Practical Wastewater Treatment E-Book

David L. Russell

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 725

Veröffentlichungsjahr: 2019

Beschreibung

The updated and expanded guide for handling industrial wastes and designing a wastewater treatment plant The revised and updated second edition of Practical Wastewater Treatment provides a hands-on guide to industrial wastewater treatment theory, practices, and issues. It offers information for the effective design of water and wastewater treatment facilities and contains material on how to handle the wide-variety of industrial wastes. The book is based on a course developed and taught by the author for the American Institute of Chemical Engineers. The author reviews the most current industrial practices and goals, describes how the water industry works, and covers the most important aspects of the industry. In addition, the book explores a wide-range of approaches for managing industrial wastes such as oil, blood, protein and more. A comprehensive resource, the text covers such basic issues as water pollution, wastewater treatment techniques, sampling and measurement, and explores the key topic of biological modeling for designing wastewater treatment plants. This important book: * Offers an updated and expanded text for dealing with real-world wastewater problems * Contains new chapters on: Reverse Osmosis and desalination; Skin and Membrane Filtration; and Cooling tower water treatment * Presents a guide filled with helpful examples and diagrams that is ideal for both professionals and students * Includes information for handling industrial wastes and designing water and wastewater treatment plants Written for civil or chemical engineers and students, Practical Wastewater Treatment offers the information and techniques needed to solve problems of wastewater treatment.

