Ammonia Removal From Water

Ozone is widely used in water treatment for disinfection and organic pollutant removal, and is also effective for ammonia (NH3-N) removal, particularly in wastewater and polluted source water. Ammonia, a key nitrogenous pollutant, contributes to eutrophication, oxygen depletion, and toxicity in aquatic ecosystems, making its removal critical for environmental compliance and water quality. While ozone alone has limited direct reactivity with ammonia, its integration with biological processes or advanced oxidation processes (AOPs) significantly enhances ammonia removal efficiency.

Ozone-based treatments have proven highly effective for reducing ammonia in wastewater, as demonstrated by case studies and white papers listed below. The Hammarby Sjöstadsverk pilot study showcased ozonation with BAF achieving ammonia nitrogen levels below 0.2 mg/L and 50% COD removal, highlighting its potential for sustainable municipal wastewater treatment. Similarly, the two-stage ozonation study achieved over 85% ammonia removal, transforming ammonia primarily into nitrate, meeting strict regulatory standards. White papers emphasize ozone’s role as a powerful oxidizer, with advancements like microbubble systems and AOP integration improving efficiency and addressing challenges like byproduct formation. Benefits include rapid reaction times, no residual chemicals, and potentially lower cost vs other methods.

Mechanisms of Ammonia Removal:

Direct Oxidation:

- Ozone can oxidize ammonia to nitrate (NO3-) or nitrogen gas (N2), but this is pH-dependent and inefficient at neutral pH (common in wastewater). At higher pH (e.g., 9–11), ozone reacts more effectively, forming hydroxyl radicals (·OH) that facilitate ammonia oxidation.

Indirect Enhancement via Biological Processes:

- Ozone’s primary benefit lies in its synergy with biological activated carbon (BAC) or biofiltration systems. Ozone increases dissolved oxygen (DO) and converts complex organic nitrogen (e.g., proteins, urea) into bioavailable ammonia or simpler substrates, boosting nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter) activity. These bacteria convert ammonia to nitrite (NO2-) and then nitrate through nitrification, or to nitrogen gas via denitrification under anoxic conditions.

Advanced Oxidation Processes (AOPs):

- Combining ozone with UV light or hydrogen peroxide generates hydroxyl radicals, enhancing ammonia oxidation to nitrate or nitrogen gas, especially in high-ammonia industrial effluents.

Applications and Effectiveness:

Municipal Wastewater:

- Studies show ozone-BAC systems achieving 80–90% ammonia removal at dosages of 4–10 mg/L, reducing ammonia from 3–10 mg/L to <0.2–1 mg/L, meeting stringent discharge standards (e.g., China’s <15 mg/L). For example, a pilot study at Hammarby Sjöstadsverk, Sweden, reduced ammonia to <0.2 mg/L using ozone-enhanced biofiltration.

Aquaculture:

- In recirculating aquaculture systems (RAS), ozone removes 40–60% of total ammonia nitrogen (TAN) at 10–20 mg/L, with biofiltration pushing efficiencies to 70%, maintaining TAN <1 mg/L for fish health.

Hospital Wastewater:

- Ozone-UV systems in Japan achieved 45–60% ammonia reduction, transforming ammonia to nitrate and reducing nitrogenous oxygen demand.

Source Water Treatment:

- In polluted drinking water sources, ozone-BAC processes removed 80–90% of ammonia, as seen in Harbin, China, where levels dropped from 3–5 mg/L to below regulatory limits.

Key Benefits:

High Efficiency:

- Ozone-BAC systems achieve 80–90% ammonia removal, far surpassing standalone biological processes (50–60%).

No Harmful Residuals:

- Ozone decomposes to oxygen, avoiding toxic byproducts like trihalomethanes formed during chlorination.

Enhanced Biological Activity:

- Ozone boosts DO and substrate availability, promoting nitrification and assimilation by bacteria, converting ammonia to protoplasm or nitrogen gas.

Versatility:

- Effective across municipal, industrial, aquaculture, and drinking water applications, handling ammonia levels from 0.3–100 mg/L.

Regulatory Compliance:

- Reduces ammonia to meet strict standards (e.g., <1 mg/L for aquaculture, <0.2 mg/L for drinking water).

Sustainability:

- On-site ozone generation minimizes chemical transport, and reduced sludge production (e.g., 43% less in some cases) lowers disposal costs.

Challenges:

pH Dependency:

- Ammonia oxidation is more effective at alkaline pH (9–11), requiring pH adjustment in neutral wastewater, which increases costs.

