The UV/free chlorine process forms reactive species such as hydroxyl radicals (HO�), chlorine atoms (Cl�) to degrade micropollutants. Yet, when this technology is used to reduce target contaminants, the precursors of disinfection by-products (DBPs) can be simultaneously altered. This study evaluated the formation of disinfection by-product formation from the UV/chlorine treatment followed by subsequent 1-day chlorination of water containing model compounds of benzoic acid (with electron-withdrawn moiety), phenol (with electron-rich organic moiety), tyrosine (typical amino acid). The former is not reactive with chlorine to form DBPs, the latter two are reactive with chlorine and tyrosine is a typical precursor of N-DBPs. UV/chlorine treatment modified the structure of either benzoic acid or phenol, and thus increased the formation of chloroform and chloral hydrate after 1-day chlorination at pH 7. As for tyrosine, UV/chlorine treatment increased the formation of chloroform and chloropicrin, but decreased the formation of dichloroacetontrile and slightly changed the formation of chloral hydrate. The variation of DBP formation was linked with the exposure of HO� and Cl�. pH affected the DBP formation by changing the radical exposure and chlorine chemistry.

Variation of DBP formation after UV/free chlorine treatment of model compounds

248th National Meeting (2014)

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