Gerardi M.H. Settleability Problems and Loss of Solids in the Activated Sludge Process

Hoboken: John Wiley & Sons. – 2002. – 191 p. The activated sludge process is the most versatile and most commonly used wastewater treatment system in North America. Although the activated sludge process is capable of efficiently treating municipal and industrial wastewaters, many activated sludge processes frequently experience operational problems related to poor compaction or settleability of secondary solids and loss of secondary solids from the clarifier. Operational problems associated with settleability problems and loss of solids include increased operational costs, loss of treatment efficiency, and permit violations. Because the activated sludge process is a biological wastewater treatment system, settleability problems and loss of solids are reviewed through undesired changes in activity and structure of the biomass—floc particles, protozoa, and metazoa. With the use of numerous tables and illustrations, this book describes the operational conditions responsible for settleability problems and loss of solids—including foam and scum production. The book also provides microscopic and analytical techniques for identifying and troubleshooting the conditions responsible for settleability problems and loss of solids. Pictures of wet mounts and smears of acceptable and unacceptable microscopic conditions of the activated sludge are included. Corrective measures for the operational conditions responsible for settleability problems and loss of solids are presented. This book is prepared for an audience of operators and technicians who are responsible for the daily operation of the activated sludge process. The book is written for troubleshooting and process control of the activated sludge process in efforts to reduce operational costs, maintain treatment efficiency, and prevent permit violations. ContentsOverview
The Activated Sludge Process
Floc Formation
A Floc Formation Model
Interruption of Floc Formation
Settleability problems and loss of solidsUndesired Filamentous Growth
Nutrient-Deficient Floc Particles
Denitrification
Sheared Floc Particles
Dispersed Floc Particles
Heavy Metals and Congealed Floc Particles
Low Dissolved Oxygen Concentration
Young Sludge Age
Floc Particles Lost Through Sludge Aging
Slug Discharge of Soluble cBOD
Viscous Bulking or Zoogloeal Growth
Increase in Percent MLVSS
Colloidal Floc Particles
Temperature
Foam and scum
Production and Accumulation of Foam and Scum
Identification of Foam
Controlling Foam Production and Accumulation
Settleability testing
Settleability Testing and Settling Rate
Settleability Testing: Microscopic Analyses
F/M, HRT, MCRT, MLVSS, SLUDGE AGE, SVI
Microscopic techniquesAbbreviations and Acronyms
Chemical Compounds and Elements