foo chiou looi · 2017-12-23 · < 0.1 no-stress 0.1 < w/q < 0.2 low stress 0.2 < w/q...
TRANSCRIPT
ASSESSMENT OF FUTURE WATER RESOURCES
SUSTAINABILITY BASED ON 4 NATIONAL TAPS OF
SINGAPORE
FOO CHIOU LOOI
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
2014/2015
ASSESSMENT OF FUTURE WATER RESOURCES
SUSTAINABILITY BASED ON 4 NATIONAL TAPS OF
SINGAPORE
FOO CHIOU LOOI
A THESIS SUBMITTED
FOR THE DEGREE OF BACHELOR OF ENGINEERING
DEPARTMENT OF CIVIL & ENVIRONMENTAL
ENGINEERING
NATIONAL UNIVERSITY OF SINGAPORE
i
Acknowledgement
I would like to thank my supervisor, Dr Pat Yeh for the guidance in this project. He
taught me what is independent research and learning. Also, Dr Vladan Babovic, who
provided valuable feedback and encouragement as my examiner.
I would also like to mention the following people:
Ying Jie: I am glad to have known you and I wish you all the best in your studies. I
will remember that I made a friend during my last year of study in the university.
Jeslyn: Thank you for listening to me. You are the only one who understands those.
You might not remember, but I appreciate the help you provided over the three years.
I hope that you can attain your academic goal and all the best to your future.
Li Ying, Yveline, Iao Tim, Guijin, Jie Ying, Yi Ru: You people add colours to my
otherwise mundane life. You know how I always say that it is difficult to achieve my
goals but you give me encouragement and believe I can do it (at least you said so). To
Iao Tim, suddenly we had a lot more to talk after I know that we have a similar project
topic. I treated those as encouragements for us. Now I wish good results for both of
us.
Last but not least, my parents who tolerated my occasional unreasonableness but still
stand by me and care for me and also, myself for not giving up.
ii
Table of Contents
Acknowledgement ........................................................................................................... i
Summary ........................................................................................................................ iv
List of Acronyms ............................................................................................................ v
List of Figures ................................................................................................................ vi
List of Tables ................................................................................................................ vii
1. Introduction ............................................................................................................. 1
1.1 Water resource situation around the world ...................................................... 1
1.2 Research motivation ......................................................................................... 2
1.3 Methodology .................................................................................................... 3
2. Water resources in Singapore .................................................................................. 4
2.1 Water supply .................................................................................................... 4
2.1.1 The first tap: local catchment water .......................................................... 4
2.1.2 The second tap: imported water ................................................................ 5
2.1.3 The third tap: NEWater ............................................................................. 5
2.1.4 The fourth tap: desalinated water .............................................................. 7
2.1.5 Estimated production cost of each tap ...................................................... 7
2.1.6 Alternate sources of water ........................................................................ 8
2.1.7 Potential future water supply .................................................................... 9
2.2 Water demand ................................................................................................ 10
2.3 Water sustainability ........................................................................................ 10
3. Estimated future water supply and demand ........................................................... 12
iii
3.1 Estimated future water demand ...................................................................... 12
3.1.1 Domestic ................................................................................................. 12
3.1.2 Non-domestic .......................................................................................... 15
3.1.3 Estimated future daily demand ............................................................... 17
3.2 Estimated future supply .................................................................................. 17
4. Sustainability index ............................................................................................... 18
5. Discussion .............................................................................................................. 19
5.1 Future demand ................................................................................................ 19
5.2 Future supply .................................................................................................. 19
5.2.1 Desalination ............................................................................................ 20
5.2.2 NEWater ................................................................................................. 22
6. Conclusion ............................................................................................................. 24
References ..................................................................................................................... 26
Appendices .................................................................................................................... 29
A. Articles read ................................................................................................... 29
B. List of figures ................................................................................................. 30
C. List of data ...................................................................................................... 33
iv
Summary
Per capita availability of fresh water is the lowest in Asia as compared to the rest of the
world, with Central Asia and parts of Southeast Asia under the condition of “high
water stress”.
Singapore is a “water-stressed” country with per capita water availability of
110.9m3/year. Its mean annual rainfall of 2400mm is high as compared to the global
average of 1050mm. The challenge is in collecting those rainfall with a limited land
space and in the absence of natural aquifers and lakes. To overcome this challenge, the
PUB has developed a diversity of water supply for Singapore over the years, which are
known as the Four National Taps.
Even though the water demand is met by the four taps now, the future contains
uncertainty. Climate change will affect the water use and the catchment volume
available. As for the second tap, it is not very stable due to the complexity of the
relationship between Singapore and Malaysia. Also, discussions on new water
agreement beyond 2061 had not been successful. Both desalination and NEWater
processes are energy-intensive and more expensive.
