Impact of Chlorination on the Formation of Odour Compounds and Their Precursors in Treatment of Drinking Water

The general purpose of this study is to optimise the removal of precursors of taste and odour compounds, especially 2,4,6-chlorophenol, at a water treatment plant. Nowadays, there are frequently problems of taste and odour in drinking water due to the presence of various types of compounds. Some of these are already present in the resource but o thers are generated during the chlorination stage at the water treatment plant. Moreover, these compounds can be detected at very low detection limit by consumers, increasing the need to remove their precursors from the water. For instance, the odour threshold of 2,4,6,-trichloroanisol (TCA), which is generated by methylation of chlorophenol during treatment or in the distribution network can be detected at concentrations between 0.05 to 0.2 ng/L. The present bibliographic study of the chlorination stage highlights the great number of by-products generated by reaction with organic matter, such as HAA, THM, chlorophenol… It also appears that the part of organic matter called precursors can be partially removed at different stages of a plant to lower the concentration of final organohalogeneted compounds. A variety of treatment processes are used: The perspectives of this work are to conduct laboratory tests on the removal of precursors of tastes and odour compounds. This future study will be carried out with 2 targets, 2,4,6,-chlorophenols and 2,4,6,-chloroanisol which are emerging compounds, and lake water with taste and odour problems. In principle, chlorination will be done after each step of treatment in order to determine an index of reactivity with organic matter.