pollution control study for tuas desalination and … control study for tuas desalination and ......

Pollution Control Study for Tuas

Desalination and Power Plant

Project ENVIRONMENTAL PROFESSIONALS

70 MGD Desalination Design Build Own Operate

(DBOO) Project Tuas Singapore, Natural Gas Power

Plant and R & D Facility

Prepared for

TuasSpring Pte Ltd

FINAL REPORT: 31 AUGUST 2011

70 MGD Tuas Desalination and Power Plant (DBOO) Project Pollution Control Study

Document quality information

ENVIRONMENTAL PROFESSIONALS Page i

Document quality information

Pollution Control Study for Tuas

Desalination and Power Plant Project

ENVIRONMENTAL PROFESSIONALS

Trade Hub 2118 Boon Lay Way #10-114

Singapore 609966

OFFICE TEL: (+65) 6465 1187 MOBILE TEL: (+65) 98362201

OFFICE FAX: (+65) 6465 1186

E-MAIL : [email protected]

WEB : www.enviroprosing.com

FINAL REPORT: 31 AUGUST 2011

Client

TuasSpring Pte Ltd

Client‟s representative

Project

Tuas Desalination and Power Plant

Project No.

EP-SIN-008

Authors

Carsten Huttche

Renan Orquiza

Yurdinus Panji Lelean

Date

31 AUGUST 2011

Approved by

Carsten Huttche

Revision Description Prepared by Checked

by Date

2 Final YPL RO CH 31.08.2011

1 Final Draft YPL RO CH 31.07.2011

Keywords Classification

Tuas Desalination and Power Plant

Pollution Control Study – Final Report

Open

Internal

Proprietary

Distribution Medium Copies

1. TuasSpring Digital 1

2. Enviro Pro Digital 1

mailto:[email protected]

http://www.enviroprosing.com/


Table of Contents

ENVIRONMENTAL PROFESSIONALS Page ii

TABLE OF CONTENTS

TABLE OF CONTENTS ii

APPENDICES iv

LIST OF TABLES v

LIST OF FIGURES vi

GLOSSARY vii

Chapter 1 - INTRODUCTION 1

1.1 Purpose of Study 1 1.2 Description of the proposed industrial activities of the facility and site plan

showing the layout of the process units and storage areas 2 1.2.1 Site plan 3 1.2.2 Layout of Process Units and Storage Areas 6

1.3 Description of the processes and the main pollution problems expected including

process flow diagrams 10 1.3.1 Pre-Treatment – Desalination Plant 13 1.3.2 Reverse Osmosis - Desalination Plant 16 1.3.3 Post-Treatment processes – Desalination Plant 17 1.3.4 Other processes – Desalination Plant 17 1.3.5 Power generating processes 18

Chapter 2 - AIR POLLUTION CONTROL 19

2.1 Sources of air pollution and sources of odour 19 2.2 Quality, rates and quantities of air emissions 20 2.3 Assessment of the impacts of the air emissions, including odorous emissions using

dispersion modelling or other acceptable methods 21 2.3.1 Existing Ambient Air Conditions at Project Location 22 2.3.2 Methodology for Air Dispersion Study 23 2.3.3 Findings of Air Dispersion Study 24

2.4 Measures to control air pollution and ensure compliance with emission standards

and requirements in the Code of Practice on Pollution Control 29 2.5 Measures to control and prevent odour nuisance 29

Chapter 3 - WATER POLLUTION 30

3.1 Sources of trade effluent and pollutant 30 3.2 Quality, rates and quantities of all wastewater streams and final trade effluent

discharges 31 3.2.1 Ambient seawater quality 32 3.2.2 Property of discharged water 39 3.2.3 Potential impact during construction stage 41 3.2.4 Potential impact during operational stage 46

3.3 Measures to ensure compliance with requirements in the Code of Practice 57 3.3.1 Measure during construction stage 57 3.3.2 Measure to minimize impacts during operations 60 3.3.3 Measure to minimize water quality impacts during operations 61

3.4 Monitoring programme – Parameters monitored, type of monitoring equipment,

frequency of monitoring 61

Chapter 4 - NOISE POLLUTION 62

4.1 Sources of noise pollution 62 4.2 Existing ambient noise 62


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ENVIRONMENTAL PROFESSIONALS Page iii

