International Conference on Desalination,
Environment, and Outfall Marine Systems
Muscat, Oman
April 2014
Impact of the Coastal Intake Environment on the
Operating Conditions of Thermal Desalination Plants:
A Case Study in United Arab Emirates
Walid Elshorbagy, Associate Professor
Civil and Environmental Engineering Department, UAE University
Ahmed Ali Basioni, PMP
ADCO, Abu Dhabi
1
PROBLEM STATEMENT
Feed Water (Mf)
Salinity [S(t)]
Temperature [T(t)]
MSF PLANT
Distillate
Production (Md)
Cooling Water (Mcw)
Demand
SEA SIDE
Coastline
Rejected Brine (Mb)
LAND SIDE
2
OBJECTIVES
 Determine the fate of brine and warm water effluent released from
the desalination plants and other nearby industrial facilities in a
coastal local area using three-dimensional advection-dispersion
surface model.
 Model outputs were used to determine suitable intake and outfall
locations to minimize the effect of salinity and temperature on
desalination plant, so that maximum efficiency and minimum
operation cost was achieved.
3
METHODOLGY
The study involved the following tasks
1.
Hydrodynamic modeling for the entire Arabian Gulf.
2.
Hydrodynamic modeling for the coastal local Area.
3.
Selection of scenarios to assess the salinity and temperature
impact on seawater intake.
4.
Proposing alternative locations for seawater intake and outfall.
5.
Carrying out cost analysis for MSF desalination plant in terms of
chemical and energy operational costs.
4
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation Results

Proposed Alternatives

Conclusions
5
Introduction
• Limited Conventional water resources in UAE for fresh water supply.
• Continuous economic expansion and growth in domestic and
industrial water requirements in UAE are satisfied through desalination
processes.
•The need of several studies to evaluate the effect of salinity and
temperature on MSF plants performance.
• In UAE, salinity is very high and temperature rises up to more than an
average of 32 °C in shallow area.
• Several measures should be considered to improve the desalination
plant performance :
Additional processing /pretreatment to remove/dilute chemical & discharged brine
Change operation conditions
Change of material
Alternative intake and outfall configurations
6
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation results

Proposed Alternatives

Conclusions
7
Salinity and Temperature Effect on MSF Performance
• Multi Stage Flash (MSF) is considered the most suitable process for
large scale production capacity.
• Salinity and Temperature at desalination intake are very important to
monitor and investigate.
• The increase of intake salinity will increase feed water (Mf) introduced to
MSF.
• The increase of intake temperature will increase the cooling water
requirements (Mcw).
• The increase of (Mf and Mcw) will increase the operational cost in terms
of chemical and energy costs.
8
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation results

Proposed Alternatives

Conclusions
9
Hydrodynamic Simulation
• General
• Delft3D is a sigma – layer model solving mass and momentum equations.
• The curvilinear forms of continuity and momentum equations are applied.
• Coastal wind is considered as most prevailing wind (North West ).
• The strategy is to simulate the entire gulf, then the local model is nested
from the regional model (entire gulf) where the boundary conditions are
extracted.
• Gulf model
• Simulation of regional Gulf model was carried out using Delft3D.
• Salinity is high near coastline, and decreases toward deeper zones.
• Temperature is increasing at shoreline, especially near industrial outfalls.
10
Hydrodynamic Simulation
• Local Model
• Several industrial facilities are entered in the model as outfall
points in addition to desalination intake and outfall.
•Water level at harbor for measured and simulated model data show
satisfactory results.
• Flow field enters the local area from west towards center, north and
east near coastal area.
• Comparison of Observed and simulated salinity and temperature at
coastal area.
11
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation Results

Proposed Alternatives

Conclusions
12
Considered Scenarios
• Three main scenarios are considered in this study
 Basic Model : current discharge from existing facilities.
 Moderate Expansion : discharge from existing facilities increased
by 5 times
 Major Expansion : extreme scenario, where discharge from existing
facilities increased by 10 times
• Simulation for these main scenarios covered summer and winter
conditions.
• Cost analysis is carried out for all scenarios in summer and winter.
13
The presentation is divided into 7 main subjects





Salinity and Temperature effect on MSF Performance

Considered Scenarios

Simulation Results

Proposed Alternatives

Conclusions
Introduction
Hydrodynamic Simulation
14
Simulation Results
Summer Results
• Higher temperature and salinity at the southern coastline.
• In moderate and major expansion, salinity and temperature are
increased at the majority of shoreline and propagate toward north area.
• Industrial facilities contribution is highly noticed in moderate and major
expansion scenarios.
Winter Results
• Higher temperature and salinity at the southern coastline.
• As in summer, industrial facilities contribution is highly noticed in
moderate and major expansion scenarios in terms of an increase in
salinity and temperature.
15
Simulation Results
Cost Analysis for main scenarios
• Cost analysis is based on the flow rate of feed water, cooling water,
and re-circulated brine.
•Operation cost in summer is higher than in winter.
Reverse wind conditions
• East wind direction considered in this scenario.
16
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation Results

