Chlorite and Chlorate ion variability IN DISTRIBUTION SYSTEMS

Abstract

This study tracked changes in chlorite ion (ClO2–) and chlorate ion (ClO3–) concentrations in the distribution system of the City of Laval, Québec, following use of chlorine dioxide (ClO2) or free chlorine. Water was collected in small‐ and large‐diameter pipes with respect to the residence time of each sampling point. In the network fed by a treatment plant using ClO2 in postdisinfection, ClO2– concentrations decreased with increasing water residence time. In the networks fed by treatment plants using free chlorine in postdisinfection, ClO2– levels remained below the method detection limit (MDL). ClO3– concentrations measured in the network following ClO2 postdisinfection were found to be either below the MDL or stable at a low level (0.09 mg/L) in cold water; ClO3– levels decreased slightly in warm water with increasing residence time. In the networks using free chlorine as a postdisinfectant, ClO3– levels showed significant variations in their overall concentrations during different samplings or with specific changes in their concentration related to residence time.

The effects of selected preoxidation strategies on I-THM formation and speciation

“…While KMnO 4 and H 2 O 2 do not form regulated DBPs, ClO 2 forms chlorite (ClO 2 À ) and some levels of haloacetic acids (HAAs), two types of regulated DBPs in the United States (Arora et al, 2001). The formation of ClO 2 À may be controlled by limiting the ClO 2 dose application to less than 1.5 mg/L due to a 30e70% conversion rate of ClO 2 to ClO 2 À (Baribeau et al, 2002).…”

An improved chloroform surrogate for chlorine dioxide‐and alum‐treated waters

“…Chlorite's MCL is 1 mg/L under the Stage 2 D/DBPR. Several studies have reported chlorite ion yields to be between 30 and 70% of the consumed ClO 2 (Alam et al, 2008; Baribeau et al, 2002; Korn et al, 2002; Gordon, 1992; Werdehoff & Singer, 1987; Aieta et al, 1984), and Schmidt et al (2000) showed that this variation can be due to source water NOM characteristics.…”

The Control of Microbiological Problems∗∗Some excerpts taken from Bajpai P (2012). Biotechnology for Pulp and Paper Processing with kind permission from Springer Science1Business Media.

“…The optimal pH is between pH 6.0 and pH 10.0 and is generally more effective against microorganisms at pH above 8.0 than chlorine (Knapp and Bettisti, 2001). Chlorine dioxide is converted to chlorite, the predominant end-product (50-70%), and to chlorate and chloride in water (Baribeau et al, 2002). The major advantage of using chlorine dioxide is that it reacts less with ammonia as compared with chlorine.…”