
The TIO for the clearwell basin can be
determined by tracer studies. (Tracer
study procedures are described in
EPA's Guidance Manual.)
On the day represented in this ex-
ample, the tracer study showed that
the Tio for the clearwell was 40
minutes at the peak hourly flow rate.
At this flow rate, water travels through
the transmission main at 211 feet per
minute. The distance between the
plant and the first customer is 1,000
feet. Thus, the Tio for the distribution
main is 4.7 minutes (1,000 feet divided
by 211 feet per minute).
Other data required for the calculation
are:
• Measured chlorine residual: 2.0
mg/L for the clearwell basin and 1.2
mg/L for the distribution main
• Water temperature: 5"C
• Water pH: 7.5
CT values required to achieve various
levels of inactivation of Giardia and
viruses depending on the water
temperature, pH, and chlorine residual
are provided in the Guidance Manual.
The calculated CT values (CTcaio)
based on actual system data are com-
pared to the CT values in the
Guidance Manual (CT'99.9 in the case
of a 1 -log inactivation) to determine
whether the inactivations achieved are
adequate.
81
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Sinca, with free chlorine, a 1 -log
Giardia inactivation provides greater
than a 4-log virus inactivation, inactiva-
tion of Giardia is the controlling factor
for determining overall reductions.
The calculation of CT and comparison
to CT values for 1-log inactivation of
Giardia provided in the EPA Guidance
Manualls shown in the box below.
For the basin:
CTcalc - Chlorine residual x contact time or
- 2.0 mg/Lx 40 minutes = 80 mg/L-min
From the EPA Guidance Manual, CTgg.9 (3-log finactivation) is
200 mg/L-min atS'C, 2 mg/L chlorine residual, ;and 7.5 pH.
CTcalo/CTg9.g » 80 mg/L-min = 0.4
200 mg/L-min
For the distribution system:
CTcalc = 1.2 mg/L x 4.7 minutes = 5.64 mg/b-min
From the EPA Guidance Manual, CTgg.9 is 183 mg/L-min at 5'C, 1.2 mg/L
chlorine residual, and 7.5 pH.
CTca!c/CT99.9 - 5.64 mg/L-min = 0.03
183 mg/L-min
Summing CTcaio/CTgg.9 for both the basin and the main results in 0.43. This is
equivalent to a 1.29-log Giardia inactivation determined by:
3 X CTcalc/CTgg.g
- 3x0.43-1.29 log
(This calculation is based on a 3-log inactivation; therefore, the ratio is
multiplied by 3.)
Thus, the 1.29-log inactivation
achieved by disinfection in this system
exceeds the 1-log additional inactiva-
tion required to meet overall treatment
objectives.
82
'U.S. Government Printing Office: 1992— 648-003/41811
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