“Fryday, May 9, 1851 … Made 22 miles to day, Good forage for the animals. Not much wood. The water of the plat is very good when settled, which we do by throwing a little alumn in and let it stand awhile.”
From the diary of Amelia Hardy in Covered wagon woman,
diaries and letters from the western trails, 1840–1890.
A number of new developments have been included in this third edition. Most of these were included by expanding existing sections, or new sections were added. However, the general organization of the second edition has been maintained in this book. Topics that have been included as new sections include algae removal and harvesting; dissolved organic nitrogen (DON) removal; wastewater treatment by coagulation and chemically enhanced primary treatment (CEPT); activated sludge bulking and foaming control and enhanced bioflocculation; inorganics removal; and turbidity and its measurement, included as an Appendix. In some cases, topics have been separated into specific treatment using metal coagulants (Chapter 4) or organic polymers (Chapter 5) to conform with the general layout of the book. These cases include algae removal and harvesting; wastewater treatment by coagulation and CEPT; and activated sludge bulking and foaming control and enhanced bioflocculation.
Despite the additions and modifications to the book, most of the comments in the Preface to the second edition are still relevant. Coagulation and flocculation play a dominant role in many water and wastewater treatment schemes, including those incorporating membrane treatment. Because of the complex interdependence of numerous factors inherent in the coagulation and flocculation processes, a thorough understanding of the phenomena involved is essential.
There are several excellent books on water treatment that include chapters and sections on coagulation and flocculation. However, current literature often does not present an in-depth account of coagulation and flocculation in a single publication. Moreover, a given publication may emphasize theoretical aspects with little indication of the practical significance of the phenomena, or largely ignores the theoretical development and presents essentially practical material only. In many cases the uninitiated reader is left without an overall picture of the processes as a whole and, without further extensive literature searching, succeeds in achieving only a superficial understanding. The intention of this book is to help remedy these inadequacies.
An attempt has been made to present the subject matter logically and sequentially from theoretical principles to practical applications. Successive chapters deal with, in turn, properties of materials present in waters and wastewaters; characteristics and types of coagulants commonly in use; mechanisms and practical implications of destabilization of waterborne material using metal coagulants and polyelectrolytes; considerations related to coagulant addition at the rapid mixing stage; theoretical and practical considerations of flocculation; and details of experimental procedures for assessing primary coagulants, flocculant aids, sludge conditioners, and flocculation parameters. Numerous examples are included as appropriate.
Treatment and disposal of sludges resulting from coagulation-flocculation related operations is dealt with in an Appendix. This important topic has been separated from the main text to avoid disturbing the continuum of the presentation.
The book in its present form evolved from material offered to undergraduate and postgraduate university students. Although it has been progressively modified and increased in scope to cater for the requirements of practicing chemists, chemical and civil engineers involved with water and wastewater treatment, the book still retains a didactic nature. Therefore, it is hoped that the book will serve three functions:
- A readable and useful presentation for the water scientist and engineer.
- A convenient reference handbook in the form of numerous examples and appended information.
- Course material for under- and postgraduate students.
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