Science Inventory

Characterization and Application of a Chlorine Microelectrode for Measuring Monochloramine within a Biofilm

Citation:

Lee, W., J. G. PRESSMAN, D. G. WAHMAN, AND P. L. BISHOP. Characterization and Application of a Chlorine Microelectrode for Measuring Monochloramine within a Biofilm. Sensors and Actuators B: Chemical. Elsevier BV, AMSTERDAM, Netherlands, 145(2):734-742, (2010).

Impact/Purpose:

To inform the public.

Description:

Chlorine microelectrodes with tip sizes of 5-15 μm were developed and used to measure biofilm monochloramine penetration profiles. The chlorine microelectrode showed response to total chlorine, including free chlorine, monochloramine, and dichloramine under various conditions. Where monochloramine dominates the system at pH 8.0 and 4:1 Cl2:N, the chlorine microelectrode had sensitivity toward monochloramine concentrations (0.1 to 30.0 mg Cl2/L) at an applied potential of +550 mV (Ag/AgCl reference electrode) at 23°C, and it was independent of pH interference at typical drinking water pH (6-9). A linear relationship existed with monochloramine concentration for a given dissolved oxygen (DO) concentration, even at high DO concentrations. However, a 3-D (response vs. DO vs. monochloramine concentration) calibration curve was constructed because the electrode response shifted with DO changes. The chlorine microelectrode successfully measured monochloramine concentration microprofiles with high spatial resolution within a biofilm. Ultimately, this research will lead to the in-situ application of chlorine microelectrodes for measurement of monochloramine within a chloraminated drinking water system biofilm and, along with other microelectrodes (e.g., ammonia, pH, DO), will aid in elucidating nitrification phenomena occurring in the biofilm.