The future supply of each tap will be estimated by taking into account of plans of
having new desalination or NEWater plants. The focus will be on the sustainability of
the processes of NEWater and desalination since they will be the major sources of
water in the future. The demand will be estimated based on equations presented in the
literature. The uncertainties in the results of the estimated future demand, the most
possible future sources of water supply and future work will also be discussed.
v
List of Acronyms
Forward Osmosis: FO
Liquefied Natural Gas: LNG
Meter: m
Millimeters: mm
Million gallons of water per day: mgd
Public Utilities Board: PUB
Reverse Osmosis: RO
Sanitary Appliance Fee: SAF
Seawater Reverse Osmosis: SWRO
Unaccounted-for-water: UFW
Variable Salinity Plant: VSP
Waterborne Fee: WBF
Water Conservation Tax: WCT
World Health Organization: WHO
vi
List of Figures
Figure 3-1: Past and estimated future population ......................................................... 12
Figure 3-2: Past per capita demand ............................................................................... 14
Figure 3-3: Past and estimated future GDP per capita .................................................. 16
Figure B- 1: Access and efficiency standards, adapted from (Ministry of the
Environment & Water Resources, 2014) ...................................................................... 30
Figure B- 2: Key figures of water supply and demand data, adapted from (Ministry of
the Environment & Water Resources, 2014) ................................................................ 30
Figure B- 3: Typical operation cost in RO, adapted from (Ghalavand et al., 2014) ..... 31
Figure B- 4: General process of FO, adapted from (Ghalavand et al., 2014) ............... 31
Figure B- 5: Comparison of flux between FO and RO, adapted from (Ghalavand et al.,
2014) ............................................................................................................................. 31
Figure B- 6: Comparison of energy consumption between FO and other processes,
adapted from (Ghalavand et al., 2014) .......................................................................... 32
vii
List of Tables
Table 1-1: Classification based on W/Q ......................................................................... 1
Table 1-2: Classification based on Q/c ........................................................................... 1
Table 2-1: Capacities of NEWater plants ....................................................................... 6
Table 2-2: Capacities of desalination plants ................................................................... 7
Table 2-3: Estimated production cost of each tap ........................................................... 8
Table 3-1: Current demand situation ............................................................................ 12
Table 3-2: Past and estimated future population ........................................................... 13
Table 3-3: Population estimates based on data from
(http://populationpyramid.net/singapore/2030/) ........................................................... 13
Table 3-4: Estimated future per capita demand ............................................................ 14
Table 3-5: Estimated future total domestic demand ..................................................... 15
Table 3-6: Estimated future total industrial demand ..................................................... 16
Table 3-7: Estimated future daily demand .................................................................... 17
Table C- 1: Population data .......................................................................................... 33
Table C- 2: Per capita domestic demand ...................................................................... 34
Table C- 3: GDP per capita ........................................................................................... 35
Introduction | 1
1. Introduction
1.1 Water resource situation around the world
70% of the Earth’s surface is covered by water. However, only 3% is fresh water. Of
those, 2.5% is locked in the polar ice caps and only 0.5% is available for human use, in
the form of aquifers, rainfall, natural lakes, reservoirs and rivers (Fry, 2006). Per
capita availability of fresh water is the lowest in Asia as compared to the rest of the
world. The Central Asia and parts of Southeast Asia are above the threshold of “high
water stress” condition as the ratio of water use to availability exceeds 0.4 (Kog, Lim,
Long, Kwa, & Nanyang Technological University. Institute of Defence andStrategic,
2002). Tables 1-1 and 1-2 summarizes the classifications of water stress indices.
Table 1-1: Classification based on W/Q
Withdrawal-to-availability ratio, W/Q Classification
< 0.1 No-stress
0.1 < W/Q < 0.2 Low stress
0.2 < W/Q < 0.4 Moderate stress
W/Q > 0.4 High stress
Singapore is a “water-stressed” country as the amount of water available for each
person is 110.9m3/year (AQUASTAT, 2014), less than 1000m3/year. The mean
annual rainfall in Singapore is 2400 millimeters (mm). This amount is high as
compared to the global average of 1050mm, as cited in p.109 of (Kog et al., 2002).
Table 1-2: Classification based on Q/c
Per capita water availability, Q/c
(m3 c-1 y-1) Classification
> 1700 No-stress
1000 < Q/c < 1700 Moderate stress
Q/c < 1000 High stress
< 500 Extreme stress
Introduction | 2
The challenge is in collecting those rainfall for use as Singapore is a small island with
limited land space and no natural aquifers and lakes to collect rainwater (PUB, 2015a).
To overcome this challenge, the Public Utilities Board (PUB), which is Singapore’s
national water agency, has developed a diversity of water supply for Singapore over
the years. Known as the Four National Taps, they are the local catchment water,
imported water from Malaysia, NEWater, and desalinated water.
1.2 Research motivation
The definition of sustainability is “development that meets the needs of the present
without compromising the ability of future generations to meet their own needs”
(United Nations, 1987). It can be translated into providing enough quality water for
the country’s use for now and in the future. For the case of Singapore, even though the
demand is met by the four taps now, the future contains uncertainty.
