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