A variable parabolic reaction coefficient model for chlorine decay in bulk water

2021 ◽  
pp. 117302
Author(s):  
Dan Zhong ◽  
Weinan Feng ◽  
Wencheng Ma ◽  
Jun Ma ◽  
Xuan Du ◽  
...  
Keyword(s):  
Bulk Water ◽  
Reaction Coefficient ◽  
Chlorine Decay

scholarly journals Estimating fast and slow reacting components in surface water and groundwater using a two-reactant model

2016 ◽  
Vol 9 (1) ◽  
pp. 19-25
Author(s):  
Priyanka Jamwal ◽  
M. N. Naveen ◽  
Yusuf Javeed
Keyword(s):  
Surface Water ◽  
Water Distribution ◽  
Distribution Networks ◽  
Bulk Water ◽  
Data Sets ◽  
Decay Data ◽  
First Order ◽  
Surface Water And Groundwater ◽  
Inorganic Matter ◽  
Chlorine Decay

Abstract. Maintaining residual chlorine levels in a water distribution network is a challenging task, especially in the context of developing countries where water is usually supplied intermittently. To model chlorine decay in water distribution networks, it is very important to understand chlorine kinetics in bulk water. Recent studies have suggested that chlorine decay rate depends on initial chlorine levels and the type of organic and inorganic matter present in water, indicating that a first-order decay model is unable to accurately predict chlorine decay in bulk water. In this study, we employed the two-reactant (2R) model to estimate the fast and slow reacting components in surface water and groundwater. We carried out a bench-scale test for surface water and groundwater at initial chlorine levels of 1, 2, and 5 mg L−1. We used decay data sets to estimate optimal parameter values for both surface water and groundwater. After calibration, the 2R model was validated with two decay data sets with varying initial chlorine concentrations (ICCs). This study arrived at three important findings. (a) We found that the ratio of slow to fast reacting components in groundwater was 30 times greater than that of the surface water. This observation supports the existing literature which indicates the presence of high levels of slow reacting fractions (manganese and aromatic hydrocarbons) in groundwater. (b) Both for surface water and groundwater, we obtained good model prediction, explaining 97 % of the variance in data for all cases. The mean square error obtained for the decay data sets was close to the instrument error, indicating the feasibility of the 2R model for chlorine prediction in both types of water. (c) In the case of deep groundwater, for high ICC levels (> 2 mg L−1), the first-order model can accurately predict chlorine decay in bulk water.

Modelling the chlorine decay process in a distribution network using a pilot system

2014 ◽  
Vol 9 (4) ◽  
pp. 534-550
Author(s):  
R. Buamah ◽  
K. Akodwaa-Boadi ◽  
M. Paintsil ◽  
E. K. Baah-Ennumh ◽  
A. A. Adjaottor
Keyword(s):  
Cast Iron ◽  
Distribution System ◽  
Water Distribution ◽  
Batch Reactor ◽  
Distribution Network ◽  
Bulk Water ◽  
Residual Chlorine ◽  
Pipe Material ◽  
Bulk Fluid ◽  
Chlorine Decay

Chlorine is one of the many disinfectants used to ensure bacteriological safety of drinking water. Usually residual chlorine is maintained within the distribution network to combat any probable re-contamination of the distributed water. This residual free chlorine, however, decays in water due to its reaction with the bulk water and the pipe material or deposits on the pipe walls. This study aimed at determining and modelling chlorine decay in the Kumasi water distribution network (KWDN) and determined locations where residual chlorine boosting is necessary. A double-jacketed batch reactor and a constructed pilot distribution system (PDS) were used to determine the bulk and wall decay coefficients. The PDS was run using aged PVC pipes (15–20 years), asbestos concrete pipes (40–50 years) and cast iron pipes (84 years) that have been in use in the KWDN. The SynerGEE® hydraulic model was used to identify the ‘zero chlorine’ points and predict top-up quantities. The bulk decay coefficient was found to be 0.053 h−1 within 8 hours at 26 °C and the residual chlorine decayed within the bulk fluid by 32–34% of its initial dose. Under the conditions tested, the cast iron pipes had the highest overall decay coefficients (K). Five locations within the network were identified as probable chlorine boosting points).

