Simultaneous Nitrogen and Phosphorus Recovery from Anaerobic Digestion Effluent via Enzymatic Bicarbonate Conversion...

Area of Science:

• Environmental Science and Engineering
• Biotechnology
• Water Treatment

Background:

• Anaerobic digestion effluent (ADE) is rich in ammonia (NH₃) and phosphate (PO₄³⁻), valuable for resource recovery.
• High bicarbonate (HCO₃⁻) concentrations in ADE buffer the solution, hindering PO₄³⁻ precipitation and increasing costs for NH₃ recovery.

Purpose of the Study:

• To develop an enzyme-based pretreatment to overcome bicarbonate interference in ADE.
• To enable simultaneous recovery of phosphate and ammonia from complex wastewater streams.

Main Methods:

• Immobilization of phosphoenolpyruvate carboxylase (PEPC) onto carboxylated polystyrene beads (PB@PEPC) for enhanced stability and reusability.
• Application of PB@PEPC to real ADE to convert HCO₃⁻ to PO₄³⁻.
• Recovery of precipitated calcium phosphate and ammonia (NH₃) using chemical precipitation and membrane contactors.

Main Results:

• PB@PEPC significantly reduced HCO₃⁻ concentration by 2.94-fold and increased PO₄³⁻ concentration 10.79-fold in ADE within 12 hours.
• Phosphate recovery as calcium phosphate exceeded 95% efficiency.
• Ammonia recovery reached 82.4% without additional alkaline agents, facilitated by elevated pH during phosphate precipitation.

Conclusions:

• Enzyme-based pretreatment effectively removes bicarbonate interference, facilitating nutrient recovery from ADE.
• The integrated process enables sustainable and simultaneous recovery of phosphate and ammonia from complex wastewater.
• Immobilized PEPC (PB@PEPC) demonstrated good stability and reusability over multiple cycles.