4.2.1 Estimates of noise levels emitted during construction 64 4.3 Impacts of the noise emissions i.e. the noise levels at the receptors surrounding

the plant especially residential housing 69 4.4 Measures to control noise pollution and ensure compliance with noise emission

standards and requirements in the Code of Practice on Pollution Control 69 4.5 Monitoring programme – Type of monitoring equipment/test carried out,

frequency of monitoring 70

Chapter 5 - MANAGEMENT OF HAZARDOUS CHEMICALS 71

5.1 Inventory and storage of hazardous chemicals 71 5.2 Evaluation of the acute and chronic hazardous impacts of each hazardous chemical

and/or by-products to the environment and public health 72 5.2.1 Human Health Risk 75 5.2.2 Environment 75

5.3 Measures for safe storage and handling of hazardous substances to ensure

compliance with requirements in the code of practice on Pollution Control and

EPMA and to safeguard the environment and public health 75

Chemicals include: Caustic soda 76

5.4 Policy and procedure to ensure all necessary measures to prevent accidents

involving hazardous substances would be adopted 77 5.5 Monitoring programme – Type of monitoring equipment to detect any leakage of

hazardous substances, frequency of checks 77

Chapter 6 - TOXIC WASTES MANAGEMENT 78

6.1 Inventory and storage of toxic industrial wastes, including waste oil, solvent and

other solid wastes 78 6.2 Measures for safe storage and handling of toxic industrial wastes to ensure

compliance with requirements in the code of Practice on pollution control 78 6.2.1 System of checks on the safe storage and handling of toxic industrial wastes 78

Chapter 7 - RECYCLING AND RESOURCES CONSERVATION 79

7.1 Study the feasibility and recommend measures to reduce, reuse and recycle

wastes generated from the plants 79 7.1.1 Water 79

7.2 Study the feasibility and recommend measures to conserve energy and water use

in the plant 79 7.2.1 Energy 79

Chapter 8 - PREVENTION OF LAND CONTAMINATION 80

8.1 Sources of potential land contamination 80 8.2 Estimates of impacts from such sources on land contamination 80 8.3 Measures to prevent land contamination 81 8.4 Monitoring programme, if appropriate 82

Chapter 9 - CONCLUSION 83

9.1 Whether the proposed measures in part 2 to 8 are adequate to insure compliance

with statutory requirements and the Code of Practice on Pollution Control 83 9.1.1 Air 84 9.1.2 Water 84 9.1.3 Noise 85 9.1.4 Management of Hazardous Substances 85 9.1.5 Toxic Waste Management 85 9.1.6 Recycling and Resources Conservation 85 9.1.7 Prevention of Land Contamination 85


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ENVIRONMENTAL PROFESSIONALS Page iv

9.2 Whether the proposed plants and their operations would pose any significant

pollution impact on the environment and on developments in their vicinity,

including odour, noise and dust nuisances 86 9.3 Limitations 87

REFERENCES 88

APPENDICES

Appendix A - Trade Effluent Regulations of Singapore

Appendix B - NEA Emission Standard for Air Pollutant from Power Plant Built After

2008

Appendix C - National Ambient Air Quality Standard (NAAQS) of the United States

Environmental Protection Agency (US-EPA)

Appendix D - Evaluation of the Brine Discharge from the Proposed Tuas Desalination

Plant

Appendix E - Air Dispersion Study

Appendix F - Evaluation of the Short Term Dredging Work at the Proposed

Tuas 2nd Desalination Plant

Appendix G - Seawater Sampling Report

Appendix H - Construction Equipment Noise Emission Levels


List of Tables

ENVIRONMENTAL PROFESSIONALS Page v

LIST OF TABLES

Table 1.2-1: Desalination Water Flows ............................................................................................................ 2

Table 1.2-2: Potential operational scenarios of proposed plants ............................................................... 3

Table 2.1-1: Identified sources of air pollution ............................................................................................ 19

Table 2.1-2: Possible sources of odours and fugitive air emission from proposed plants ................ 19

Table 2.1-3: Fossil Fuel Emission Levels at Pounds per Billion Btu of Energy Input ........................... 20

Table 2.2-1: The emission rate of air pollutants of natural gas power plant ........................................ 20

Table 2.3-1: Summary of potential health impact of air pollutants ......................................................... 21

Table 2.3-2: The Limit of Emission Standard (NEA) and Ambient Standard (US-EPA) ..................... 22

Table 2.3-3: Summary of Pollutant Standard Index of Singapore ............................................................ 23

Table 2.3-4: Average ambient conditions of concerned pollutants in Singapore industrial area in

2009 ................................................................................................................................................ 23

Table 2.3-5: Maximum additional ground level concentrations ............................................................... 25

