Modeling Cyanogen Chloride Kinetics in Distribution Systems: A Semi-Batch C t Protocol for Natural Waters

Experiments were undertaken with the primary objective of developing kinetic relationships for the formation of cyanogen chloride (CNCl), which could then be integrated into a multi-constituent water quality model. The use of ozone in combination with monochloramine has been reported in the literature to enhance CNCl formation. A procedure to determine C t, a surrogate used to estimate the level of microbial inactivation achieved, was also developed using a semi-batch methodology. Water collected from the Mannheim Water Treatment Plant (WTP) (Waterloo, Ontario, Canada) at 7°C and 20°C was ozonated using a semi-batch procedure to achieve a desired level of inactivation. A series of specific steps were then followed to simulate treatment at the Mannheim WTP as closely as possible at bench-scale. Three different levels of microbial inactivation were selected to simulate 0.5-log Giardia inactivation, and both 1.0-log and 3.0-log Cryptosporidium inactivation. Kinetic relationships were developed which described CNCl formation as a function of log Cryptosporidium inactivation, monochloramine concentration, and time. It was concluded that CNCl formation followed an exponential function of time that depended on both monochloramine concentration and microbial inactivation level.