water treatment solutions for the dechloramination - Water and Wastewater - Water Treatment

Chlorine reacts with compounds in the swimming pool water to give rise to by-products. Although there is potentially a large number of chlorine-derived disinfection by-products (DBPs), the substances produced in the greatest quantities are chloramines. Chlorine reacts extremely rapidly with ammonia in the water to form chloramines (monochloramine, dichloramine and trichloramine).

Trichloramine (nitrogen trichloride, NCl3) is an undesirable by-product of disinfection, which has a strong irritating effect on the eyes, nose, throat and bronchial tubes. Its odour is similar to that of chlorine. Trichloramine is formed, along with other chlorine-nitrogen compounds, in the chlorination of swimming and bathing pool water. It belongs to the compounds that are subsumed under the chemical parameter ‘combined chlorine’.

Combined chlorine is defined as the sum of the following compounds:

  • monochloramine, NH2Cl
  • dichloramine, NHCl2
  • trichloramine, NCl3
  • all chlorinated derivatives of urea and organic nitrogen compounds such as creatinine and amino acids.

The process to reduce the amount of chloramines in water is called “dechloramination”, and it is often used in public swimming pools.

Chloramines can be broken down by direct action of UV light (photolysis). The two present lamp technologies, LP and MP, have different effects on the single compounds:

  • Low-pressure UV lamps emit a single wavelength (254nm) able to break down only monochloramine. LP lamps are not able to break down the dichloramine and trichloramine, the most irritant chloramine forms.
  • Medium-pressure UV lamps emit wavelenghts between 200 and 400 nm, which are able to break down all three components of bounded chlorine: mono-, di-, and trichloramine.

bestUV offers the equipment and know-how to design the right UV system for the pool water characteristics at site.