Leseprobe

Table of Contents

Cover

Acknowledgments

Preface

1 Composition, Chemistry, and Regulatory Framework

1.1 Water Composition

1.2 Water Characteristics and Physical Properties

1.3 Solution Chemistry: Salts and Ions in Water

1.4 Disassociation Constants for Weak Acid and Bases

1.5 Sources of Water

1.6 Analytical Methods

1.7 Laboratory Guidance

1.8 Regulatory Framework of Water Regulations

1.9 Water Use Data and Some Discharge Characteristics

2 What is Water Pollution?

2.1 Pollution Defined

2.2 Chemical Industry

2.3 Cooling Towers

2.4 Boilers

2.5 Iron and Steel Industry

2.6 Mining Industries

2.7 Fracking for Oil and Gas

2.8 Petroleum Exploration

2.9 Petroleum Refining

2.10 Agricultural and Food Processing

2.11 Crop Water Use

2.12 Vegetable and Fruit Processing

2.13 Animal Farming and Concentrated Animal Feeding Operations

2.14 Livestock and Concentrated Animal Feeding Operations

2.15 Slaughterhouse and Meat Packing and Processing Wastes

2.16 Dairy Wastes

2.17 Measuring Pollution

2.18 The Sampling Plan

2.19 Analytical Methods and the Role of the Laboratory

3 Groundwater and its Treatment

3.1 Hydraulics of Groundwater

3.2 Soil Particles and Surface Areas

3.3 Well Hydraulics

3.4 Well Packing and Screens

3.5 Trenches

3.6 Compressible Flow

3.7 Groundwater Treatment

4 Statistics of Measurements

4.1 Introduction to Statistical Measurements: Background

4.2 Significant Figures

4.3 Probable Error

4.4 Repeat Measurements

4.5 Net Process Measurements

4.6 Statistical Distributions for Environmental Events

4.7 Black Swans and Data Analysis

5 The Flow of Water and Wastewater

5.1 Statistical Basis for Error Estimation

5.2 Open Channel Hydraulics

5.3 Froude Number

5.4 Types of Flowmeters

5.5 Weir Plates

5.6 Alignment Errors

5.7 Samples and Sampling

5.8 Conclusion

6 Troubleshooting and Emergency Planning

6.1 Fault Tree Analysis

6.2 Reverse Fault Tree Analysis

6.3 Analysis: The Five Whys

6.4 Regulatory Requirements

6.5 Software Solutions

6.6 Emergency Response Planning

7 Chemistry and Analyses

7.1 Aquatic Testing

7.2 Bacterial Testing

7.3 Dissolved Organic Materials – BOD, COD, and TOC

7.4 Common Ion Species

7.5 Hardness

7.6 Chemical Water Softening

7.7 Nitrogen

7.8 Phosphorus

7.9 Sulfur

7.10 Chlorine

7.11 Other Halogens

7.12 Metals

7.13 Solids

7.14 Organic Chemicals

8 Basic Water and Wastewater Treatment Techniques

8.1 Removal of Metals

8.2 Chromium

8.3 Arsenic

8.4 Cadmium

8.5 Iron

8.6 Zinc

8.7 Mercury

8.8 Radium

8.9 Anions

8.10 Solvents and Oils

8.11 Chlorinated Organics

9 Biological Wastewater Treatment

9.1 The Microbial World

9.2 Order of Treatment

9.3 Types of Organisms

9.4 Chemistry and Activated Sludge

9.5 Growth Conditions and Nitrification

9.6 Denitrification and Phosphate Removal

9.7 Biological Growth Equation

9.8 Principles of Biological Treatment Systems

9.9 Activated Sludge and its Variations

9.10 Substrate Removal Definitions

9.11 Trickling Filters and Variations

9.12 Clarification for Biological Removals

9.13 Other Solids Removals

9.14 Biological Synthesis and Oxidation

9.15 Biological Treatment of Toxic Wastes

9.16 Modeling the Biological Process

10 Anaerobic Treatment

10.1 Basic Anaerobic Processes for Wastewater

10.2 Phosphorus Removal

10.3 Basic Anaerobic Processes for Digestion and Treatment

10.4 Anaerobic Pretreatment

10.5 Upflow Anaerobic Sludge Blanket Reactors

10.6 Other Digester Configurations

10.7 Siloxane Removals

10.8 Sludge Digestion

10.9 Gas Production Emphasis

10.10 New Technologies

10.11 Sludge Treatment

10.12 Anaerobic Digester Model ADM1

10.13 Struvite and Anaerobic Processes

11 Precipitation and Sedimentation

11.1 Theory of Sedimentation

11.2 Clarifiers and their Design

11.3 Lamellas and Specialty Devices

12 Granular Filtration Theory and Practice

12.1 Granular Media Filtration

12.2 Filtration Hydraulics

12.3 Particle Size Removals

12.4 Backwash Hydraulics

13 Skin Filtration

13.1 Introduction

13.2 Microstrainers and Screens

13.3 Belt Filters

13.4 Plate and Frame Filters

13.5 Cloth vs. Paper Filters

13.6 Precoat

13.7 Head Loss Through Cloth Filters

13.8 Bag Filters

14 Membrane Filters and Reverse Osmosis

14.1 Introduction

14.2 Design Values

14.3 Process Selection

14.4 Reverse Osmosis

14.5 Mass Transfer Theory

14.6 Membrane Design Software

14.7 Membrane Materials

14.8 Membrane Configurations

14.9 RO Design Considerations

14.10 Design Parameters

15 Disinfection

15.1 Introduction

15.2 Rate of Kill – Disinfection Parameters

15.3 Chlorine

15.4 Ozone

15.5 Ultraviolet Light

15.6 Other Disinfecting Compounds

15.7 Disinfection by Ultra Filtration

16 Phosphorus and Nitrogen Removal

16.1 General

16.2 BardenPho© Processes

16.3 Chemical Phosphorus Removal

16.4 Nitrogen Removal

16.5 Conclusions

17 Carbon Adsorption

17.1 Introduction

17.2 The Freundlich and Langmuir Equations

17.3 Carbon Adsorption Physical Coefficients and Economics

17.4 Other Considerations

18 Ion Exchange

18.1 Resins

18.2 Physical Characteristics

18.3 Chemical Structure

18.4 Design Considerations

19 Dissolved Air Flotation and Techniques

19.1 Design Basics for DAF

19.2 Operating Parameters

19.3 Theory and Design

19.4 Ranges of Data

19.5 Electroflotation

19.6 Electrocoagulation

20 Coagulation, Flocculation and Chemical Treatment

20.1 Introduction

20.2 Sols

20.3 Flocculation and Mixing

20.4 Practice

20.5 Modeling

21 Heat Transfer Processes: Boilers, Heat Exchangers and Cooling Towers

21.1 Boilers

21.2 Boiler Classifications

21.3 Boiler Water Quality Requirements

21.4 Cooling Towers

22 Evaluating an Existing Wastewater Treatment Plant Design using Modeling Software

22.1 Step 1: Information Gathering

22.2 Step 2: Model Selection

22.3 Step 3: Laboratory and Other Data Organization

22.4 Step 4: Flow Sheet Setup and Model Organization

22.5 Step 5: Model Compilation and Setup

22.6 Step 6: Input and Output File Preparation

22.7 Step 7: Initialization of the Model Parameters and First Runs

22.8 Step 8: Parameter Adjustments

Index

End User License Agreement

List of Tables

Chapter 1

Table 1.1 Approximate conductivity of various chemicals in water where the subst...

Table 1.2 Solubility of oxygen in mg l

−1

in water exposed to water‐saturat...

Table 1.3 Molar Henry's law constants for aqueous solutions at 25 °C.

Table 1.4 Aqueous disassociation constants.

Table 1.5 Solubility of common minerals in freshwater.

Table 1.6 Some of the most common elements dissolved in seawater.

Table 1.7 Principal groundwater contaminants found in petroleum.

Table 1.8 Principal analytical methods for contaminants in water.

Table 1.9 Solubility rules for simple inorganic compounds in water.

Table 1.10 The 65 priority water pollutants according to the US code.

Table 1.11 UK list of priority pollutants.

Table 1.12 UK water quality sampling table for determining compliance with stand...

Table 1.13 EU list of priority water pollutants.

Table 1.14 Typical breakout of Federal Register effluent guidelines and standard...

Table 1.15 ASME boiler water quality guidelines.

Table 1.16 Wastewater characteristics from petroleum refining.

Table 1.17 Principal chemicals added to enhance one fracked well in Pennsylvania...

Chapter 2

Table 2.1 American Society of Mechanical Engineers (ASME) guidelines for water t...

Table 2.2 Common chemicals used in fracking.

Table 2.3 Concentration of select metal constituents in unconventional drilling ...

Table 2.4 Concentration of radionuclides in selected unconventional oil‐ and gas...

Table 2.5 Typical values (mg l

−1

) for effluent characteristics from petrol...

Table 2.6 Summary of discharge data for refineries connected to a POTW.

Table 2.7 2010 crop production data and water use.

Table 2.8 Typical waste loadings for different types of fruit and vegetable proc...

Table 2.9 A comparison of water use by specific crop type vs. animal production.

Table 2.10 Water use on a dairy farm based on 160 acres and 2000 head of cattle.

Table 2.11 Animal equivalents for pollution generation.

Table 2.12 Quantity of wastes generated by various animals in Concentrated Anima...

Table 2.13 Organic matter characteristics associated with digestion of CAFO wast...

Table 2.14 Common analytical methods for wastewater.

Table 2.15 Analytical method errors for common metals in water by ICP.

Table 2.17 Standard deviations for two types of COD measurements.

Table 2.18 Variation of

k

o

with temperature.

Chapter 3

Table 3.1 Hydraulic conductivity of various soils.

Table 3.2 Selected porosities and specific yields for common soil types.

Table 3.3 Frequently occurring natural compounds in water and their treatment.

Chapter 5

Table 5.1 Typical values for coefficient of

n

in the Manning equation.

Table 5.2 Hydraulic properties of various cross‐sections used in calculation of ...

Table 5.3 Properties of a Parshall flume.

Table 5.4 Standard discharge formulae for weirs.

Chapter 6

Table 6.1 Calculation of initiating and intermediate event probabilities for oil...

Chapter 7

Table 7.1 Theoretical oxidation products of common organic compounds.

Table 7.2 Relationship between BOD

5

, COD, and TOD for certain compounds.

Table 7.3 BOD, COD, and TOC for selected compounds and aromatic chemicals.

Table 7.4 Disassociation constants for common chemicals in water.

Table 7.5 Calcium carbonate equivalents for common ions in water.

Table 7.6 Water softening example.

Table 7.7 Metal solubility products and solubility constants for inorganic compo...

Chapter 8

Table 8.1 Selective comparison of solubility products or solubilities* for certa...

Table 8.2 Solubility products of cadmium ions in water.

Table 8.5 Solubility products for mercury in water.

Table 8.6 Characteristics of radium‐bearing waters from Piast Mine in western Po...

Table 8.7 Results of radium removal trials – results are in Be/l.

Table 8.8 Toxicity of cyanide compounds.

Table 8.9 List of banned or highly regulated pesticides, both organic and inorga...

Chapter 9

Table 9.1 Principal microorganisms in wastewater treatment.

Table 9.2 Bacteria that oxidize ammonia to nitrite.

Table 9.3 Bacteria that oxidize nitrite to nitrate.

Table 9.4 Conditions and organisms that result in poor sludge settling.

Table 9.5 Various kinetic constants for domestic wastewater.

Table 9.6 Kinetic constraints for industrial wastes.

Table 9.7 Aerobic wastewater treatment plant characterizations by loading rate.

Table 9.8 Typical design parameters for activated sludge process modifications.

Table 9.9 Formulation for parameter sensitive switches in activated sludge kinet...

Table 9.10 The Petersen Matrix for activated sludge equations.

Table 9.11 Properties of trickling filter media.

