Impact of reactive settler models on simulated WWTP performance

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Biochemical Engineering

Background:

• Wastewater treatment plant (WWTP) models often neglect biological reactions in settler sludge blankets.
• Accurate simulation of settler processes is crucial for optimizing nitrogen removal.

Purpose of the Study:

• To investigate the impact of incorporating reactive settler models into Activated Sludge Model 1 (ASM1) simulations.
• To compare the performance of a fully reactive ASM1 settler model against a simplified return sludge model and a non-reactive model.

Main Methods:

• Simulations were conducted using a whole plant model with a non-reactive Takács settler as a reference.
• Two reactive settler models were evaluated: a fully reactive ASM1 Takács settler and a return sludge model block with oxygen/nitrate removal.
• Performance was assessed under both steady-state and dynamic influent conditions.

Main Results:

• The fully reactive ASM1 settler model predicted significant improvements in nitrogen (N) removal: 15.3% for steady-state and 7.4% for dynamic conditions.
• The oxygen/nitrate return sludge model showed a 10% improvement in N removal under dynamic conditions.
• The simplified return sludge model is computationally more efficient and avoids overestimating decay processes.

Conclusions:

• Reactive settler models enhance the accuracy of WWTP simulations, particularly for nitrogen removal.
• The fully reactive ASM1 settler model offers superior performance prediction, while the simplified return sludge model presents a computationally efficient alternative.
• Model selection should consider the trade-off between simulation accuracy and computational cost for ASM1 plants.