A unified theory for upscaling aerobic granular sludge sequencing batch reactors

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment Technologies

Background:

• Aerobic granular sludge sequencing batch reactors (SBRs) are an advanced technology for effective wastewater treatment.
• Aerobic granulation in SBRs is understood to be influenced by specific selection pressures on microorganisms.

Purpose of the Study:

• To review and unify the identified selection pressures governing aerobic granulation in SBRs.
• To propose a single theoretical basis for understanding and manipulating aerobic granule formation and characteristics.

Main Methods:

• Literature review of existing studies on aerobic granular sludge SBRs.
• Analysis of identified selection pressures: settling time, volume exchange ratio, and discharge time.
• Development of a unified selection pressure theory based on minimal bio-particle settling velocity.

Main Results:

• Three key selection pressures (settling time, volume exchange ratio, discharge time) can be unified into a single parameter: minimal settling velocity of bio-particles.
• This unified selection pressure is the primary determinant of aerobic granulation in SBRs.

Conclusions:

• The unified selection pressure theory provides a robust framework for optimizing aerobic granule formation and characteristics in SBRs.
• This theory offers a foundational engineering principle for the successful scale-up of aerobic granular sludge SBR systems.