Chapter 10

Table 10.1 Biochemical reactions and corresponding oxidation reduction potential...

Table 10.2 Anaerobic pretreatment design parameters for contact stabilization an...

Table 10.3 Biogas composition and production from various sources.

Chapter 12

Table 12.1 Comparison of filter types.

Chapter 14

Table 14.1 Membrane separation properties and performance.

Table 14.2 Typical effluent concentration after membrane filtration.

Table 14.3 RO modeling software.

Table 14.4 RO model input parameters.

Table 14.5 Summary of pretreatment methods for reverse osmosis.

Table 14.6 Typical (Dow) membrane performance.

Table 14.7 Summary of operational parameters for RO systems.

Chapter 15

Table 15.1 Comparison of bacterial disinfection rates – the relative ease of dis...

Table 15.2 Comparison between ozone and peroxone oxidation.

Table 15.3 Ion species of bromine with pH (compare with Figure 15.4 for chlori...

Chapter 16

Table 16.1 Precipitation reactions for various phosphate forms (solubility of ph...

Table 16.2 Some of the compounds which are toxic to nitrifiers, and which would ...

Chapter 17

Table 17.1 Summary of carbon adsorption capacities, from EPA data.

Chapter 18

Table 18.1 Selective chelating resins in ion exchange.

Table 18.2 Ion preference and affinity for selected compounds.

Chapter 21

Table 21.1 ASME guidelines for water quality in continuously operated water and ...

Table 21.2 The recommended guidelines for steam purity limits for both startup a...

Chapter 22

Table 22.1 Input variables to each of the three principal activated sludge model...

List of Illustrations

Chapter 1

Figure 1.1 Solubility of oxygen in water at varying temperatures, and values of...

Figure 1.2 Solubility of nitrogen gas (N

2

) in water at temperatures between 0 °...

Figure 1.3 Ionized vs. free ammonia (%) at various pH levels at 0 °C.

Chapter 2

Figure 2.1 Typical profiles for chemical plant wastewater discharges, showing t...

Figure 2.2 Schematic for a typical induced‐draft cooling tower.

Figure 2.3 Chain of custody record.

Figure 2.4 Variation of BOD with temperature.

Figure 2.5 The oxygen sag curve illustrating oxygen depletion.

Figure 2.6 Variation of aquatic species with contaminated water.

Chapter 3

Figure 3.1 Darcy's law – determining permeability.

Figure 3.2 Common types of monitoring wells.

Figure 3.3 Typical trench utilization for dewatering.

Figure 3.4 Movement of groundwater contamination.

Figure 3.5 Flow profiles for properly and improperly designed injection wells a...

Figure 3.6 Horizontal well and distribution trench for subsurface cleanup.

Figure 3.7 Groundwater well hydraulics.

Figure 3.8 Plan and elevation views for determining effectiveness of an air inj...

Chapter 4

Figure 4.1 Precision versus accuracy. (a) High precision, low accuracy and (b) ...

Figure 4.2 Wastewater flows from a paper mill with solid deposition and floodin...

Figure 4.3 Gurley‐Price current meter.

Figure 4.4 P‐Type pitot tube often used in closed conduits and for air velocity...

Figure 4.5 (a) Gaussian frequency distribution. (b) Lognormal frequency distrib...

Chapter 5

Figure 5.1 Energy and hydraulic relationships for open channel flow.

Figure 5.2 Flow characteristics in a circular sewer.

Figure 5.3 Water surface profiles and slopes for open channel flows.

Figure 5.4 Elements of a hydraulic jump.

Figure 5.6 Pygmy current meter by Gurley instruments.

Figure 5.7 Hach Marsh‐McBirney Flowdar radar flowmeter.

Figure 5.8 Sutro or proportional weir.

Figure 5.9 Other types of weirs commonly in use.

Figure 5.10 Comparison of the accuracy of flow composite samplers under various...

Figure 5.11 One of several varieties of wastewater samplers. Shown without wate...

Chapter 6

Figure 6.1 Example of a fault tree analysis program.

Figure 6.2 Basic fault tree symbols.

Figure 6.3 Fault tree analysis for an oil spill.

Figure 6.4 Calculation of fault tree probabilities.

Figure 6.5 Bow tie analysis example.

Chapter 7

Figure 7.1 Warburg respirometer – drawing from US Patent Office.

Figure 7.2 BOD bottle.

Figure 7.3 Variation of BOD and rate constant with temperature.

Figure 7.4 Graphical representation of alkalinity determination by titration.

Figure 7.5 Relationships in carbonate alkalinity.

Figure 7.6 Hardness relationships in water.

Figure 7.7 Ion balance example.

Figure 7.8 Nitrogen in the environment.

Figure 7.9 Effects of pH and temperature on distribution of ammonia and ammoniu...

Figure 7.10 Metal solubilities at various pH levels. Source: USEPA Electroplati...

Chapter 8

Figure 8.1 API separator from DKV Refinery, Salambatta, Hungary.

Chapter 9

Figure 9.1 Anatomy of a bacterial cell.

Figure 9.2 Wastewater population dynamics.

Figure 9.3 Population dynamics in activated sludge wastewater treatment.

Figure 9.4 Some common types of organisms found in wastewater.

Figure 9.5 Determining the Monod growth rate coefficient.

Figure 9.6 Basic schematic of activated sludge system.

Figure 9.7 Basic wastewater treatment plant definitions.

Figure 9.8 Typical configurations for single and two‐stage trickling filter pla...

Figure 9.9 Waste generation rates from biological treatment plants.

Figure 9.10 Comparison between orbal and oxidation ditch wastewater treatment p...

Figure 9.11 Screen shot of STEADY program.

Figure 9.12 Screen shot of Hydromantis software GPSX.

Figure 9.13 Example of a SUMO interface window.

Figure 9.14 Graphical calculation of sludge retention time (SRT) example in SUM...

Figure 9.15 Partial screen shot of SIMBA control panel interface showing functi...

Figure 9.16 WEST software typical plant configuration.

Figure 9.17Figure 9.17 WEST configuration for a two‐tank sequencing batch react...

Figure 9.18 Example of WEST dynamic control output graphics.

Chapter 10

Figure 10.1 Anaerobic digestion process. Source:

Methane Recovery for Animal Ma

...

Figure 10.2 Bicarbonate and pH requirements for sludge digestion..

Figure 10.3 Classification of anaerobic digesters based on solids content of di...

Figure 10.4 Dual compartment anaerobic digester.

Figure 10.5 Two‐stage, high‐rate anaerobic digestion system.

Figure 10.6 Upflow anaerobic sludge blanket reactor.

Chapter 11

Figure 11.1 Change in specific gravity of a particle with water entrainment.

Figure 11.2 Typical design and configuration for clarifiers. (a) Rectangular cl...

