Rheology evolution of sludge through high-solid anaerobic digestion

Area of Science:

• Environmental Engineering
• Biotechnology
• Material Science

Background:

• Sludge rheology significantly impacts the efficiency of wastewater treatment processes.
• Understanding rheological changes during high-solid anaerobic digestion (AD) is crucial for process optimization.
• Factors like sludge retention time (SRT) and temperature influence AD performance and sludge characteristics.

Purpose of the Study:

• To investigate the rheology evolution of sludge during high-solid anaerobic digestion (AD).
• To determine the dependency of sludge rheology on sludge retention time (SRT) and reactor temperature.
• To evaluate the operational performance of high-solid AD reactors.

Main Methods:

• High-solid anaerobic digestion (AD) experiments were conducted.
• Sludge rheology was analyzed by measuring parameters such as shear stress, viscosity, yield stress, consistency index, and flow behavior index.
• Operational performance of AD reactors was monitored.

Main Results:

• Sludge exhibited significantly improved flowability after high-solid AD.
• Longer SRT resulted in sludge with lower shear stress, viscosity, yield stress, and consistency index, and a higher flow behavior index.
• Thermophilic AD reactors produced sludge with better flowability than mesophilic reactors, despite higher solid content, attributed to increased free and interstitial moisture.

Conclusions:

• High-solid AD enhances sludge flowability, making it easier to handle and transport.
• Sludge rheology is significantly influenced by SRT and temperature, offering potential for process control.
• Sludge rheology can be a feasible parameter for controlling and optimizing the anaerobic digestion process.