Book excerpt: The most common activated sludge operating problems causing poor plant performance are related to solids separation. Especially common are bulking and foaming. Without a proper scientific foundation to support the efforts of wastewater treatment plant management, many attempts to thwart bulking and foaming have failed. Manual on Solving Activated Sludge Bulking, Foaming, and Other Solids Separation Problems provides the critical scientific and practical underpinnings needed to understand and combat these problems. The third edition of this flagship text is a comprehensive, concise guide to the microbiological and technical aspects of controlling all types of solid separation problems. The scientific theory is applied to real-world scenarios, greatly increasing the number of real-world examples of successful control methods. New information is also included on filamentous organism growth and its application in the control of sludge bulking and foaming. Now plant operators, regulators and wastewater engineers have a complete guide for battling these formidable design and operating problems.