PHYSICAL - CHEMICAL TREATMENT OF WATER AND WASTEWATER - CHAPTER 0 pdf

PHYSICAL–CHEMICAL
TREATMENT OF WATER
AND WASTEWATER
CRC PRESS
Boca Raton London New York Washington, D.C.
PHYSICAL–CHEMICAL
TREATMENT OF WATER
AND WASTEWATER
Arcadio P. Sincero Sr., D.Sc., P.E.
Morgan State University
Baltimore, Maryland
Gregoria A. Sincero, M. Eng., P.E.
Department of the Environment
State of Maryland

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© 2003 by A. P. Sincero and G. A. Sincero
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International Standard Book Number 1-58716-124-9
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Printed on acid-free paper

Library of Congress Cataloging-in-Publication Data

Sincero, Arcadio P. (Arcadio Pacquiao)
Physical–chemical treatment of water and wastewater / Arcadio Pacquiao Sincero, Sr.,
Gregoria Alivio Sincero.
p. cm.
Includes bibliographical references and index.
ISBN 1-58716-124-9 (alk. paper)
1. Water—Purification. 2. Sewage—Purification. I. Sincero, Gregoria A. (Gregoria Alivio)
II. Title
TD430 .S47 2002
628.1

′

62—dc21 2002023757

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Preface

This textbook is intended for undergraduate students in their junior and senior years
in environmental, civil, and chemical engineering, and students in other disciplines
who are required to take the course in physical–chemical treatment of water and
wastewater. This book is also intended for graduate students in the aforementioned
disciplines as well as practicing professionals in the field of environmental engi-
neering. These professionals include plant personnel involved in the treatment of
water and wastewater, consulting engineers, public works engineers, environmental
engineers, civil engineers, chemical engineers, etc. They are normally employed in
consulting firms, city and county public works departments, and engineering depart-
ments of industries, and in various water and wastewater treatment plants in cities,
municipalities, and industries. These professionals are also likely to be employed in
government agencies such as the U.S. Environmental Protection Agency, and state
agencies such as the Maryland Department of the Environment.
The prerequisites for this textbook are general chemistry, mathematics up to
calculus, and fluid mechanics. In very few instances, an elementary knowledge of
calculus is used, but mostly the mathematical treatment makes intensive use of
algebra. The entire contents of this book could be conveniently covered in two
semesters at three credits per semester. For schools offering only one course in
physical–chemical treatment of water and wastewater, this book gives the instructor
the liberty of picking the particular topics required in a given curriculum design.
After the student has been introduced to the preliminary topics of water and
wastewater characterization, quantitation, and population projection, this book covers
the unit operations and unit processes in the physical–chemical treatment of water
and wastewater. The unit operations cover flow measurements and flow and quality

equalization; pumping; screening, sedimentation, and flotation; mixing and floccu-
lation; conventional filtration; advanced filtration and carbon adsorption; and aeration,
absorption, and stripping. The unit processes cover water softening, water stabiliza-
tion, coagulation, removal of iron and manganese, removal of phosphorus, removal
of nitrogen, ion exchange, and disinfection.
The requirements for the treatment of water and wastewater are driven by the
Safe Drinking Water Act and Clean Water Act, which add more stringent require-
ments from one amendment to the next. For example, the act relating to drinking
water quality, known as the Interstate Quarantine Act of 1893, started with only the
promulgation of a regulation prohibiting the use of the common cup. At present, the
Safe Drinking Water Act requires the setting of drinking water regulations for some
83 contaminants. The act relating to water quality started with the prohibition of
obstructions in harbors as embodied in the Rivers and Harbors Act of 1899. At
present, the Clean Water Act requires that discharges into receiving streams meet
water quality standards; in fact, regulations such as those in Maryland have an

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antidegradation policy. In recent years, problems with

Cryptosporidium parvum

and

Giardia lamblia

have come to the fore. Toxic substances are being produced by
industries every day which could end up in the community water supply. These acts
are technology forcing, which means that as we continue to discover more of the