Water demand increased by 5% per day on average when Singapore experienced the
driest period in March 2014 (Ee, 2014). Prolonged dry weather will also affect the
catchment volume available. As for the second tap, it is not very stable due to the
complexity of the relationship between Singapore and Malaysia. Also, discussions on
new water agreement beyond 2061 had not been successful (Kog et al., 2002). Even
though the cost of desalination process has decreased over the years, as cited in p.64 of
(Kog et al., 2002), it is still higher than the first two sources. Besides, both
desalination and NEWater processes are energy-intensive (PUB, 2013b).
Therefore, there is a need evaluate the sustainability of the water resources in
Singapore.
Introduction | 3
1.3 Methodology
This thesis aims to assess the sustainability of the water resources in Singapore. The
future supply of each tap will be estimated, since the capacity of local catchment is
confidential. Plans of having new desalination or NEWater plants will also be taken
into account. The focus will be on the processes of NEWater and desalination since
they will be the major sources of water in the future. The demand will be estimated
based on equations presented in the literature.
Water resources in Singapore | 4
2. Water resources in Singapore
2.1 Water supply
2.1.1 The first tap: local catchment water
The first reservoir in Singapore, the Thomson Road Reservoir (known as MacRitchie
Reservoir now), was the result of a donation of $13000 from philanthropist Tan Kim
Seng for waterworks in 1857. It was formed by impounding the water with an earth
dam. In 1867, after the embankment was completed, municipal water supply was
available (Kog et al., 2002).
The catchment area currently covers two-thirds of Singapore’s land surface.
Rainwater and used water are collected in different systems. Rainwater is collected in
the storm water collection system which consists of drains, canals, rivers, storm water
collection ponds, pumping stations and connecting pipelines before it is stored in the
17 reservoirs (PUB, 2015a). The reservoirs were built either by damming the river
estuaries or from ground up. The Reservoir Integration Scheme connects the various
reservoirs through a system of pumps and pipelines. This allows excess water
collected in one reservoir to be pumped into another reservoir for storage to reduce
wastage (Onn, 2010).
According to (Kog et al., 2002), the storage capacity of the 14 reservoirs in 2002 was
140 million m3 (30800 million gallons). However, no data on the storage capacity is
available after the opening of Marina Reservoir, Punggol Reservoir and Serangoon
Reservoir. Dr Vladan Babovic suggested that it is reasonable to assume the capacity
of the local catchment to be around 250 million m3 (55000 million gallons). The
production cost of water from the local catchment is also not available.
Water resources in Singapore | 5
2.1.2 The second tap: imported water
The causeway between Singapore and Malaysia was completed in 1924.
Subsequently, water agreements were signed between both countries in 1927 and
1961. The 1961 agreement replaced the one in 1927 and had expired in 2011.
The only agreement in force now is the 1962 Agreement, which is known as the “Johor
River Water Agreement”. It allows Singapore to draw up to 250 million gallons of
water per day (mgd) from the Johor River until 2061 (Onn, 2010). Singapore is to pay
Johor 3 Malaysia sen per 1000 gallons of raw water while Johor pays Singapore 50
Malaysia sen per 1000 gallons of treated water it buys back from Singapore. Based on
the above, the production cost from this tap is S$0.20/m3 (including 2.40 Malaysian
Ringgit to treat 1000 gallons of raw water). The 1990 agreement allowed Singapore to
dam Sungei Linggiu for additional water to be drawn on top of the 250mgd (Kog et al.,
2002).
The cost of the additional water is the maximum of these two formulas: (1) half the
difference between the price of water sold in Singapore and the price paid, less
operating, distribution and management costs; (2) 115% of the price the Johor State
charges its population for water.
The contract will expire in 2061, as cited in p.15 of
(Segal, 2004).
2.1.3 The third tap: NEWater
When Singapore began treating its sewage instead of releasing it into the sea in 1974,
it also experimented with water recycling. However, the first test recycling plant was
closed in 1975 as it was expensive and unreliable. In 1998, the idea of NEWater was
Water resources in Singapore | 6
generated from a collaboration between the PUB and the then Ministry of the
Environment (now known as the Ministry of the Environment and Water Resources).
In May 2000, the NEWater prototype plant at the Bedok water reclamation plant began
operations. Since then, studies were carried out to evaluate the quality of NEWater for
potable use. The Bedok and Kranji NEWater plants, with a capacity of 6mgd and
5mgd respectively, were opened in February 2003, after validating its quality and
reliability. The Seletar NEWater plant with a capacity of 9mgd was opened in June
2004 (Onn, 2010). However, it was decommissioned in 2011, together with the
closure of Seletar Water Reclamation Plant (PUB, 2011). The Ulu Pandan NEWater
plant, which will supply 32mgd of NEWater for a period of 20 years, was opened in
March 2007. The Changi NEWater plant was opened in May 2010 with a capacity of
50mgd (PUB, 2013b). The production cost of NEWater is around 50% of desalinated
water (Kog et al., 2002).
NEWater currently meets up to 30% of Singapore’s water demand and is mainly for
non-potable use. The plan of PUB is to increase the capacity of the NEWater plants so
that it can meet up to 55% of the future water demand by 2060 (PUB, 2015a).
