Shrinking the Aeration Footprint: Innovative Approaches to Nitrogen Removal in MBR Systems

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Bioreactor Systems

Background:

• Membrane bioreactor (MBR) systems are crucial for advanced wastewater treatment.
• Optimizing MBR design can lead to cost savings and improved efficiency.
• The role of biological processes within the membrane tank itself requires further clarification.

Purpose of the Study:

• To evaluate the biological treatment performance of the membrane tank in an MBR system.
• To compare MBR performance with and without an upstream aeration basin.
• To determine if biological reactions in the membrane tank significantly contribute to overall treatment efficiency.

Main Methods:

• Conducted a 7-month pilot investigation in Tacoma, WA.
• Compared two operating schemes: with and without an upstream aeration basin.
• Monitored effluent quality for biochemical oxygen demand (BOD), carbonaceous BOD (cBOD), ammonia, soluble chemical oxygen demand (sCOD), denitrification, and biological phosphorus removal.

Main Results:

• Effluent concentrations of BOD, cBOD, and ammonia were similar across both operating schemes.
• Denitrification and biological phosphorus removal were also observed within the membrane tank.
• The presence or absence of the upstream aeration basin did not significantly alter key effluent parameters.

Conclusions:

• Biological processes occurring within the membrane tank play a significant role in MBR treatment performance.
• MBR system designers should consider the biological activity within the membrane tank when determining reactor sizing.
• Potential exists to reduce the aerated volume in MBR systems by leveraging in-tank biological reactions.