Identifying key pipe attributes and locations to best determine chlorine decay coefficients within a water distribution system

Abstract

Water distribution system (WDS) characteristics can impact drinking water quality. Kinetic reaction coefficients of residual disinfectant associated with bulk water (kb) and pipe wall (kw) during water distribution can lead to water quality degradation. Determining these coefficients can be expensive and time-consuming. The main objective of this study is to determine the most relevant pipe characteristics and locations to best determine chlorine decay coefficients in a WDS. This article aims to evaluate various scenarios of kb and kw values and compare them to measured data in a full-scale WDS. The most accurate scenario is also compared with the lowest-cost scenario to identify the most effective information needed to determine these coefficients, in terms of location within the WDS and pipe characteristics (age, diameter, and material). Results showed that the scenario with the highest kw and kb values corresponds best to the field-measured data. Moreover, determining specific kinetic coefficients was shown to be more accurate for gray cast iron pipes, pipes installed in a period before 1960, and vulnerable zones for residual chlorine decay. HIGHLIGHTS The most important part of the WDS to determine specific kinetic coefficients are the ones with free residual chlorine (FRC) of less than 0.2 mg/L (vulnerable zones).; The most important pipe characteristics for estimating specific kinetic coefficients are pipe material, more specifically grey cast iron (GCI) and period of installation, more specifically pipes installed before 1960.; Since the determination of specific kinetic coefficients can be expensive and time-consuming, the identified pipe characteristics can help locations representing a wise investment for investigation.; Close to 20% percent of pipes in our case study are located in vulnerable zones, which should be monitored more closely.;

Keywords

• chlorine concentration
• decay coefficients
• vulnerable zone
• water quality