Table 2-1: Capacities of NEWater plants
Plant Year of commissioning Capacity (mgd)
Bedok 2002 19
Kranji 2002 17
Ulu Pandan 2007 32
Changi 2010 50
Total 118
Water resources in Singapore | 7
2.1.4 The fourth tap: desalinated water
Singapore determined that desalination was technically feasible and financially viable
in 1995 after conducting study trips to the plants in other countries when it has been
evaluating desalination technologies since the 1970s. In 1998, a test desalination plant
was built through a collaboration between Singapore Power, AquaGen, and Singapore
Technologies (Onn, 2010).
In 2005, the first desalination plant, SingSpring Desalination Plant, was built with a
capacity of 30mgd. Together with the second desalination plant, the Tuaspring
Desalination Plant with a capacity of 70mgd, desalinated water currently meets up to
25% of Singapore’s water demand. The plan of PUB is to increase the capacity of
desalination plants so that it can meet up to 25% of the future water demand by 2060
(PUB, 2013a). Desalinated water is the domestic and industrial supplies for the
western part of Singapore.
Table 2-2: Capacities of desalination plants
Plant Year of commissioning Capacity (mgd)
SingSpring 2005 30
Tuaspring 2013 70
Total 100
2.1.5 Estimated production cost of each tap
It was reported that the selling price of desalinated water from Tuaspring Desalination
Plant for the first year was $0.45/m3 while the selling price of desalinated water from
SingSpring Desalination Plant for the first year was S$0.78/m3 (TODAY Online,
2013).
Water resources in Singapore | 8
Table 2-3 summarizes the estimated production costs of water from each tap. The
production cost of water from the local catchment is assumed to be S$0.30/m3.
Imported water from Malaysia is the cheapest source while desalinated water cost the
most. Note: all costs are relative; they may not reflect the actual costs at the present as
they are not accessible.
Table 2-3: Estimated production cost of each tap
2.1.6 Alternate sources of water
Alternate sources of water are also available for private use. These include rainwater
harvesting, greywater recycling and use of seawater (PUB, 2014). Developers who
satisfy the conditions imposed by PUB are allowed to build rainwater collection
systems to collect rainwater for non-potable use within their own premises.
“Greywater” is untreated used water which has not come into contact with toilet waste.
This includes used water from washings, such as showers, and laundry and excludes
used water from the toilets and kitchen sinks. Greywater recycling is to reuse treated
greywater after it has gone through treatment such as membrane filtration and
disinfection to ensure the quality of the treated greywater for non-potable use. The
treated greywater may be used for toilet flushing and general washing. It is not
allowed for use in high pressure jet washing, irrigation sprinklers and general washing
at markets and food establishments due to public health concerns.
Tap Production Cost (S$/m3)
Local catchment 0.30
Imported water from Malaysia 0.20
NEWater 0.23
Desalinated water 0.45
Water resources in Singapore | 9
The use of seawater is encouraged for cooling and process use for industries located on
offshore islands or near the sea.
2.1.7 Potential future water supply
2.1.7.1 Variable Salinity Plant
As all the major rivers are dammed to create reservoirs, the Variable Salinity Plant
(VSP) can tap water from the smaller streams near the shoreline as damming these
small catchments is not cost effective. It can produce clean water from canal water
during rainy season. When the weather is dry, it can perform seawater desalination.
The demonstration plant at Sungei Tampines since 2007 proves that the technology is
viable. The aim of PUB is to increase the overall catchment area of Singapore to 90%
with VSP so that more rainwater can be harvested to increase the domestic water
supply at a lower cost (PUB, 2013b).
2.1.7.2 Groundwater
A study is currently being carried out on the possibility of groundwater in the Western
and Southern parts of Singapore and Jurong Island underlying Jurong Formation as it
may contain aquifers (Eco-Business, 2013). The groundwater will only be extracted if
the groundwater models developed indicate that there will be no impact on the existing
buildings and infrastructure. Even if substantial amount of groundwater cannot be
extracted regularly, it can serve as "water banks" for drought periods.
2.1.7.3 Water from Indonesia
An agreement between Singapore and Indonesia was signed in 1991 for the supply of
water (1000mgd) at S$0.01/m3 from Riau in Indonesia via undersea pipelines. A joint
venture was created in 1992 to develop supply of water from Bintan but the project
was not continued due to political uncertainty in Indonesia (Kog et al., 2002).
Water resources in Singapore | 10
2.2 Water demand
The current water demand in Singapore is around 400mgd with 45% belonging to the
domestic at 151 liters/capita/day and 55% belonging to the non-domestic (PUB,
2015b). The demand is managed through a range of water conservation plans which
encourage the people not to waste water. The per capita domestic water demand had
decreased from 165 litres/day in 2003 to the current 150.4/day. PUB aims to lower
this figure to 147 litres by 2020 and 140 litres by 2030. The total projected demand
could be doubled by 2060, where 70% would be non-domestic demand, according to
PUB.
2.3 Water sustainability
PUB tracks some standards on water sustainability under the Environment and Water
Regulations and Standards (SEWERAGE AND DRAINAGE ACT) which are listed in
appendices.