Nitrate Formation:

- Nitrification produces nitrate, which may require additional denitrification to prevent health risks (e.g., methemoglobinemia in drinking water).

Energy Costs:

- Ozone generation (10–15 kWh/kg O3) and dosages (4–15 mg/L) can be energy-intensive, necessitating optimization.

Byproduct Risks:

- In bromide-rich waters, ozone may form bromate, requiring careful dosage control.

Practical Considerations:

Dosage:

- Typical dosages range from 4–15 mg/L, with 5–10 mg/L common for municipal wastewater. Higher doses (10–20 mg/L) are used for high-ammonia or organic-rich effluents.

Integration:

- Combining ozone with BAC, sand filtration, or AOPs maximizes ammonia removal while minimizing energy use and byproducts.

Optimization:

- Pilot testing is essential to tailor dosage, contact time (3–10 minutes), and pH to specific water characteristics, ensuring cost-effectiveness.

Pilot Testing:

Wastewater can vary greatly depending upon source, pre-treatment, and other factors.  Do this, it is commonly helpful to perform bench testing or pilot testing on-site.  Should this be an option, please consider our treatability testing options.  Contact our office for help determining the right ozone dosage rate for your application, and proper process design for the best final outcome.

Conclusion:

Ozone is one tool for ammonia removal, excelling when paired with biological processes like BAC.  The ability to enhance nitrification, oxidize organic nitrogen, and achieve high removal efficiencies (80–90%) makes it ideal for addressing ammonia pollution in diverse water treatment scenarios. However, best results are typically achieved when ozone is used in conjunction with other technologies.

Some great case studies and white papers are listed below showcasing real-world examples of the use of ozone for ammonia removal from water.

Case Studies and White Papers:

Below are specific Case Studies and White Papers on Ozone for Ammonia Reduction in Wastewater

Ozone Enhanced Biofiltration at Hammabry Sjostadsverk, Stockholm, Sweden

Overview: A pilot study initiated in January 2014 at Hammarby Sjöstadsverk Wastewater Treatment Plant investigated ozonation combined with biologically active filtration (BAF) to treat municipal wastewater sustainably. The process included an ozone contactor followed by biological active filters using anthracite and granular activated carbon (GAC).

Findings:

- Achieved approximately 50% COD (Chemical Oxygen Demand) removal.

- Reduced ammonia nitrogen to less than 0.2 mg/L, demonstrating high efficacy in ammonia removal.

- Both anthracite and GAC media produced similar results, indicating flexibility in filter media choice.

- The synergistic effects of ozonation and BAF reduced operating costs related to performance, media replacement, and ozone dosage.

Read the full study here.

Two-Stage Ozone Oxidation for Ammonia Nitrogen Wastewater

Findings: In the primary stage, with an ozone flow rate of 1 L/min and initial pH of 11, ammonia removal efficiency reached 59.32%, with pH decreasing to 6.63. The second stage achieved over 85% removal efficiency, reducing ammonia concentration to below 15 mg/L, meeting China’s national discharge standards. Ammonia was primarily transformed into nitrate (NO3−-N), with minimal nitrite (NO2−-N) formation, and no significant conversion to nitrogen gas (N2). The optimal ozone flow rate was 1 L/min, as higher flows reduced contact time, slowing hydroxyl radical (·OH) generation and direct ammonia oxidation.

Read the full study here.

Emerging Treatment Strategies of Pharmaceutical Pollutants: Reactive Physiochemical and Innocuous Biological Aproaches

Ozonation is one of the oxidative treatment processes to reduce the amount of toxic pollutants present in wastewater. This process uses molecular ozone to mineralize the toxic pollutants in wastewater and convert them into less toxic ones. With an oxidation potential of 2.07 V, molecular ozone is effectively one of the strong oxidants. The process depends on the presence of hydroxyl radicals, the concentration of which determines the ozonation rate of the pharmaceutical pollutants. The rate of ozonation is directly proportional to the presence of hydroxyl radicals in the wastewater matrix (Wang & Wang, 2016). Molecular ozone reacts selectively with the organic molecules. The selectivity of the ozonation depends on the presence of nucleophilic moieties which includes aromatic rings, double-bonded carbon and functional groups like oxygen, nitrogen, sulfur, or phosphorus. The ozonation of such moieties resulted in mineralization of the targeted molecules (Oppenländer, 2003). Being a strong oxidation process, ozonation is appropriate for the treatment of industrial or municipal pharmaceutical wastewaters that contain lethal concentrations of toxic chemicals and drugs. It not only mineralizes the toxic chemicals but also reduces the presence of pathogenic bacteria (Loeb, 2002). Ozonation is useful because it completely deteriorates the toxic pollutants into their nontoxic and easily biodegradable forms (Zhou & Smith, 2001). However, further study is required on the relationship between the wastewater matrix and the hydroxyl radicals to increase the effectivity of the ozonation process.