harmful effects of pollutants on public health and welfare and the environment,
advanced technology will continue to be developed to meet the needs of treatment.
The discipline of environmental engineering has mostly been based on empirical
knowledge, and environmental engineering textbooks until recently have been writ-
ten in a descriptive manner. In the past, the rule of thumb was all that was necessary.
Meeting the above and similar challenges, however, would require more than just
empirical knowledge and would require stepping up into the next level of sophisti-
cation in treatment technology. For this reason, this textbook is not only descriptive
but is also analytical in nature. It is hoped that sound concepts and principles will
be added to the already existing large body of empirical knowledge in the discipline.
These authors believe that achieving the next generation of treatment requirements
would require the next level of sophistication in technology. To this end, a textbook
written to address the issue would have to be analytical in nature, in addition to
adequately describing the various unit operations and processes.
This book teaches both principles and design. Principles are enunciated in the
simplest way possible. Equations presented are first derived, except those that are
obtained empirically. Statements such as “It can be shown…” are not used in this
book. These authors believe in imparting the principles and concepts of the subject
matter, which may not be done by using “it-can-be-shown” statements. At the end
of each chapter, where appropriate, are numerous problems that can be worked out
by the students and assigned as homework by the instructor.
The question of determining the correct design flows needs to be addressed. Any
unit can be designed once the flow has been determined, but how was the flow
determined in the first place? Methods of determining the various design flows are
discussed in this book. These methods include the determination of the average daily
flow rate, maximum daily flow rate, peak hourly flow rate, minimum daily flow rate,
minimum hourly flow rate, sustained high flow rate, and sustained low flow rate.
What is really meant when a certain unit is said to be designed for the average
flow or for the peak flow or for any flow? The answer to this question is not as easy
as it may seem. This book uses the concept of the probability distribution to derive

these flows. On the other hand, the loss through a filter bed may need to be
determined or a deep-well pump may need to be specified. The quantity of sludge
for disposal produced from a water softening process may also be calculated. This
book uses fluid mechanics and chemistry without restraint to answer these design
problems.
Equivalents and equivalent mass are two troublesome and confusing concepts.
If the chemistry and environmental engineering literature were reviewed, these
subjects would be found to be not well explained. Equivalents and equivalent mass
in a unified fashion are explained herein using the concept of the reference species.
Throughout the unit processes section of this book, reference species as a method
is applied. Related to equivalents and equivalent mass is the dilemma of expressing
concentrations in terms of calcium carbonate. Why, for example, is the concentration

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of acidity expressed in terms of calcium carbonate when calcium carbonate is basic
and acidity is acidic? This apparent contradiction is addressed in this book.
As in any other textbook, some omissions and additions may have produced
some error in this book. The authors would be very grateful if the reader would
bring them to our attention.

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Acknowledgments

First, I acknowledge Dr. Joseph L. Eckenrode, former Publisher, Environmental
Science & Technology, Technomic Publishing Company, Inc. Dr. Eckenrode was
very thorough in determining the quality, timeliness, and necessity of the manuscript.

It was only when he was completely satisfied through the strict peer review process
that he decided to negotiate for a contract to publish the book. Additionally, I
acknowledge Brian Kenet and Sara Seltzer Kreisman at CRC Press.
This book was written during my tenure at Morgan State University. I acknowl-
edge the administrators of this fine institution, in particular, Dr. Earl S. Richardson,
President; Dr. Clara I. Adams, Vice President for Academic Affairs; Dr. Eugene M
DeLoatch, Dean of the School of Engineering; and Dr. Reginald L. Amory, Chairman
of the Department of Civil Engineering. I make special mention of my colleague,
Dr. Robert Johnson, who was the acting Chairman of the Department of Civil
Engineering when I came on board. I also acknowledge my colleagues in the
department: Dr. Donald Helm, Prof. A. Bert Davy, Dr. Indranil Goswami, Dr. Jiang Li,
Dr. Iheanyi Eronini, Dr. Gbekeloluwa B. Oguntimein, Prof. Charles Oluokun, and
Prof. Neal Willoughby.
This acknowledgment would not be complete if I did not mention my advisor
in doctoral studies and three of my former professors at the Asian Institute of
Technology (A.I.T.) in Bangkok, Thailand. Dr. Bruce A. Bell was my advisor at the
George Washington University where I earned my doctorate in Environmental–Civil
Engineering. Dr. Roscoe F. Ward, Dr. Rolf T. Skrinde, and Prof. Mainwaring B. Pescod
were my former professors at A.I.T., where I earned my Masters in Environmental–
Civil Engineering.
I acknowledge and thank my wife, Gregoria, for contributing Chapter 2 (Con-
stituents of Water and Wastewater) and Chapter 7 (Conventional Filtration). I also
acknowledge my son, Roscoe, for contributing Chapter 17 (Disinfection). Gregoria
also contributed a chapter on solid waste management when I wrote my first book

