Ammonia is a contaminant found in many types of industrial water and wastewater, resulting from chemical and agro-industrial processes as well as waste treatment. Its removal is essential to prevent negative environmental impacts and damage to industrial processes. There are two main technologies for ammonia removal: stripping towers with downstream removal and reverse osmosis.

Ammonia Removal Using Stripping Towers

Stripping towers utilize the principle of ammonia volatilization in an alkaline environment to separate it from water. The process takes place in several stages:

• Increasing the pH: Add an alkalizing agent (e.g., NaOH) to convert ammonium (NH₄⁺) into free ammonia (NH₃).
• Air or steam stripping: Water is passed through a tower filled with a high-surface-area packing material, while a stream of blown air facilitates the transfer of ammonia into the gas phase.
• Downstream abatement: Ammonia-laden gases are treated in acid scrubbers to neutralize the ammonia and reduce emissions into the atmosphere.

• Proven and effective technology for high concentrations of ammonia.
• Significant reduction in dissolved ammonia, up to 90–95%.
• Potential for recovering ammonia for industrial reuse.

Ammonia Removal via Reverse Osmosis

Reverse osmosis (RO) is an alternative technology for removing ammonia from water with low to moderate concentrations. The process uses semipermeable membranes to separate ammonia and other contaminants.

However, the effectiveness of reverse osmosis in removing ammonia depends on key operating parameters:

• Water pH: At neutral or acidic pH levels, ammonia exists as the ammonium ion (NH₄⁺), which is more easily retained by membranes. At an alkaline pH, it becomes NH₃, which is less stable.
• Operating pressure: must be appropriate for the ammonia concentration and the type of membrane used.
• Membrane selectivity: Some RO membranes are more effective at removing ammonium ions than others.
• Pre-treatment and post-treatment: Combining these processes with ion exchange or degassing systems can improve removal efficiency.

• Effective technology for low- and medium-concentration ammonia.
• Lower environmental impact compared to chemical-physical processes.
• Greater control over operating parameters for optimal efficiency.

Integrating Technologies for Maximum Efficiency

The two technologies can be integrated to achieve a highly efficient combined treatment. Water treated using the stripping tower can then be further purified via reverse osmosis, reducing the final waste volume by up to 90%. This solution results in significant savings on disposal costs and a lower environmental impact, making the process both sustainable and cost-effective.