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Views: 222 Author: Carie Publish Time: 2025-04-16 Origin: Site
Content Menu
● Understanding Ammonia in Sewage Treatment
● Sources and Impacts of Ammonia
>> Sources of Ammonia in Sewage
>> Environmental and Regulatory Impacts
● Biological Methods for Ammonia Removal
>> Nitrification and Denitrification Processes
>> Enhancing Biological Removal
>> Fixed-Film and MBBR Systems
● Chemical Methods for Ammonia Removal
>> Ion Exchange
● Physical Methods for Ammonia Removal
>> Lagoon Management and Aeration
● Process Optimization and Plant Upgrades
● Case Studies and Practical Applications
>> Fixed-Film Media in Lagoons
>> Supernatant Diversion for Irrigation
● Visual Aids and Video Resources
>> Videos
● FAQ
>> 1. What are the main sources of ammonia in sewage treatment plants?
>> 2. Why is ammonia removal important in wastewater treatment?
>> 3. What is the most efficient biological method for ammonia removal?
>> 4. How does ammonia stripping work, and when is it used?
>> 5. Can small sewage treatment plants achieve low ammonia levels?
● Citation
Ammonia is a significant pollutant in wastewater, posing environmental risks and regulatory challenges for sewage treatment plants (STPs). Elevated ammonia levels can harm aquatic ecosystems, deplete oxygen, and lead to non-compliance with environmental standards. Effectively reducing ammonia in sewage treatment is essential for protecting water quality and ensuring sustainable operations. This comprehensive guide delves into the origins of ammonia in wastewater, its environmental impacts, and the most effective strategies—biological, chemical, and physical—for ammonia removal. The article includes visual aids and video references to enhance understanding, followed by a detailed FAQ section.
Ammonia in wastewater is primarily generated from the breakdown of nitrogenous organic matter, such as proteins, urea, and other nitrogen-rich compounds found in human waste and industrial effluents. In the wastewater environment, ammonia exists in two forms:
- Free ammonia (NH3): Toxic to aquatic life, especially at higher pH and temperature.
- Ammonium ion (NH4+): Less toxic, predominant at lower pH levels.
The equilibrium between these two forms depends on factors like pH, temperature, and ionic strength. During sewage treatment, the goal is to convert ammonia into harmless nitrogen gas (N2) through biological processes, or remove it physically or chemically before discharge.
- Domestic Wastewater: Urine and fecal matter are primary sources, releasing significant ammonia during decomposition.
- Industrial Effluents: Fertilizer manufacturing, plastics, explosives, and other industries discharge nitrogen-rich waste.
- Sludge Digestion: During anaerobic digestion, ammonia is released from organic nitrogen breakdown.
- Recycling Streams: Effluents from sludge dewatering and thickening can contain concentrated ammonia.
- Aquatic Toxicity: Ammonia is highly toxic to fish and aquatic invertebrates, affecting reproduction and survival.
- Oxygen Depletion: Ammonia undergoes nitrification, consuming oxygen and causing hypoxia in receiving waters.
- Eutrophication: Excess ammonia leads to nutrient overload, promoting algal blooms that deplete oxygen and harm ecosystems.
- Regulatory Non-Compliance: Many jurisdictions impose strict limits on ammonia concentrations in effluent, necessitating effective removal strategies.
Biological treatment remains the most sustainable and cost-effective approach for ammonia removal, leveraging naturally occurring bacteria to oxidize ammonia into less harmful forms.
The biological removal of ammonia involves two key steps:
1. Nitrification:
Ammonia-oxidizing bacteria (AOB), such as Nitrosomonas, convert ammonia into nitrite (NO2-), which is then further oxidized to nitrate (NO3-) by nitrite-oxidizing bacteria (NOB), like Nitrobacter.
Reaction:
NH4+ + 1.5 O2 → NO2- + 2H+ + H2O
NO2- + 0.5 O2 → NO3-
2. Denitrification:
Under anoxic conditions, denitrifying bacteria reduce nitrate to nitrogen gas ($$N_2$$), which escapes into the atmosphere, effectively removing nitrogen from the water.
Reaction:
2 NO3- + 10 e- + 12 H+ → N2 + 6 H2O
Activated Sludge Process:
This is the most common biological method, where aeration provides oxygen for nitrifiers, and anoxic zones facilitate denitrification.
- Optimizing Dissolved Oxygen (DO): Maintaining DO levels above 2 mg/L is crucial for nitrification.
- Temperature Control: Nitrification is temperature-sensitive, with optimal activity between 15°C and 35°C.
- Sludge Age and Retention Time: Longer sludge ages favor nitrifier growth, improving ammonia conversion.
- pH Adjustment: Maintaining pH around 7.5–8.5 enhances nitrification efficiency.
Fixed-film media, such as bio-balls or plastic media, provide surfaces for nitrifying bacteria, increasing biomass and nitrification capacity, especially in lagoons or decentralized plants.
When biological methods are insufficient or impractical, chemical techniques provide alternative or supplementary solutions.
Ammonia stripping is a physical process that involves raising the pH to convert ammonium ions into free ammonia gas, which is then volatilized and captured.
Process Overview:
- Add alkali (lime or sodium hydroxide) to increase pH above 10.5.
