Nitrogen (N) in Water Treatment

Quick Answer

Nitrogen (N) is a nonmetal with atomic number 7. PubChem lists its standard state as gas and its relative atomic mass as 14.007.

Nitrogen is managed mainly as ammonia, nitrite, nitrate and organic nitrogen. Biological nitrification-denitrification, ion exchange and membrane processes are selected according to the nitrogen species and discharge or reuse target.

Interesting Facts

Nitrogen makes up about 78% of Earth’s atmosphere, yet aquatic systems are often limited by biologically available nitrogen.
“Total nitrogen” can hide very different species: ammonia, nitrite, nitrate and organic nitrogen do not share one toxicity or treatment route.
Nitrification converts ammonia to nitrate; nitrogen leaves the water as N₂ only after a suitable denitrification or recovery step.

Water-treatment Design Implications

An element name alone is not enough to select treatment equipment. Confirm chemical form or speciation, total and dissolved concentration, pH, alkalinity, competing ions and the product-water target. Send the water-analysis results to Watermart to identify additional testing and shortlist processes before equipment is specified.

Summary Data Sources

1. Basic Information

Atomic number: 7
Symbol: N
Atomic weight: 14.0067
Group on the periodic table: Group 15 (pniktogen)
Period on the periodic table: Period 2

2. Physical and Chemical Properties

A non-metallic element that at room temperature and atmospheric pressure is a diatomic gas
Colorless, odorless, and tasteless
Only slightly soluble in water
Forms many important compounds, including ammonia, nitric acid, and organic compounds such as amino acids, proteins, and nucleic acids
Boiling point: -195,8°C
Melting point: -210°C

3. Presence in Water & Health Effects

Nitrogen exists in the form of nitrate (NO3-) and nitrite (NO2-) dissolved in water
Natural sources include decomposition of organic matter and thunderstorms
Major anthropogenic sources are fertilizers and animal/human waste
High concentrations of nitrate (>10 mg/L NO3-N) in drinking water can cause methemoglobinemia in infants
Nitrite can react with amines and amides to form nitrosamines which are carcinogenic

4. Applications & Removal Methods in Water Treatment

Ion exchange using anion exchange resins can remove nitrate and nitrite
- Type 1 strong base resins such as AmberSep™ 21K XLT are effective for water with low sulfate/nitrate ratio
- For high sulfate/nitrate ratios, nitrate selective resins such as AmberLite™ PWA5 are more suitable
Reverse osmosis and nanofiltration can also remove nitrate and nitrite
Biological denitrification using anaerobic bacteria converts nitrate to nitrogen gas

6. Environmental Impact & Sustainability Considerations

Excessive nitrogen concentrations in waters can lead to eutrophication and harmful algae blooms
Water treatment methods that remove nitrogen must properly manage the residue/concentrate so as not to pollute the environment
Energy-efficient technologies such as denitrification are preferred over energy-intensive methods such as reverse osmosis where possible

8. Interesting Facts

About 78% of Earth’s atmosphere is nitrogen, but most of it cannot be directly utilized biologically
In the field of water treatment, biological filaments of the genus Thiothrix can cause froth and odor problems due to high nitrate concentrations in wastewater

This is a comprehensive summary of nitrogen relevant to water treatment. Despite the challenges in managing nitrogen compounds, promising technologies and approaches continue to be developed.