Figure B-1 lists the percentage of access to drinking water sources and improved
sanitation, the quality of our drinking water and the percentage of unaccounted for
water over the years. Singaporeans have 100% access to drinking water sources and
improved sanitation, and our quality of drinking water is assured since it passed all the
tests on drinking water quality, meeting the standards set by World Health
Organization (WHO).
Unaccounted-for-water (UFW) refers to the water lost in the network of pipelines
between the drinking water treatment plants and the consumers due to leakage or other
reasons. This is often due to the lack of maintenance which results in the deterioration
of the network over time. The percentage of UFW has been reduced to about 5% over
Water resources in Singapore | 11
the years due to the comprehensive maintenance regime. UFW in other countries can
range from 10% to 30% (PUB, 2015a).
Figure B-2 lists some data on water supply and demand over the years. In short, these
are the data that is available.
Estimated future water supply and demand | 12
3. Estimated future water supply and demand
Data on population and GDP per capita was obtained from Singstat
(www.singstat.gov.sg). Data on per capita water demand was obtained from the PUB
website. Only data from the years 1995 to 2014 was taken into consideration for
consistency.
Table 3-1: Current demand situation
Current per
capita
demand
(litres/day)
Current
population
Current total
domestic
demand
(litres/day)
Current total
non- domestic
demand
(litres/day)
Current total
demand
(litres/day)
Current
total
demand
(mgd)
150.4 5,469,724 822,646,490 1,005,456,821 1,828,103,310 402.1
3.1 Estimated future water demand
3.1.1 Domestic
3.1.1.1 Estimated future population
The future population was estimated based on the past trend. A polynomial trend line
of order 2 was selected as it fits the data the most.
Figure 3-1: Past and estimated future population
y = 2628.2x2 - 1E+07x + 1E+10R² = 0.9773
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
8,000,000
1990 2000 2010 2020 2030
Population
Years
Past population
Poly. (Past population)
Estimated future water supply and demand | 13
Table 3-2: Past and estimated future population
Year Actual population Estimated
population Error (%)
2014 5,469,724 5,560,272 1.7
2020 6,560,326
2030 8,647,599
2040 11,260,519
2050 14,399,084
2060 18,063,296
2070 22,253,153
However, the estimates after the year 2020 seem to be unrealistic. So, the projections
from (http://populationpyramid.net/singapore/2030/) were adopted.
Table 3-3: Population estimates based on data from (http://populationpyramid.net/singapore/2030/)
Year Estimated population
2020 6,057,000
2030 6,577,000
2040 6,904,000
2050 7,064,000
2060 7,096,000
2070 6,988,000
Estimated future water supply and demand | 14
3.1.1.2 Estimated future per capita demand
Figure 3-2: Past per capita demand
The future per capita demand was estimated using the least square method with the
latest two data points (in the year 2013 and 2014) in a linear trend.
Table 3-4: Estimated future per capita demand
Year Estimated per capita demand (litres/day)
2020 146.8
2030 140.8
2040 134.8
2050 128.8
2060 122.8
2070 116.8
3.1.1.3 Estimated future total domestic demand
The total domestic demand is calculated based on the equation,
𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 × 𝑑𝑎𝑖𝑙𝑦 𝑝𝑒𝑟 𝑐𝑎𝑝𝑖𝑡𝑎 𝑑𝑒𝑚𝑎𝑛𝑑
( 3-1)
145
150
155
160
165
170
175
1990 1995 2000 2005 2010 2015
Per capita demand
(litres/day)
Year
Past per capita demand
Estimated future water supply and demand | 15
Table 3-5: Estimated future total domestic demand
Year
Estimated
future
population
Estimated future
per capita
demand
(litres/day)
Estimated future
total domestic
demand
(litres/day)
Estimated future
total domestic
demand (mgd)
2020 6,057,000 146.8 889,167,600 195.6
2030 6,577,000 140.8 926,041,600 203.7
2040 6,904,000 134.8 930,659,200 204.7
2050 7,064,000 128.8 909,843,200 200.1
2060 7,096,000 122.8 871,388,800 191.7
2070 6,988,000 116.8 816,198,400 179.5
3.1.2 Non-domestic
In this project, the non-domestic demand will be assumed as industrial demand only.
As there is a relationship between GDP per capita and industrial demand, data on GDP
and current industrial demand will be needed. The future GDP per capita was
estimated by extending the past trend and the present industrial demand was scaled to
the current GDP per capita, such that a relationship was obtained between the amounts
of water used per $1000. The equation used was:
𝑠𝑐𝑎𝑙𝑒 × 𝐺𝐷𝑃 𝑝𝑒𝑟 𝑐𝑎𝑝𝑖𝑡𝑎
(3-2)
Estimated future water supply and demand | 16
3.1.2.1 Estimated future GDP per capita
Figure 3-3: Past and estimated future GDP per capita
The future GDP per capita was estimated based on the past trend. A polynomial trend
line of order 2 was selected as it fits the data the most.
