Increasing urine nitrification performance with sequential membrane aerated biofilm reactors.

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Bioreactor Design and Optimization

Background:

• Stored urine presents challenges for nitrification due to high pH and ammonia concentrations.
• Conventional methods for urine treatment often involve combined organic depletion and nitrification, leading to inefficiencies.
• Membrane aerated biofilm reactors (MABRs) offer a potential solution for specialized bioreactor applications.

Purpose of the Study:

• To investigate the impact of separating organic matter depletion from nitrification on overall urine treatment performance.
• To evaluate the efficacy of membrane aerated biofilm reactors (MABRs) in facilitating this separation.
• To assess nitrification rates and operational parameters in MABRs for treated urine.

Main Methods:

• Organics depletion was performed using membrane aerated biofilm reactors (MABRs) and continuous flow stirred tank reactors (CSTRs).
• Nitrification of organics-depleted urine was studied in MABRs, CSTRs, and sequencing batch reactors (FBRs).
• Ammonia recovery strategies were implemented by utilizing off-gas from the organics depletion stage for downstream nitrification.

Main Results:

• Separating organics depletion achieved 70% organic removal and significantly reduced ammonia loss compared to conventional methods.
• Upstream organics depletion doubled nitrification rates, reaching up to 1500 mg N L⁻¹ d⁻¹ in MABRs with oxygen-enriched air.
• The MABR system demonstrated robustness at high pH and reduced hydraulic retention time (HRT) to 2-3 days, compared to 4-8 days for combined systems.

Conclusions:

• Separating organics depletion from nitrification using MABRs substantially improves urine nitrification efficiency and robustness.
• The MABR technology shows high potential for efficient and stable ammonium nitrate production from source-separated urine.
• Optimized operational parameters in MABRs further enhance nitrification rates and process stability.