Figure 11.3 Circular clarifier under construction. Observe the center baffle th...

Figure 11.4 Innards of a sludge thickener. Note the steeply sloping sides and m...

Figure 11.5 Drawing of a lamella.

Figure 11.6 Lamella model and drawing by Parkson taken at WEFTEC'03.

Figure 11.7 Spaghetti strand hollow tube membrane filter clarifier.

Chapter 12

Figure 12.1 Comparison of conventional and mixed media filters.

Figure 12.2 Head loss comparison between mixed media and conventional sand filt...

Figure 12.3 Grain size distribution of a natural sand versus desired sizing for...

Figure 12.4 Type of filtration versus size of particles removed.

Figure 12.5 Example of a hydraulic distribution problem for a filter bed. Durin...

Chapter 13

Figure 13.1 Typical drum microstainer installation..

Figure 13.2 Parabolic screen. Water flow is from the top and runs along the par...

Figure 13.3 Buchner funnel and a cutaway view of a Nutsche filter. Note the sim...

Figure 13.4 Municipal belt‐fed, continuous filter press. Note the torturous pat...

Figure 13.5Figure 13.5 A sludge filter press with the belt tension relaxed.

Figure 13.6 A plate and frame filter press in partial disassembly.

Figure 13.7 A plate and frame filter press with steam assist. Note the similari...

Figure 13.8 Diagram of a precoat layer on a skin filter.

Chapter 14

Figure 14.1 Cartridge filter system for RO systems.

Figure 14.2 Construction of a spaghetti strand filter cartridge.

Figure 14.3 Spaghetti strand membrane filter cartridge cutaway photograph.

Figure 14.4 Construction of a cartridge membrane filter unit.

Figure 14.5 Cutaway view of a spiral wound membrane element.

Chapter 15

Figure 15.1 Sample plot of polio virus survival ratio in disinfection experimen...

Figure 15.2 Time vs. concentration for 99% kill of

E. coli

and three viruses by...

Figure 15.3 f

2

virus and coliform inactivation in a chlorine contact tank under...

Figure 15.4 Distributions of hypochlorous (HOCl

−

) and hypochlorite (OCl

−

...

Figure 15.5 Break point chlorination by the formation of chloramines. The free ...

Figure 15.6 Schematic drawing of corona discharge method for making ozone.

Figure 15.7 UV spectra for various types of lamps. A low pressure lamp has the ...

Figure 15.8 UV lamp disinfection unit with horizontal configuration. Vertical c...

Figure 15.9 Schematic drawing of a bypass iodinator – United States patent 4 55...

Chapter 16

Figure 16.1 Photographs showing the effects of algal blooms in lakes due to pho...

Figure 16.2 Principal phosphorus removal systems: (a) modified activated sludge...

Figure 16.3 BardenPho process using two tanks. Note that the tanks need to be l...

Figure 16.4 Modified Ludzack–Ettinger process for phosphate removal. Requires l...

Figure 16.5 Schematic of the Phostrip process. The sludge is treated chemically...

Figure 16.6 Various phosphate forms and precipitation with metals.

Figure 16.7 Temperature effects on the maximum growth rates of nitrifiers.

Figure 16.8 Temperature dependence of the half‐saturation constants for nitrifi...

Figure 16.9 Effect of pH on ammonia oxidation by

Nitrosomonas

.

Figure 16.10 Oxidation of nitrate by

Nitrobacter

.

Figure 16.11 EPA Data for nitrification rates at select locations.

Figure 16.12 Effect of temperature on nitrification.

Figure 16.13 Some of the many biological nitrogen removal systems.

Figure 16.14 Schematics of BardenPho and conventional nitrogen removal systems ...

Figure 16.15 Ammonia removal data from Blue Plains (Washington, DC) publicly ow...

Figure 16.16 Efficiency of ammonia stripping at several loading rates under dif...

Figure 16.17 Isotherms for ammonia absorption in mixed solutions.

Chapter 17

Figure 17.1 Breakthrough curve for carbon adsorption.

Figure 17.2 Schematic diagram of Zimpro wet oxidation process for treating and ...

Chapter 19

Figure 19.1 Performance of typical dissolved air flotation systems. Source: Eck...

Figure 19.2 Configuration of a dissolved air flotation system.

Figure 19.3 Typical electroflotation system grid configuration.

Chapter 20

Figure 20.1 Zeta potential of a colloid (ionic charges and double layer around ...

Figure 20.2 Effect of cations on Zeta potential of a colloid.

Figure 20.3 Schematic of mixer and flocculator used in treating drinking water ...

Figure 20.4 Photo of a Stuart Flocculation Jar Tester – 6 place. The model show...

Chapter 21

Figure 21.1 Schematic of a fire tube boiler.

Figure 21.2 Water tube boiler schematic.

Chapter 22

Figure 22.1 Labeled flow sheet: number of completely stirred tank reactors (CST...

Figure 22.2 Example of a simple flow sheet. Note that the Combiners are only ma...

Guide

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Practical Wastewater Treatment

Second Edition

David L. Russell, PE

Lilburn, Georgia Global Environmental Operations Inc.

Copyright

This edition first published 2019

© 2019 John Wiley & Sons Inc.

Edition History

John Wiley & Sons Inc. (1e, 2006).

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Library of Congress Cataloging‐in‐Publication Data

Names: Russell, David L. (David Lloyd), 1943- author.

Title: Practical wastewater treatment / David L.Russell, PE, Lilburn,

Georgia, Global Environmental Operations Inc.

Description: Second edition. | Hoboken, NJ, USA : Wiley, 2019. | Includes

index. |

Identifiers: LCCN 2018035677 (print) | LCCN 2018036545 (ebook) | ISBN

9781119527053 (Adobe PDF) | ISBN 9781119527121 (ePub) | ISBN 9781119100850

(hardcover)

Subjects: LCSH: Water treatment plants. | Sewage–Purification.

Classification: LCC TD434 (ebook) | LCC TD434 .R87 2019 (print) | DDC

628.1/683–dc23

LC record available at https://lccn.loc.gov/2018035677

Cover design by Wiley

Cover image: © DLR‐GEO photo

Dedication

I want to thank several people for their inspiration. A second edition of a book is harder than writing a first edition, and a lot more work to ensure that one has something to say.

The following people provided motivation for this effort:

Elizabeth Ann Eason

Marianne Russell (1942–2007)

My girls: Laura Russell and Jennifer Russell

and

their girls: Edda, Zola and Miriam

Also a special note of thanks to Dr Benito Jose Marinas, Distinguished Professor and current head of the College of Civil and Environmental Engineering at the University of Illinois, Urbana, Illinois, for recognition.

And finally, Bob Esposito of Wiley for patience with an author.

