Four Ways to Treat High-Ammonia Wastewater

In industrial wastewater and municipal sewage, nitrogen pollution is one of the biggest challenges for meeting discharge standards. High concentrations of ammonia and hard-to-degrade organic nitrogen compounds (such as DMF, pyridine, and azo compounds) are difficult for traditional biological methods. This article reviews the main types of nitrogen wastewater and four common treatment technologies, giving engineers useful references for design and process selection.

 

💧 Common Types of Nitrogen Wastewater

• Inorganic nitrogen: ammonia (ionized and free ammonia), nitrate, nitrite. These are the most common targets in treatment.
• Organic nitrogen: proteins, urea, amino acids, nucleic acids. These can usually be treated by standard biological methods.
• Hard-to-degrade organic nitrogen: DMF, pyridine, azo compounds. These require advanced oxidation, catalytic oxidation, or combined processes for deep removal.

📊 By industry standards:

• < 50 mg/L ammonia → low concentration wastewater
• 500 mg/L ammonia → high concentration wastewater

Different concentrations require different treatment methods.

 

🔹 Four Common Treatment Methods

1. 🧪 Biological Denitrification (for low to medium concentration)

Biological methods remain the mainstream solution. A²/O process (Anaerobic–Anoxic–Aerobic) removes nitrogen step by step:

• Organic nitrogen → ammonification
• Ammonia → nitrification
• Nitrate → denitrification into N₂ gas

✔ Low cost, widely used. ⚠️ But efficiency drops with high concentrations. Sensitive to temperature, carbon source, and pH.

 

2. 🌬️ Ammonia Stripping (for high concentration)

When ammonia > 500 mg/L, microorganisms cannot handle the load. 👉 Ammonia stripping is used:

• Add alkali to raise pH 10–11
• Convert ammonia into free ammonia
• Use air or steam to remove it ✔ Effective for high loads ⚠️ But energy use and cost are high → better for emergencies or local control.

 

3. 🧴 Breakpoint Chlorination (for low to medium concentration)

This method adds strong oxidants (e.g., sodium hypochlorite, chlorine) to react with ammonia.

• Forms chloramines
• Finally converts into nitrogen gas ✔ Fast and effective for medium concentration wastewater ⚠️ Risk: excess chlorine → may harm the downstream biological system. Careful control of chlorine dosage and injection point is required.

 

4. 🔄 Ion Exchange (for low concentration)

Special resins selectively remove ammonium ions. ✔ High removal rate, simple operation ⚠️ Resin replacement and regeneration cost is high → not suitable for high-load wastewater. 👉 Best used for polishing treatment or final-stage nitrogen removal.

 

✅ Conclusion

High-nitrogen wastewater is complex, and no single method solves all cases. Engineers must choose based on concentration, wastewater type, and cost. 🔑 A combined or staged process is often the most practical choice for stable compliance.