Study & Modelling of Chlorine Decay in Abu DhabiStudy & Modelling of Chlorine Decay in Abu Dhabi

CWMAG Presentation 2013 CWMAG Presentation 2013

1

2

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

3

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

4

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

5

Study & Modelling of Chlorine DecayOutput Data

Site 1 Outlet

Site 2 Inlet

Site 2 Outlet

Intermediate Point 1

Intermediate Point 2

Site 3 Inlet

6

Study & Modelling of Chlorine DecayField Testing – Scope

AAAAAAAAAAA AAAA

AAAAA

AAAAAAAA

AAAAAA AAAAAAA

AA

AA

AAAA

AA

A

A AA

A

A

A

A

AAA AAAA

AAA

AAA

AAAA

AAAA

A

AAA

A

AAA

AAAAAAAAAAAA A

AA

AA

AA

A

A

A

A AAAAA

AAAAAAAAA

AAAAAAAAAAAAAAAAAA

AAAAA

AAAAAAAAAAAA

A

AAAA

AA

A

A

AAA

A

AAA A

AA

AAAAAAA

AAA

AAAAAA

AAAA

AA

AA

AAAA

AA

AA

A

AAAAA

AAAAAAA

AA AAA

A

AAA

AAAA AAA

AA

AA

AAAAAAAAA

AAAAAAAAA

AAAA

A

A

AAAAA

A

AAA

A

A

A

AA

AA

AAAAA

A

A

A

A A

AAAAA

AA AAA

A AA AAA AAAMMMM

MMMM

MMM

MMM

MMMM

MMMMMMMMMMM

MMMMMMMMMMMM

MMMMMMMMMM

MMM

MMMMMMMMMMM

MMMMMMMMMMM

MMMMMMMMMM MMMMMMMMMMMMM

MMMMMMMMMMMM

MMMMMMMMMMMMMMMMMMMMMMMM

MMMMMMMMM

MMMMMMMMMMM

MMMMM

MMMMM

MMMMMM

MMMMMMMMMMMMMMMM

MMMM

MMMMMM

MMM

MMMMMMM

MMMMMMMMMMMMMMMMMMMMMMMM

MMMMMMMMMMMMMMMM

MMMMMMMMMMMMMM

MMMMMMMMMM

MMMMMMMMMMMMMMMMMMMMMM MMMMMMMMMMMMMMM

MMMMMMMMMMMMM

MMMMMMMMMMMMMMMMMMMMMM

MTTTTTT

TTT

TTTTTTT

TT

TTTT

T TTTTT

TTT TTT̂̂̂̂

^

^

^̂̂̂

^̂̂

^̂̂̂̂

^̂̂̂̂̂^̂^̂ ^̂̂̂

^̂̂̂

^̂̂

^

^̂̂

^̂̂

^̂̂̂̂̂

^^̂^̂

^

^

^

^

^̂̂̂^̂̂̂̂̂^̂

^̂^̂

^̂̂̂̂̂

^̂^̂̂̂

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

7

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)

8

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)

9

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

10

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

11

Study & Modelling of Chlorine DecayModel Overview

A

AAAA

A

A

A

A

A

AAA

MMMMMMMMMMMMMMMM

^

^

^

^

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

12

13

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.

14

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

15