Table 2.3-6: Maximum predicted increase of ground concentrations at border ................................ 27

Table 2.3-7: Estimation of Normalized Total Ground Level Concentration ....................................... 28

Table 3.1-1: Identified sources of water pollution ...................................................................................... 30

Table 3.2-1: Flow Rates and Characteristics of All Wastewater Stream .............................................. 31

Table 3.2-2: Average temperature of seawater in the vicinity of the site ............................................. 33

Table 3.2-3: Seawater surface temperature of adjacent to the proposed site .................................... 34

Table 3.2-4: Average salinity of seawater in the vicinity of the site ....................................................... 34

Table 3.2-5: Average DO in the vicinity of the site .................................................................................... 35

Table 3.2-6: Average pH in the vicinity of the site ..................................................................................... 35

Table 3.2-7: Average turbidity in the vicinity of the site ........................................................................... 36

Table 3.2-8: Measured secchi depth around the site ................................................................................. 37

Table 3.2-9: Measured water quality at Intake and outfall of proposed plants .................................... 38

Table 3.2-10: Seawater content for design condition of desalination plant ............................................ 39

Table 3.2-11: Considered scenario for the purpose of this study ............................................................ 40

Table 3.2-12: Properties of discharged water for Scenario 1 and 2 ........................................................ 41

Table 3.2-13: Assumed Initial Boundary Condition ...................................................................................... 43

Table 3.2-14: Test scenarios of outfall discharge (TDS and Temperature) ............................................ 47

Table 4.2-1: Summary of Ambient Noise at Proposed Site ...................................................................... 63

Table 4.2-2: Summary of ambient noise at Singspring perimeter ............................................................ 66

Table 4.2-3: Summary of Ambient Noise at Senoko Perimeter .............................................................. 69

Table 4.4-1: Boundary Noise Requirements ................................................................................................ 70

Table 5.1-1: Chemicals used in proposed facilities ..................................................................................... 71

Table 5.2-1: Human Health & Environmental Risks of Stored Chemicals ............................................ 72

Table 9.1-1: Summary of pollutive emissions from proposed plants ...................................................... 83


List of Figures

ENVIRONMENTAL PROFESSIONALS Page vi

LIST OF FIGURES

Figure 1.2-1: General Location Map of Proposed Plants ............................................................................... 5

Figure 1.2-2: Overall Site Layout of Proposed Facility ................................................................................... 9

Figure 1.3-1: Process flow of the proposed facilities ................................................................................. 12

Figure 1.3-2: Example of intake chamber configuration where intake head is located inside the

chamber. Advised maximum intake velocity using this configuration is 30 cm/s;

otherwise is10 cm/s. ................................................................................................................... 14

Figure 2.3-1: Cross-border profile line and points of predicted concentrations. ............................... 24

Figure 2.3-2: Estimated ground level concentrations of PM10 showing typical dispersion pattern of

pollutants at ground during different seasons. ...................................................................... 26

Figure 2.3-3: Spatial profile of additional PM10 concentration at ground level towards the border 27

Figure 3.2-1: Location of EIA's water quality survey station ..................................................................... 32

Figure 3.2-2: Distribution of TSS plume in West Johore Strait over 1 tidal cycle (12 hours), at 2-

hour interval – Scenario A (source TSS – 200 ppt). ........................................................... 44

Figure 3.2-3: Distribution of TSS plume in West Johore Strait over 1 tidal cycle (12 hours), at 2-

hour interval – Scenario B (source TSS – 400 ppt). ............................................................ 45

Figure 3.2-4: A schematic sketch of the outfall pipe. ................................................................................. 47

Figure 3.2-5: A schematic sketch of the outfall diffuser with discharge nozzle. ................................... 48

Figure 3.2-6: A diagrammatic representation of the core flow and the secondary flow as a result of

flow entrainment in the receiving water body. .................................................................... 49

Figure 3.2-7: The trajectory at an inclined 60 degree angle with a terminal rise height (Zt) and

return point (Xr). Zo indicates the height of the height of the discharge point above

seafloor level. The shades in the plume are indicative of the brine dilution. ................ 50

Figure 3.2-8: The dilution profile (minimum and averageTDS concentration) – Scenario 2. ............ 51

Figure 3.2-9: The dilution profile (minimum and average TDS concentration) – Scenario 4. ........... 52

Figure 3.2-10: The dilution profile (minimum and average temperature) – Q = 509.8 MLD at 36.4

deg C. ............................................................................................................................................. 53

