Comparison of Spectrophotometric Methods for Measuring Chlorine Dioxide in Drinking Water

Abstract

The recognition that chlorine disinfection of drinking water may not be effective in controlling pathogens such as Cryptosporidium may lead to the greater use of stronger alternative disinfectants, such as chlorine dioxide. Typical chlorine dioxide residual concentration requirements for disinfection may extend to less than 0.1 mg l⁻¹, thus requiring very good quantitation methods for optimal process control. Traditional methods have been cumbersome and sometimes inaccurate. This study examined three spectrophotometric methods for measuring chlorine dioxide in the <0.1 mg l⁻¹ to 2 mg l⁻¹ range, using acid chrome violet k (ACVK), lissamine green B, and amaranth reagents. Each method was assessed using both laboratory reagent water and various natural waters to identify the respective linear range, method precision, and the possible interference from natural colour due to aqueous organic matter. Interferences arising from the presence of chlorine, chloramines, chlorite, chlorate, and permanganate were also evaluated, along with the potential need to correct for temperature changes.

Keywords:

• Chlorine dioxide
• disinfection
• ACVK
• lissamine
• amaranth