A novel fuzzy-logic control strategy minimizing N₂O emissions.

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Microbial Ecology in Wastewater

Background:

• Nitrous oxide (N₂O) is a potent greenhouse gas emitted during wastewater treatment.
• Ammonium (NH₄⁺) effluent concentration is a key indicator of treatment efficiency.
• Autotrophic ammonia-oxidizing bacteria (AOB) and heterotrophic denitrifiers contribute to N₂O production.

Purpose of the Study:

• To propose and evaluate a novel control strategy for simultaneously reducing N₂O emissions and effluent NH₄⁺.
• To investigate the efficacy of a fuzzy logic controller based on inlet/outlet ammonium and nitrate measurements.
• To determine the optimal control approach for different N₂O production pathways in wastewater treatment plants.

Main Methods:

• Development of a fuzzy logic controller utilizing ammonium and nitrate concentrations.
• Simulation-based testing of the controller across various model structures and parameters.
• Analysis of N₂O mitigation capabilities under different microbial conditions (AOB denitrification vs. NH₂OH oxidation).

Main Results:

• The proposed fuzzy logic controller effectively reduces N₂O emissions and effluent NH₄⁺ when AOB denitrification is the primary N₂O source.
• A cascade controller optimizing oxygen supply based on effluent NH₄⁺ is more effective for incomplete NH₂OH oxidation pathways.
• The strategy's performance is validated through comprehensive simulations.

Conclusions:

• The developed fuzzy logic control strategy is a viable tool for mitigating N₂O emissions in specific wastewater treatment scenarios.
• Tailoring control strategies to dominant N₂O production pathways is crucial for effective greenhouse gas reduction.
• Further research and implementation in real-world plants are recommended to confirm findings.