scholarly journals Estimating fast and slow reacting component in surface and groundwater using 2R model

2015 ◽  
Vol 8 (2) ◽  
pp. 197-217 ◽  
Author(s):  
P. Jamwal ◽  
M. N. Naveen ◽  
Y. Javeed
Keyword(s):  
Surface Water ◽  
Water Distribution ◽  
Distribution Networks ◽  
Bulk Water ◽  
Water Distribution Networks ◽  
Reactant Ratio ◽  
Surface Water And Groundwater ◽  
Decay Test ◽  
Chlorine Decay ◽  
Surface And Groundwater

Abstract. Maintaining residual chlorine levels in a water distribution networks is a challenging task; especially in the context of developing countries where water is usually supplied intermittently. To model chlorine decay in water distribution networks, it is very important to understand chlorine kinetics in bulk water. Recent studies suggested that chlorine decay rate depends on initial chlorine levels and type of organic and inorganic matter present in water, indicating that first order decay model is unable to accurately predict chlorine decay in bulk water. In this study, we employed two reactant model (2R) to estimate the fast and slow reacting components in surface water and groundwater. We carried out bench scale test for surface and groundwater at initial chlorine level of 1, 2 and 5 mg L−1. We used decay datasets to estimate optimal parameter values for both surface water and groundwater. After calibration, the 2R model was validated with two decay dataset with varying initial chlorine concentration (ICC). This study came up with three important findings (a) the ratio of slow to fast reacting components in groundwater was thirty times greater than that of the surface water, (b) 2R model can accurately predict chlorine decay in surface water, 98 % of the variance in the chlorine decay test was explained by the model and (c) in case groundwater, 2R model prediction accuracy reduced with the decrease in ICC levels, only 87 % variance in data was explained by the model. This could be attributed to high slow to fast reactant ratio in groundwater.

STEM measurement of subcellular water distributions

1993 ◽  
Vol 51 ◽  
pp. 568-569
Author(s):  
R.D. Leapman ◽  
S.Q. Sun ◽  
S-L. Shi ◽  
R.A. Buchanan ◽  
S.B. Andrews
Keyword(s):  
Water Content ◽  
Internal Standard ◽  
Dry Weight ◽  
Dry Mass ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Bulk Water ◽  
Inelastic Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

Recent advances in rapid-freezing and cryosectioning techniques coupled with use of the quantitative signals available in the scanning transmission electron microscope (STEM) can provide us with new methods for determining the water distributions of subcellular compartments. The water content is an important physiological quantity that reflects how fluid and electrolytes are regulated in the cell; it is also required to convert dry weight concentrations of ions obtained from x-ray microanalysis into the more relevant molar ionic concentrations. Here we compare the information about water concentrations from both elastic (annular dark-field) and inelastic (electron energy loss) scattering measurements.In order to utilize the elastic signal it is first necessary to increase contrast by removing the water from the cryosection. After dehydration the tissue can be digitally imaged under low-dose conditions, in the same way that STEM mass mapping of macromolecules is performed. The resulting pixel intensities are then converted into dry mass fractions by using an internal standard, e.g., the mean intensity of the whole image may be taken as representative of the bulk water content of the tissue.

Bulk water treatment unit performance: For the cameras or the community?

Waterlines ◽  
2012 ◽  
Vol 31 (1-2) ◽  
pp. 53-66 ◽  
Author(s):  
Richard Luff ◽  
Caetano Dorea
Keyword(s):  
Water Treatment ◽  
Bulk Water ◽  
Treatment Unit ◽  
Unit Performance

MODELLING CHLORINE DECAY IN DRINKING WATER MAINS

2008 ◽  
Vol 7 (6) ◽  
pp. 737-741 ◽  
Author(s):  
Diana Robescu ◽  
Nicolae Jivan ◽  
Dan Robescu
Keyword(s):  
Drinking Water ◽  
Water Mains ◽  
Chlorine Decay

Investigating artificial groundwater recharge to ensure the water supply to the city of Graz