Acknowledgments

I have been privileged to have known several giants in the environmental field. Many of them have already passed on, but their contribution of time and effort to the field of environmental engineering cannot be overlooked. Standing on the shoulders of these giants has given me a platform to be able to look out at the field and write a series of environmental books on various topics, including this work. I wish to acknowledge their contributions to the field of environmental engineering at this point:

Professor Richard S. Englebrecht

, former head of the Environmental Engineering Department at the University of Illinois, Urbana, for encouragement to follow my dreams.

Dr John Austin

(U of I), for assistance at a difficult time in my academic career.

Dr Benjamin Ewing

(U of I), for invaluable advice on career selection.

Dr V. T. Chow

(U of I), for his body of work on open channel flow and hydrology.

And some really great bosses over the years:

Leon Mattioli

and

Richard Sobel

of Allied Chemical Specialty Chemicals Division, Claymont, DE, and Morristown, NJ.

J. S. Lagarias

, and

Dr Louis McCabe

of Resources Research, Inc. (Division of Hazelton Laboratories, Reston, VA).

Dr Robert Irvine, PhD

, rediscoverer of the Sequencing Batch Reactor.

Dr Pieter VanRolleghem

, mathematician, engineer, and creator of WEST software.

And some very dear friends and professional associates:

Dr Charles Calmbacher, PhD, CIH

David R. Vaughn, PE

Dr Jeremy Dudley, PEng

Thomas McGowan, PE

Dr Donald Ray, PE

Leroy Staska

Thank you all.

David L. Russell, PE

Lilburn, Georgia

Global Environmental Operations Inc.

Preface

The first edition of this book was developed from a course I taught for the American Institute of Chemical Engineers. It was a first attempt to introduce industrial wastewater treatment theory, practices, and issues into the Chemical Engineering community as a stand‐alone discipline. It ultimately led to the first edition of this book.

There is a natural separation between industry and academia, and consequently the academics teach the basics of engineering, but more and more the separation between the way the subject material is taught and the way it is practiced is growing. Historically, much of the wastewater treatment field has been the provenance of the civil engineering community because of its association with sanitary engineering. Much of the time I spent in consulting, designing, and supervising the construction of municipal wastewater treatment plants was profoundly formulaic, and a largely mechanical exercise requiring little imagination and presenting few new challenges. The treatment of industrial wastes was far more interesting because the wastes varied so greatly, and their treatment required imagination and research.

My introduction to industrial wastewater treatment came through a Philadelphia‐based consulting company, and then subsequent work assignments for companies specializing in industrial wastewater treatment, and ultimately into the chemical industry. At one point, along the way, I realized that I was much more at home with the chemical engineers than with the civil engineers, and I still am.

This book was developed to give the student and the experienced practitioner some information and balance with regard to industrial practices and goals, and to describe how the water industry works, and what is important in it. I have tried to cover a wide range of topics to dump the more than 40 years of my experience into this brief volume to help the reader investigate the topics, and point out useful tools for further study and mastery of the subjects. I do not try to solve problems for the reader, but have provided a few problems on topics of interest.

Mistakes in this volume are mine alone. In compiling this work, I have amassed a wide list of reference materials, and have attempted to download a copy of the references for my own use, and to make them available to others. The Internet is full of both permanent and temporary information. Some of the information I have provided through links will undoubtedly be obsolete by the time this book is published or has a few years of age on it. So, if in researching the topics in the book, one finds that a key topic or paper is missing, contact me, and I will send you a copy of the individual paper, or the entire set of references for your digital library.

Dave Russell, PE

([email protected])

1Composition, Chemistry, and Regulatory Framework

Much water goeth by the mill

That the miller knoweth not of.

John Heywood (1497–1580)

1.1 Water Composition

Water is composed of two parts hydrogen and one part oxygen. It is not the materials of the water but the contaminants in it that make it important. If we look at a chemical reaction, we would be extremely satisfied with a reaction yield of 99% purity, as many reactions are in the 70–90% range. However, for water, even a 1% level of impurity is unacceptable. The levels of contaminants that we often consider insignificant in many products and foods can prevent us from using water. Impurities in water at the 1% level are equivalent to 10 000 ppm or mg l−1. At that level, even things like sodium chloride, table salt, in the water will render it undrinkable or harmful if consumed. In other instances, even a few milligrams of the right compound can render the water unpalatable or unusable for many aquatic purposes.

From another standpoint, the challenges that are presented to a wastewater treatment plant can be formidable. From a process standpoint, the reaction yields we look for produce a treated effluent with contamination levels of less than 10 mg l−1, and in a number of instances under 2 mg l−1 of particular contaminants. That is pretty good for a waste stream which may start out at 500 mg l−1 or more – it represents a 99.6% removal efficiency.

The usability of the water depends upon the compounds either dissolved in it or suspended in it. Contaminants can be organic or inorganic, solids or liquids. The usability of the water also depends upon the purpose of the use. For example, water used for cooling does not necessarily need to be of the same quality (purity) as that used for drinking or food preparation. Fecal and bacterial contamination of cooling water is often unavoidable in cooling towers, and tower water is treated with chemicals to reduce corrosion and inhibit excessive bacterial growth. In all cases, this water quality is not suitable for food preparation, nor for drinking. The sterility, turbidity, and dissolved constituents in the water are important quality control issues, but not all three are necessary for a specific use.

Water can also be too pure for a specific use. As an example, there are a number of locations worldwide that have their drinking water from thermal desalination sources. At one specific facility in the Middle East, the water is slightly above 43 °C, which is a bit uncomfortable for drinking, but because it is from a thermal desalination plant, it is distilled. Hence the water is aggressive because it is so low in carbonates and minerals that it has the effect of leaching the calcium from the asbestos‐cement piping, thus weakening it. Similarly, distilled water will corrode iron and steel piping, and drinking distilled water can also cause health problems such as diuresis, and a change in the electrolyte concentration in the body1 .

1.2 Water Characteristics and Physical Properties

Water (H2O) is dense, weighing in at 999.972 kg m−3, boiling at 99.98 °C (212.96 °F), and melting at 0.0 °C. It is the standard for viscosity, at 1 centipoise (cp) at 20 °C, and has a vapor pressure which is temperature‐dependent, from 611 Pa (0.180 in. of Hg) at 0 °C to 101 901.3548 Pa at 100 °C. The formula for vapor pressure of water in that range is

where A = 8.07131, B = 1730.63, and C = 233.426 and the temperature T is in Celsius between 0 °C and 100 °C. Pw is in pascals; for reference, 1 atmosphere is 101 325 Pa, or 764.2602 mm of Hg, and 1 mm of Hg is equal to 133.333 Pa.

