Jumat, 13 Januari 2012

HANDBOOK OF WATER AND WASTEWATER TREATMENT TECHNOLOGIES



HANDBOOK OF WATER AND WASTEWATER TREATMENT TECHNOLOGIES

Chapter I
AN OVERVIEW OF
WATER AND WASTEWATER
TREATMENT
INTRODUCTION
We may organize water treatment technologies into three general areas: Physical
Methods, Chemical Methods, and Energy Intensive Methods. Physical methods of
wastewater treatment represent a body of technologies that we refer largely to as
solid-liquid separations techniques, of which filtration plays a dominant role.
Filtration technology can be broken into two general categories - conventional and
non-conventional. This technology is an integral component of drinking water and
wastewater treatment applications. It is, however, but one unit process within a
modern water treatment plant scheme, whereby there are a multitude of equipment
and technology options to select from depending upon the ultimate goals of
treatment. To understand the role of filtration, it is important to make distinctions
not only with the other technologies employed in the cleaning and purification of
industrial and municipal waters, but also with the objectives of different unit
processes.
Chemical methods of treatment rely upon the chemical interactions of the
contaminants we wish to remove from water, and the application of chemicals that
either aid in the separation of contaminants from water, or assist in the destruction
or neutralization of harmful effects associated with contaminants. Chemical
treatment methods are applied both as stand-alone technologies, and as an integral
part of the treatment process with physical methods.
Among the energy intensive technologies, thermal methods have a dual role in
water treatment applications. They can be applied as a means of sterilization, thus
providing high quality drinking water, and/or these technologies can be applied to
the processing of the solid wastes or sludge, generated from water treatment
applications. In the latter cases, thermal methods can be applied in essentially the
same manner as they are applied to conditioning water, namely to sterilize sludge
contaminated with organic contaminants, and/or these technologies can be applied
to volume reduction. Volume reduction is a key step in water treatment operations,

2 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
because ultimately there is a tradeoff between polluted water and hazardous solid
waste.
Energy intensive technologies include electrochemical techniques, which by and
large are applied to drinking water applications. They represent both sterilization
and conditioning of water to achieve a palatable quality.
All three of these technology groups can be combined in water treatment, or they
may be used in select combinations depending upon the objectives of water
treatment. Among each of the general technology classes, there is a range of both
hardware and individual technologies that one may select from. The selection of not
only the proper unit process and hardware from within each technology group, but
the optimum combinations of hardware and unit processes from the four groups
depends upon such factors as:
1. How clean the final water effluent from our plant must be;
2. The quantities and nature of the influent water we need to treat;
3. The physical and chemical properties of the pollutants we need to remove
or render neutral in the effluent water;
4. The physical, chemical and thermodynamic properties of the solid wastes
generated from treating water; and
5. The cost of treating water, including the cost of treating, processing and
finding a home for the solid wastes.
To understand this better, let us step back and start from a very fundamental
viewpoint. All processes are comprised of a number of unit processes, which are
in turn made up of unit operations. Unit processes are distinct stages of a
manufacturing operation. They each focus on one stage in a series of stages,
successfully bringing a product to its final form. In this regard, a wastewater
treatment plant, whether industrial, a municipal wastewater treatment facility, or
a drinking water purification plant, is no different than, say, a synthetic rubber
manufacturing plant or an oil refinery. In the case of a rubber producing plant,
various unit processes are applied to making intermediate forms of the product,
which ultimately is in a final form of a rubber bale, that is sold to the consumer.
The individual unit processes in this case are comprised of: (1) a catalyst reparation
stage - a pre-preparation stage for monomers and catalyst additives; (2)
polymerization - where an intermediate stage of the product is synthesized in the
form of a latex or polymer suspended as a dilute solution in a hydrocarbon diluent;
(3) followed by finishing - where the rubber is dried, residual diluent is removed
and recovered, and the rubber is dried and compressed into a bale and packaged for
sale. Each of these unit process operations are in turn comprised of individual unit
operations, whereby a particular technology or group pf technologies are applied,
which, in turn, define a piece of equipment that is used along the production line.
Drinking water and wastewater treatment plants are essentially no different. There
are individual unit processes that comprise each of these types of plants that are
applied in a succession of operations, with each stage aimed at improving the
quality of the water as established by a set of product-performance criteria. The
criteria focuses on the quality of the final water, which in the case of drinking water