2008 ◽  
Vol 3 (3) ◽  
Author(s):  
Wilhelm Tischendorf ◽  
Hans Kupfersberger ◽  
Christian Schilling ◽  
Oliver Gabriel
Keyword(s):  
Water Supply ◽  
Groundwater Recharge ◽  
Water Demand ◽  
Bulk Water ◽  
Retention Rates ◽  
Subsurface Water ◽  
Artificial Groundwater Recharge ◽  
Advantages And Disadvantages ◽  
Water Recharge ◽  
Water Supply Company

Being Austria's fourth largest water-supply company, the Grazer Stadtwerke AG., has ensured the successful water-supply of the Styrian capital with 250.000 inhabitants for many years. The average daily water demand of the area amounts to about 50,000 m3. Approximately 30 % of the total demand is covered by the bulk water supply from the Zentral Wasser Versorgung Hochschwab Süd. The waterworks Friesach and Andritz, which cover the additional 70 % of the water demand, operate by means of artificial groundwater recharge plants where horizontal filter wells serve as drawing shafts. The groundwater recharge systems serve to increase the productivity of the aquifer and to reduce the share of the infiltration from the Mur River. Protection areas have been identified to ensure that the water quality of the aquifer stay at optimal levels. The protection areas are divided into zones indicating various restrictions for usage and planning. Two respective streams serve as the source for the water recharge plants. Different infiltration systems are utilised. Each of the various artificial groundwater recharge systems displays specific advantages and disadvantages in terms of operation as well as maintenance. In order to secure a sustainable drinking water supply the recharge capacity will be increased. Within an experimental setting different mixtures of top soils are investigated with respect to infiltration and retention rates and compared to the characteristics of the existing basins. It can be shown that the current operating sand basin with more than 90% grains in the range between 0.063 and 6.3 mm represents the best combination of infiltration and retention rates. In future experiments the performance of alternative grain size distributions as well as planting the top soil will be tested. Additionally, in order to optimize the additional groundwater recharge structures the composition of the subsurface water regarding its origin is statistically analyzed.

scholarly journals Behavior and properties of water in silicate melts under deep mantle conditions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bijaya B. Karki ◽  
Dipta B. Ghosh ◽  
Shun-ichiro Karato
Keyword(s):  
Electrical Conductivity ◽  
Molar Volume ◽  
Water Solution ◽  
Pure Water ◽  
Electrical Conductance ◽  
Water Structure ◽  
Bulk Water ◽  
Silicate Melts ◽  
Pressure Regime ◽  
Low Pressures

AbstractWater (H2O) as one of the most abundant fluids present in Earth plays crucial role in the generation and transport of magmas in the interior. Though hydrous silicate melts have been studied extensively, the experimental data are confined to relatively low pressures and the computational results are still rare. Moreover, these studies imply large differences in the way water influences the physical properties of silicate magmas, such as density and electrical conductivity. Here, we investigate the equation of state, speciation, and transport properties of water dissolved in Mg1−xFexSiO3 and Mg2(1−x)Fe2xSiO4 melts (for x = 0 and 0.25) as well as in its bulk (pure) fluid state over the entire mantle pressure regime at 2000–4000 K using first-principles molecular dynamics. The simulation results allow us to constrain the partial molar volume of the water component in melts along with the molar volume of pure water. The predicted volume of silicate melt + water solution is negative at low pressures and becomes almost zero above 15 GPa. Consequently, the hydrous component tends to lower the melt density to similar extent over much of the mantle pressure regime irrespective of composition. Our results also show that hydrogen diffuses fast in silicate melts and enhances the melt electrical conductivity in a way that differs from electrical conduction in the bulk water. The speciation of the water component varies considerably from the bulk water structure as well. Water is dissolved in melts mostly as hydroxyls at low pressure and as –O–H–O–, –O–H–O–H– and other extended species with increasing pressure. On the other hand, the pure water behaves as a molecular fluid below 15 GPa, gradually becoming a dissociated fluid with further compression. On the basis of modeled density and conductivity results, we suggest that partial melts containing a few percent of water may be gravitationally trapped both above and below the upper mantle-transition region. Moreover, such hydrous melts can give rise to detectable electrical conductance by means of electromagnetic sounding observations.

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