Pure water is an excellent insulator, but water is seldom, if ever, pure, and contains small quantities of dissolved salts and many materials. The known maximum resistivity of pure water is 182 KΩ m−1 at 25 °C, (or 5.4945 × 10−6 S m−1 or 0.054945 µS cm−1).2 Very small levels of contaminants, sometimes in the parts per trillion (ppt) range (10−12 g l−1), can cause large increases in its conductivity. The conductivity of water is dependent not only on the quantity of contaminant, but on the type of contaminant. If the contaminant has an interaction with the water, and a secondary and/or tertiary ionization constant, it is much harder to relate conductivity to concentration.

When water has salts (ionic material) in it, it can become an excellent conductor. The electrical conductivity of water can be used to estimate the dissolved solids concentration in water if that value is less than about 1500 mg l−1. Above that point, the conductivity to dissolved solids curve flattens out and becomes unreliable. Most conductivity meters use a formula of:

Depending upon the water source and components, the value of C can vary anywhere from 0.51 to 0.83.3 At higher levels of dissolved solids, the coefficient changes. Table 1.1 illustrates the difference in conductivity of certain soluble materials in water. It should be noted that the conductivity is a function of the molecular structure of the solid or gas, and in some cases, substances that have second ionization constants or which react with water have substantially different values for conductivity which will not follow the formula shown above. Multiple ions in solution will have a nonlinear relationship to the values given in the table.

Table 1.1 Approximate conductivity of various chemicals in water where the substance is the principal contaminant.

Salt

Conductivity equivalent

TDS/conductivity

Sodium chloride

1.00 ppm TDS = 2.04 µS cm

−1

0.49

Sodium sulfate

1.00 ppm TDS = 1.49 µS cm

−1

0.67

Calcium sulfate

1.00 ppm TDS = 1.36 µS cm

−1

0.74

Sodium bicarbonate

1.00 ppm TDS = 1.06 µS cm

−1

0.91

Conductivity can also be used to measure the amount of calcium carbonate in water, if that is the principal dissolved salt. Calcium carbonate and its forms are referred to as hardness, and represent the ability of the water to leave CaCO3 deposits in piping, on heat exchangers, cooling towers, and so on. We will cover hardness in later chapters.

If an electric current is passed through water, it will generate hydrogen and oxygen in the ratio of 2:1 by volume. If there are salts such as sodium chloride in the water, a quantity of chlorine gas (Cl2) will be generated along with the hydrogen and oxygen. If large concentrations of high purity salt are dissolved in the water, and the positive and negative electrodes are separated by a membrane, the electric current becomes the basis for an electrolytic cell used in the chemical industry for the generation of chlorine gas and caustic soda (NaOH). With water having a conductivity less than 1200 µ℧, the voltage requirements increase as the salt concentration becomes proportionally less.

1.2.1 Solubility of Gases in Water

The most important dissolved gas is oxygen, and the second most important gas is nitrogen, because it comprises approximately 79% of our atmosphere, and is a potential source of nutrients for certain aquatic plants.

The solubility of various gases in water is given in many tables found in chemical and analytical handbooks, and on many commercial websites, including www.engineeringtoolbox.com, and in handbooks and analytical reference materials.4

Table 1.2 is a listing of the solubility of oxygen in water at temperatures between 0 °C and 30 °C, for various values of salts in the water. Table 1.2 shows the solubility of selected gases in water.

Table 1.2 Solubility of oxygen in mg l−1 in water exposed to water‐saturated air at atmospheric pressure (101.3 kPa).

Temperature

Chlorinity

0

5

10

15

20

25

 0

14.621

13.728

12.888

12.097

11.355

10.657

 1

14.216

13.356

12.545

11.783

11.066

10.392

 2

13.829

13.000

12.218

11.483

10.790

10.139

 3

13.460

12.660

11.906

11.195

10.526

 9.897

 4

13.107

12.335

11.607

10.920

10.273

 9.664

 5

12.770

12.024

11.320

10.656

10.031

 9.441

 6

12.447

11.727

11.046

10.404

 9.799

 9.228

 7

12.139

11.442

10.783

10.162

 9.576

 9.023

 8

11.843

11.169

10.531

 9.930

 9.362

 8.826

 9

11.559

10.907

10.290

 9.707

 9.156

 8.636

10

11.288

10.656

10.058

 9.493

 8.959

 8.454

11

11.027

10.415

 9.835

 9.287

 8.769

 8.279

12

10.777

10.183

 9.621

 9.089

 8.586

 8.111

13

10.537

 9.961

 9.416

 8.899

 8.411

 7.949

14

10.306

 9.747

 9.218

 8.716

 8.242

 7.792

15

10.084

 9.541

 9.027

 8.540

 8.079

 7.642

16

 9.870

 9.344

 8.844

 8.370

 7.922

 7.496

17

 9.665

 9.153

 8.667

 8.207

 7.770

 7.356

18

 9.467

 8.969

 8.497

 8.049

 7.624

 7.221

19

 9.276

 8.792

 8.333

 7.896

 7.483

 7.090

20

 9.092

 8.621

 8.174

 7.749

 7.346

 6.964

21

 8.915

 8.456

 8.021

 7.607

 7.214

 6.842

22

 8.743

 8.297

 7.873

 7.470

 7.087

 6.723

23

 8.578

 8.143

 7.730

 7.337

 6.963

 6.609

24

 8.418

 7.994

 7.591

 7.208

 6.844

 6.498

25

 8.263

 7.850

 7.457

 7.083

 6.728

 6.390

26

 8.113

 7.711

 7.327

 6.962

 6.615

 6.285

27

 7.968

 7.575

 7.201

 6.845

 6.506

 6.184

28

 7.827

 7.444

 7.079

 6.731

 6.400

 6.085

29

 7.691

 7.317

 6.961

 6.621

 6.297

 5.990

30

 7.559

 7.194

 6.845

 6.513

 6.197

 5.896

L.E. Geventman published a research paper on the solubility of selected gases in water.5 Geventman's paper states that the solubility of the selected gases can be calculated by the following formula:

where T* = T/100 K, and X1 is the solubility of the gas. A, B, and C are determined experimentally from chemical data. His paper provides a list of the coefficients. All values refer to a partial pressure of the gas of 101.325 kPa (1 atm).

The concentration of oxygen in water at any temperature is given by the following equation found in Standard Methods:6

where Chl is the chlorinity measured in grams/kilogram and is defined as chlorinity = salinity/1.80655, and salinity is approximately equal to total solids in water after carbonates have been converted to oxides and after all bromide and iodide have been replaced by chloride.

Figure 1.1 illustrates the solubility of oxygen in water at varying temperatures and values of chlorinity of zero and 1000 mg l−1.

Figure 1.1 Solubility of oxygen in water at varying temperatures, and values of chlorinity of zero and 1000 mg l−1.

