[Comparison of Operating Performance of Partial Nitritation Systems with Two Different Inhibition Strategies]

Area of Science:

• Environmental Biotechnology
• Wastewater Treatment
• Microbial Ecology

Background:

• Partial nitrification is crucial for efficient nitrogen removal in wastewater treatment.
• Maintaining system stability under high ammonia loading presents significant challenges.
• Dual inhibition strategies are explored to control nitrification processes.

Purpose of the Study:

• To investigate methods for controlling the stability of partial nitrification systems.
• To evaluate the effectiveness of dual inhibition strategies (FNA/DO and FA/DO) under high ammonia loading.

Main Methods:

• Two Sequencing Batch Reactors (SBRs) were operated under high ammonia loading (1 kg·m^-3·d^-1).
• Different dual inhibition strategies were applied: free ammonia (FA) and dissolved oxygen (DO), or free nitrous acid (FNA) and DO.
• Nitrification rates (ammonia and nitrite oxidation) and effluent quality were monitored.

Main Results:

• Both FNA/DO and FA/DO dual inhibition strategies enabled partial nitrification at high ammonia concentrations (1000 mg·L^-1) and 35°C.
• The FNA/DO strategy resulted in a nitrite oxidizing rate of 0.02 mg·(g·h)^-1 and ammonia oxidizing rate of 45 mg·(g·h)^-1.
• The FA/DO strategy showed a lower nitrite oxidizing rate (0.3 mg·(g·h)^-1) and ammonia oxidizing rate (20 mg·(g·h)^-1), with a 43.60% decrease.
• Effluent NO₂^--N/NH₄⁺-N ratio was approximately 1, with near-zero NO₃^--N, suitable for Anammox.

Conclusions:

• Dual inhibition of high FNA and low DO is a superior strategy for achieving stable partial nitrification.
• This method offers advantages including a shorter cultivation period, high biological activity, and stable operation.
• The FNA/DO strategy is highly suitable for partial nitrification processes, particularly as a precursor to Anammox treatment.