Diminution des sous-produits de la desinfection dans l'eau potable par ozonation et chloramination

Disinfection of drinking water produces undesirable by-products that may cause adverse health effects. Indeed, disinfection by-products (DBP) such as trihalomethanes (THMs) and haloacetics acids (HAAS) are considered potentially carcinogenic and have been recently associated to reproduction outcomes. The Quebec regulation respecting the quality of drinking water (RRQDW) published in June 2001 establishes a maximum average level for total THMs of 80 mug/L. This standard is difficult to meet by small municipalities served by surface water and which apply a limited treatment before disinfection. This is the case of the municipalities of Saint-Aubert and Saint-Jean-Port-Joli located in the region of Bas-Saint-Laurent (Quebec). The current water treatment strategy does produce high concentration of THMs and HAAS in the distribution system. The purpose of this research is to develop a protocol that would lead to the identification of alternative water treatment and disinfection strategies to reduce THMs and HAAS in order to comply with the new provincial standards. This protocol involves pilot studies and laboratory assays that simulate the formation of THMs and HAAs in the distribution system. Those water treatment alternatives involve ozone followed by slow sand filtration, chloramines and/or chlorine. The results showed that the highest THM and HAA reduction is reached using ozone and chloramines as a disinfection strategy.