Modelling an industrial anaerobic granular reactor using a multi-scale approach.

Area of Science:

• Environmental Engineering
• Biochemical Engineering
• Mathematical Modeling

Background:

• Anaerobic digestion is crucial for wastewater treatment and biogas production.
• Accurate modeling of anaerobic digesters is essential for process optimization and control.
• Existing models often require enhancements to capture complex microbial and physical dynamics.

Purpose of the Study:

• To present results from an industrial project on modeling anaerobic digesters.
• To develop and validate a multi-scale mathematical approach for digester simulation.
• To extend the Anaerobic Digestion Model No 1 (ADM1) with phosphorus, sulfur, and ethanol dynamics.

Main Methods:

• A multi-scale mathematical model integrating hydrodynamics, granule growth, and microbial competition.
• Extension of ADM1 with P, S, and Et-OH fate.
• Utilized Benchmark Simulation Model No 2 (BSM2) for dynamic wastewater conditions.
• Model validation against two plant data sets (#D1, #D2).

Main Results:

• The model accurately describes organic and nutrient transformation, and methane/CO2/sulfide production (avg. 10% deviation).
• Predicted stratified granule structure due to loading rates, mass transfer, and bacterial affinity.
• Identified distinct microbial zones within granules (inerts/methanogens inner; acidogens/acetogens outer).
• Assessed effects of pH and S:COD loading on performance and intra-granular precipitation.

Conclusions:

• The developed multi-scale model satisfactorily simulates anaerobic digester performance.
• The model provides insights into granule structure and its impact on microbial distribution.
• The approach offers opportunities for engineering optimization of anaerobic digestion processes.