Nitrification and microalgae cultivation for two-stage biological nutrient valorization from source separated urine

Area of Science:

• Environmental Science
• Biotechnology
• Wastewater Treatment

Background:

• Urine is a rich source of nutrients in urban wastewater.
• Nutrient recovery from wastewater is crucial for sustainability.
• Stabilization of undiluted urine is challenging due to its high salt content.

Purpose of the Study:

• To explore biological nutrient recovery from undiluted urine using nitrification and microalgae cultivation.
• To identify and utilize halotolerant nitrifying inoculums for efficient urine stabilization.
• To evaluate the performance of nitrified urine as a growth medium for Arthrospira platensis.

Main Methods:

• Screening of nitrifying inoculums for halotolerance.
• Start-up of two nitrification membrane bioreactors with undiluted urine.
• Comparison of a commercial aquaculture inoculum with municipal activated sludge.
• Cultivation of Arthrospira platensis using nitrified urine.

Main Results:

• Complete nitrification of undiluted urine was achieved at high conductivity (75mScm(-1)) and loading rates (>450mgNL(-1)d(-1)).
• A halotolerant inoculum reduced nitrification start-up time by 54%.
• Nitrified urine supported superior growth of Arthrospira platensis, yielding 62% protein content.

Conclusions:

• A two-stage strategy of urine nitrification followed by microalgae cultivation is effective for biological nutrient recovery.
• Halotolerant inoculums enhance the efficiency of urine nitrification.
• Nitrified urine is a viable and nutrient-rich medium for microalgae cultivation.