Aerobic granulation under the combined hydraulic and loading selection pressures

Area of Science:

• Environmental Biotechnology
• Wastewater Treatment Engineering
• Microbial Ecology

Background:

• Aerobic granulation is a key process for efficient wastewater treatment.
• Understanding the interplay of physical and chemical factors is crucial for optimizing granulation.
• Sequencing Batch Reactors (SBRs) offer a flexible platform for studying granulation dynamics.

Purpose of the Study:

• To assess the feasibility of aerobic granulation in SBRs.
• To investigate the impact of combined hydraulic shear force and organic loading rate (OLR) on granulation.
• To determine optimal operating conditions for stable aerobic granulation and reactor performance.

Main Methods:

• Two SBR reactors were operated under varying superficial upflow air velocities (3.2 and 2.4 cm/s).
• Organic Loading Rates (OLRs) were systematically increased from 6.0 to 15.0 kg COD/m³d.
• Reactor performance (effluent quality, stability) and granule characteristics were monitored.

Main Results:

• Stable aerobic granulation and good reactor performance were achieved at 3.2 cm/s upflow air velocity across OLRs from 6.0 to 15.0 kg COD/m³d.
• At 2.4 cm/s, stable operation was limited to OLRs of 6.0-9.0 kg COD/m³d, with granule deterioration at higher loads.
• Higher hydraulic shear force, facilitated by higher air velocity, was critical for robust granulation under elevated OLRs.

Conclusions:

• The combination of hydraulic shear force and substrate loading significantly influences aerobic granulation.
• Higher upflow air velocity (3.2 cm/s) promotes stable aerobic granulation and superior reactor performance over a wider OLR range.
• Optimizing shear and loading pressures is essential for successful aerobic granulation in SBR systems.