Environmental Engineering: A Design Approach

. This book was published by Pren-
tice Hall and is being adopted as a textbook by several universities here and abroad.
This book has been recommended as a material for review in obtaining the Diplomate

in Environmental Engineering from the Academy of Environmental Engineers.
Lastly, I dedicate this book to members of my family: Gregoria, my wife; Roscoe
and Arcadio Jr., my sons; the late Gaudiosa Pacquiao Sincero, my mother; Santiago
Encarguiz Sincero, my father; and the late Aguido and the late Teodora Managase
Alivio, my father-in-law and my mother-in-law, respectively. I also dedicate this
book to my brother Meliton and to his wife Nena; to my sister Anelda and to her
husband Isidro; to my other sister Feliza and to her husband Martin; and to my
brother-in-law Col. Miguel M. Alivio, MD and to his wife Isabel. My thoughts also
go to my other brothers-in-law: the late Tolentino and his late wife Mary, Maximino

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and his wife Juanita, Restituto and his wife Ignacia, the late Anselmo and his wife
Silvina, and to my sisters-in-law: the late Basilides and her late husband Dr. Alfonso
Madarang, Clarita and her late husband Elpidio Zamora, Luz and her husband
Perpetuo Apale, and Estelita.

Arcadio P. Sincero

Morgan State University

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About the Authors

Arcadio P. Sincero

is Associate Professor of Civil Engineering at Morgan State

University, Baltimore, MD. He was also a former professor at the Cebu Institute of
Technology, Philippines. He holds a Bachelor’s degree in Chemical Engineering
from the Cebu Institute of Technology, a Master’s degree in Environmental–Civil
Engineering from the Asian Institute of Technology, Bangkok, and a Doctor of
Science degree in Environmental–Civil Engineering from the George Washington
University. He is a registered Professional Engineer in the Commonwealth of Penn-
sylvania and in the State of Maryland and was a registered Professional Chemical
Engineer in the Philippines. He is a member of the American Society of Civil Engi-
neers, a member of the American Institute of Chemical Engineers, a member of the
Water Environment Federation, a member of the American Association of University
Professors, and a member of the American Society of Engineering Education.
Dr. Sincero has a wide variety of practical experiences. He was a shift supervisor
in a copper ore processing plant and a production foreman in a corn starch processing
plant in the Philippines. He was CPM (Critical Path Method) Planner in a construc-
tion management firm and Public Works Engineer in the City of Baltimore. In the
State of Maryland, he was Public Health Engineer in the Bureau of Air Quality and
Noise Control, Department of Health and Mental Hygiene; Water Resources Engi-
neer in the Water Resources Administration, Department of Natural Resources; Water
Resources Engineer in the Office of Environmental Programs, Department of Health
and Mental Hygiene; Water Resources Engineer in the Water Management Admin-
istration, Maryland Department of the Environment. For his positions with the State
of Maryland, Dr. Sincero had been Chief of his divisions starting in 1978. His last
position in the State was Chief of Permits Division of the Construction Grants and
Permits Program, Water Management Administration, Maryland Department of the
Environment. These practical experiences have allowed Dr. Sincero to gain a wide
range of environmental engineering and regulatory experiences: air, water, solid
waste, and environmental quality modeling.

Gregoria A. Sincero

is a senior level Water Resources Engineer at the Maryland
Department of the Environment. She was also a former professor at the Cebu Institute
of Technology, Philippines. She holds a Bachelor’s degree in Chemical Engineering
from the Cebu Institute of Technology and a Master’s degree in Environmental–Civil
Engineering from the Asian Institute of Technology, Bangkok, Thailand. She is a
registered Professional Environmental Engineer in the Commonwealth of Pennsyl-
vania and was a registered Professional Chemical Engineer in the Philippines. She
is a member of the American Institute of Chemical Engineers.
Mrs. Sincero has practical experiences both in engineering and in governmental
regulations. She was Senior Chemist/Microbiologist in the Ashburton Filters of

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Baltimore City. In the State of Maryland, she was Water Resource Engineer in the
Water Resources Administration, Department of Natural Resources and Water
Resources Engineer in the Office of Environmental Programs, Department of Health
and Mental Hygiene, before joining her present position in 1988 at MDE. At MDE,
she is a senior project manager reviewing engineering plans and specifications and
inspecting construction of refuse disposal facilities such as landfills, incinerators,
transfer stations, and processing facilities. Also, she has experiences in modeling of
surface waters, groundwaters, and air and statistical evaluation of groundwater and
drinking water data using EPA’s Gritstat software.

