Disturbances Detection in Activated Sludge Systems

Activated sludge systems are biological processes greatly used in wastewater treatment plants (WWTPs). These systems are composed of an aerated tank where the biochemical phase occurs and a settler where the physical phase takes place. Solid-liquid separation is one of the most critical steps in activated sludge processes. This stage presents three main objectives: sludge thickening, effluent clarification, and sludge storage. Sludge settling ability is usual dependent of the structure, density and microbial aggregates size, which are prone to change, due to variations and disturbances of WWTPs conditions (Wilen et al., 1999). When the operating conditions are not perfect, mainly in terms of organic load, nutrients and oxygen supply, some malfunctions may occur such as pinpoint flocs formation, filamentous bulking, dispersed growth, and zoogleal or viscous bulking.