One-stage partial nitritation and anammox in membrane bioreactor

Area of Science:

• Environmental Microbiology
• Water Treatment Engineering

Background:

• Ammonium-rich wastewater with low C/N ratio poses treatment challenges.
• Classical nitrification/denitrification processes are energy-intensive and costly.

Purpose of the Study:

• To investigate the technical feasibility of a one-stage partial nitritation and anammox (PN/A) process in a lab-scale membrane bioreactor (MBR).
• To analyze the bacterial community dynamics during the PN/A process.
• To evaluate the nitrogen removal performance and cost-effectiveness of the PN/A system.

Main Methods:

• Implementation of a one-stage PN/A process in an MBR.
• Control of dissolved oxygen for partial nitritation.
• Seeding with anammox biomass.
• Molecular cloning and 16S rRNA sequence analysis for bacterial community identification.

Main Results:

• Stable partial nitritation achieved with a NO2(-)-N/NH4(+)-N ratio of 1.13 ± 0.08.
• Maximum nitrogen removal rate of 1.45 kg N/m(3)/day with 89.5% efficiency over 300 days.
• Identification of Nitrosomonas sp. and Nitrosospira sp. for nitritation, and Candidatus Brocadia sp. for anammox.
• Enrichment of Nitrosomonas sp. as the predominant ammonia oxidizers.
• Detection of nitrite oxidizers and denitrifiers in symbiosis, indicating potential for further nitrogen removal.

Conclusions:

• The one-stage PN/A process is technically feasible for treating ammonium-rich wastewater with low C/N ratios.
• The PN/A system demonstrates high nitrogen removal efficiency and rates.
• The process offers significant operational cost reductions compared to conventional nitrification/denitrification.
• Microbial community analysis revealed key functional bacteria and their interactions, including the dominance of Nitrosomonas sp.