In a quest for high-efficiency mainstream partial nitritation-anammox (PN/A) implementation: One-stage or two-stage?

Area of Science:

• Environmental Engineering
• Biotechnology
• Water Treatment

Background:

• Partial nitritation-anammox (PN/A) is an energy-efficient wastewater nitrogen removal technology with potential for energy-neutral treatment plants.
• Current PN/A processes, in one-stage or two-stage configurations, face challenges in large-scale implementation for low-strength municipal wastewater due to low efficiency.
• Achieving desired effluent quality is hindered by difficulties in out-selecting nitrite-oxidizing bacteria (NOB).

Purpose of the Study:

• To comprehensively analyze one-stage and two-stage PN/A processes.
• To evaluate the engineering application potential of PN/A systems for mainstream wastewater treatment.
• To identify critical operational challenges and propose strategies for improved nitrogen removal.

Main Methods:

• Comparative analysis of one-stage and two-stage PN/A process configurations.
• Evaluation of operational strategies, including oxygen levels and reactor design.
• Assessment of nitrogen removal efficiency (NRE) and nitrogen removal rate (NRR).

Main Results:

• Out-selection of NOB is a critical challenge affecting effluent quality.
• Low oxygen strategies in one-stage systems limit NRR.
• A two-stage system with high dissolved oxygen in the PN reactor and a granular anammox reactor achieved high NRR and good effluent quality.

Conclusions:

• Two-stage PN/A systems offer a promising approach for high efficiency and economic benefits in mainstream wastewater treatment.
• Further development of two-stage PN/A processes is recommended for large-scale application.
• Optimizing operational parameters like oxygen levels and reactor configuration is crucial for successful PN/A implementation.