Read the full study here.

Emerging Treatment Strategies of Pharmaceutical Pollutants: Reactive Physiochemical and Innocuous Biological Aproaches

The wastewater reclamation is the need of today's world. Advanced oxidation processes (AOPs) are considered as a good option for removing recalcitrant organic materials in wastewater by oxidation reactions with powerful, non-selective hydroxyl radical (OH•). Ozone alone does not cause complete oxidation of some refractory organic compounds and has a low reaction rate. The ozone is combined with H₂O₂, UV light, catalyst, ultrasound to enhance the generation of hydroxyl radicals to increase the efficiency of the treatment process. The ozone-based AOPs have been proved to be effective in detoxifying an ample range of industrial effluents containing recalcitrant organics, pharmaceutical products, pesticides, phenols, dyes, etc. Ozone based AOP processes such as O₃/UV, O₃/H₂O₂, O₃/Fe (II), O₃/metal oxide catalyst, O₃/activated carbon, O₃/ultrasound, O₃/Fenton, photocatalytic ozonation were discussed. A review of ozone-based AOP processes as a combination of ozonation with other techniques for the degradation and mineralization of recalcitrant organics present in the industrial/municipal wastewater based on the recently published work were reported.

Read the full study here.

Ozonation of Ammonia in Wastewater

An investigation of the effects of ozone on ammonia in municipal wastewaters is described and discussed relative to the application of ozone for advanced waste treatment. Ammonia is oxidized completely to nitrate, thereby eliminating the nitrogenous oxygen demand of the waste. In buffered solutions of ammonium chloride, the reaction is first-order with respect to the concentration of ammonia, and the rate increases with increasing pH over the range 7–9, and with increasing ozone partial pressure. In wastewater, the reaction is particularly sensitive to pH, with effective removal of ammonia occurring only if the pH of the wastewater can be maintained alkaline. Due to the elevated pH's required for effective ammonia oxidation, ozonation is especially attractive in conjunction with lime clarification and precipitation of phosphate. Application of ozone for disinfection purposes requires recognition of the ozone demand exerted by ammonia.

Read the full study here.

Whole Effluent Toxicity Reduction by Ozone

An investigation of the effects of ozone and ozone-in- duced hydroxyl radical on reducing whole effluent tox- icity is discussed relative to the application of ozone for industrial water treatment. Results from operation of an ozone system treating industrial effluent from a lead/zinc mine in Colorado arepresmted. i%e mine discharges 1,000 gpm (227 m3/hrJ of wastewater and has historically exceeded whole Effluent Toxicity (WT) limits. On occasion, it has exceeded numeric limits for copper, ammonia, and cyanide. Based on test results, an applied ozone to COD ratio of 3:l by weight and a contact time of 30 minutes was found to be effective for reducing whole effluent toxicity at pH 11 but not at pH 7, indicating oxidation by by- droxyl radical to be the dominant mechanism respnsi- ble for toxicity reduction. At an applied ozone to COD ratio of 3.1 and a pH of 11, toxicity was reduced with survival increasing improved from 0 percent survival to 100 percent survival for Ceriodaphnia dubia and fat- head minnow (Pimephales promelas) based on 48-hour and %-hour WET tests, respectively. This application rate of ozone with a 99percent mass transfer effiency was also effective in reducing total cyanidefrom an av- erage of 0.45 mg/L to less than 0.05 mg/L and COD from 28 mg/L to 9 mg/L. The rate of ammonium nitm gen oxidation appeared to follow first-order kinetics; however, the rate of oxidation was decreased signifi- cantly by the presence of COD. 

Read the full study here.

Ammonia, Nitrite and Nitrate Nitrogen Removal from Polluted Source Water with Ozonation and BAC Processes

Studies on the removal of ammonia-, nitrite-, and nitrate nitrogen with ozonation (O₃), sand filtration (SF), biological activated carbon (BAC), SF-BAC, and/or O₃-BAC processes were carried out in two pilot plants and a full scale plant, respectively. The results showed that all of the tested processes exhibited certain nitrogen removal efficiencies, of which both the O₃-SF-BAC and O₃-BAC processes were most effective and efficient in removing ammonia nitrogen, with mean removal efficiencies of some 90 and 80 percent, respectively.

