AWWA WQTC60609

Non-ionic or anionic polymers are largely used as flocculants in drinking water treatment. While the use of synthetic cationic polymers in the U.S. and other countries is a common practice, in France these chemicals have just received approval from the health and sanitary department as materials to be used for drinking water. Cationic polymeric coagulants can be efficient for enhanced coagulation of surface waters or for direct filtration of source waters. Tests with these coagulants have been performed during the 2001-2003 period, at laboratory and pilot scale, to prepare the use on drinking water works at industrial scale during 2004. This study focused on the selection and the assessment of the technical and economic interest for using cationic polymers as coagulants for drinking water. The objective was to establish the level of clarification process performance that can be achieved on various types of waters for both natural organic matter (NOM) and turbidity removal and the corresponding type and dose of chemical. The major interest of the tested polymers has been found to be their joint use with mineral coagulant: combination with aluminum salt for enhanced conventional coagulation and with ferric salt for direct filtration. The optimal substitution ratio of mineral coagulant by organic coagulant has been found to be 30%. Potential byproducts formation (NDMA) have been controlled during the tests. Under the usual operating conditions (polymer dose and disinfectant residual) no NDMA was formed and therefore the risk of byproducts formation was evaluated to be very low. Includes 28 references, tables, figures.