study & modelling of chlorine decay in abu dhabi cwmag ... · 2/7/2017 · study &...
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Study & Modelling of Chlorine Decay in Abu DhabiStudy & Modelling of Chlorine Decay in Abu Dhabi
CWMAG Presentation 2013 CWMAG Presentation 2013
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Study & Modelling of Chlorine DecayPresentation Overview
• Origins and Scope of the Project
• Field Testing
• Chlorine Decay Theory
• Model Components and Calibration
• Model Usage and Results
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Study & Modelling of Chlorine DecayProject Origins
● Regulations Supervision Bureau (RSB)
● Chlorination System Evaluation Project in 2009 undertaken by Atkins
● Quantifying efficiency within the Emirate’s Chlorination
● Some areas found not to be maintaining a Chlorine residual of >0.2mg/L
● Different interpretations of the permitted Chlorine residuals found
● Various recommendations arose, including constructing a Chlorine decay model
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Study & Modelling of Chlorine DecayProject Scope
• The Client was TRANSCO
• Enhancing their water quality capability
• Highlighting the need for better control of dosing
• Project split into 4 Phases:
Phase 1: Data Collection, Data analysis and laboratory tests
Phase 2: Modelling and calibration of a Chlorine decay model
Phase 3: Improvement of TRANSCO water quality
Phase 4: Technology Transfer
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Study & Modelling of Chlorine DecayOutput Data
Site 1 Outlet
Site 2 Inlet
Site 2 Outlet
Intermediate Point 1
Intermediate Point 2
Site 3 Inlet
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Study & Modelling of Chlorine DecayField Testing – Scope
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500 Km
● 13 field tests in total, typically lasting 7 days
● Logged up to 14 locations in each field test
● Lab Tests carried out to determine chemical parameters of 5 source waters
● Mostly logged at reservoir sites
● Logged Temperature, pH and recorded several WQ parameters
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1st Order (incorporating Arrhenius)
Nth Order
Where:
Study & Modelling of Chlorine DecayChlorine Decay Theory – Bulk Decay (kb)
1st Order Arrhenius
[Cl2] = chlorine concentration (mg/l)[Cl2] 0 = initial chlorine concentration (mg/l)t = time (days)
A = Arrhenius pre-exponential factor (takes same units as kb)
n = Order NumberEa = Activation energy (J/mol)R = Gas constant (8.3144621 J/mol.K)T = Temperature (K)
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Where:
Study & Modelling of Chlorine DecayChlorine Decay Theory – Wall Decay (kw)
[Cl2] = chlorine concentration (mg/l)[Cl2] 0 = initial chlorine concentration (mg/l)kw = wall coefficientkf = mass transfer coefficientR = radius of pipe (m)t = time (days)
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Study & Modelling of Chlorine DecayModel Components
InfoWater Model
MSX Module
Dynamic Chlorine
Decay Model
Hydraulics
Demand Data
Bulk Reaction Equations
Pipe wall Reaction Equations
Mixing Equations
Chemical Parameters for 5 different sources
Temperature Profiles
Bulk Phase temperature relationships
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Study & Modelling of Chlorine DecayModel Software Comparison
InfoWater InfoWater + MSX
Pipe wall (kw) Set on individual mains Set on individual mains
Bulk coefficient (kb) Single Value
Varies with temperature, varies with source, varies with mixing
from multiple sources
TemperatureEffects cannot be taken into
account
Taken into account using Arrhenius equation coupled with
lab results
Contaminant Single contaminant can be modelled
Reactions between multiple contaminants can be modelled
Multiple Sources Cannot be modelled Multiple source can be modelled with mixing proportions calculated
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Study & Modelling of Chlorine DecayModel Overview
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Al Ain Reception
● Model split into subzones based on each field test.
● Each subzone model adjusted to run for between 4 to 6 days depending on the time of travel
● Three comparison days in run time (Calibration, verification and validation)
● Comparison data applied to validate flow and chlorine data during calibration
● Calibrated for each field test and then aggregated into a summer and winter model of the whole of Abu Dhabi
Source
Reservoir SiteLogged
location
Logged location
Adjust kw values on mains
Study & Modelling of Chlorine DecayModel Calibration – Example Process
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Study & Modelling of Chlorine DecayModel Usage and Results ● Identified which areas were not
within PCV limits of 0.2 to 0.5 mg/l.
● Highlighted mains that suffered from particularly high decay rates and hence need further investigation (Red Mains)
● Enabled identification of where chlorine dosing could be increased or reduced.
● Identified critical areas where extra monitoring was required.
● Highlighted the need for better control of dosing.
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Study & Modelling of Chlorine DecayPersonal Highlights ● Programming element required
in MSX before modelling
● Increasing my knowledge base
● Uniqueness of the project
● Field testing challenge and scale
● No two days working on this project were the same!
Thank YouThank You
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