Table 3-6: Estimated future total industrial demand
Year GDP per capita (S$)
Current total
non- domestic
demand
(litres/day)
Amount of
water used
per $1000
(litres)
Estimated
future total
industrial
demand
(litres/day)
Estimated
future
total
industrial
demand
(mgd)
2014 71,318.00 1,005,456,821 14,098,220
2020 98,332.75 1,386,316,730 304.9
2030 150,471.07 2,121,374,200 466.6
2040 217,907.61 3,072,109,374 675.8
2050 300,642.38 4,238,522,252 932.3
2060 398,675.37 5,620,612,834 1236.4
2070 512,006.58 7,218,381,120 1587.8
y = 76.491x2 - 304575x + 3E+08R² = 0.963
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
1990 2000 2010 2020 2030
GDP per capita (S$)
Year
Past GDP percapita
Poly. (Past GDPper capita)
Estimated future water supply and demand | 17
3.1.3 Estimated future daily demand
Table 3-7: Estimated future daily demand
Year Daily demand
(mgd)
Percentage of
domestic demand
(%)
Percentage of
industrial demand
(%)
2020 500.5 39.1 60.9
2030 670.3 30.4 69.6
2040 880.5 23.3 76.7
2050 1132.5 17.7 82.3
2060 1428.0 13.4 86.6
2070 1767.4 10.2 89.8
3.2 Estimated future supply
According to PUB, plans are made to ensure that NEWater and desalination can meet
80% of our water demand by 2060. With the expansion of the Changi and Kranji
NEWater factories and the implementation of Tuas NEWater factory, by year 2030 the
capacity of NEWater plants will increase by more than 160mgd. There will be plans to
increase capacity of Changi NEWater plant by more than 50mgd over the next 5–10
years and a new Tuas NEWater factory with an initial plant treatment capacity of
25mgd. The Kranji NEWater plant will be expanded by 22,710 m3/d (5mgd).
A third desalination plant, Tuas 3 seawater desalination plant, will be in operation by
the end of 2016 (Global Water Intelligence, 2014). It will have an initial capacity of
136,260 m3/day (30mgd). The remaining 20% will be met by our local catchment and
VSP.
Sustainability index | 18
4. Sustainability index
The water resource sustainability index (SI) is used to define sustainability of the water
resource. If the water supply is greater than the water demand, then
𝑆𝐼 =𝑤𝑎𝑡𝑒𝑟 𝑠𝑢𝑝𝑝𝑙𝑦 − 𝑤𝑎𝑡𝑒𝑟 𝑑𝑒𝑚𝑎𝑛𝑑
𝑤𝑎𝑡𝑒𝑟 𝑠𝑢𝑝𝑝𝑙𝑦
(4-1)
If the water supply is less than or equal to the water demand, then
𝑆𝐼 = 0
(4-2)
Therefore, the water supply should at least be greater than the water demand in order
to be sustainable. The SI was not calculated as the supply for the years of calculated
demand was not known.
Discussion | 19
5. Discussion
5.1 Future demand
There are uncertainties in the results of estimated future demand. The future
population presented in Table 3-2 was estimated based on polynomial trend. However,
actual population is dependent on factors such as birth/death rates,
immigration/emigration rates. Table 3-3 presents a more realistic estimate of the
future population. The future per capita demand was estimated using the least square
method in a linear trend. However, future per capita demand may not follow a linear
trend and is affected by weather and conservation measures implemented. The future
GDP per capita was estimated based on polynomial trend. However, GDP is an
economic product and there is an economic way of forecasting annual growth rate.
Since the results were based on extrapolation, the further the estimated year, the more
uncertainty it carries.
5.2 Future supply
The most possible future sources of water supply are local catchment, NEWater and
desalination. The chance of Singapore renewing the water agreement with Malaysia is
not high given the past unsuccessful negotiations and the complex relationship
between the two countries. The chance of importing water from Indonesia is very low,
as the construction cost of the submarine pipeline is around half of the construction
cost. Besides, the project has been delayed for a long time with no update. Whichever
is the case, the supply needs to be greater than the estimated future demand to ensure
sufficiency and sustainability.
Discussion | 20
5.2.1 Desalination
Desalination methods can be divided into four categories (Ghalavand, Hatamipour, &
Rahimi, 2014). They are thermal, crystallization, membrane, others. Under the
membrane category there are four methods: Reverse Osmosis (RO), Forward Osmosis
(FO), Electro Dialysis (ED) and microbial cell. The technology adopted in Singapore
is Seawater Reverse Osmosis (SWRO).
5.2.1.1 Reverse Osmosis (RO)
RO is the most commonly used technology in membrane desalination where the
process is based on separation. In this process, water flows opposite to the natural
flow across the membrane as an external pressure higher than the osmotic pressure is
applied on the sea water to overcome the osmotic pressure. This leaves the dissolved
salts behind the membrane. Since no heating or phase separation change is required, it
is the most energy efficient desalination process in practice (Baten & Stummeyer,
2013). Most of the energy required for desalting is for the pressurizing of the sea
water feed as much energy is used for pumping, due to the high pressure gradient.
Figure B-3 shows the typical operation cost in a RO process.
