Mdodeling a nitrite-dependent anaerobic methane oxidation process: parameters identification and model evaluation.

Area of Science:

• Environmental Microbiology
• Biogeochemical Cycles
• Microbial Ecology

Background:

• Nitrite-dependent anaerobic methane oxidation (n-damo) is a recently identified microbial process crucial for methane cycling.
• This process involves bacteria oxidizing methane using nitrite, producing nitrogen gas.

Purpose of the Study:

• To develop and validate a kinetic model for the n-damo bioprocess.
• To determine key kinetic parameters for n-damo bacteria under specific conditions.
• To identify optimal operational parameters for enhancing n-damo efficiency.

Main Methods:

• Development of a kinetic model incorporating Monod-type kinetics and diffusion-reaction principles.
• Conducting batch activity tests to obtain essential kinetic parameters.
• Operating a sequencing batch reactor (SBR) for 100 days to gather real-world performance data.

Main Results:

• Key kinetic parameters for n-damo bacteria at 30 °C were determined: growth rate (0.0277 d⁻¹), decay rate (0.00216 d⁻¹), methane affinity (0.092 mmol L⁻¹), nitrite affinity (0.91 mmol L⁻¹), and inhibition constant (4.1 mmol L⁻¹).
• The developed model accurately simulated SBR performance for the initial 76 days.
• Methane was found not to be a limiting factor at atmospheric pressure due to high bacterial affinity.
• The optimal nitrite concentration for the process was identified as 1.92 mmol L⁻¹.

Conclusions:

• The kinetic model effectively describes the n-damo bioprocess and can predict performance.
• Understanding kinetic parameters is vital for optimizing n-damo processes in environmental applications.
• Methane availability is generally sufficient, while nitrite concentration is a critical factor for controlling n-damo efficiency.