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Contents

Background Prerequisites

Introduction
Wastewater
Physical–Chemical Treatment of Water and Wastewater
Unit Operations and Unit Processes
Coverage
Clean Water Act
Regulatory Requirements
Federal Financial Assistance
Permits and Enforcement
Federal and State Relationships
Safe Drinking Water Act
Highlights of the Safe Drinking Water Act
Development of MCLs and MCLGs
Drinking Water Regulations under the Act
Federal Financial Assistance
Federal and State Relationships
Relationship of This Book to the Acts
Glossary
Background Chemistry and Fluid Mechanics
Units Used in Calculation
General Chemistry
Equivalents and Equivalent Masses
Methods of Expressing Concentrations
Activity and Active Concentration
Equilibrium and Solubility Product Constants
Acids and Bases
Fluid Mechanics
Integration Symbols
Vectors

Gauss–Green Divergence Theorem
Partial versus Total Derivative
Reynolds Transport Theorem
Glossary
Problems
Bibliography

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PART I

Characteristics of Water and Wastewater

Chapter 1

Quantity of Water and Wastewater
1.1 Probability Distribution Analysis
1.1.1 Addition and Multiplication Rules
of Probability
1.1.2 Values Equaled or Exceeded
1.1.3 Derivation of Probability from
Recorded Observation
1.1.4 Values Equaled or Not Exceeded
1.2 Quantity of Water
1.2.1 Design Period
1.3 Types of Wastewater
1.4 Sources and Quantities of Wastewater
1.4.1 Residential
1.4.2 Commercial

1.4.3 Institutional
1.4.4 Recreational
1.4.5 Industrial
1.5 Population Projection
1.5.1 Arithmetic Method
1.5.2 Geometric Method
1.5.3 Declining-Rate-of-Increase Method
1.5.4 Logistic Method
1.5.5 Graphical Comparison Method
1.6 Derivation of Design Flows of Wastewaters
1.6.1 Design Flows
1.7 Deriving Design Flows of Wastewaters from Field Survey
1.7.1 Average Daily Flow Rate
1.7.2 Peak Hourly Flow Rate
1.7.3 Maximum Daily Flow Rate
1.7.4 Minimum Hourly Flow Rate and Minimum
Daily Flow Rate
1.7.5 Sustained Peak Flow Rate and Sustained Minimum
Flow Rate
1.7.6 Infiltration–Inflow
1.7.7 Summary Comments for Deriving Flow Rates
by the Probability Distribution Analysis
Glossary
Symbols
Problems
Bibliography

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Chapter 2

Constituents of Water and Wastewater
2.1 Physical and Chemical Characteristics
2.1.1 Turbidity
2.1.2 Color
2.1.3 Taste
2.1.4 Odor
2.1.5 Temperature
2.1.6 Chlorides
2.1.7 Fluorides
2.1.8 Iron and Manganese
2.1.9 Lead and Copper
2.1.10 Nitrate
2.1.11 Sodium
2.1.12 Sulfate
2.1.13 Zinc
2.1.14 Biochemical Oxygen Demand
2.1.15 Nitrification in the BOD Test
2.1.16 Mathematical Analysis of BOD Laboratory Data
2.1.17 Solids
2.1.18 pH
2.1.19 Chemical Oxygen Demand
2.1.20 Total Organic Carbon
2.1.21 Nitrogen
2.1.22 Phosphorus
2.1.23 Acidity and Alkalinity
2.1.24 Fats, Oils, Waxes, and Grease
2.1.25 Surfactants
2.1.26 Priority Pollutants

2.1.27 Volatile Organic Compounds
2.1.28 Toxic Metal and Nonmetal Ions
2.2 Normal Constituents of Domestic Wastewater
2.3 Microbiological Characteristics
2.3.1 Bacteria
2.3.2 Test for the Coliform Group
2.3.3 The Poisson Distribution
2.3.4 Estimation of Coliform Densities
by the MPN Method
2.3.5 Interpolation or Extrapolation of the MPN Table
2.3.6 Viruses
2.3.7 Protozoa
Glossary
Symbols
Problems
Bibliography

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PART II

Unit Operations of Water
and Wastewater Treatment

Chapter 3

Flow Measurements and Flow and Quality Equalizations
3.1 Flow Meters
3.1.1 Rectangular Weirs

3.1.2 Triangular Weirs
3.1.3 Trapezoidal Weirs
3.1.4 Venturi Meters
3.1.5 Parshall Flumes
3.2 Miscellaneous Flow Meters
3.3 Liquid Level Indicators
3.4 Flow and Quality Equalizations
Glossary
Symbols
Problems
Bibliography

Chapter 4

Pumping
4.1 Pumping Stations and Types of Pumps
4.2 Pumping Station Heads
4.2.1 Total Developed Head
4.2.2 Inlet and Outlet Manometric Heads; Inlet
and Outlet Dynamic Heads
4.3 Pump Characteristics and Best Operating Efficiency
4.4 Pump Scaling Laws
4.5 Pump Specific Speed
4.6 Net Positive Suction Head and Deep-Well Pumps
4.7 Pumping Station Head Analysis
Glossary
Symbols
Problems
Bibliography