Ozonation was found able to oxidize some organic nitrogen into ammonia, and nitrite ion into nitrate ion. It was also found out, with interest, that the O₃-BAC process can carry the nitrification process to the end under sufficient DO content, as well as more hydrocarbon substrates through ozonation that are more easily assimilated by some strains of nitrobacter that can multiply heterotrophically in its carbon beds. In the BAC process, both the DO and easily assimilated substrate contents were too low in its carbon beds due to no ozonation to sustain nitrobacter growth; but the nitrite conversion bacteria, like nitrosornas, can survive under such conditions. As a result, nitrite or nitrate ion content increased multiply in the effluents from BAC or O₃-BAC processes over their influents. respectively.

The removal mechanisms of various processes for the three forms of nitrogen were studied and discussed, and the optimum design parameters were determined as well.

Key Findings:

- High Ammonia Removal Efficiency: The O3-SF-BAC and O3-BAC processes achieved mean ammonia nitrogen (NH3-N) removal efficiencies of 90% and 80%, respectively, significantly outperforming standalone BAC (61.2%) and O3-SF (52.4%) processes.

- Mechanisms of Removal: Ammonia removal was primarily driven by biological assimilation (conversion to bacterial protoplasm) and nitrification (oxidation to nitrite/nitrate) in BAC beds, enhanced by ozonation. Ozonation oxidized organic nitrogen to ammonia and nitrite to nitrate, boosting substrate availability for nitrifying bacteria (e.g., Nitrosomonas, Nitrobacter).

- Role of Ozonation: Ozone increased dissolved oxygen (DO) and easily assimilated hydrocarbon substrates, promoting vigorous biological activity (e.g., zooglea, protozoa) in O3-BAC beds, enabling complete nitrification. Without ozonation, BAC beds had insufficient DO and substrates, leading to partial nitrification and nitrite accumulation.

- Nitrite and Nitrate Dynamics: O3-BAC effectively reduced nitrite (high removal efficiency), while BAC alone increased nitrite due to incomplete nitrification. Nitrate levels rose slightly due to nitrification, but biological assimilation and anoxic denitrification limited excessive nitrate accumulation.

- Full-Scale Performance: The Songjiang Cannery plant, using microflocculation/direct filtration (MF/DF) and BAC, achieved 83% total ammonia removal (72% from MF/DF), with biological activity and coagulation contributing significantly.

Study Context: The research highlights the environmental challenge of ammonia-driven eutrophication in water bodies and the limitations of chlorination (high costs, THM formation). The O3-BAC process offers a sustainable solution by leveraging ozone’s oxidative power and BAC’s biological capacity without harmful residuals.

Key Takeaways on Benefits of Ozone for Ammonia Removal

- Enhanced Biological Activity: Ozone increases DO and bioavailable substrates, fostering robust nitrifying bacterial communities (e.g., Nitrobacter) in BAC beds, achieving 80–90% ammonia removal.

- High Efficiency: O3-BAC and O3-SF-BAC processes remove 80–90% of ammonia, far surpassing standalone BAC (61.2%) or sand filtration (52.4%), suitable for high-ammonia waters (3–10 mg/L).

- No Harmful Byproducts: Unlike chlorination, ozonation avoids trihalomethanes, decomposing into oxygen and leaving no toxic residues.

- Versatile Nitrogen Management: Ozone oxidizes organic nitrogen to ammonia and nitrite to nitrate, enabling comprehensive nitrogen removal when paired with BAC’s assimilation and denitrification.

- Sustainability: On-site ozone generation and biological processes reduce chemical use, aligning with eco-friendly treatment goals.

- Scalability: Proven effective in pilot (8 m³/day, 500 L/day) and full-scale (500 m³/day) plants, demonstrating practical application in municipal and industrial settings.

- Nitrite Control: O3-BAC prevents nitrite accumulation (unlike BAC alone), ensuring safer effluent by completing nitrification to nitrate or nitrogen gas.

Read the full study here.

Harnessing Ozone for Ammonia Removal: A Game-Changer in Water Treatment

Ammonia in water is more than a nuisance—it’s a serious pollutant that fuels algal blooms, depletes oxygen, and threatens aquatic life. For water treatment professionals, controlling ammonia is essential to meet strict environmental regulations and protect ecosystems. While ozone is widely known for its disinfection power and ability to degrade organic pollutants, its role in ammonia removal is less familiar but equally transformative. By combining ozone with biological processes or advanced oxidation techniques, treatment facilities can significantly reduce ammonia while prioritizing sustainability.

Read the full study here.