The Influence of Total Hardness on Chlorine Decay in Water Distribution Systems

2014 ◽  
Vol 535 ◽  
pp. 776-784
Author(s):  
Jing Qing Liu ◽  
Wei Jiang ◽  
Jian Min Wu ◽  
Cong Li
Keyword(s):  
Drinking Water ◽  
Metal Ions ◽  
Distribution Systems ◽  
Water Hardness ◽  
Free Chlorine ◽  
Chlorine Concentration ◽  
Total Hardness ◽  
Decay Constants ◽  
Chlorine Decay ◽  
The Impact

Free chlorine decay is a main issue in drinking water treatment since free chlorine concentration is a common indicator in drinking water security. The current view of free chlorine decay is that the process is mainly affected by the natural organic matter in water, temperature and initial chlorine concentration, on which temperature has the most evidently effect. As is generally accepted, total hardness has no effect on it. This paper investigated the impact of water hardness on the chlorine decay. The influence of varying metal ions concentrations which contribute to water hardness on effective chlorine decay constants was assessed. The results implied that total hardness had an evidently influences on the chlorine decay in tap water or DI water. For the range of metal ions concentration in this experiment effective chlorine decay constants ranged from an increase by +182% to +349% from the different concentration of metal ions.

Effect of Water Hardness on Efficacy of Sodium Hypochlorite Inactivation of Escherichia coli O157:H7 in Water

2017 ◽  
Vol 80 (3) ◽  
pp. 497-501 ◽  
Author(s):  
Sara Swanson ◽  
Tong-Jen Fu
Keyword(s):  
Escherichia Coli ◽  
Sodium Hypochlorite ◽  
Water Hardness ◽  
Hard Water ◽  
Free Chlorine ◽  
Total Hardness ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Effect Of Water ◽  
The Impact

ABSTRACT This study examined how the hardness of water affected the efficacy of sodium hypochlorite in inactivating Escherichia coli O157:H7 in water. Water was prepared at different degrees of total hardness (0, 50, 100, 200, 500, 1,000, 2,000, and 5,000 mg/liter CaCO3). Inactivation was assessed at different levels of free chlorine (0, 0.2, 0.5, and 1.0 ppm) at 2 to 4°C and pH 6.5. Thirty milliliters of chlorinated water was inoculated with 6 log CFU/ml of E. coli O157:H7 and allowed to mix for 3, 10, 20, or 30 s. In the absence of sodium hypochlorite, no reduction in counts of E. coli O157:H7 was observed regardless of the degree of water hardness. However, in the presence of hard water, under certain chlorine concentrations and exposure times, the reduction of E. coli O157:H7 in chlorinated hard water was significantly less than the reduction observed in chlorinated deionized water. For example, after exposure to 0.5 ppm of free chlorine for 10 s, E. coli O157:H7 counts were reduced by 4.8 ± 1.4, 2.0 ± 1.3, 1.6 ± 0.7, 0.5 ± 0.7, and 0.0 ± 0.1 log CFU/ml in water containing 0, 100, 1,000, 2,000, and 5,000 mg/liter CaCO3, respectively. With the exception of 5,000 mg/liter CaCO3, the effect of water hardness was no longer visible after 20 s of exposure to 0.5 ppm of free chlorine. Also, hard water significantly lowered the efficacy of sodium hypochlorite at 3 s of exposure to 1.0 ppm of free chlorine. But after 20 s of exposure to 1.0 ppm of free chlorine, the impact of water hardness was no longer observed. This study demonstrated that water hardness can affect the germicidal efficacy of sodium hypochlorite, and such an impact may or may not be apparent depending on the condition of the solution and the treatment time at which the observation is made. Under the conditions typically seen in commercial produce washing operations, the impact of water hardness on chlorine efficacy is likely to be insignificant compared with that of organic load.