Chapter 5

Screening, Settling, and Flotation
5.1 Screening
5.1.1 Head Losses in Screens and Bar Racks
5.1.2 Head Loss in Microstrainers
5.2 Settling
5.2.1 Flow-Through Velocity and Overflow Rate
of Settling Basins

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5.2.2 Discrete Settling
5.2.3 Outlet Control of Grit Channels
5.2.4 Flocculent Settling
5.2.5 Primary Settling and Water-Treatment
Sedimentation Basins
5.2.6 Zone Settling
5.2.7 Secondary Clarification and Thickening
5.3 Flotation
5.3.1 Laboratory Determination of Design Parameters
Glossary
Symbols
Problems
Bibliography

Chapter 6

Mixing and Flocculation

6.1 Rotational Mixers
6.1.1 Types of Impellers
6.1.2 Prevention of Swirling Flow
6.1.3 Power Dissipation in Rotational Mixers
6.2 Criteria for Effective Mixing
6.3 Pneumatic Mixers
6.3.1 Prediction of Number of Bubbles and Rise Velocity
6.3.2 Power Dissipation in Pneumatic Mixers
6.4 Hydraulic Mixers
6.4.1 Power Dissipation in Hydraulic Mixers
6.4.2 Mixing Power for Hydraulic Jumps
6.4.3 Volume and Detention Times of Hydraulic-Jump Mixers
6.4.4 Mixing Power for Weir Mixers
6.5 Flocculators
Glossary
Symbols
Problems
Bibliography

Chapter 7

Conventional Filtration
7.1 Types of Filters
7.2 Medium Specification for Granular Filters
7.3 Linear Momentum Equation Applied to Filters
7.4 Head Losses in Grain Filters
7.4.1 Clean-Filter Head Loss
7.4.2 Head Losses Due to Deposited Materials
7.5 Backwashing Head Loss in Granular Filters
7.6 Cake Filtration

7.6.1 Determination of
α

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7.6.2 Design Cake Filtration Equation
7.6.3 Determination of Cake Filtration Parameters
Glossary
Symbols
Problems
Bibliography

Chapter 8

Advanced Filtration and Carbon Adsorption
8.1 Electrodialysis Membranes
8.1.1 Power Requirement of Electrodialysis Units
8.2 Pressure Membranes
8.2.1 Membrane Module Designs
8.2.2 Factors Affecting Solute Rejection and Breakthrough
8.2.3 Solute-Water Separation Theory
8.2.4 Types of Membranes
8.2.5 Membrane Performance Characterization
8.3 Carbon Adsorption
8.3.1 Activation Techniques
8.3.2 Adsorption Capacity
8.3.3 Determination of the Freundlich Constants
8.3.4 Determination of the Langmuir Constants
8.3.5 Bed Adsorption and Active Zone

8.3.6 Relative Velocities in Bed Adsorption
8.3.7 Head Losses in Bed Adsorption
Glossary
Symbols
Problems
Bibliography

Chapter 9

Aeration, Absorption, and Stripping
9.1 Mass Transfer Units
9.2 Interface for Mass Transfer, and Gas and Liquid Boundary Layers
9.3 Mathematics of Mass Transfer
9.4 Dimensions of the Overall Mass Transfer Coefficients
9.5 Mechanics of Aeration
9.5.1 Equipment Specification
9.5.2 Determination of Aeration Parameters
9.5.3 Calculation of Actual Oxygen Requirement, the AOR
9.5.4 Time of Contact
9.5.5 Sizing of Aeration Basins and Relationship to Contact Time
9.5.6 Contact for Bubble Aerators
9.6 Absorption and Stripping
9.6.1 Sizing of Absorption and Stripping Towers
9.6.2 Operating Line

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9.6.3 Tower Height
9.6.4 Ammonia Stripping (or Absorption)

Glossary
Symbols
Problems
Bibliography

PART III

Unit Processes of Water
and Wastewater Treatment

Chapter 10

Water Softening
10.1 Hard Waters
10.2 Types of Hardness
10.3 Plant Types for Hardness Removal
10.4 The Equivalent CaCO

3

Concentration
10.5 Softening of Calcium Hardness
10.6 Softening of Magnesium Hardness
10.7 Lime–Soda Process
10.7.1 Calculation of Stoichiometric Lime Required
in the Lime–Soda Process
10.7.2 Key to Understanding Subscripts
10.7.3 Calculation of Stoichiometric Soda Ash Required
10.7.4 Calculation of Solids Produced
10.8 Order of Removal

