Difference Between Nitrification and Denitrification

Difference Between Nitrification and Denitrification: Nitrification and Denitrification are two main stages in the Nitrogen cycle. Molecular nitrogen cannot be utilized directly by plants so it is fixed in the form of nitrites and nitrates with the help of specialized bacteria. Nitrogen recycling is done with the Nitrogen cycle. Stages include- Nitrogen fixation, Nitrification, Assimilation, Ammonification and Denitrification.

Nitrification is the process of converting ammonia to nitrite and then nitrate with the help of nitrifying bacteria. It is an oxidation process that works under aerobic conditions. Denitrification, on the other hand, is a reduction process that converts nitrate into nitrogen gas and works under anaerobic conditions. In this article, we will look into the difference between nitrification and denitrification, its mechanism, and its significance.

Difference Between Nitrification and Denitrification

The nitrification vs denitrification is given below:

Criteria	Nitrification	Denitrification
Process	Converts ammonia to nitrates and nitrites.	Converts nitrogen salts to nitrogen.
Bacteria involved	Nitrifying bacteria are involved.	Denitrifying bacteria are involved.
Types of Bacteria	Ammonium oxidising organisms and nitrate oxidising organisms are involved.	Ammonium oxidising organisms and nitrate oxidising organisms are not involved.
Type of Bioprocess	Aerobic microbes are involved.	Anaerobic organisms are involved.
Importance	It plays an important role in nitrogen fixation.	It plays an important role in nitrogen cycling.
Mode of Nutrition	Autotrophic.	Heterotrophic.
Examples of Microorganisms involved	Nitrosomonas and nitrobacter are main examples.	Pseudomonas and azotobacter are main examples.

What is Nitrification?

Nitrification is the process by which ammonia is converted into nitrites (NO^2-) and further to nitrates (NO^3-) by nitrifying bacteria. This salts can be easily utilised by plants.

NH₄⁺(Ammonium) → NO^2- (Nitrite) → NO^3- (Nitrate).

Mechanism of Nitrification

Mechanism of Nitrification includes two main stages.

• Oxidation of Ammonia to Nitrate
• Oxidation of Nitrate to Nitrites

Nitrification begins with the oxidation of ammonia to nitrites, a process catalysed by ammonia-oxidising bacteria (AOB). These bacteria utilise ammonia as an energy source and produce nitrites as a byproduct. This step is catalysed by ammonium monooxygenase The next step involves the oxidation of nitrites to nitrates, facilitated by nitrite-oxidising bacteria (NOB). This reaction is catalysed by nitrite oxidoreductase. These bacteria complete the conversion of ammonia to nitrates, making it available for uptake by plants and thereby nitrogen is fixed in the living world and further transferred through the nitrogen cycle.

Nitrifying Bacteria

Nitrifying bacteria are classified into:

• Ammonia-Oxidizing Bacteria (AOB): AOB are bacteria that initiate the nitrification process by oxidising ammonia to nitrites. Examples of AOB include species belonging to the genera Nitrosomonas and Nitrosospira.
• Nitrite-Oxidizing Bacteria (NOB): NOB are bacteria that further oxidise nitrites produced by AOB into nitrates. Examples of NOB include species belonging to the genera Nitrobacter and Nitrospira.

Significance of Nitrification

Nitrification is an important process in the nitrogen cycle in the ecosystem:

• Nutrient Source of Plant: Nitrification converts ammonia (NH₃), which is often toxic to plants, into nitrate (NO^3-) form, which is the primary source of nitrogen for plant nutrition. Nitrate is readily taken up by plants and used to synthesise amino acids, proteins, and other essential molecules.
• Increase Agricultural Yield: Nitrates play an important role in plant nutrition as it is a major nutrient.
• Increase Soil Fertility: Nitrification replenishes soil nitrogen, maintaining soil fertility over time.
• Maintain Water Quality: Nitrification regulates ammonia in aquatic environments and thereby reduces eutrophication or algal bloom.
• Important in Wastewater Treatment: In sewage treatment plants, nitrifying bacteria are utilised to convert ammonia present in wastewater into nitrate, which can then be further processed or removed, reducing environmental pollution.

What is Denitrification?

Denitrification is another key process in the nitrogen cycle, where nitrate (NO^3-) is converted back into nitrogen gas (N₂) or nitrous oxide (N₂O) by denitrifying bacteria.

2NO^3- (Nitrate) + 10e^– + 12H⁺ → N₂ (Nitrogen) + 6H₂O

Mechanism of Denitrification

Denitrifying Bacteria make use of ammonia and back-convert them to atmospheric nitrogen. Denitrifying bacteria require organic carbon or other organic compounds as a source of electrons for the denitrification process. This involves two processes:

• Reduction of nitrate to nitrite
• Reduction of nitrite to nitrogen

Denitrifying bacteria use nitrate (NO^3-) as an electron acceptor in place of oxygen during respiration. The first step involves the reduction of nitrate to nitrite (NO^2-) by the enzyme nitrate reductase.

Significance of Denitrification

Nitrogen salts get converted to free nitrogen.

• Cycling of Nitrogen.
• Remove excess nitrogen.
• Reduce greenhouse gas emissions.
• Maintain ecological balance.

Similarities Between Nitrification and Denitrification

Although they have many differences, few of the similarities between Nitrification and Denitrification are :

• pH requirement is slightly alkaline.
• Both are microbial processes.
• Plays major role in nitrogen cycle of earth.

Conclusion – Difference Between Nitrification and Denitrification

Nitrogen has an important role as a structural and functional compound in the living world. The nitrification and denitrification stages play a crucial role in maintaining the nitrogen cycle. But these stages differe from each other. The difference between nitrification and denitrification are discussed in this article. Understanding and managing these processes are essential for sustainable agriculture, wastewater treatment, and environmental conservation efforts. By studying and harnessing the mechanisms of nitrification and denitrification, we can mitigate nitrogen pollution and promote healthier ecosystems for future generations.

FAQs on Nitrification and Denitrification

What is the Principle of Nitrification?

Nitrification is a microbially-catalysed process whereby ammonia (NH₃) is oxidised to nitrite (NO^2-) and subsequently to nitrate (NO^3-).

Is Denitrification Exothermic?

Yes, Denitrification is exothermic in nature.

Is Denitrification done by Chemoautotrophs?

It is an aerobic process. Chemoautotrophic bacteria converts ammonia into nitrite by the process of oxidation. Nitrococcus and Nitrosomonas are major examples.

What does Nitrification and Denitrification have in Common?

Nitrification and Denitrification are microbial processes .Both the processes require an optimum pH range lying between 6 to 8.

Does Denitrification require Oxygen?

Biological denitrification requires hypoxic or anaerobic conditions with dissolved oxygen (DO) concentration less than 0.2 mg/L. This is because Denitrification bacteria require anaerobic conditions for its survival.

What are the Examples of Nitrifying and Denitrifying Bacteria?

Nitrifying bacteria like Nitrosomonas and Nitrobacter convert ammonia into nitrites and nitrates. Denitrifying bacteria such as Thiobacillus denitrificans and Achromobacter convert nitrates back into nitrogen gas.

What is the Main Difference Between Nitrogen Fixation and Denitrification?

Nitrogen fixation converts atmospheric nitrogen into ammonia or related compounds, while denitrification converts nitrates into nitrogen gas, returning nitrogen to the atmosphere