Proposed Alternatives

Conclusions
17
Proposed Alternatives
• Three proposed alternatives are considered and investigated in
this study
 Alternative 1 : extending the intake location offshore (about
1000m) to an area receiving cooler and less saline water.
 Alternative 2 : extending the outfall location offshore (about
1000m) to an area in order to reduce the impact on intake
configuration.
 Alternative 3 : have the outfall discharge the effluent to deeper
zone.
18
The presentation is divided into 7 main subjects

Introduction

Salinity and Temperature effect on MSF Performance

Hydrodynamic Simulation

Considered Scenarios

Simulation Results

Proposed Alternatives

Conclusions
19
Conclusions
• Simulation results showed little reduction in salinity and temperature,
especially for existing scenario.
• The existing intake location configurations had been carefully selected.
Since the sheltered location of intake minimizes the effect of effluent
brine discharged from existing industrial facilities.
• Cost analysis showed that intake water temperature has more
pronounced effect on the annual energy cost compared with salinity
impact on chemical cost.
• The annual operational costs estimated for three scenarios were as
4.58, 23.5 and 48.5 Million USD.
20
Conclusions
• Simulation results drew great attention to consider alternative 1 as first
recommended proposal to be investigated in case of expanding existing
industrial facilities.
• Alternative 1 reflects noticeable savings in the annual operational costs,
especially for moderate and major scenarios ( 291,000 USD (1.5%) and
1,193,000 USD (2.5%)]
• Considering the reverse wind conditions is expected to produce larger
savings in case of expanding industrial facilities (ONLY).
21
THANK YOU
22
23
Feed Seawater Flow Rate (kg/s)
860
840
820
800
780
760
740
34000 35000 36000 37000 38000 39000 40000
Xf( Seaw ater Intake Salinity )- ppm
24
5000
4500
Cooling Seawater Flow rate (kg/s)
4000
3500
3000
2500
2000
1500
1000
500
0
15
20
25
30
35
40
Seaw ater IntakeTem perature (Tcw )-C
25
Annual Chemical cost ( Thousands
USD/yr)
350
300
USD 307
H=50
USD261
250
USD 246
USD209
H=40
200
150
USD154
H=25
USD131
100
50
0
0
5
10
15
20
25
30
35
40
45
Intake S alinity (Xf) - ppt
Annual Power Cost - Thousands(USD
/yr)
USD 350
USD 300
USD 276
USD 250
USD 221
USD 200
H=50
USD 150
H=40
USD 95
USD 100
USD 76
USD 50
USD 138
H=25
USD 48
USD 0
15
17
19
21
23
25
27
29
31
Intake Wate r Te mpe rature Tcw (C)
26
• Salinity contour at summer.
• Salinity is about 46 ppt at
coastline area and decreases to
about 43 ppt toward the center
of the gulf.
• Salinity contour at winter.
• Salinity is about 44 ppt at
coastline area and decreases to
about 37 ppt away from shoreline
area.
27
• Temperature contour at summer.
• Temperature is about 35°C at
coastline area and decreases
toward the center of the gulf to
about 32°C.
• Temperature contour at winter.
• Salinity is about 23°C at
coastline area and decreases to
about 19°C away from shoreline
area.
28
2.5
Water level
1.5
0.5
Model
-0.5
Measured
-1.5
-2.5
15-Jun
20-Jun
25-Jun
30-Jun
Time
29
30
Desalination intake
Petrochemical
Refinery
Desalination outfall
31
32
Water Level at Harbour for measured and computed data
Water Level (m)
1.5
1
0.5
w ater level
w ater level (measured)
0
-0.5 0
50
100
150
200
250
300
350
-1
Time(hrs)
33
Observed Salinity at Summer
Simulated Salinity at Summer
34
Observed Temperature at Summer
Simulated Temperature at Summer
35
Temperature contour in
summer for Current
Facilities
Temperature contour in
summer for Moderate
Expansion
Temperature contour
in summer for Major
Expansion
36
Salinity contour in summer
for Current Facilities
Salinity contour in
summer for Moderate
Expansion
Salinity contour in
summer for Major
Expansion
37
Salinity at intake in summer
45.55
