Nitrogen removal performance using anaerobic ammonium oxidation at low temperatures

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Technologies
• Biogeochemical Cycles

Background:

• The anaerobic ammonium oxidation (anammox) process is effective for treating ammonia-rich wastewater.
• Anammox application has been limited at low temperatures (below 15°C) due to reduced microbial activity.
• Novel methods are needed to enable anammox in cold environments.

Purpose of the Study:

• To investigate the feasibility and performance of an anammox process using gel-entrapped bacteria at low temperatures.
• To determine the temperature dependence and kinetic parameters of anammox activity in a cold environment.
• To assess the stability of anammox performance under sub-optimal temperature conditions.

Main Methods:

• Utilized gel carriers to immobilize anammox bacteria for enhanced stability and activity.
• Conducted continuous feeding tests to evaluate nitrogen removal rates at various temperatures (6-32°C).
• Performed batch experiments to characterize temperature dependence and calculate apparent activation energies.

Main Results:

• Stable nitrogen removal was achieved at temperatures as low as 6°C, with a conversion rate of 0.36 kg N m⁻³ day⁻¹.
• Significant anammox activity was maintained below 20°C for over 130 days.
• The optimum temperature for anammox bacteria was 37°C, with a change in temperature dependence observed around 28°C.

Conclusions:

• Gel-entrapped anammox bacteria demonstrate robust nitrogen removal performance at low temperatures.
• The study overcomes previous limitations, paving the way for anammox application in cold industrial wastewater.
• Kinetic analysis revealed distinct temperature-dependent behaviors, crucial for process optimization.