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 3
is established based upon legal criteria (e.g., the Safe Drinking Water Act, SDWA),
and if non-potable or process plant water, may be operational criteria (e.g., nonbrackish
waters to prevent scaling of heat exchange equipment).
The number and complexity of unit processes and in turn unit operations
comprising a water purification or wastewater treatment facility are functions of the
legal and operational requirements of the treated water, the nature and degree of
contamination of the incoming water (raw water to the plant), and the quantities of
water to be processed. This means then, that water treatment facilities from a
design and operational standpoints vary, but they do rely on overlapping and even
identical unit processes.
If we start with the first technology group, then filtration should be thought of as
both a unit process and a unit operation within a water treatment facility. As a
separate unit process, its objective is quite clear: namely, to remove suspended
solids. When we combine this technology with chemical methods and apply
sedimentation and clarification (other physical separation methods), we can extend
the technology to removing dissolved particulate matter as well. The particulate
matter may be biological, microbial or chemical in nature. As such, the operation
stands alone within its own block within the overall manufacturing train of the
plant. Examples of this would be the roughening and polishing stages of water
treatment. In turn, we may select or specify specific pieces of filtration equipment
for these unit processes.
The above gives us somewhat of an idea of the potential complexity of choosing the
optimum group of technologies and hardware needed in treating water. To develop
a cost-effective design, we need to understand not only what each of the unit
processes are, but obtain a working knowledge of the operating basis and ranges
for the individual hardware. That, indeed, is the objective of this book; namely, to
take a close look at the equipment options available to us in each technology group,
but not individually. Rather, to achieve an integrated and well thought out design,
we need to understand how unit processes and unit operations complimem each
other in the overall design.
This first chapter is for orientation purposes. Its objectives are to provide an
overview of water treatment and purification roles and technologies, and to
introduce terminology that will assist you in understanding the relation of the
various technologies to the overall schemes employed in waster treatment
applications. Recommended resources that you can refer to for more in-depth
information are included at the end of each chapter. The organization of these
resources are generally provided by subject matter. Also, you will find a section for
the student at the end of each chapter that provides a list of Questions for Thinking
and Discussing. These will assist in reinforcing some of the principles and concepts
presented in each chapter, if the book is used as a primary or supplement textbook.
We should recognize that the technology options for water treatment are great, and
quite often the challenge lies with the selection of the most cost-effective
combinations of unit processes and operations. In this regard, cost-factors are
examined where appropriate in our discussions within later chapters.

4 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
WHAT WE MEAN BY WATER PURIFICATION
When we refer to water purification, it makes little sense to discuss the subject
without first identifying the contaminants that we wish to remove from water. Also,
the source of the water is of importance. Our discussion at this point focuses on
drinking water. Groundwater sources are of a particular concern, because there are
many communities throughout the U.S. that rely on this form. The following are
some of the major contaminants that are of concern in water purification
applications, as applied to drinking water sources, derived from groundwater.
Heavy Metals - Heavy metals represent problems in terms of groundwater
pollution. The best way to identify their presence is by a lab test of the water or by
contacting county health departments. There are concerns of chronic exposure to
low levels of heavy metals in drinking water.
T u r b i d i t y - Turbidity refers to suspended solids, i.e. muddy water, is very turbid.
Turbidity is undesirable for three reasons:
aesthetic considerations,
solids may contain heavy metals, pathogens or other contaminants,

