Nitrate residual as a key parameter to efficiently control partial denitrification coupling with anammox

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Shortcut nitrogen removal strategies face challenges in consistent nitrite-oxidizing bacteria (NOB) out-selection.
• Partial denitrification (PdN) coupled with anaerobic ammonium-oxidizing bacteria (AnAOB) presents an alternative pathway.

Purpose of the Study:

• To investigate a novel metabolic selection strategy for PdN using nitrate residual concentration as the primary control parameter.
• To evaluate the efficiency and flexibility of this PdN-AnAOB approach for nitrogen removal.

Main Methods:

• A novel acetate dosing control strategy was developed, focusing on maintaining a specific nitrate residual concentration (>2 mg N/L).
• The strategy was tested in systems with and without AnAOB to assess PdN efficiency and carbon source requirements.

Main Results:

• Partial denitrification efficiencies exceeding 80% were achieved using the nitrate residual-based control.
• The metabolic selection strategy demonstrated flexibility, allowing transitions between partial and full denitrification.
• The PdN-AnAOB concept required a low external carbon source addition (2.2 g COD/g TIN removed).

Conclusions:

• Nitrate residual concentration is a critical and reliable control parameter for metabolic PdN selection.
• This approach ensures nitrite availability for AnAOB, overcoming limitations of NOB out-selection strategies.
• The PdN-AnAOB concept offers significant savings in carbon source demand, presenting a competitive nitrogen removal alternative.