Sensory aspects of drinking water in contact with epoxy lined copper pipe

2007 ◽  
Vol 55 (5) ◽  
pp. 161-168 ◽  
Author(s):  
T.H. Heim ◽  
A.M. Dietrich
Keyword(s):  
Water Quality ◽  
Drinking Water ◽  
Organic Compounds ◽  
Sensory Analysis ◽  
Water Samples ◽  
Distribution System ◽  
Distribution Systems ◽  
Free Chlorine ◽  
Copper Pipe

Pipe relining via in situ epoxy lining is used to remediate corroded plumbing or distribution systems. This investigation examined the effects on odour, TOC, THM formation and disinfectant demand in water exposed to epoxy-lined copper pipes used for home plumbing. The study was conducted in accordance with the Utility Quick Test, a migration/leaching method for utilities to conduct sensory analysis of materials in contact with drinking water. The test was performed using water with no disinfectant and levels of chlorine and monochloramines representative of those found in the distribution system. Panelists repeatedly and consistently described a “plastic/adhesive/putty” odour in the water from the pipes. The odour intensity remained relatively constant for each of two subsequent flushes. Water samples stored in the epoxy-lined pipes showed a significant increase in the leaching of organic compounds (as TOC), and this TOC was demonstrated to react with free chlorine to form trichloromethane. Water stored in the pipes also showed a marked increase in disinfectant demand relative to the water stored in glass control flasks. A study conducted at a full scale installation at an apartment demonstrated that after installation and regular use, the epoxy lining did not yield detectable differences in water quality.

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.

scholarly journals EXPERIMENTAL HYGIENIC ESTIMATION OF CALCIUM AND MAGNESIUM CONCENTRATIONS IN DRINKING WATER, AND ITS HARDNESS

2019 ◽  
Vol 98 (8) ◽  
pp. 811-819
Author(s):  
E. M. Trofimovich ◽  
S. A. Nedovesova ◽  
Roman I. Aizman
Keyword(s):  
Drinking Water ◽  
Thyroid Hormones ◽  
Quantitative Estimation ◽  
Experimental Studies ◽  
Water Hardness ◽  
Blood Parameters ◽  
Plasma Metabolites ◽  
Total Hardness ◽  
Calcium And Magnesium ◽  
Plasma Magnesium

Introduction. The lack of hygienic norms for Mg2+ and Ca2+ in drinking water and the wide ranges of acceptable hygienic norms (AHN) of these cations in water packaged in containers determine the relevance of experimental studies on the substantiation of AHN of Mg2+, Ca2+ and the hardness of drinking water with a centralized water supply to the population. Material and methods. Chronic experiments were performed on 5 groups of adult Wistar rats (n = 50): control animals received drinking water (Ca2+ 20.0; Mg2+ 6.0 mg / dm3, hardness 1.5-1.8 mEq/dm3); four other groups received model drinking water with different contents of Ca2+ (50, 80, 100 and 140 mg/dm3) and Mg2+ (20, 40, 55 and 85 mg/dm3) by adding CaCl2 or MgSO4 salts to the control water. The effect of these drinking water samples on kidney function, ion osmotic blood parameters, plasma metabolites of lipid and protein metabolism, as well as the concentration of thyroid hormones (T3 and T4) and cortisol were studied. Results. Prolonged action of increased concentrations of Ca2+ and Mg2+ on the organism was established to cause alterations in fat metabolism, the adaptive activation of osmoregulatory and ion regulatory kidney functions, increasing the concentration of thyroid hormones and a decrease of cortisol titer in plasma. Magnesium led to more pronounced changes in water-salt metabolism, and at a concentration of 85.0 mg/dm3 (7.0 mg-Eq/dm3) - to depletion of secretion of the described hormones. Conclusion. Based on the obtained results, individual ranges for AHN of calcium and magnesium concentrations in water were recommended. The upper limit of AHN of drinking water total hardness is of 7.0 mg-Eq/dm3 at the joint presence of Ca2+and Mg2+. The rule of hygienic qualitative and quantitative estimation of calcium and magnesium types of drinking water hardness is formulated.

scholarly journals Effects of residual disinfectants on the redox speciation of lead(ii)/(iv) minerals in drinking water distribution systems

2021 ◽  
Author(s):  
Sumant Avasarala ◽  
John Orta ◽  
Michael Schaefer ◽  
Macon Abernathy ◽  
Samantha Ying ◽  
...  
Keyword(s):  
Drinking Water ◽  
Reaction Kinetics ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution Systems ◽  
Free Chlorine ◽  
Oxidative Transformation ◽  
Drinking Water Distribution Systems ◽  
Drinking Water Distribution ◽  
Free Bromine

This study investigated the reaction kinetics on the oxidative transformation of lead(ii) minerals by free chlorine (HOCl) and free bromine (HOBr) in drinking water distribution systems.

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.

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