Chlorine decay in drinking-water transmission and distribution systems: Pipe service age effect

2007 ◽  
Vol 41 (2) ◽  
pp. 387-396 ◽  
Author(s):  
A.O. Al-Jasser
Keyword(s):  
Drinking Water ◽  
Distribution Systems ◽  
Age Effect ◽  
Chlorine Decay ◽  
Water Transmission ◽  
Transmission And Distribution

Dependency of bulk chlorine decay rates on flow velocity in water distribution networks

2003 ◽  
Vol 3 (1-2) ◽  
pp. 209-214 ◽  
Author(s):  
J. Menaia ◽  
S.T. Coelho ◽  
A. Lopes ◽  
E. Fonte ◽  
J. Palma
Keyword(s):  
Drinking Water ◽  
Flow Velocity ◽  
Distribution Systems ◽  
Distribution Networks ◽  
Decay Rates ◽  
Decay Kinetics ◽  
Decay Rate Constant ◽  
Chlorine Residual ◽  
Chlorine Decay ◽  
Static Conditions

Understanding chlorine residual decay kinetics and the factors that influence them are essential for such current tasks as siting chlorination facilities, dosage optimisation, choice of sampling locations and frequencies, and general design and operational control of drinking water networks, increasingly accomplished with the help of simulation models. Available constants for bulk chlorine decay are typically determined under static conditions. However, as for all fast reactions in water flows, chlorine consumption rates in drinking water pipes may be influenced by the existing mixing regimes, a function of flow turbulence, which is primarily controlled by flow velocity and pipe diameter. Flow velocities vary greatly in space and time in water transmission and distribution systems; pipe diameters are seldom uniform. Although both variables are readily available in the currently available network analysis simulators that implement chlorine models, such variations are not accounted for. Instead, a single preset decay rate constant is generally used for describing chlorine residual consumption throughout an entire system. In addition to highlighting how negligible PVC pipe wall chlorine consumption is, as such, this paper presents experimental evidence of a significant correlation between pipe flow velocity and bulk chlorine decay rates, and proposes a simple but effective approach to implement this dependency in current simulators.

Prediction of chlorine and trihalomethanes concentration profile in bulk drinking water distribution systems from laboratory data

2003 ◽  
Vol 3 (1-2) ◽  
pp. 239-246 ◽  
Author(s):  
G. Kastl ◽  
I. Fisher ◽  
V. Jegatheesan ◽  
J. Chandy ◽  
K. Clarkson
Keyword(s):  
Drinking Water ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Laboratory Data ◽  
Water Distribution Systems ◽  
Optimum Level ◽  
Drinking Water Distribution Systems ◽  
Drinking Water Distribution ◽  
Chlorine Decay

Nearly all drinking water distribution systems experience a “natural” reduction of disinfection residuals. The most frequently used disinfectant is chlorine, which can decay due to reactions with organic and inorganic compounds in the water and by liquid/solids reaction with the biofilm, pipe walls and sediments. Usually levels of 0.2-0.5 mg/L of free chlorine are required at the point of consumption to maintain bacteriological safety. Higher concentrations are not desirable as they present the problems of taste and odour and increase formation of disinfection by-products. It is usually a considerable concern for the operators of drinking water distribution systems to manage chlorine residuals at the “optimum level”, considering all these issues. This paper describes how the chlorine profile in a drinking water distribution system can be modelled and optimised on the basis of readily and inexpensively available laboratory data. Methods are presented for deriving the laboratory data, fitting a chlorine decay model of bulk water to the data and applying the model, in conjunction with a simplified hydraulic model, to obtain the chlorine profile in a distribution system at steady flow conditions. Two case studies are used to demonstrate the utility of the technique. Melbourne’s Greenvale-Sydenham distribution system is unfiltered and uses chlorination as its only treatment. The chlorine model developed from laboratory data was applied to the whole system and the chlorine profile was shown to be accurately simulated. Biofilm was not found to critically affect chlorine decay. In the other case study, Sydney Water’s Nepean system was modelled from limited hydraulic data. Chlorine decay and trihalomethane (THM) formation in raw and treated water were measured in a laboratory, and a chlorine decay and THM model was derived on the basis of these data. Simulated chlorine and THM profiles agree well with the measured values available. Various applications of this modelling approach are also briefly discussed.

Energy Dissipation Mechanisms in Water Distribution Systems

2003 ◽  
Author(s):  
Bryan W. Karney ◽  
Yves R. Filion
Keyword(s):  
Energy Dissipation ◽  
Distribution System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Primary Energy ◽  
Transient Simulations ◽  
Surge Control ◽  
Water Transmission ◽  
Transmission And Distribution

An important issue in the context of design and analysis of a water distribution system is the rate of energy dissipation of a transient disturbance. In this paper, a preliminary numerical investigation is undertaken to establish the role and significance of primary energy dissipation mechanisms commonly found in water transmission and distribution systems. The role of steady friction, unwanted leaks, topological complexity and surge control devices in the decay of transient energy is preliminarily investigated. An energy approach previously derived is reviewed and used to track the progress of dissipation in a system. Transient simulations are run on a hypothetical series pipeline and distribution network with a waterhammer simulator to explore the dissipative effectiveness of some of the primary mechanisms.

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