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 5
9 turbidity decreases the effectiveness of water treatment techniques by
shielding pathogens from chemical or thermal damage, or in the case of
UV (ultra violet) treatment, absorbing the UV light itself.
Organic Compounds - Water can be contaminated by a number of organic
compounds, such as chloroform, gasoline, pesticides, and herbicides from a variety
of industrial and agricultural operations or applications. These contaminants must
be identified in a lab test. It is unlikely groundwater will suddenly become
contaminated, unless a quantity of chemicals is allowed to enter a well or
penetrating the aquifer. One exception is when the aquifer is located in limestone.
Not only will water flow faster through limestone, but the rock is prone to forming
vertical channels or sinkholes that will rapidly allow contamination from surface
water. Surface water may show great variations in chemical contamination levels
due to differences in rainfall, seasonal crop cultivation, and industrial effluent
levels. Also, some hydrocarbons (the chlorinated hydrocarbons in particular) form
a type of contaminant that is especially troublesome. These are a group of
chemicals known as dense nonaqueous phase liquids, or DNAPLs. These include
chemicals used in dry cleaning, wood preservation, asphalt operations, machining,
and in the production and repair of automobiles, aviation equipment, munitions, and
electrical equipment. These substances are heavier than water and they sink quickly
into the ground. This makes spills of DNAPLs more difficult to handle than spills
of petroleum products. As with petroleum products, the problems are caused by
groundwater dissolving some of the compounds in these volatile substances. These
compounds can then move with the groundwater flow. Except in large cities,
drinking water is rarely tested for these contaminants. Disposal of chemicals that
have low water solubility and a density greater than water result in the formation
of distinct areas of pure residual contamination in soils and groundwater. These
chemicals are typically solvents and are collectively referred to as Dense Non-
Aqueous Phase Liquids (DNAPLs). Because of their relatively high density, they
tend to move downward through soils and groundwater, leaving small amounts
along the migratory pathway, until they reach an impermeable layer where they
collect in discrete pools. Once the DNAPLs have reached an aquitard they tend to
move laterally under the influence of gravity and to slowly dissolve into the
groundwater, providing a long-term source for low level contamination of
groundwater. Because of their movement patterns DNAPL contamination is
difficult to detect, characterize and remediate.
Pathogens - These include protozoa, bacteria, and viruses. Protozoa cysts are the
largest pathogens in drinking water, and are responsible for many of the waterborne
disease cases in the U.S. Protozoa cysts range is size from 2 to 15 #m (a micron
is one millionth of a meter), but can squeeze through smaller openings. In order to
insure cyst filtration, filters with a absolute pore size of 1 #m or less should be used.
The two most common protozoa pathogens are Giardia lamblia (Giardia) and
Cryptosporidium (Crypto). Both organisms have caused numerous deaths in recent
years in the U.S. and Canada, the deaths occurring in the young and elderly, and
the sick and immune compromised. Many deaths were a result of more than one of

