Some images are technical illustrations. Real installation photographs where marked.
Overview
The CG Ammonia Nitrogen Stripping Tower™ is a packed-column air stripping system designed to remove high concentrations of free ammonia nitrogen (NH₃-N) from industrial and municipal wastewater where biological treatment is ineffective, severely inhibited, or impractical due to very high ammonia loads. By raising wastewater pH to 10.5–11.5 (converting ammonium ion NH₄⁺ to free ammonia NH₃) and passing it counter-currently through a packed column with high-volume air, free ammonia transfers from the liquid to the gas phase. The ammonia-laden exhaust air passes through an acid absorption scrubber where it reacts with sulphuric acid to form ammonium sulphate — a valuable nitrogen fertiliser. Critical for landfill leachate, fertiliser plant effluent, high-strength anaerobic digestate, and concentrated distillery streams where NH₃-N concentrations exceed the biological toxicity threshold (>1,500 mg/L).
Working Principle
Feed wastewater is pH-adjusted to 10.5–11.5 using hydrated lime or caustic soda in a pH adjustment tank. The pH-adjusted feed is pumped to the top of the packed stripping column and distributed uniformly over the packing surface. Ambient or heated air is introduced counter-currently at the base by a centrifugal blower. As wastewater contacts the packing in thin films, the large air-liquid interface enables NH₃ mass transfer from liquid to gas phase. The stripped wastewater exits the base with NH₃-N typically <50 mg/L. The ammonia-laden exhaust air exits through an acid absorber containing circulating dilute sulphuric acid, where NH₃ reacts with H₂SO₄ to form (NH₄)₂SO₄ solution sold as liquid fertiliser.
Key Technical Features
- NH₃-N removal efficiency: >90%
- Inlet NH₃-N range: 500–30,000 mg/L
- Packed column: structured packing (Sulzer MellapakPlus) or random packing
- Integrated pH adjustment system (lime or NaOH)
- Counter-current air flow — blower at base, liquid at top
- Acid absorber scrubber — produces (NH₄)₂SO₄ fertiliser
- Construction: FRP, polypropylene, or SS316
- Heating option for cold climates
- PLC control of pH, air flow, and absorber
- Removes NH₃ inhibition — protects downstream biology
- Air-to-liquid ratio: 100–500 m³/m³
Design Parameters
| Parameter | Value |
|---|---|
| NH₃-N Inlet | 500–30,000 mg/L |
| NH₃-N Removal | >90% |
| Operating pH | 10.5–11.5 |
| Air-Liquid Ratio | 100–500 m³/m³ |
| Packing | Structured/Random |
| Construction | FRP/PP/SS316 |
| By-product | (NH₄)₂SO₄ Fertiliser |
Applications
- Landfill leachate — high NH₃-N removal before biological polishing
- Fertiliser plant and nitrogen chemical production wastewater
- Urea and ammonia manufacturing plant wastewater
- High-strength distillery effluent with elevated ammonia
- Anaerobic digester reject water (centrate/filtrate)
- Livestock and poultry farm wastewater
- Pre-treatment before biological systems to remove toxicity
Advantages
- Removes ammonia concentrations that would kill biological treatment
- Valuable by-product: (NH₄)₂SO₄ fertiliser reduces operating cost
- No biological sludge from ammonia removal step
- Operates continuously — high flow capacity
- pH control system protects downstream biological treatment
- FRP/PP construction resists highly alkaline conditions
Frequently Asked Questions
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