- Aerate or heat the wastewater to promote ammonia volatilization.
- Capture ammonia gas using scrubbers containing sulfuric acid, forming ammonium sulfate, a useful fertilizer.
Advantages:
- High removal efficiency (>90%) for high-strength ammonia waste streams.
- Suitable for side-stream treatment.
Limitations:
- High energy consumption due to aeration and heating.
- Chemical costs and secondary waste management.
Ion exchange resins or zeolites selectively adsorb ammonium ions, providing a polishing step for effluents.
Benefits:
- High selectivity and capacity.
- Regenerable media, allowing reuse.
Drawbacks:
- Resin fouling and regeneration waste management.
- Higher operational costs compared to biological methods.
Membrane degassing systems use gas-permeable membranes to transfer ammonia from wastewater into a gas phase, which can be captured or converted.
Features:
- Compact and modular.
- Suitable for side-stream treatment or polishing.
Challenges:
- Membrane fouling.
- Capital and maintenance costs.
- Enhanced Lagoon Aeration: Using paddle wheels or diffused aeration to promote nitrification.
- Supernatant Management: Diverting high-ammonia supernatant for alternative uses like irrigation, reducing load on the main treatment process.
- Increase Aeration: Ensuring adequate oxygen supply enhances nitrification.
- Extend Retention Time: Longer sludge age allows nitrifiers to develop and improve ammonia removal.
- pH and Temperature Control: Maintaining optimal pH and temperature conditions boosts biological activity.
- Sludge Recycling: Recycling nitrified sludge increases biomass and nitrification capacity.
- Adding Fixed-Film Media: Installing biofilm carriers in lagoons or reactors.
- Implementing Sequencing Batch Reactors (SBRs): Providing controlled environments for nitrification and denitrification.
- Side-Stream Treatment Units: Installing ammonia stripping towers or ion exchange units for high-strength waste streams.
In a municipal lagoon system, installing plastic biofilm media increased nitrification rates, achieving up to 98% ammonia removal during summer months. The media provided surfaces for nitrifiers, especially in colder months when biological activity slows.
A wastewater treatment plant diverted high-ammonia supernatant to agricultural fields, using it as a fertilizer. This not only reduced ammonia load on the main treatment process but also provided a sustainable nutrient source for crops.
Small decentralized plants faced challenges meeting ammonia standards. Upgrades included extending aeration periods, installing fixed-film media, and adding side-stream ammonia stripping units, resulting in compliance with discharge limits.
Reducing ammonia in sewage treatment plants is a multifaceted challenge that requires a combination of biological, chemical, and physical strategies tailored to specific plant conditions. Biological nitrification-denitrification remains the most sustainable and cost-effective method, especially when optimized through process control and infrastructure upgrades. Chemical methods like ammonia stripping and ion exchange serve as effective adjuncts, particularly for high-strength waste streams or polishing effluents. Physical methods, including membrane degassing and lagoon aeration, provide additional options for specialized applications.
Achieving compliance with ammonia discharge standards not only protects aquatic ecosystems but also enhances the sustainability and reputation of wastewater treatment facilities. Continuous innovation, process optimization, and adaptive management are essential for maintaining low ammonia levels and ensuring environmental stewardship.
Ammonia primarily originates from human waste (urine and feces), industrial effluents rich in nitrogen compounds, and sludge digestion processes. Recycle streams from sludge dewatering can also contribute significant ammonia loads.
Ammonia is toxic to aquatic life, causes oxygen depletion through nitrification, and can lead to eutrophication. Regulatory agencies impose strict limits on ammonia in effluent to protect water bodies.
The activated sludge process, especially when configured for nitrification-denitrification, is the most widely used and effective biological method. Fixed-film systems and sequencing batch reactors (SBRs) also provide high removal efficiencies.
Ammonia stripping involves raising pH and aerating wastewater to volatilize ammonia gas, which is then captured in scrubbers. It is suitable for treating high-strength ammonia streams or as a side-stream process.
Yes, through operational adjustments like extended aeration, process upgrades such as adding fixed-film media, and side-stream treatments like ammonia stripping, small plants can meet regulatory standards.
[1] https://www.waterworld.com/wastewater-treatment/article/16200638/tackling-ammonia-at-the-wastewater-treatment-plant
[2] https://www.linkedin.com/pulse/importance-ammonia-removal-sewage-treatment-pvbcf
[3] https://www.waterworld.com/home/article/16194158/addressing-the-challenge-of-removing-ammonia-from-wastewater
[4] https://www.canada.ca/content/dam/eccc/migration/main/eu-ww/5a71856b-688f-4a15-84e7-0f799773712a/ammonia_exec_sum_e.pdf
[5] https://cdn.thomasnet.com/ccp/30674085/169814.pdf
[6] https://www.owp.csus.edu/research/papers/wastewater/SSB-Lit-Review-Final.pdf
[7] https://onlinelibrary.wiley.com/doi/10.1155/2018/3181087
[8] https://www.academia.edu/34687841/UPGRADING_OF_SMALL_SEWAGE_TREATMENT_PLANTS_FOR_AMMONIA_REMOVAL_CASE_OF_A_UNIVERSITY_CAMPUS