10.9 Role of CO

2

in Removal
10.10 Excess Lime Treatment and Optimum Operational pH
10.11 Summary of Chemical Requirements
and Solids Produced
10.12 Sludge Volume Production
10.13 Chemical Species in the Treated Water
10.13.1 Limits of Technology
10.13.2 Concentration of Ca

2

+

10.13.3 Concentration of Mg

2

+

10.13.4 Concentration of
10.13.5 Concentration of
10.13.6 Concentration of Na

+

10.14 Relationships of the Fractional Removals

10.15 Notes on Equivalent Masses
10.16 Typical Design Parameters and Criteria
10.17 Split Treatment
10.18 Use of Alkalinity in Water Softening Calculations
Glossary
HCO
3
−
CO
3
2 −

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Symbols
Problems
Bibliography

Chapter 11

Water Stabilization
11.1 Carbonate Equilibria
11.1.1 Ionic Strength
11.1.2 Equilibrium Constant as a Function of Temperature
11.1.3 ’s for Pertinent Chemical Reactions
of the Carbonate Equilibria
11.2 Criteria for Water Stability at Normal Conditions
11.2.1 Saturation pH and the Langelier Index
11.2.2 Determination of {Ca

2+

}
11.2.3 Total Alkalinity as Calcium Carbonate
11.2.4 Precipitation Potential
11.2.5 Determination of Percent Blocking Potential of Pipes
11.3 Recarbonation of Softened Water
Glossary
Symbols
Problems
Bibliography

Chapter 12

Coagulation
12.1 Colloid Behavior
12.2 Zeta Potential
12.3 Colloid Destabilization
12.4 Coagulation Process
12.4.1 Coagulants for the Coagulation Process
12.4.2 Coagulant Aids
12.4.3 Rapid Mix for Complete Coagulation
12.4.4 The Jar Test
12.5 Chemical Reactions of Alum
12.5.1 Determination of the Optimum pH
12.6 Chemical Reactions of the Ferrous Ion
12.6.1 Determination of the Optimum pH
12.7 Chemical Reactions of the Ferric Ion
12.7.1 Determination of the Optimum pH

12.8 Jar Tests for Optimum pH Determination
12.9 Chemical Requirements
12.9.1 Chemical Requirements in Alum Coagulation Treatment
12.9.2 Key to Understanding Subscripts
12.9.3 Chemical Requirements in Ferrous Coagulation Treatment
12.9.4 Chemical Requirements in Ferric Coagulation Treatment
12.10 Chemical Requirements for pH Adjustments
∆H
298
o

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12.11 Alkalinity and Acidity Expressed as CaCO

3

12.12 Sludge Production
Glossary
Symbols
Problems
Bibliography

Chapter 13

Removal of Iron and Manganese by Chemical Precipitation
13.1 Natural Occurrences of Iron and Manganese
13.2 Modes of Removal of Iron and Manganese
13.3 Chemical Reactions of the Ferrous and the Ferric Ions

13.3.1 Practical Optimum pH Range for the Removal
of Ferrous and Ferric
13.4 Chemical Reactions of the Manganous Ion [Mn(II)]
13.4.1 Determination of the Optimum pH
13.4.2 Practical Optimum pH Range
for the Removal of Manganese
13.5 Oxidation of Iron and Manganese
to Reduce Precipitation pH
13.6 Unit Operations for Iron and Manganese Removal
13.6.1 High pH Range
13.6.2 Low pH Range
13.7 Chemical Requirements
13.7.1 Requirements in the Ferrous Reactions
13.7.2 Requirements in the Manganous Reactions
13.8 Alkalinity Expressed in OH

−

and Acidity Expressed in H

+

13.9 Chemical Requirements for pH Adjustments
13.10 Sludge Production
Glossary
Symbols
Problems
Bibliography

Chapter 14

Removal of Phosphorus by Chemical Precipitation
14.1 Natural Occurrence of Phosphorus
14.2 Modes of Phosphorus Removal
14.3 Chemical Reaction of the Phosphate Ion with Alum
14.3.1 Determination of the Optimum pH Range
14.4 Chemical Reaction of the Phosphate Ion with Lime
14.4.1 Determination of the Optimum pH
and the Optimum pH Range
14.5 Chemical Reaction of the Phosphate Ion with the Ferric Salts
14.5.1 Determination of the Optimum pH
and the Optimum pH Range

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14.6 Comments on the Optimum pH Ranges
14.7 Effect of the

K

sp

’s on the Precipitation of Phosphorus
14.8 Unit Operations for Phosphorus Removal
14.9 Chemical Requirements
14.10 Sludge Production
Glossary
Symbols
Problems

