Kinetics of chlorine decay

Abstract

Models of chlorine kinetics in distribution systems characterize chlorine decay as a combination of first‐order decay in the bulk liquid and first‐order or zero‐order decay reactions at the pipe wall. Proper understanding, characterization, and prediction of water quality behavior in drinking water distribution systems are critical to ensure meeting regulatory requirements and customer‐oriented expectations. This article investigates the factors leading to loss of chlorine residual in water distribution systems. Kinetic rate equations describing the decay of chlorine were developed, tested, and evaluated using data collected in field‐sampling studies conducted at several water utility sites. Results indicated that chlorine decay in distribution systems can be characterized as a combination of first‐order reactions in the bulk liquid and first‐order or zero‐order mass transfer–limited reactions at the pipe wall. Wall reaction kinetic constants were inversely proportional to pipe roughness coefficients. Wide variations in both bulk reaction constants and wall reaction constants were observed among the sites.

Water Supply System Performance for Different Pipe Materials Part I: Water Quality Analysis

“…Chlorine decay in distribution systems can be characterised as a combination of first-order reactions in the bulk liquid and first-order or zero-order mass transfer-limited reactions at the pipe wall (Vasconcelos et al 1997). In water quality modelling tools chlorine decay is often simplified to first-order kinetics:…”

“…Chlorine is used either as free chlorine or as monochloramine to disinfect the bulk water in drinking water distribution systems and to control the growth of biofilms (Jegatheesan et al 2000;Maier et al 2000;Vikesland et al 2001). It is important to maintain adequate chlorine residual throughout the whole distribution system in order to sustain the chemical and microbial quality of distributed water (Vasconcelos et al 1997;Munavalli and Mohan Kumar 2003). However, being a strong oxidiser, chlorine reacts readily with organic and inorganic compounds and thus decays inside the distribution system through reactions both in the bulk phase and at the pipe wall (Vasconcelos et al 1997;Kiéne et al 1998;Powell et al 2000a;Clark and Sivaganesan 2002;Munavalli and Mohan Kumar 2003;Clark and Haught 2005).…”

“…It is important to maintain adequate chlorine residual throughout the whole distribution system in order to sustain the chemical and microbial quality of distributed water (Vasconcelos et al 1997;Munavalli and Mohan Kumar 2003). However, being a strong oxidiser, chlorine reacts readily with organic and inorganic compounds and thus decays inside the distribution system through reactions both in the bulk phase and at the pipe wall (Vasconcelos et al 1997;Kiéne et al 1998;Powell et al 2000a;Clark and Sivaganesan 2002;Munavalli and Mohan Kumar 2003;Clark and Haught 2005). In addition, chlorine can be consumed by the corrosion process of the pipe material (Vasconcelos et al 1997;Clark and Haught 2005) as well as due to the biofilm attached to the pipe wall.…”

“…However, being a strong oxidiser, chlorine reacts readily with organic and inorganic compounds and thus decays inside the distribution system through reactions both in the bulk phase and at the pipe wall (Vasconcelos et al 1997;Kiéne et al 1998;Powell et al 2000a;Clark and Sivaganesan 2002;Munavalli and Mohan Kumar 2003;Clark and Haught 2005). In addition, chlorine can be consumed by the corrosion process of the pipe material (Vasconcelos et al 1997;Clark and Haught 2005) as well as due to the biofilm attached to the pipe wall. The decay caused by biofilms varies largely, however, and the interactions between biofilms and disinfectants are still inadequately understood (Kiéne et al 1998;Jegatheesan et al 2000).…”

Validation of a Computational Fluid Dynamics Model for a Novel Residence Time Distribution Analysis in Mixing at Cross-Junctions

“…This problem could produce the formation of biofilm on pipe walls [1,2], promoting bacterial growth and its transport through water. On the other hand, the system's own useful life, the intermittency in the supply, the leaks level, and the demands behaviour cause a great variety of residence times of the drinking water and variations of reaction of the disinfectant in the network [3,4].…”