A typical large SWRO plant consists of feed water pre-treatment, high pressure
pumping, membrane separation, and permeate post-treatment. The major design
considerations for sea water RO plants are the conversion or recovery ratio, flux,
membrane life, permeate salinity, power consumption, and feed water temperature.
The power consumption is about 2–5 kWh/m3 of water processed.
5.2.1.2 Forward Osmosis (FO)
Unlike RO, FO requires osmotic pressure instead of hydraulic pressure. A
concentrated solution of high osmotic pressure called draw solution is used so that
Discussion | 21
water can be induced to flow from saline water across the membrane, leaving behind
the salt. The draw solution is now diluted and needs to be re-concentrated before the
system can yield potable water, and the process repeats. Figure B-4 illustrates the
general process of FO.
As compared to RO, FO has more desalination flux and uses less pumping energy.
Figures B-5 and B-6 show the comparison of flux between FO and RO and energy
consumption between FO and other processes respectively. Researchers at Yale
University and in Singapore are looking into FO technology (Likhachev & Li, 2013).
5.2.1.3 Towards sustainability
Over the years, the market share of SWRO has increased steadily in countries of
Cooperation Council for the Arab States of the Gulf (GCC) and non-GCC countries.
On top of this, substantial efficiency improvements have been achieved through energy
recovery, improved membrane characteristics, improved pump efficiencies and the use
of variable frequency drives for controlling the pump heads. As compared to plants
being built in the 1980s with specific power demand as high as 10kWh/m3, the SWRO
plants now require approximately 3–5kWh/m3, depending on specific conditions and
constraints such as temperature and salinity of seawater, and the detailed process
configuration (Baten & Stummeyer, 2013).
There does not seem to have any technology now with the potential to bring the energy
efficiency of SWRO lower. However, renewable energy may have a potential to
improve the sustainability of desalination since almost all desalination plants today are
powered by fossil energy.
Discussion | 22
Singapore receives modest amounts of insolation and is often interrupted by clouds on
most days. It is calculated that 40km2 of photovoltaic (PV) solar panels would be
required to power Singapore, so solar energy does not seem feasible as it is expensive.
Singapore has low wind speeds and large wind farms cannot be built with limited land
and sea areas. Tapping on wave or tidal energy is not feasible as waves which are
more 1 meter (m) in height are rare in the Singapore Straits (Friess & Oliver, 2015).
It has been reported that hot springs are found in Singapore (Michelle, Palmer, Oliver,
& Tjiawi, 2013). A study was carried out by (Michelle et al., 2013) on the feasibility
of having geothermal desalination in Singapore. It was found that even though it is
possible to have geothermal desalination in Singapore and the cost of operation may be
less than that of a SWRO plant, it does not seem economically feasible to invest in
geothermal desalination in Singapore with the current knowledge of the geothermal
resource. Further research would need to be done to know more about the geothermal
resource and to determine if geothermal desalination is feasible in Singapore.
Otherwise, the cold energy released from the cooling of Liquefied Natural Gas (LNG)
can be used for desalination by freezing (Efrat, 2011) since Singapore handles the
distribution of LNG (Friess & Oliver, 2015).
5.2.2 NEWater
NEWater is produced from a three-stage production process known as Microfiltration
(MF), Reverse Osmosis (RO) and Ultraviolet (UV) disinfection (PUB, 2015a).
In the process of MF, the treated used water is passed through membranes so that
suspended solids, colloidal particles, disease-causing bacteria, some viruses and
Discussion | 23
protozoan cysts are filtered and retained on the surface of the membrane. The filtered
water therefore contains only dissolved salts and organic molecules. In RO, a semi-
permeable membrane with very small pores is used. It allows only very small
molecules like water molecules to pass through, excluding contaminants such as
bacteria, viruses, heavy metals, nitrate, chloride, sulphate, by-products of disinfection,
aromatic hydrocarbons, pesticides which are undesirable. The water is then free from
bacteria, viruses and the amount of salts and organic matters it has is negligible.
After going through RO, the water is already of high quality. As a safety precaution,
UV disinfection is used to ensure the inactiveness of all organisms and the purity of
the product water. The NEWater is then ready for use after some alkaline chemicals
are added to restore the pH balance.
Similar to desalination, the use of geothermal as a replacement of the existing source
of energy for RO in the process of NEWater or the adoption of FO instead can be
considered to improve the sustainability of NEWater.
Conclusion | 24
6. Conclusion
The fact that Singapore is enjoying a reliable and diversified water supply, credit has
to be given to PUB and the government of Singapore. Since imported water from
Malaysia is one of the cheapest sources of water supply, effort has been made to
engage in negotiations on the renewal of the water agreement. On top of that, PUB is
always looking into new ways to augment our water supply. This can be seen from the
researches in VSP and groundwater, and also attempts to diversify our water import
from Malaysia and Indonesia. Researches are also conducted for the processes of
desalination and NEWater to decrease the energy use.