Bibliography

Chapter 15

Removal of Nitrogen by Nitrification–Denitrification
15.1 Natural Occurrence of Nitrogen
15.2 To Remove or Not to Remove Nitrogen
15.3 Microbial Thermodynamics
15.3.1 Enthalpy and Entropy
15.3.2 Free Energy
15.4 Oxidation-Reduction Reactions of Nitrogen Foods
15.4.1 Criterion for Spontaneous Process
15.5 Modes of Nitrogen Removal
15.6 Chemical Reactions in Nitrogen Removal
15.6.1 Nitrification:

Nitrosomonas

Stage
15.6.2 Nitrification:

Nitrobacter

Stage
15.6.3 Overall Nitrification
15.6.4 Denitrification: Heterotrophic Side Reaction Stage
15.6.5 Denitrification: Normal Anoxic Stage
15.6.6 Denitrification: NO

2

-Reduction Side
Reaction Stage
15.7 Total Effluent Nitrogen
15.7.1 Units of Cell Yields
15.8 Carbon Requirements for Denitrification
15.9 Alkalinity Production and Associated Carbon Requirement
15.10 Reaction Kinetics
15.10.1 Kinetics of Growth and Food Utilization
15.10.2 Material Balance around the Activated Sludge Process
15.10.3 Nitrification Kinetics
15.10.4 Denitrification Kinetics
15.10.5 Carbon Kinetics
15.10.6 Reactor Sizing
15.10.7 Determination of Kinetic Constants
Glossary
Symbols
Problems
Bibliography

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Chapter 16

Ion Exchange
16.1 Ion Exchange Reactions
16.2 Unit Operations of Ion Exchange
16.3 Sodium, Hydrogen Cycle, and Regeneration
16.4 Production of “Pure Water”

16.5 Active or Exchange Zone
16.6 Design of Ion Exchangers
16.6.1 Quantity of Exchange Materials
16.6.2 Quantity of Regenerant
16.6.3 Wastewater Production
16.7 Head Losses in Ion Exchangers
Glossary
Symbols
Problems
Bibliography

Chapter 17

Disinfection
17.1 Methods of Disinfection and Disinfectant Agents Used
17.2 Factors Affecting Disinfection
17.2.1 Time of Contact and Intensity of Disinfectant
17.2.2 Age of the Microorganism
17.2.3 Nature of the Suspending Fluid
17.2.4 Effect of Temperature
17.3 Other Disinfection Formulas
17.4 Chlorine Disinfectants
17.4.1 Chlorine Chemistry
17.4.2 Design of Chlorination Unit Operations Facilities
17.5 Dechlorination
17.5.1 Chemical Reactions Using Sulfur
Dechlorinating Agents
17.5.2 Chemical Reactions Using Activated Carbon
17.5.3 Effect of Dechlorinated Effluents on Dissolved Oxygen
of Receiving Streams

17.5.4 Unit Operations in Dechlorination
17.6 Disinfection Using Ozone
17.6.1 Unit Operations in Ozonation
17.7 Disinfection Using Ultraviolet Light
17.7.1 Unit Operations in UV Disinfection
Glossary
Symbols
Problems
Bibliography

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Appendices and Index

Appendix 1

Density and Viscosity of Water

Appendix 2

Atomic Masses of the Elements Based on C-12

Appendix 3

Saturation Values of Dissolved Oxygen Exposed to Saturated
Atmosphere at One Atmosphere Pressure
at Given Temperatures

Appendix 4

SDWA Acronyms

Appendix 5

Sample Drinking Water VOCs

Appendix 6

Sample Drinking Water SOCs and IOCs

Appendix 7

Secondary MCLs for a Number of Substances

Appendix 8

Some Primary Drinking-Water Criteria

Appendix 9

Some Secondary Drinking-Water Criteria

Appendix 10

Physical Constants

Appendix 11

Conversion Factors

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Background Prerequisites

The background prerequisites for this textbook are general chemistry, mathematics
up to calculus, and fluid mechanics. In very few instances, an elementary knowledge
of calculus is used, but mostly the mathematical treatment makes intensive use of
algebra. In fluid mechanics, the only sophisticated topic used is the Reynolds trans-
port theorem. Although this topic is covered in an undergraduate course in fluid
mechanics, it was thought advantageous to review it here. The other background
prerequisite is general chemistry. Environmental engineering students and civil engi-
neering students, in particular, seem to be very weak in chemistry. This part will
therefore also provide a review of this topic. Depending upon the state of knowledge
of the students, however, this part may or may not be discussed. This state of
knowledge may be ascertained by the instructor in the very first few days of the
course, and he or she can tailor the discussions accordingly.
The contents of this “Background Prerequisites” section are not really physical–
chemical treatment but just background knowledge to comfortably understand the
method of approach used in the book. This book is analytical and therefore must
require extensive use of the pertinent chemistry, mathematics, and fluid mechanics.
This section contains two chapters: “Introduction” and “Background Chemistry and
Fluid Mechanics.”

