Assessing microbial competition in a hydrogen-based membrane biofilm reactor (MBfR) using multidimensional modeling

Area of Science:

• Environmental biotechnology
• Biofilm engineering
• Wastewater treatment

Background:

• Membrane biofilm reactors (MBfRs) deliver hydrogen to denitrifying bacteria (DNB) for efficient wastewater treatment.
• Hydrogen also fuels competing sulfate-reducing bacteria (SRB) and methanogens (MET), especially at low nitrate concentrations near the biofilm base.
• MBfRs may inadvertently promote SRB and MET due to high hydrogen availability at the biofilm base.

Purpose of the Study:

• To investigate strategies for controlling SRB and MET proliferation in MBfRs.
• To compare the applicability of 1-D and 2-D biofilm models for simulating competition in counter-diffusional biofilms.
• To identify key factors influencing denitrification efficiency and microbial competition within MBfRs.

Main Methods:

• Utilized computational modeling (1-D and 2-D) to simulate microbial competition within MBfRs.
• Investigated the impact of hydrogen concentration control via intramembrane pressure.
• Assessed the effects of biofilm management strategies, including sloughing and erosive detachment, and biofilm thickness.

Main Results:

• Controlling hydrogen concentration through intramembrane pressure is crucial for limiting SRB and MET growth.
• Maintaining thinner biofilms enhances denitrification rates and suppresses SRB and MET.
• Periodic biofilm sloughing effectively controls slow-growing SRB and MET.
• 2-D modeling revealed that rough membrane surfaces create niches favoring SRB and MET, a mechanism missed by 1-D models.

Conclusions:

• MBfR performance relies on managing hydrogen supply and biofilm characteristics to outcompete undesirable microorganisms.
• Biofilm management, including controlling thickness and inducing sloughing, is essential for efficient MBfR operation.
• 2-D modeling provides a more comprehensive understanding of complex microbial interactions in MBfRs compared to 1-D models.