CHLORITES AND CHLORATES : FIELD TOOLS TO MONITOR CHLORINE DIOXIDE TREATMENT

摘要

Chlorine dioxide is often used as an alternative to chlorine (for disinfection inrndrinking water production and distribution) for its advantage of limiting thernformation of chlorination by-products. However, the use of chlorine dioxide alsornleads to the formation of chlorides and oxichlorine groups, such as chlorites andrnchlorates. It is important to have reliable analysis methods to monitor theirrnformation and presence.rnReference method wich allow to the determination of ClO_2rn~- and ClO_3rn~- is the ionicrnchromatography. This method, wich is complex and costly, must berncomplemented by fields methods to allow operators to carry out regular on-siternanalysis.rnThe method developed is based on the oxidation of orthotolidine by chlorinerndioxide (formed by chlorite under acidic conditions) or by chlorine (formed byrnchlorate under other acidic conditions). The concentrations are determinated byrnspectrophotometric measurement.rnThe operating conditions such as reagents’concentration, kinetics, measurement’srnwavelength, sample pretreatment were optimized. Spiked waters as well as realrnwater were analysed by the method developed and ionic chromatography.