Differentiating biosynthesis from heterotrophic nitrification/aerobic denitrification for total-nitrogen removal

Area of Science:

• Environmental Microbiology
• Biotechnology
• Wastewater Treatment

Background:

• Conventional nitrogen removal in wastewater treatment relies on nitrification/denitrification.
• Heterotrophic nitrification and aerobic denitrification (HNAD) is a novel aerobic nitrogen removal process.
• Nitrogen assimilation into biomass offers an alternative aerobic nitrogen removal strategy.

Purpose of the Study:

• To evaluate the fungus Apiotrichum loubieri for ammonium-N and total-N removal under aerobic conditions.
• To determine the required Chemical Oxygen Demand (COD) to Nitrogen (N) ratio for nitrogen removal by biosynthesis alone.
• To assess the efficacy of A. loubieri in enhancing nitrogen removal in heterotrophically deficient biomass.

Main Methods:

• Isolation of the fungus Apiotrichum loubieri, confirmed to lack nitrification and denitrification capabilities.
• Cultivation of A. loubieri under aerobic conditions for nitrogen removal experiments.
• Mass balance calculations for Nitrogen (N) and COD to differentiate removal pathways.

Main Results:

• Apiotrichum loubieri achieved total-N removal solely through biosynthesis when supplied with a sufficiently high COD:N ratio (24 g COD/g N).
• The fungus demonstrated a molecular formula of C5H7.9O2N.
• Supplementing nitrogen-deficient biomass with A. loubieri resulted in complete N removal via biosynthesis at a COD:N ratio of approximately 28 g COD/g N.

Conclusions:

• Nitrogen assimilation by Apiotrichum loubieri is a viable strategy for aerobic total-N removal in wastewater.
• Sufficiently high influent COD:N ratios are critical for achieving nitrogen removal by biosynthesis.
• Mass balance analysis of N and COD effectively distinguishes between nitrogen removal via biosynthesis and HNAD.