Post-anoxic denitrification via nitrite driven by PHB in feast-famine sequencing batch reactor

Area of Science:

• Environmental Science
• Microbiology
• Water Treatment Engineering

Background:

• Aerobic/extended-idle regimes can induce excess phosphorus removal.
• Simultaneous nitrogen and phosphorus removal is a key goal in wastewater treatment.

Purpose of the Study:

• To investigate the introduction of an anoxic period after aeration for simultaneous nitrogen and phosphorus removal.
• To optimize partial nitrification for enhanced nutrient removal.

Main Methods:

• Controlled aeration duration (2.5h) to achieve partial nitrification.
• Introduction of an anoxic period post-aeration.
• Fluorescence in situ hybridization (FISH) analysis to study microbial populations.

Main Results:

• Stable partial nitrification achieved with 2.5h aeration, preventing nitrite to nitrate conversion.
• Sufficient poly-3-hydroxybutyrate accumulation (1.5mmolCg(-1) VSS) for subsequent denitrification.
• High correlations between nitrite accumulation and nutrient removal efficiencies (N: 95%, P: 99%).
• Faster growth of ammonia-oxidizing bacteria than nitrite-oxidizing bacteria drove nitrite accumulation.
• Negligible secondary phosphorus release and excellent nutrient removal under low ammonia conditions.

Conclusions:

• The modified aerobic/anoxic regime effectively achieves simultaneous nitrogen and phosphorus removal.
• Optimized partial nitrification and internal carbon source accumulation are crucial for high nutrient removal efficiencies.
• Microbial dynamics, specifically the growth rates of ammonia and nitrite oxidizing bacteria, are key to process performance.