1.2.1.1 Nitrogen

Nitrogen is soluble in water, but in the gaseous or N2 form is essentially inert. Principal forms of nitrogen in water are ammonia, nitrate, and nitrite. The only time one has to worry about the solubility of nitrogen is in its ionized forms, as ammonia nitrite, or nitrate (to be discussed later) or when one is designing a pressure flotation system.

Figure 1.2 illustrates the solubility of nitrogen gas (N2) in water at temperatures between 0 °C and 60 °C.

Figure 1.2 Solubility of nitrogen gas (N2) in water at temperatures between 0 °C and 60 °C (liters per kg of water).

Other common gases soluble in water are shown in Table 1.3 in terms of millimols. This enables calculation of the volume of the listed gases as a function of pressure. There is an example below.

Table 1.3 Molar Henry's law constants for aqueous solutions at 25 °C.

Gas

Constant (Pa (mol dm

−3

)

−1

)

Constant (atm (mol dm

−3

)

−1

)

He

282.7 × 10

6

2865.0

O

2

74.68 × 10

6

 756.7

N

2

  155 × 10

6

1600.0

H

2

121.2 × 10

6

1228.0

CO

2

2.937 × 10

6

  29.76

NH

3

 5.69 × 10

6

  56.9

1.2.2 Henry's Law

Henry's law gives us some idea of the solubility of other gases. In 1803, William Henry stated: “At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.”

where P is the partial pressure of the gas, C is its molar concentration, and K′C is the Henry's law constant. This is universally true for almost all liquids. However, as the concentrations and partial pressures increase, deviations from Henry's law become noticeable. This behavior is very similar to the behavior of gases, which deviate from the ideal gas law as pressures increase and temperatures decrease. Solutions that obey Henry's law are sometimes called ideal dilute solutions. Values of the Henry's law constants for many gases in many different organic compounds and gases have been measured. The inverse of the Henry's law constant, multiplied by the partial pressure of the gas above the solution, is the molar solubility of the gas.

Henry's law does not hold for gases that react with water and which have secondary and tertiary ionization constants. Some of those gases include hydrogen sulfide, chlorine, and carbon dioxide. The reactions of these gases are often pH‐dependent, and the free molar form of the gas is directly related to the inverse of the pH at which it is most soluble. For example, ammonia tends to form NH3OH in water, which is ammonium hydroxide, and is a strongly ionized base. As the pH of the water increases, the equilibrium reaction of:

shifts leftward, releasing more free ammonia into the solution. At a value of pH 12, the reaction is essentially complete and there is essentially no ionic ammonia left in aqueous solution. This relationship is shown in Figure 1.3.

Figure 1.3 Ionized vs. free ammonia (%) at various pH levels at 0 °C.

The value of the Henry's law constant is temperature‐dependent. The value generally increases with increasing temperature. As a consequence, the solubility of gases generally decreases with increasing temperature. One example of this can be seen when water is heated on a stove. The gas bubbles appearing on the sides of the pan well below the boiling point of water are bubbles of air, which evolve due to the lowered solubility from hot water. The addition of boiled or distilled water to a fish tank will cause the fish to die of suffocation unless the water has been allowed to re‐aerate before addition.

A very complete listing of many Henry's law constants can be found at http://www.henrys‐law.org/henry.pdf. The US Environmental Protection Agency (USEPA) has “Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations,” which has a section on calculation of Henry's law coefficients: http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_species_reregistration_workgroup/esa_reporting_fate.htm.

The US Geological Survey lists many Henry's law coefficients for organic compounds starting on page 16 of their Survey Professional Paper: Transport, Behavior and Fate of Volatile Organic Compounds in Streams. This can be found at http://www.books.google.com/booksid=uVLwAAAAMAAJ&pg=RA5‐PA16&lpg=RA5‐PA16&dq=allintext:+Calculating+Henry%27s+Law+Coefficients&source=bl&ots=Dshx6nVwbi&sig=DNbPSdFW4rXGdLYznU0MdRQNm5w&hl=en&sa=X&ei=ZS9RVMfXFYSYgwTKsoCoAg&ved=0CFQQ6AEwCQ#v=onepage&q=allintext%3A%20Calculating%20Henry's%20Law%20Coefficients&f=false. And, there is a Henry's gas law calculator on the Internet at http://www.webqc.org/henry_gas_law.html.

A computer program for calculating Henry's law coefficients can be found at http://www.srcinc.com/what‐we‐do/environmental/tools‐and‐models.html. The program is called the EPI Suite, which was developed for the USEPA, and it can also be found at http://www.epa.gov/opptintr/exposure/pubs/episuite.htm. The program is used for predicting chemical values of spilled substances, but is not limited to those applications.

If you have one value for a Henry's coefficient at a given set of conditions (m3 atm/mol) it can be transformed to another set of conditions by the equation:

where HTS is the coefficient at temperature TS, and TR is the reference temperature in degrees kelvin. The term HV,TS is the enthalpy of vaporization at TS in units of cal/mol, and Rc is the gas constant, which has a value of 1.9872 cal (mol K)−1. The enthalpy can be obtained either from steam tables for water or chemical engineering tables for other fluids, or by using an alternative procedure for estimating the enthalpy of vaporization from the USEPA website: http://www.epa.gov/athens/learn2model/part‐two/onsite/esthenry.html. Henry's coefficients may not really be considered as constants, but will vary with temperature and pressure.7

The study of Henry's law gained renewed interest in the environmental field when the remediation of benzene, toluene, ethylbenzene, xylene, and MTBE from leaking underground gasoline storage tanks became a US government funded program through a tax‐supported trust fund. The study of Henry's law led to various remediation options, including vacuum stripping of volatile organics that were trapped in the soil above the water table.

Henry's law is useful in a number of ways, as illustrated below.

Example 1.1 Oxygen in Water

Oxygen at 1 atm would have a molar solubility of (1/756.7) mol dm−3, or 1.32 mmol dm−3. The following examples will help in understanding this concept.

The amount of oxygen dissolved in air‐saturated water under normal atmospheric conditions at 25 °C can be calculated as follows:

Normal atmospheric condition is 20.948 mol% oxygen, which makes the partial pressure of oxygen 0.20948 atm or 20.67 kPa. Using Henry's law, the concentration of oxygen is 0.20948 atm/(756.7 atm (mol dm−3)−1), which is 0.2768 mmol dm−3; given the weight of 32 g mol−1, that comes out to be 0.0000088576 g dm−3 or about 8.85 mg l−1, which is to be compared with the value of 8.263 mg l−1 from Table 1.2 .

Example 1.2 Dissolved Air Flotation Systems

If we want to run a dissolved air flotation (DAF) system at 50 psig (pounds per square inch gauge, or 115.23 ft of water pressure or 3.4473785 bar) for the pressure for flotation, how much nitrogen and oxygen will be produced when we release the pressure back to atmospheric?

