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Struvite pellet crystallization in a high-strength nitrogen and phosphorus stream
Yongmei Li1, Mingyan Liu, Zhiwen Yuan
1State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai, China
Summary
Struvite crystallization effectively recovers nutrients from wastewater. This method achieved over 95% removal of nitrogen, phosphorus, and magnesium, even at pH 7.6, forming 3-4 mm struvite pellets.
Area of Science:
- Environmental Engineering
- Water Treatment Technologies
- Chemical Precipitation
Background:
- Wastewater treatment faces challenges in nutrient removal and resource recovery.
- Struvite crystallization offers a sustainable solution for nutrient management.
Purpose of the Study:
- To investigate nutrient recovery from synthetic wastewater via struvite pellet formation.
- To determine optimal conditions for struvite crystallization and nutrient removal efficiency.
Main Methods:
- Laboratory-scale experiments using synthetic wastewater with high orthophosphate and ammonia-nitrogen concentrations.
- Controlled variation of pH (6.2-9.0) and analysis of struvite pellet size.
- Assessment of nutrient (N, P, Mg) removal rates and impact of clarifier supernatant recycling.
Main Results:
- Struvite crystal growth occurred within ammonia-nitrogen (100-1,000 mg/L) and orthophosphate (221-2,214 mg/L) ranges.
- Harvested struvite pellets averaged 3-4 mm in size.
- Over 95% removal of nitrogen, phosphorus, and magnesium was achieved at pH 7.6, with higher removals at elevated pH.
- Clarifier supernatant recycling did not significantly enhance nutrient removal.
Conclusions:
- Struvite crystallization is a viable method for recovering nitrogen, phosphorus, and magnesium from high-strength wastewater.
- Effective nutrient recovery can be achieved at near-neutral pH (7.6).
- Optimizing pH is crucial for maximizing nutrient removal efficiency in struvite precipitation.
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