Part 21: Using gas scrubbing and air stripping to produce ammonium sulphate in wastewater treatment1. Technology DescriptionAmmonium sulphate pr...
Published on by Hossein Ataei Far, Deputy Manager of the Research, Technology Development, and Industry Relations Center at NWWEC
1. Technology Description
Ammonium sulphate production involves recovering nitrogen from wastewater via physicochemical processes, specifically through air stripping and gas scrubbing. Usually, this process is used in wastewater treatment plants with a capacity of 100,000 population equivalents or more.
Process Overview
Ammonia Stripping (First column):
Ammonium-rich liquor is heated (55–65 °C) and air-stripped at an alkaline pH (9–11).
Carbon dioxide is removed to increase pH, and sodium hydroxide may be added.
The ammonia (NH₃) is desorbed into the gas phase.
Gas Scrubbing (Second Column):
Ammonia gas reacts with a sulfuric acid solution to form ammonium sulphate (NH₄)₂SO₄.
The ammonia-free air is reused for stripping.
Key Parameters:
The air-to-liquor flow ratio is crucial for performance (typically 500 to 2000–3000).
Product
Ammonium sulphate solution, a nitrogen fertilizer (37-40% concentration).
Fertilizer Efficiency
The recovered ammonium sulphate solution's fertilizer efficiency is between 89% and 103% higher than that of commercial ammonium sulphate (depending on plant and soil type).
2. Flow Scheme of the Technology
3. Synergetic Effects and Motivation for Technology
Robustness: Unlike biological nitrogen removal processes (nitrification/denitrification), this method is not reliant on microorganisms, making it more robust.
Reduction of N₂O Emissions: The air stripping method helps to mitigate a potent greenhouse gas.
4. Requirements for Implementation
Ammonium Concentration: The process is effective with ammonium concentrations between 800 mg/L and 4000 mg/L. Lower concentrations may still be feasible, but economic feasibility should be assessed.
Potential Enhancements: Combining anaerobic digestion with thermal pressure hydrolysis can increase ammonium concentrations by degrading organic compounds.
Process Water Feed Parameters
NH₄-N concentration: 800 to 4000 mg/L
Total Solids (DM): ≤2%
TSS concentration: ≤600 mg/L
pH: 8 to 11
Temperature: 55 to 65°C
5. Key Performance Indicators (KPIs)
N-Recovery Rate:
Influent Nitrogen Recovery: 80-98%
Influent WWTP Recovery: 10-20%
6. Related Topics & Case Studies
Ammonium Sulphate Production:
Air Stripping: Case study “Braunschweig” (NextGen), Case study in Tain, UK (Ultimate)
Membrane Stripping: Case study “Altenrhein” (NextGen), Case study “Spernal” (NextGen)
Vacuum Degasification: Circular Agronomics: D3.1, Chapter 3 (Kleyböcker et al., 2020)
References:
[1] Kleyböcker, A. et al. (2022)
[2] Böhler, M., et al. (2012)
[3] Kleyböcker, A., et al. (2020)
[4] NextGen D1.5 (In preparation)
[5] Szymańska, M., et al. (2019)
This project has received funding from the European Union’s Horizon 2020 research and innovation program.