The density of water is about 1 kg dm−3 or 1000 kg m−3. The basic pressure on the water from the DAF system (50 psig) is approximately equal to a column of water 34.474 m high. A column of water 34.47 m high would exert a pressure of 344.737 kg dm−2 on its base, which converts to 344.73748 kPa pressure. The total system pressure is atmospheric pressure plus compression or 101.325 kPa + 344.7375 kPa or a total of 446.0625 kPa. (This is equivalent to 446.0625/101.325 = 4.4023 atm.) The pressure change of 3.4023 atm (4.4023 atm total − 1 atm = 3.4023 atm) will produce a concentration change of 3.4023/1600 = 0.0021264375 mol dm−3. (The pressure change of 344.738 kPa will cause a concentration change of 2.12644 mmol dm−3.) For each gallon of water the amount of nitrogen generated is 3.785 × 2.12644 mmol = 8.418 mmol of nitrogen per gallon, or about 189 ml of nitrogen per cubic foot.8

For oxygen, the change is about 4.496 mmol dm−3 or about 89.2 ml of O2 per cubic foot. (Note that the proportionality is approximately equal to the ratio of the Henry's constants for each of the gases.) The total volume for flotation is about 89.2 + 189 = 278.2 ml of gas per cubic foot.

Example 1.3 Benzene Concentration

In a remediation situation, the client has spilled gasoline. You use a calibrated portable ionization detector and determine that the concentration of benzene in the soil gas is 20 ppm. What is the concentration of benzene in the groundwater?

First, let's look at the Henry's law coefficient for benzene. A good source of data is the USEPA Superfund Guidance section.9 The tabular values for that reference list the following parameters:

CAS No.

Name

Sol. (mg l

−1

)

K

c

(atm‐M

3

mol

−1

)

K

c

′ (dimensionless)

71‐43‐2

Benzene

1.75E+03

5.55E‐03

2.28E‐01

where Kc′ is a dimensionless value for the Henry's law coefficient.

Assuming that the soil vapor and the water are in equilibrium, what is the concentration in the water? The mol. wt of benzene is 78.114 g mol−1.

20 ppm in air is a volume measurement; in order to get mg m−3 we need to multiply the gram molecular weight by the concentration and divide it by 23.235 (which is the volume of a mole (22.41 l) at 0 °C corrected for the temperature of the ground which is approximately 10 °C). So concentration C in mg m−3 = 20 × 78.114/23.235 = 67.238 mg m−3 in air. The molar concentration is then 67.238/78.114 = 0.8608 mmol m−3 or 0.0008608 mol m−3. Then C = 0.00555/0.0008608 or 0.00645 mol m−3 or 0.503 g m−3 = 0.503 mg l−1.

1.3 Solution Chemistry: Salts and Ions in Water

Water is the universal solvent. Everything dissolves in water to a greater or lesser extent. Depending upon the various elements and their combinations, organic and inorganic compounds are more or less soluble in water. Chemists use the solubility product as an indication of the solubility of a substance. In a later chapter we will discuss the practical uses of solubility product manipulation for the purposes of wastewater and drinking water treatment.

The solubility product is calculated by the following:

If we call the substance AC, the formula is then

Or if the substance is A2C3 then

where the substances in brackets are the molar concentrations.

But if one wants to calculate the solubility of the compound AC in water, make the substitution [A] = [C] and that would give you either [A]2 or [C]2 and the concentration of the compound would be [A] = [C] =√Ksp or the square root of the solubility product. If the compound is more complex and has the general formula of A2C3, then

The appropriate substitution to get the solubility of the compound would be:

where C or A represent moles of ion in solution, and we get 1.5 mole of A for every mole of C at equilibrium.

These equations assume that the substance does not react with water to form a weak acid or a weak base. It is also useful to note that the solubility product can be used to manipulate the solubility of specific compounds in water. If one adds or subtracts selected ions from the water, the solubility will be increased or decreased until equilibrium is restored.

Example 1.4 Copper Chloride

Copper (cuprous) chloride (CuCl) has a Ksp = 1.2 × 10−6. If one had a saturated solution of CuCl, at equilibrium, the concentration of copper would be equal to the quantity of chloride in solution or [Cu] = = 1.0954 × 10−3 mol l−1 = 0.06961 g l−1, or 69.1 mg l−1.

If we need to get copper in the solution down to 1 mg l−1 or less, that can be done by adding chloride: 1 mg l−1 = 0.000015737 mol l−1 = 1.5737 × 10−5 mol l−1. Back‐calculating to the Ksp: 1.2 × 10−6/1.5737 × 10−5 = 0.07626 mol l−1 of chloride in solution to reduce the Cu concentration to 1 mg l−1 or less. 0.07626 mol l−1 of chloride required is 35.453 × 0.07626 = 2.703 g l−1.

A list of metals and their solubility products will be presented in a later chapter on precipitation.

Hydroxide precipitation is also to be covered later, but it represents an exception to the general principles of solubility. Some metals form hydroxyl precipitates, which have optimum pH precipitation ranges. Outside those ranges, the solubility of the metal is higher. An example is aluminum hydroxide Al(OH)3, which has an optimum precipitation range at approximately pH = 5.5.10

1.4 Disassociation Constants for Weak Acid and Bases

Strong acids and bases fully disassociate in water. HCl, NaOH, HNO3, and others completely disassociate in water to form acids and bases. Weak acids or bases partially disassociate, and the equation used to describe that disassociation is similar to the one used for solubility. It is called an ionization constant, and if the compound is an acid, it would generally be expressed as

where H+ represents the cation (generally hydrogen) and A is the acid portion of the compound, for example, H2SO4 or HCl.

For bases, the base would be written

where M is generally a metal and OH− is the hydroxyl ion from water, for example, NaOH or Ca(OH)2.

The equilibrium constant is written slightly differently from the solubility product:

As a convention, the square brackets are used to express solids in solution, and the round brackets are used for weak acids and bases.

Take for an example:

and

The first and second ionization constants are:

So for H2CO3, which is obtained when CO2 is bubbled through water, K1 = 4.45 × 10–7, and K2 = 4.65 × 10−11.

The equations can be simplified and combined so that for CO2 bubbled through water the overall reaction may be combined into K1 × K2 = (H+)2(CO32−)/(H2CO3) which gives a combined value of K1–2 of 2.06925 × 10−17.

Another way of expressing the disassociation constant is similar to the way in which we express the acidity or alkalinity of a liquid, or pH. For water, pH is defined as the negative logarithm (to the base 10) of the concentration of ions in the water, or pH = −1 log10 (H+) or −log10 (1/(H+))