The sustainability of our water resources is managed from the supply and demand
sides. It is ensured that the people have access to drinking water sources of good
quality and improved sanitation. The UFW has also decreased over the years with
comprehensive maintenance regime to reduce wastage. The water tariffs also reflect
the scarcity value of our water with the Water Conservation Tax (WCT) and Sanitary
Appliance Fee (SAF) and Waterborne Fee (WBF). This is logical as higher water
prices encourage conservation and the result is seen from the decreasing per capita
demand over the years.
Sustainability of the water supply is achieved when it is sufficient and affordable in
terms of resources used to meet the current and future demand. The sustainability of
the local catchment depends on the weather. It might not be that sustainable if
Singapore experiences more frequent droughts in the future as the volume collected
would be affected. In addition, higher temperature could increase the concentration of
water pollutants and make the local catchment more prone to pollution. VSP would be
Conclusion | 25
more sustainable since it can produce clean water from the rain water collected or
perform seawater desalination otherwise. The same goes for imported water from
Malaysia as climate change affects not only Singapore. It seems to affect Malaysia
more, as seen from the occasions of water rationing due to dry spells. Desalination
and NEWater can be more sustainable if the researches on decreased energy use are
successful.
The work done in this thesis could be better. Besides the extrapolation of data which
might lead to greater uncertainties for results in the further years, equation 3-1 is also
not comprehensive. Per capita demand is also affected by the weather, for example
drier weather will see an increase in per capita demand. However, it is not taken into
account. On top of that, climate change may result in unreliable supply from the local
catchment due to droughts and floods.
An integration of the above using system dynamics may be possible if the governing
equations are known. System dynamics has been widely used in water resources
planning and management. It enables the understanding of the behaviour of complex
systems over time and captures the internal feedback loops and time delays that are
affecting the behaviour of the entire system (Xi & Poh, 2014).
It might also be useful to compare the current demand among different countries to
have a better idea of the water demand situation of Singapore.
References | 26
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Appendices | 29
Appendices
A. Articles read
Brown, Thomas C., Foti, Romano, & Ramirez, Jorge A. (2013). Projected freshwater
withdrawals in the United States under a changing climate. Water Resources Research,
49(3), 1259-1276. doi: 10.1002/wrcr.20076
Kiguchi, Masashi, Shen, Yanjun, Kanae, Shinjiro, & Oki, Taikan. (2014). Re-evaluation of
future water stress due to socio-economic and climate factors under a warming
climate. Hydrological Sciences Journal, 60(1), 14-29. doi:
10.1080/02626667.2014.888067
Onn, Lee Poh. (2003). The Water Issue Between Singapore and Malaysia: No Solution In
Sight? - The Water Issue Between Singapore and Malaysia: No Solution In Sight?1.
ISEAS Working Papers.Economics and Finance, 1.
Shen, Yanjun, Oki, Taikan, Kanae, Shinjiro, Hanasaki, Naota, Utsumi, Nobuyuki, & Kiguchi,
Masashi. (2014). Projection of future world water resources under SRES scenarios: an
integrated assessment. Hydrological Sciences Journal, 59(10), 1775-1793. doi:
10.1080/02626667.2013.862338
Appendices | 30
B. List of figures
Figure B- 1: Access and efficiency standards, adapted from (Ministry of the Environment & Water
Resources, 2014)
Figure B- 2: Key figures of water supply and demand data, adapted from (Ministry of the Environment &
Water Resources, 2014)
Appendices | 31
Figure B- 3: Typical operation cost in RO, adapted from (Ghalavand et al., 2014)
Figure B- 4: General process of FO, adapted from (Ghalavand et al., 2014)
Figure B- 5: Comparison of flux between FO and RO, adapted from (Ghalavand et al., 2014)
Appendices | 32
Figure B- 6: Comparison of energy consumption between FO and other processes, adapted from (Ghalavand
et al., 2014)
Appendices | 33
C. List of data
Table C- 1: Population data
Year Total Population
1995 3,524,506
1996 3,670,704
1997 3,796,038
1998 3,927,213
1999 3,958,723
2000
(Census) 4,027,887
2001 4,138,012
2002 4,175,950
2003 4,114,826
2004 4,166,664
2005 4,265,762
2006 4,401,365
2007 4,588,599
2008 4,839,396
2009 4,987,573
2010
(Census) 5,076,732
2011 5,183,688
2012 5,312,437
2013 5,399,162
2014 5,469,724
Appendices | 34
Table C- 2: Per capita domestic demand
Year Per capita domestic demand
(litres per capita per day)
1995 172.0
1996 170.0
1997 170.0
1998 166.0
1999 165.0
2000 165.0
2001 165.0
2002 165.0
2003 165.0
2004 162.0
2005 160.0
2006 158.0
2007 157.0
2008 156.0
2009 155.0
2010 154.0
2011 153.0
2012 152.0
2013 151.0
2014 150.4
Appendices | 35
Table C- 3: GDP per capita
Year S$
1995 35,346
1996 37,031
1997 39,179
1998 36,525
1999 36,944
2000 41,018
2001 38,660
2002 39,423
2003 41,070
2004 46,320
2005 49,715
2006 53,355
2007 59,114
2008 56,201
2009 56,111
2010 63,498
2011 66,816
2012 68,205
2013 70,047
2014 71,318