[Achieving Partial Nitritation in a Continuous-flow Aerobic Granular Sludge Reactor at Different Temperatures Through...

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Aerobic granular sludge (AGS) systems offer potential for efficient wastewater treatment.
• Controlling nitritation is crucial for nitrogen removal processes.
• Partial nitritation is a key step in advanced nitrogen removal.

Purpose of the Study:

• To investigate the feasibility of partial nitritation in a continuous-flow AGS reactor.
• To determine the optimal dissolved oxygen to ammonia nitrogen ratio (R value) for partial nitritation at different temperatures (30, 20, and 10°C).
• To assess the impact of the ratio control strategy on ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) populations.

Main Methods:

• Inoculation of mature AGS in a continuous-flow reactor.
• Implementation of a dissolved oxygen (DO) to ammonia nitrogen (NH4+-N) ratio control strategy.
• Monitoring of nitritation performance at varying temperatures.
• Fluorescence in situ hybridization (FISH) to quantify AOB and NOB populations.

Main Results:

• Stable partial nitritation was achieved using the ratio control strategy.
• The required R values were 0.50 (±0.05) at 30°C, 0.35 (±0.03) at 20°C, and 0.20 (±0.02) at 10°C.
• Lower temperatures necessitated stronger oxygen-limiting conditions.
• FISH analysis showed a stable AOB concentration and a reduced relative abundance of NOB.

Conclusions:

• Ratio control is an effective strategy for achieving stable nitritation in continuous-flow AGS reactors.
• Lower temperatures require more stringent oxygen control for partial nitritation.
• The strategy is suitable for partial nitritation of low ammonia wastewater and potentially full nitritation of high ammonia wastewater.