Controlling cold temperature partial nitritation in moving bed biofilm reactor

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Bioreactor Design

Background:

• Partial nitritation is a key process in nitrogen removal from wastewater.
• Low temperatures and high COD/N ratios pose challenges for conventional nitritation processes.
• Biofilm reactors offer potential for stable microbial community development.

Purpose of the Study:

• To investigate control strategies for partial nitritation in a moving bed biofilm reactor (MBBR) at low temperatures (10°C).
• To evaluate the effectiveness of different control methods, including biofilm age, oxygen limitation, and pH control.
• To develop a dynamic process control algorithm for successful partial nitritation under challenging conditions.

Main Methods:

• Utilized a moving bed biofilm reactor (MBBR) with synthetic wastewater.
• Investigated three control strategies: media replacement (biofilm age), oxygen limitation, and combined oxygen limitation with pH control.
• Monitored nitrogen species (NH4-N, NO2-N, NO3-N) and COD concentrations during steady-state operation.

Main Results:

• Successful partial nitritation was achieved only when combining oxygen limitation with pH control.
• Achieved average concentrations of NH4-N (16.0 ± 1.6 mg/L), NO2-N (15.7 ± 2.4 mg/L), and residual NO3-N (2.6 ± 2.2 mg/L).
• Demonstrated the feasibility of partial nitritation in MBBRs treating wastewater with low nitrogen, high COD/N ratios, and at low temperatures.

Conclusions:

• Partial nitritation can be effectively controlled in MBBRs under challenging conditions (low temperature, low N, high COD/N).
• The combination of oxygen limitation and pH control is crucial for successful partial nitritation.
• Developed a dynamic process control algorithm applicable to partial nitritation in biofilm reactors.