How Ultraviolet Light Destroys Chloramine

Chloramines are eye irritants that form through chemical reactions in pool water.

Chloramines are products formed by the reaction between certain organic compounds and free chlorine in swimming pools. Since they are strong eye and respiratory irritants, it's desirable to keep levels of these compounds as low as possible.

Prevention/Solution

Chloramines are responsible for the familiar "chlorine smell" many swimmers associate with pools. Inadequate chlorination of pool water is generally the culprit behind chloramine buildup; superchlorination can eliminate the chloramines in the pool water. Ultraviolet light can break down chloramines as well.

Function

When a photon of ultraviolet light is absorbed by an electron in a molecule of chloramine, the electron jumps to a higher molecular orbital. It can only absorb photons of light that carry energy equivalent to the difference in energy between two molecular orbitals the electron can occupy. Since bonds are formed by sharing electrons between atoms, this process can potentially break a bond, causing the molecule to split up.

Effects

According to a 2009 study published in the journal "Environmental Science and Technology," the primary products of ultraviolet degradation of chloramines are nitrate, nitrite, nitrous oxide and ammonium. The reaction process that turns chloramines into these products involves multiple steps and is complex. Certain wavelengths break chloramines down to a greater extent than others, and dichloramine and trichloramine are more susceptible to ultraviolet than monochloramine.

References

• American Chemistry: Chloramines
• Environmental Science and Technology: UV Photodegradation of Inorganic Chloramines