New insights in morphological analysis for managing activated sludge systems

Area of Science:

• Environmental Science
• Microbiology
• Chemical Engineering

Background:

• Activated sludge (AS) processes are crucial for wastewater treatment.
• Operational parameters are widely assumed to influence AS efficiency via sludge properties.
• A deeper understanding of these complex interactions is needed.

Purpose of the Study:

• To investigate the relationship between operational parameters and activated sludge floc morphology.
• To quantify AS floc properties using automated image analysis.
• To identify how specific operational conditions affect floc structure and process performance.

Main Methods:

• A laboratory-scale activated sludge system was subjected to sequential operational modifications.
• Automated image analysis quantified AS floc morphology (size, circularity, convexity, solidity, aspect ratio) for over 100,000 flocs per sample.
• 3D distributions combining morphological properties were introduced to analyze floc populations.

Main Results:

• Filamentous bulking was identified by a shift towards larger flocs with lower solidity and circularity.
• Washout phenomena correlated with smaller AS flocs and increased solidity.
• Increased recycle ratios and decreased COD:N ratios led to reduced floc sizes and stable shape evolution.
• Volume-based 3D distributions effectively combined size and shape data for analysis.

Conclusions:

• Automated image analysis and 3D distribution analysis provide powerful tools for understanding AS floc dynamics.
• Floc morphology is a sensitive indicator of process disturbances like bulking and washout.
• This approach enhances the understanding of activated sludge process control and optimization.