Denitratation des eaux a potabiliser sur resines echangeuses d'ions—Impact sur la qualite chimique de l'eau traitee

Abstract

The increase in nitrate concentration in public water supplies is becoming an important problem in certain countries. Among the treatment processes available, the removal of nitrates by ion exchange has been thoroughly studied in recent years with regard to problems of capacity and selectivity. The use of anionic resins in drinking water treatment imply that these compounds do not induce secondary degradation in the quality of the treated water. The purpose of this paper is to examine the chemical quality of water treated by a strong base ion exchange resin (IRA 400) regenerated by sodium chloride. Two sources of organic compounds can be found in water treated with a filter of ion exchange resin: The constitution monomers leached from IRA 400 (styrene, divinylbenzene, trimethylamine and their derivatives). The micropollutants liable to be adsorbed, desorbed or produced during the exhaustion cycles of denitratation. The evolution of the concentration synthesis monomers in treated water was studied during the conditioning and the exhaustion cycles of the resin. Moreover the adsorption isotherms of the IRA 400 for different kinds of micropollutants (aromatic compounds, chlorinated solvents, herbicides, nitrosamines) were determined and the concentration of an added micropollutant (phenol) was measured during an exhaustion cycle. As for the formation of organic compounds during the treatment, we have limited our study to the analysis of N-dimethylnitrosamine during the exhaustion cycle, since this compound has been detected in water demineralized by an ion exchange resin.