Figure 3.2-11: Distribution of TDS plume in West Johore Strait over 1 tidal cycle (12 hours), at 2-

hour interval – Scenario 2. ........................................................................................................ 54

Figure 3.2-12: Distribution of TDS plume in West Johor Strait over 1 tidal cycle (12 hours), at 2-

hour interval – Scenario 4. ........................................................................................................ 55

Figure 3.2-13: Distribution of thermal plume in West Johore Strait over 1 tidal cycle (12 hours), at

2-hour interval. The discharge rate is 509.8 MLD. .............................................................. 56

Figure 4.2-1: Ambient Noise at Proposed Site. Point N1 & N5 are located at seaward corner, N2,

N3, N4 are located at pedestrian lane at eastern border of the site. The bar indicates

the range of recorded value; the dot indicates mean value. ............................................. 63

Figure 4.2-2: Location of noise measurements at Tuas area ..................................................................... 64

Figure 4.2-3: Noise level at the perimeter of SingSpring Desalination Plant. ........................................ 65

Figure 4.2-4: Location of noise measurements at Senoko Power Plant Area ....................................... 67

Figure 4.2-5: Representative noise level data collected at the perimeter of Senoko Power Plant . 68


Glossary

ENVIRONMENTAL PROFESSIONALS Page vii

GLOSSARY

AWQG : Ambient Water Quality Guideline

Brine : Highly concentrated salt solution

CIP : Cleaning in Place, cleaning of plant membranes in their installed location

CPPC : Code of Practice on Pollution Control

dBA : decibel, units to express the level of noise to approximate the human ear‟s

response to sound

DBOO : Design, Build, Own and Operate

EIA : Environmental Impact Assessment

EPD : Environmental Protection Division of the NEA

EPMA : Environmental Protection and Management Act

GLC : Ground Level Concentration

MGD : Million Gallon per Day

MLD : Million Litre per Day

MRL : Mean River Level: A tidal datum

NAAQS : National Ambient Air Quality Standard of USEPA

NEA : National Environmental Agency

Permeate Water : Desalinated water produced by the RO process

pH : (Logarithmic) concentration of hydrogen ions

PM10 : Respirable particulate matters at size of maximum 10 microns (μm)

ppt : parts per thousand

PSU : Practical Salinity Unit, approximately equal to part per thousand (ppt)

PUB : Public Utilities Board

RIAM : Rapid Integrated Assessment Matrix

RO : Reverse Osmosis

TDS : Total Dissolved Solids

TSS : Total Suspended Solids

UF : Ultra-filtration, removal of fine particles at size of 0.005-0.01 microns

USEPA : United States Environmental Protection Agency


Chapter 1 - Introduction

ENVIRONMENTAL PROFESSIONALS Page 1

Chapter 1 - INTRODUCTION

To secure Singapore‟s future demand of water, the country‟s Four National Taps Strategy lists

desalination of seawater as a key strategy. By 2013, 30% of the total water demand will be met by

desalinated water. The proposed 70 MGD TuasSpring desalination plant, developed by Hyflux Ltd as

a DBOO project, will contribute to this objective and to the overall sustainable water supply strategy

for Singapore.

TuasSpring Pte Ltd is a fully owned subsidiary of Hyflux Ltd, a water treatment company with

operations in Singapore, China and Malaysia. It‟s wholly owned subsidiary Tuaspring Pte Ltd is

developing the combined 70 MGD RO desalination plant and a 530 MW natural gas power plant at

Tuas South Avenue 3. The desalination plant is to produce potable water from seawater using the

reverse osmosis (RO) process for supply to the Public Utilities Board (PUB). The power plant will,

amongst others, support the operation of the desalination plant by providing electrical power and the

cooling water.

1.1 Purpose of Study

The above mentioned project requires a Pollution Control Study (PCS) as provided under Section 36

of the Environmental Protection and Management Act (EPMA) and approval of the PCS by National

Environmental Agency (NEA) is part of the permitting process. Specifically the PCS will:

Identify sources of emission of air pollutants, discharge of trade effluent, generation of waste

and emission of noise.

Quantify and evaluate the impacts of such pollutive emissions.

Recommend the measures to be incorporated in the design and operation of the plant to

reduce the pollutive emissions to acceptable levels that would not pose nuisance or harm to

the people and to the environment.

Recommend a monitoring program to review the effectiveness of implemented mitigation

measures on regular basis.