45.5
Salinity (ppt)
45.45
Basic Model ( Q)
45.4
Moderate Expansion Model (
5Q)
45.35
Major Expansion Model ( 10Q)
45.3
45.25
45.2
0
100
200
300
400
Time(hrs)
38
Temperature at intake in summer
36.2
36
Temperature (C)
35.8
35.6
Basic Model ( Q)
35.4
Moderate Expansion Model ( 5Q)
35.2
Major Expansion Model ( 10Q)
35
34.8
34.6
0
100
200
300
400
Time (hrs)
39
Temperature contour in
winter for Current
Facilities
Temperature contour in
winter for Moderate
Expansion
Temperature contour
in winter for Major 40
Expansion
Salinity contour in winter
for Current Facilities
Salinity contour in winter
for Moderate Expansion
Salinity contour in
winter for Major
Expansion
41
Salinity at intake in winter
45.7
45.6
Salinity (ppt)
45.5
Basic Model ( Q)
45.4
Moderate Expansion
Model ( 5Q)
Major Expansion Model (
10Q)
45.3
45.2
45.1
45
0
100
200
300
400
500
Time(hrs)
42
Temperature at intake in winter
23.4
23.2
Temperature (C)
23
Basic Model ( Q)
22.8
Moderate Expansion
Model ( 5Q)
Major Expansion Model (
10Q)
22.6
22.4
22.2
22
21.8
0
100
200
300
400
500
Time (hrs)
43
• MSF desalination plant annual chemical and electric cost at summer and Winter
Basic Model
Moderate Expansion
Major Expansion
Scenario
Summer
Winter
Summer
Winter
Summer
Winter
Intake Salinity (ppt)
45.24
45.07
45.36
45.30
45.48
45.60
Temperature C
34.8
22.1
35.3
22.5
35.9
23.1
(Mf) kg/s
2092
2077
10511
10485
21125
21229
(Mcw) kg/s
8397
970
48778
5098
111914
11046
(Mb) kg/s
1352
1337
6811
6785
13725
13829
kg/s
11841
4384
66100
22368
146764
46104
Power (KWh) for H (m)
1871
692.89
10447
3535
23196
7287
Pumping cost (M$/yr)
1.23
0.46
6.86
2.32
15.24
4.79
Chemical Cost (M$/yr)
3.59
3.56
18.02
17.98
36.22
36.40
Sub Total (M$/yr)
4.82
4.02
24.89
20.30
51.46
41.19
Mtotal
Total (M$/yr)
4.58
23.51
48.38
44
Total Annual Cost million ($/yr)
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Basic Model
Moderate
Expansion
Model
Major Expansion
Model
Sim ulation Scenarios
45
46
Proposed outfall (Alt.2)
Proposed intake(Alt.1)
Existing outfall
Existing intake
47
Summer (Alt.1)
Scenario
Winter(Alt.1)
Salinity (ppt)
Temperature
(°C)
Salinity (ppt)
Temperature
(°C)
Basic Model
45.23
34.6
45.06
22.06
Moderate Expansion
45.32
35.1
45.25
22.3
Major Expansion
45.42
35.5
45.5
22.6
Summer (Existing Conditions)
Winter (Existing Conditions)
Salinity (ppt)
Temperature
(°C)
Salinity (ppt)
Temperature
(°C)
Basic Model
45.24
34.8
45.07
22.1
Moderate Expansion
45.36
35.3
45.30
22.5
Major Expansion
45.48
35.9
45.60
23
48
• Cost comparison for three scenarios considering alternative 1.
Scenario
Total Annual Cost
(Existing Conditions)
Total Annual Cost
(Alternative 1)
Difference In
Cost
Saving
(%)
Basic Model
4,576,840
4,553,330
23,500
0.51%
Moderate
Expansion
Model
23,511,996
23,221,017
291,000
1.24%
Major
Expansion
Model
48,382,096
47,189,741
1,193,000
2.46%
49
Summer (Alt.2)
Scenario
Winter(Alt.2)
Salinity (ppt)
Temperature
(°C)
Salinity (ppt)
Temperature
(°C)
Basic Model
45.23
34.8
45.06
21.8
Moderate Expansion
45.36
35.3
45.25
22.35
Major Expansion
45.48
35.9
45.50
22.6
Summer (Existing Conditions)
Winter (Existing Conditions)
Salinity (ppt)
Temperature
(°C)
Salinity (ppt)
Temperature
(°C)
Basic Model
45.24
34.8
45.07
22.1
Moderate Expansion
45.36
35.3
45.30
22.5
Major Expansion
45.48
35.9
45.60
23
50
• Cost comparison for three scenarios considering alternative 2.
Scenario
Total Annual Cost
(Existing Conditions)
Total Annual Cost
(Alternative 2)
Basic Model
4,576,840
4,573,609
3,231
0.07%
Moderate
Expansion Model
23,511,996
23,496,427
15,569
0.07%
Major Expansion
Model
48,382,096
48,305,722
76,374
0.16%
Difference in
cost
Saving
(%)
51
Proposed intake(Alt.1)
Proposed outfall (Alt.2)
Existing outfall
Existing intake
52
Proposed intake(Alt.1)
Proposed outfall (Alt.2)
Existing outfall
Existing intake
53
Existing intake
54