6 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
these conditions. Neither disease is likely to be fatal to a healthy adult, even if
untreated. For example in Milwaukee in April of 1993, of 400,000 who were
diagnosed with Crypto, only 54 deaths were linked to the outbreak, 84 % of whom
were AIDS patients. Outside of the U.S. and other developed countries, protozoa
are responsible for many cases of amoebic dysentery, but so far this has not been
a problem in the U.S., due to the application of more advanced wastewater
treatment technologies. This could change during a survival situation. Tests have
found Giardia and/or Crypto in up to 5 % of vertical wells and 26 % of springs in
the U.S.
Bacteria are smaller than protozoa and are responsible for many diseases, such as
typhoid fever, cholera, diarrhea, and dysentery. Pathogenic bacteria range in size
from 0.2 to 0.6 ~m, and a 0.2 ~m filter is necessary to prevent transmission.
Contamination of water supplies by bacteria is blamed for the cholera epidemics,
which devastate undeveloped countries from time to time. Even in the U.S., E. coli
is frequently found to contaminated water supplies. Fortunately, E. coli is relatively
harmless as pathogens go, and the problem isn't so much with E. coli found, but
the fear that other bacteria may have contaminated the water as well. Never the
less, dehydration from diarrhea caused by E. coli has resulted in fatalities.
One of hundreds of strains of the bacterium Escherichia coli, E. coli O157:H7 is
an emerging cause of food borne and waterborne illness. Although most strains of
E. coli are harmless and live in the intestines of healthy humans and animals, this
strain produces a powerful toxin and can cause severe illness. E. coli 0157:H7 was
first recognized as a cause of illness during an outbreak in 1982 traced to
contaminated hamburgers. Since then, most infections are believed to have come
from eating undercooked ground beef. However, some have been waterborne. The
presence of E. coli in water is a strong indication of recent sewage or animal waste
contamination. Sewage may contain many types of disease-causing organisms.
Since E. coli comes from human and animal wastes, it most often enters drinking
water sources via rainfalls, snow melts, or other types of precipitation, E. coli may
be washed into creeks, rivers, streams, lakes, or groundwater. When these waters
are used as sources of drinking water and the water is not treated or inadequately
treated, E. coli may end up in drinking water. E. coli 0157 :H7 is one of hundreds
of strains of the bacterium E. coli. Although most strains are harmless and live in
the intestines of healthy humans and animals, this strain produces a powerful toxin
and can cause severe illness. Infection often causes severe bloody diarrhea and
abdominal cramps; sometimes the infection causes non-bloody diarrhea.
Frequently, no fever is present. It should be noted that these symptoms are common
to a variety of diseases, and may be caused by sources other than contaminated
drinking water. In some people, particularly children under 5 years of age and the
elderly, the infection can also cause a complication, called hemolytic uremic
syndrome, in which the red blood cells are destroyed and the kidneys fail. About
2%-7% of infections lead to this complication. In the U.S. hemolytic uremic
syndrome is the principal cause of acute kidney failure in children, and most cases
of hemolytic uremic syndrome are caused by E. coli O157:H7. Hemolytic uremic

AN OVERVIEW OF WATER AND WASTEWATER TREATMENT 7
syndrome is a life-threatening condition usually treated in an intensive care unit.
Blood transfusions and kidney dialysis are often required. With intensive care, the
death rate for hemolytic uremic syndrome is 3 %-5 %. Symptoms usually appear
within 2 to 4 days, but can take up to 8 days. Most people recover without
antibiotics or other specific treatment in 5-10 days. There is no evidence that
antibiotics improve the course of disease, and it is thought that treatment with some
antibiotics may precipitate kidney complications. Antidiarrheal agents, such as
loperamide (Imodium), should also be avoided. The most common methods of
treating water contaminated with E. coli is by using chlorine, ultra-violet light, or
ozone, all of which act to kill or inactivate E. coli. Systems, using surface water
sources, are required to disinfect to ensure that all bacterial contamination is
inactivated, such as E. coll. Systems using ground water sources are not required
to disinfect, although many of them do. According to EPA regulations, a system
that operates at least 60 days per year, and serves 25 people or more or has 15 or
more service connections, is regulated as a public water system under the Safe
Drinking Water Act (SDWA). If a system is not a public water system as defined
by EPA's regulations, it is not regulated under the SDWA, although it may be
regulated by state or local authorities. Under the SDWA, EPA requires public
water systems to monitor for coliform bacteria. Systems analyze first for total
coliform, because this test is faster to produce results. Any time that a sample is
positive for total coliform, the same sample must be analyzed for either fecal
coliform or E. coli. Both are indicators of contamination with animal waste or
human sewage. The largest public water systems (serving millions of people) must
take at least 480 samples per month. Smaller systems must take at least five samples
a month, unless the state has conducted a sanitary survey - a survey in which a
state inspector examines system components and ensures they will protect public
health- at the system within the last five years.
Viruses are the 2nd most problematic pathogen, behind protozoa. As with protozoa,
most waterborne viral diseases don't present a lethal hazard to a healthy adult.
Waterborne pathogenic viruses range in size from 0.020-0.030/~m, and are too
small to be filtered out by a mechanical filter. All waterborne enteric viruses
affecting humans occur solely in humans, thus animal waste doesn't present much
of a viral threat. At the present viruses don't present a major hazard to people
drinking surface water in the U.S., but this could change in a survival situation as
the level of human sanitation is reduced. Viruses do tend to show up even in remote
areas, so a case can be made for eliminating them now.
THE DRINKING WATER STANDARDS
When the objective of water treatment is to provide drinking water, then we need
to select technologies that are not only the best available, but those that will meet
local and national quality standards. The primary goals of a water treatment plant

