The decrease of UV absorbance as an indicator of TOX formation

The decrease in UV absorbance (ΔUV) caused by chlorination of NOM correlates linearly with the amount of TOX formed, for a remarkably wide range of water quality conditions and reaction times. THM formation also correlates with ΔUV, but the relationship is more sensitive to solution pH and is probably not linear over the entire range of conditions/times relevant for water treatment. It appears that all Cl-DOC reactions that destroy UV absorbance generate TOX, but substantial amounts of THMs are formed only after a significant amount of reaction has occurred.