The distinction between total nitrogen, nitrate nitrogen and ammonia nitrogen and the resin removal technology

Total Nitrogen: 

Total Nitrogen (TN) is a comprehensive indicator, representing the total amount of nitrogen elements in all nitrogen-containing substances in water. 
Total nitrogen = Inorganic nitrogen + Organic nitrogen 
Inorganic nitrogen (accounting for approximately 30-70% of total nitrogen, with a higher proportion in polluted water): 
Ammonia nitrogen 
Nitrate nitrogen 
Nitrous nitrogen

 
Organic nitrogen (derived from organisms and their metabolic products): 
Proteins, polypeptides, amino acids 
Urea, nucleic acid 
Nitrogen in humus 

Environmental significance:

The total nitrogen index reflects the overall nitrogen pollution level of the water body and is a key parameter for assessing the risk of water body eutrophication.

Ammonia nitrogen:

Ammonia nitrogen (NH₃-N) specifically refers to nitrogen in the form of ammonia. In water, it exists in two dynamic equilibrium forms: 
Free ammonia: Chemical formula NH₃, is volatile and liposoluble, and has extremely strong toxicity to aquatic organisms. 
Ammonium ion: Chemical formula NH₄⁺, carries a positive charge, and has relatively low toxicity. 

The ratio of the two is determined by the pH value and temperature of the water body: 
When the pH is less than 7, almost all exist in the form of NH₄⁺. 
When the pH value is greater than 11, almost all exist in the form of NH₃. 

The higher the temperature, the greater the proportion of NH₃. 
This form transformation is of crucial importance for the selection of treatment processes. Ammonia nitrogen represents the reduced state in the nitrogen cycle.

Nitrate nitrogen:

Nitrate nitrogen (NO₃-N) is the final product of nitrogen oxidation and mainly exists in the form of nitrate ions. 
High solubility:It is highly soluble in water and is not easily adsorbed by soil or sediment.
Chemical stability: Can exist for a long time in an oxygen-rich environment. 
Charged negatively: Exists in the form of NO₃⁻, which determines the method of its removal 
Oxidation state: The nitrogen element is in its highest oxidation state (+5 valence)

Detailed Explanation of Resin Removal Technology:

Ammonia nitrogen removal resin 
Working principle: 
Using highly selective cation exchange resins, ammonium ions (NH₄⁺) are preferentially bound. 
Ion exchange: The functional groups of the resin (such as sulfonic acid groups, carboxyl groups) release Na⁺ or H⁺, and exchange with NH₄⁺. 
pH regulation: When the pH is between 6 and 8, ammonia nitrogen mainly exists as NH₄⁺, which is most conducive to ion exchange.

Nitrate nitrogen removal resin 
Using strongly basic anion exchange resins, it has a special selectivity for nitrate ions (NO₃⁻). By adjusting the polymer matrix and functional groups of the resin, its affinity for NO₃⁻ is higher than that for sulfate ions, chloride ions, etc.

Total Nitrogen Control Comprehensive Plan

As total nitrogen contains multiple forms, a single resin is difficult to completely remove it, and a combined strategy needs to be adopted: 
First, remove the ammonia nitrogen. Then, convert the remaining ammonia nitrogen into nitrate nitrogen through biological processes. Finally, deeply remove it using nitrate nitrogen resins. 
It is also possible to adopt a simultaneous processing method:

For complex wastewater containing organic nitrogen, ammonia nitrogen and nitrate nitrogen: 
Pre-treatment: Ozone oxidation or hydrolysis acidification convert organic nitrogen into ammonia nitrogen. 
Segmented operation: Ammonia nitrogen resin + Nitrate nitrogen resin operate in parallel or series connection. 
Post-treatment: If necessary, add a denitrification biological treatment unit.