August 2007, Vol. 19, No.8

Water Volumes

Sewer Processes: Microbial and Chemical Process Engineering of Sewer Networks

Thomas M. Walski

Thorkild Hvitved–Jacobsen (2002). CRC Press, 6000 Broken Parkway, N.W., Boca Raton, FL 33487, 256 pp., $149.95, hardcover, ISBN 1-56676-926-4.

Most wastewater professionals know that all sorts of biological and chemical processes occur in sewers, but for the most part, these processes have been ignored, and the emphasis has been placed on water quality at the treatment plant headworks. With this publication, the author finally gives biological and chemical processes the kind of attention they deserve.

The book is an excellent description of the chemistry that occurs in sewers. While it is not written for the layman, most engineers and managers with a reasonable knowledge of college chemistry can appreciate the subject matter.

The author does a very good job of explaining the processes involved in sewers, with chapters on kinetics, substrate, and mass transfer. The distinctions among aerobic, anoxic, and anaerobic processes are emphasized throughout.

The book also claims to enable engineers to design sewers and incorporate sewer processes into design. However, it falls somewhat short in actually describing how to do this. Only two examples are included, and they are more descriptive than quantitative. Some worked-out numerical examples would have illustrated how to perform calculations.

Preliminary review of this book leads the reader to expect it will answer such questions as how much oxygen, peroxide, permanganate, and nitrate need to be fed into a sewer to prevent hydrogen sulfide formation. The author discusses this topic a great deal but never gets to the point of showing how to perform the calculations. Another area that should have been discussed is what slopes, depths, and flow rates can prevent hydrogen sulfide production.

While the author explains that the collection system should be part of a holistic approach to treatment, most of the book is devoted to the theory of the processes and does not help engineers and operators understand how to change the system to make it perform better. Therefore, this book falls short of other publications, such as the American Society of Chemical Engineers’ manual Sulfide in Wastewater Collection and Treatment Systems, in terms of being a practical, “how-to” book.

In spite of its shortcomings as an operator or engineer cookbook, the book is a valuable resource for those who want to know exactly what is going outside and inside sewers.

Thomas M. Walski is senior advisory product manager at Bentley Systems Inc. (Nanticoke, Pa.).