Waste water treatment is the largest biotechnology industry in the world, handling and disposing of domestic and industrial wastes so they present no threat to the general populace or the environment at large. The activated sludge process is the cornerstone of sewage treatment systems. Although it is a biological process and has been in use for more than 80 years, we still lack detailed understanding of how it works and how its performance might be better controlled and manipulated. This book presents a comprehensive review of what is currently known about the general microbiology of activated sludge and some of the bacteria responsible for the major operational problems encountered. Current understanding and the existing literature are critically assessed and new potentially valuable areas for research suggested. Methodology particularly appropriate to the study of the bacteria that cause bulking and foaming is described, and there is an identification section consisting of photomicrographs and detailed descriptions of the filamentous and other bacteria commonly seen in activated sludge plants. The impact of molecular methods on our understanding of activated sludge microbiology is emphasized throughout the book. The book will be of immediate interest to both microbiologists and waste water engineers, and has been written so as to be relevant and understandable to both. It will also be of interest and value to postgraduate students and researchers working in the fields of environmental engineering, general microbiology and microbial ecology.

This book has been a long time in preparation. Initially it grew out of our frustrating attempts over the past ten years to identify the filamentous bacteria seen in large numbers in most activated sludge plants, and the realization that we know very little about them and the other microbial populations in these systems. Unfortunately this book does not provide many answers to the problems these filamentous bacteria can cause, but we hope it might encourage microbiologists and engineers to communi cate more with each other and to spend some time trying to understand the tax onomy, ecology and physiology of activated sludge microbes. It is now very timely, for example, to try to provide these filamentous bacteria with proper taxonomically valid names and to determine their correct place in bacterial classifications. This book is not meant to compete directly with the books by Gray (1989, 1990) nor the excellent manual published by Jenkins and coworkers (1993b), which has been invaluable to us and others trying to identify filamentous bacteria. Wanner's book (1994a) also provides an excellent account of the problems of bulking and foaming caused by filamentous bacteria. These publications and others by Eikelboom's group have made an enormous contribution to the study of filamentous bacteria, and will con tinue to do so."