Colloids, flocculation and carbon capture - a comprehensive plant-wide model

Area of Science:

• Environmental Engineering
• Biotechnology
• Wastewater Treatment

Background:

• High-rate activated sludge (HRAS) systems are crucial for carbon capture in water resource and recovery facilities (WRRFs).
• Existing models inadequately simulate biological reactions in low solids retention time (SRT) systems, limiting optimization of carbon recovery and methane potential.
• There is a need for advanced models to accurately describe processes in short SRT conditions.

Purpose of the Study:

• To develop and validate a new model for simulating biological reactions in activated sludge systems operating at very short SRTs.
• To improve the understanding of colloidal material removal, extracellular polymeric substance (EPS) generation, flocculation, and intracellular storage.
• To extend the applicability of whole plant models to a wider range of SRTs, including low SRT operations.

Main Methods:

• Development of a novel mathematical model incorporating colloidal material removal and EPS dynamics.
• Testing the model against pilot-scale reactor data from an A-stage (adsorption) process.
• Validation of the model's performance in simulating chemical oxygen demand (COD) and colloid removal at low SRTs.
• Further testing on systems with longer SRTs and in digestion processes with decay-generated colloids.

Main Results:

• The new model accurately matched pilot reactor performance data for COD and colloid removal at low SRT.
• The model demonstrated effectiveness in simulating systems with longer SRTs and in digestion scenarios.
• The model successfully captures key biological reactions crucial for carbon capture and organic recovery in HRAS systems.

Conclusions:

• The developed model provides a robust tool for simulating activated sludge processes across a broad range of SRTs, particularly at very short SRTs.
• This advancement enables better optimization of carbon capture, organic carbon recovery, and methane production in WRRFs.
• The model enhances the predictive capability of whole plant models for diverse operational conditions in wastewater treatment.