8 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
for over a century have
remained practically the same:
namely to produce water that is
biologically and chemically
safe, is appealing to the
consumer, and is noncorrosive
and nonscaling. Today, plant
design has become very
complex from discovery of
seemingly innumerable
chemical substances, the
multiplying of regulations, and
trying to satisfy more
discriminating palates. In
addition to the basics, designers must now keep in mind all manner of legal
mandates, as well as public concerns and en-vironmental considerations, to provide
an initial prospective of water works engineering planning, design, and operation.
The growth of community water supply systems in the United States started in the
early 1800s. By 1860, over 400, and by the turn of the century over 3000 major
water systems had been built to serve major cities and towns. Many older plants
were equipped with slow sand filters. In the mid 1890s, the Louisville Water
Company introduced the technologies of coagulation with rapid sand filtration.
The first application of chlorine in potable water was introduced in the 1830s for
taste and odor control, at that time diseases were thought to be spread by odors. It
was not until the 1890s and the advent of the germ theory of disease that the
importance of disinfection in potable water was understood. Chlorination was first
introduced on a practical scale in 1908 and then became a common practice.
Federal authority to establish standards for drinking water systems originated with
the enactment by Congress in 1883 of the Interstate Quarantine Act, which
authorized the Director of the United States Public Health Services (USPHS) to
establish and enforce regulations to prevent the introduction, transmission, or
spread of communicable diseases.
Today resource limitations have caused the United States Environmental Protection
Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey
indicated there were approximately 202,000 public water systems in the United
States. About 29 percent of these were community water systems, which serve
approximately 90 percent of the population. Of the 58,908 community systems that
serve about 226 million people, 51,552 were classified as "small" or "very small."
Each of these systems at an average serves a population of fewer than 3300 people.
The total population served by these systems is approximately 25 million people.
These figures provide us with a magnitude of scale in meeting drinking water
demands in the United States. Compliance with drinking water standards is not

8 WATER AND WASTEWATER TREATMENT TECHNOLOGIES
for over a century have
remained practically the same:
namely to produce water that is
biologically and chemically
safe, is appealing to the
consumer, and is noncorrosive
and nonscaling. Today, plant
design has become very
complex from discovery of
seemingly innumerable
chemical substances, the
multiplying of regulations, and
trying to satisfy more
discriminating palates. In
addition to the basics, designers must now keep in mind all manner of legal
mandates, as well as public concerns and en-vironmental considerations, to provide
an initial prospective of water works engineering planning, design, and operation.
The growth of community water supply systems in the United States started in the
early 1800s. By 1860, over 400, and by the turn of the century over 3000 major
water systems had been built to serve major cities and towns. Many older plants
were equipped with slow sand filters. In the mid 1890s, the Louisville Water
Company introduced the technologies of coagulation with rapid sand filtration.
The first application of chlorine in potable water was introduced in the 1830s for
taste and odor control, at that time diseases were thought to be spread by odors. It
was not until the 1890s and the advent of the germ theory of disease that the
importance of disinfection in potable water was understood. Chlorination was first
introduced on a practical scale in 1908 and then became a common practice.
Federal authority to establish standards for drinking water systems originated with
the enactment by Congress in 1883 of the Interstate Quarantine Act, which
authorized the Director of the United States Public Health Services (USPHS) to
establish and enforce regulations to prevent the introduction, transmission, or
spread of communicable diseases.
Today resource limitations have caused the United States Environmental Protection
Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey
indicated there were approximately 202,000 public water systems in the United
States. About 29 percent of these were community water systems, which serve
approximately 90 percent of the population. Of the 58,908 community systems that
serve about 226 million people, 51,552 were classified as "small" or "very small."
Each of these systems at an average serves a population of fewer than 3300 people.
The total population served by these systems is approximately 25 million people.
These figures provide us with a magnitude of scale in meeting drinking water
demands in the United States. Compliance with drinking water standards is not

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