The Activated Sludge (AS) Process is old technology but is still widely adopted worldwide for its convenience and simplicity: an impressive number (many hundred of thousands) of this kind of system are in operation. Occasionally, problems such as bulking and foaming occur, causing regulation violations and large investment is often required immediately to control them. For this reason, an intense research effort has been made during the last few decades to face these problems, and this report details the work undertaken by the IWA Specialist Group on Activated Sludge Population Dynamics. This Scientific and Technical Report describes the main reasons fslyuor the growth of the different filamentous microorganisms in activated sludge, and the biological molecular tools available today for the identification of the main biomass components. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of seven chapters, presenting up-to-date technical and scientific aspects of these processes. Scientific and Technical Report No. 16

Activated Sludge Separation Problems: Theory, Control Measures, Practical Experiences, Second Edition, describes the most common activated sludge separation problems and explains the main reasons for the growth of the different filamentous microorganisms in activated sludge. The book summarizes the identification techniques for important groups of activated sludge microorganisms both based on conventional microscopic analysis and using the biological molecular tools available today (FISH and PCR). This new edition, with 70% new and updated material, also provides explanation of basic activated sludge process principles and of parameters necessary for process control and operation. The theory of secondary clarifies is described to the extent necessary for understanding the construction and operation of secondary clarifiers. The activated sludge reactor and secondary clarifies are treated as one system and the interactions are explained. The wide range of experiences around the world is documented and the methods to avoid the proliferation of these organisms are presented and critically reviewed. Activated Sludge Separation Problems consists of six chapters, presenting up-to-date technical and scientific aspects of these processes. The new edition also features an extended list of literature references for further reading. The book will be a valuable help for students of environmental engineering, wastewater specialists, plant operators and designers of activated sludge plants. It is also useful for specialists in wastewater operation laboratories, especially for those studying activated sludge separation properties.