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Introduction

This book is titled

Physical–Chemical Treatment of Water and Wastewater

. This
chapter begins by defining wastewater and physical–chemical treatment of water
and wastewater and treats briefly the coverage. It also addresses the unit operations
and unit processes. In addition, in the environmental engineering field, construction
of water and wastewater treatment plants and the requirements of their levels of
performance are mostly driven by government laws and regulations. For example,
the Clean Water Act mandates construction of wastewater treatment facilities that,
at least, must produce the secondary level of treatment. The Safe Water Drinking
Water Act also requires performance of treatment plants that produce drinking water
of quality free from harmful chemicals and pathogens. For these reasons, the Clean
Water Act and the Safe Drinking Water Act are discussed at length, detailing their
developments and historical perspectives.

WASTEWATER

Wastewater

is the spent water after homes, commercial establishments, industries,
public institutions, and similar entities have used their waters for various purposes.
It is synonymous with

sewage

, although sewage is a more general term that refers
to any polluted water (including wastewater), which may contain organic and inor-
ganic substances, industrial wastes, groundwater that happens to infiltrate and to

mix with the contaminated water, storm runoff, and other similar liquids. A certain
sewage may not be a spent water or a wastewater.
The keyword in the definition of wastewater is “used” or “spent.” That is, the
water has been used or spent and now it has become a

waste water

. On the other
hand, to become a sewage, it is enough that water becomes polluted whether or not
it had been used. When one uses the word wastewater, however, the meaning of the
two words is blended such that they now often mean the same thing.

Wastewater

equals

sewage

.

PHYSICAL–CHEMICAL TREATMENT OF WATER
AND WASTEWATER

What is physical–chemical treatment of water and wastewater? The dictionary
defines

physical

as having material existence and subject to the laws of nature.

Chemical

, on the other hand, is defined as used in, or produced by chemistry. Being
used in and produced by chemistry implies a material existence and is subject to
the laws of nature. Thus, from these definitions, chemical is physical. The fact that
chemical is physical has not, however, answered the question posed.

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To explore the question further, we go to the definition of chemistry.

Chemistry

is defined as the branch of science that deals with the composition, structure, and
properties of substances and the transformation that they undergo. Now, from this
definition can be gleaned the distinguishing feature of chemical—the transformation
that the substance undergoes. The transformation changes the original substance into
an entirely different substance after the transformation. Chemical transformation can
be distinguished from physical transformation. In physical transformation, although
also involving a change, the change is only in appearance but not in substance. For
example, FeO in the beginning is still FeO in the end; the size of the particles may
have changed, however, during the process. We now define physical treatment of
water and wastewater as a process applied to water and wastewater in which no
chemical changes occur. We also define chemical treatment of water and wastewater
as a process applied to water and wastewater in which chemical changes occur.
Gleaning from these definitions of physical and chemical treatments, in the overall
sense, physical–chemical treatment of water and wastewater is a process applied to
water and wastewater in which chemical changes may or may not occur.

UNIT OPERATIONS AND UNIT PROCESSES

Figure 1 shows the schematic of a conventional wastewater treatment plant using
primary treatment. Raw wastewater is introduced either to the screen or to the
comminutor. The grit channel removes the larger particles from the screened sewage,
and the primary clarifier removes the larger particles of organic matter as well as
inorganic matter that escapes removal by the grit channel. Primary treated sewage
is then introduced to a secondary treatment process train downstream (not shown)
where the colloidal and dissolved organic matter are degraded by microorganisms.
The scheme involves mere physical movement of materials, no chemical or
biological changes occur. In addition, the function of the various operations in the
scheme, such as screening, may be applied not only to the primary treatment of
sewage as the figure indicates but to other plant operations as well. For example,
bagasse may be screened from sugar cane juice in the expression of sugar in a sugar
mill, or the larger particles resulting from the cleaning of pineapples in a pineapple
factory may be screened from the rest of the wastewater. To master the function of
screening, it is not necessary that this be studied in a wastewater treatment plant, in

FIGURE 1

A primary treatment system.
Raw
sewage
Comminutor
Grit channel
Screen
Primary
clarifier
Effluent
Sludge

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