80

which deserves considerable praise, both to the authors of the chapters and also to the efforts of the editors.

D. E. BROWN

Coagulation and Flocculation With an emphasis on water and wastewater treatment

by John Bratby Published by Uplands Press, Croydop, 1980; xi + 354 pp.; price 830.00

The subsidiary title of this book is some- thing of an understatement, since the text is almost exclusively concerned with water and wastewater treatment. The use of the terms ‘coagulation’ and ‘flocculation’ and the distinction drawn between them follows accepted practice in the water industry, ‘coagulation’ referring to the destabilization of particles and the formation of small aggregates, and ‘flocculation’ to the produc- tion of larger aggregates by some form of agitation.

The author has set himself the formidable task of covering both fundamental and applied aspects of the subject in some detail and it must be said that he has been much more successful in the latter than the former. The treatment in Chapter 2 of such topics as the electrical double layer, electrokinetics, van der Waals forces (which Dr. Bratby persistently attributes to van der Waal) and DLVO theory is not entirely satisfactory and a number of misconceptions are apparent. Far too much unnecessary detail is included and the author cannot resist frequent digressions into such topics as the statistical definition of entropy, the electron orbitals of water and. the derivation of the capacity of a flat con- denser. The detailed treatment of colloid stability theory might have been justified if the results were used in subsequent chapters, but this is not the case. A concise, qualitative account of destabilization mechanisms would have been adequate and less daunting to the uninitiated reader.

In Chapter 3 we are introduced, in a refreshingly down-to-earth manner, to the various types of coagulant available with information such as the kind of bags in which aluminium sulphate is supplied. There are

brief accounts of the chemistry of hydrolys- ing metal salts and of polyelectrolytes, together with a useful description of some dosing techniques.

There follow more detailed chapters on destabilization with metal coagulants and polyelectrolytes, including their use in the removal of phosphate and organic colour from water. These are good, up-to-date summaries of the present state of the art.

The very important practical topics of rapid mixing and flocculation are given separate chapters, which will be useful to those working in this field. The flocculation chapter (including flotation and direct filtra- tion for good measure) is a particularly good account of the subject, with a great deal of attention directed towards design problems. The final chapter considers the various test methods which are available.

There are some useful appendices, includ- ing lists of approved polymers, a comprehen- sive ‘ready reference’ guide to coagulation and flocculation applications and a brief survey of the problem of sludge treatment and disposal.

The author has a slight tendency towards verbosity, ‘meritoriousness’ and ‘relative celerity’ being examples, but otherwise the book is quite well written. The reproduction direct from typescript has not detracted too much from the appearance of the book, although there are some very confusing splits between lines which could easily have been avoided. Some of the figures reproduced from other sources are too small to convey much useful information. Excellent author and subject indexes are provided.

On the whole, this work is a valuable addition to the water treatment literature and, despite a few shortcomings, is highly recommended to practitioners in the field.

JOHN GREGORY

Dynamics, Exposure and Hazard Assessment of Toxic Chemicals

Edited by R. Haque Published by Ann Arbor Science Publishers Inc., Ann Arbor, Michigan, 1980; 496 pp.; price $18.50

This volume is a collection of papers dealing primarily with the transport and fate of chemicals in the environment. In this context, transport refers to the transport and