Nitrogen Cycle Overview

The largest reservoir of nitrogen is in the atmosphere as N2 gas.

Nitrogen is essential for life because it is a crucial component of proteins, which are vital for building cells, tissues, enzymes, and hormones.

Most living organisms cannot directly use atmospheric nitrogen (N2). It must be converted into usable forms like nitrates (NO3-) through various biological processes.

The nitrogen cycle is a series of natural processes that move nitrogen through different forms in the environment, involving various biological and chemical conversions.

Ammonification is the decomposition of organic nitrogen compounds (like plant and animal waste) into ammonia (NH3).

Nitrification is the conversion of ammonia (NH3) into nitrates (NO3-) through a two-step process carried out by specific bacteria called nitrifiers.

Nitrifiers are aerobic chemoautotrophs. They obtain energy from oxidizing ammonia and use inorganic carbon as their carbon source.

Denitrification is the process where nitrates (NO3-) are converted to nitrogen gas (N2) under anaerobic conditions by denitrifying bacteria.

Denitrifiers are facultative anaerobes. They prefer oxygen, but can use nitrates as electron acceptors when oxygen is scarce.

The anammox process is an anaerobic reaction where ammonium (NH4+) is oxidized using nitrite (NO2-) as an electron acceptor, producing nitrogen gas (N2).

Anammox bacteria are found in the Planctomycetes phylum and are vital for nitrogen removal in various environments.

Nitrogen fixation is the crucial process where atmospheric nitrogen gas (N2) is converted into ammonia (NH3) by nitrogen-fixing microorganisms.

Nitrogen-fixing microorganisms are often found in the roots of legumes, forming symbiotic relationships. They require a lot of energy to convert N2 to NH3.

Ammonia is a main form of nitrogen in fresh wastewater. It can come from organic waste decomposition or human excrement.

Eutrophication is the excessive growth of algae and plants due to high levels of nutrients like nitrogen in water bodies.

High nitrate levels in drinking water can cause methemoglobinemia, also known as "blue baby syndrome", which reduces oxygen transport in the blood.

Organic nitrogen in wastewater is converted to ammonia through ammonification. The ammonia is then nitrified to nitrates, which are further removed through denitrification.

Nitrification converts ammonia to nitrates, which are more soluble and easier for plants to absorb. It's important in agricultural systems.

Denitrification is used in wastewater treatment to remove nitrogen effectively, preventing environmental pollution and eutrophication.

The Anammox process can be used in wastewater treatment to remove nitrogen, potentially saving energy compared to traditional nitrification-denitrification methods.

Oxidizing agents gain electrons, becoming reduced. Reducing agents lose electrons, becoming oxidized.

In nitrification, ammonia (NH4+) is the electron donor, becoming oxidized to nitrates (NO3-), while oxygen (O2) is the electron acceptor and is reduced to water (H2O).

In denitrification, an organic compound like methanol (CH3OH) is the electron donor, while nitrate (NO3-) is the electron acceptor, leading to the production of nitrogen gas (N2).

The balanced equation for a reaction accounts for all elements and their respective charges, ensuring that the total charge and number of atoms on both sides of the equation are equal.

The energy reaction represents the energy released or absorbed during the process, while the synthesis reaction shows how organic matter is produced using the energy obtained.

The yield coefficient (Y) represents the amount of biomass produced per unit of substrate consumed, indicating the efficiency of the process.

Nitrifiers are slow growers because the oxidation of ammonia to nitrates releases less energy per electron equivalent compared to other energy sources.

Denitrification is used to remove excess nitrogen from wastewater, protecting aquatic ecosystems from eutrophication.

Nitrification-denitrification is a common wastewater treatment process where ammonia is converted to nitrates, then denitrified to nitrogen gas, effectively removing nitrogen from effluent.