Citation:

Zhao, Y., J. Yang, Y. Shao, AND T. Zhang. The Dependence of Chlorine Decay and DBP Formation Kinetics On Pipe Flow Properties in Drinking Water Distribution. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 141:32-45, (2018).

Impact/Purpose:

This journal article is to communicate to technical communities on the most recent research results of chlorine decay and disinfection by-products formation kinetics in drinking distribution system. New insights are presented on how distribution system operation affects water quality.

Description:

Simultaneous chlorine decay and disinfection byproduct (DBP) formation has long been discussed because of its regulatory and operational significance. This study further examines the water quality changes under hydrodynamic settings during drinking water distribution. Comparative experiments and modeling analysis aimed to determine the kinetic variability of overall chlorine decay ( ) and trihalomethane (THM) formation potential under a set of physiochemical and flow conditions, including three devices of different wall demand and two types of natural organic materials (NOM). The results show the relative importance of wall demand ( ), DBP-forming chlorine decay ( ), and other bulk demand ( ) with Re=0-52000, in a pipe flow of competitive chlorine reactions. It is found that chlorine reactivity of natural organic matter (NOM) is the overriding factor. For tap water NOM, pipe flow properties (Re or u) can also significantly change , the THM yield , and the time to reach the maximum THM concentration ( ). These observations, corroborating with turbidity variations, cannot be explained alone by chlorine transfer to and from the pipe wall. In addition to solute transfer, mass exchanges through deposition and scale detachment are considered to be the other responsible mechanism depending on the flow velocity and shear stress on pipe walls. We propose to incorporate the effects of NOM reactivity, pipe types (wall demand), and flow hydraulics in a proposed framework in order to better simulate water quality in the pipe flow field, and thus to optimize network operations.

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