To carry out the Pollution Control Study, TuasSpring Pte Ltd has appointed Environmental

Professionals (ENVIRO PRO) as the project‟s environmental consultant to conduct the necessary

pollution control study. Enviro Pro assisted in determining the proposed plant‟s anticipated pollution

load once operational and describing appropriate pollution abatement technologies such that the

facility is in compliance with stipulated standards for air emissions, trade effluent discharge, noise

emission, waste disposal, etc. Where required, application for a waiver from these standards is

considered.




The consultant carried out site investigations in 2010 and 2011 to assess the submitted plans in

relation to the site. Computer modelling techniques were used to predict the dilution of discharge

components into the sea and to estimate the dispersion of air pollutants released by the proposed

power plant.

It is important to highlight that PUB has conducted an initial Environmental Impact Assessment (EIA)

of the proposed activities in 2010, with the technical EIA report submitted by PUB‟s consultant DHI

International in January 2011. The EIA study had addressed potential environmental impacts primarily

attributed to the increase salinity and temperature of the discharge trade effluent into seawater. At

the outfall diffuser, the salinity is estimated to be at 80% higher than the intake seawater; the

temperature is expected to be higher than the receiving water bodies within the mixing zone, beyond

which ambient condition prevails. Minor disturbances are predicted to happen during construction

phase due to various construction activities in the site, inland and offshore. The study, which uses

Rapid Integrated Assessment Matrix (RIAM) approach, also classifies the impact of proposed activities

as either Slight or No Impact (PUB, 2011).

1.2 Description of the proposed industrial activities of the facility

and site plan showing the layout of the process units and storage

areas

The proposed plant will consist of two components: (i) the desalination of seawater to obtain

potable water and; (ii) generation of power to be used by the desalination plant and supply to the

national electricity grid. The desalination plant is designed to operate for 25 years using reverse

osmosis technology with a warranted capacity of 318,500 m3/d (nominally 70 MGD). The power

plant will generate electric power of approximately 530 MW. Due to site constrains, the likely type

of power plant is a natural gas or a combination of natural gas and fuel oil firing plant. The power

plant is expected to use the seawater as cooling water. Flow characteristics of water in the proposed

desalination facilities are shown on Table 1.2-1.

Table 1.2-1: Desalination Water Flows

Service Flow rate (MLD) Remarks

Desalination Plant intake 828 Under maximum design flow (warranted capacity)

Treated water flow 318.5 Warranted treated water capacity from the plant

Brine discharge 509.8 From Siemens Plant Performance

Estimation Program job ID 41104

Source: Hyflux design, 2011




To achieve a greater efficiency, integration of the two plants could be realized by several options: (i)

use of discharged elevated temperature cooling water from the power plant as source water for the

desalination plant; (ii) use of discharged water from power plant as blending water to reduce salinity

of rejected brine from desalination plant and; (iii) share of facilities such as intake and outfall

structures. Notwithstanding the possible integration, the design will allow each plant to operate

independently. This requirement sets out several potential operational modes of both plants (Table

1.2-2).

Table 1.2-2: Potential operational scenarios of proposed plants

Scenario Plant operation Comments

1 Power Plant in service at 100% load

Desalination Plant not in service

Outfall temperature higher than incoming

seawater temperature


Desalination Plant in service at 100%

output





output



4 Power Plant not in service


output

During power plant outage for periodic

maintenance

Outfall temperature same as incoming




output

During power plant outage for periodic

maintenance





output

Product water being discharged to the

outfall

This could be expected at start up during

the performance trials.

Power Station not available to operate

during this time



Source: Hyflux design scenario, 2011

1.2.1 Site plan

The proposed facility will be located at Tuas South Avenue 3. It will occupy 14 hectares of reclaimed

land, which is allocated for utility development under the URA Master Plan. The international marine

border between Singapore and Malaysia lies in the Western Strait of Johor approximately 850m at

west of the site. Figure 1.2-1 shows the general site location of the proposed facilities.




The Western Strait of Johor is a relatively narrow body of water, approximately 900m wide in the

north at the Singapore-Malaysia Causeway, extending to approximately 8 km wide at the northern tip

of Tuas Peninsula. The western entrance of the straits is used for shipping, mainly for serving the

Port of Tanjung Pelepas (PTP) in Johor, Malaysia. which is located within 5 km distance west of the

site. The Tanjung Piai Ramsar1 Site of Malaysia is located to the south west of the site at

approximately 13 km and is designated as an internationally important wetland site.

Other industries operate adjacent to the site. This includes shipping, manufacturing and Singapore‟s

first desalination plant (SingSpring), south of the site. Even further south, the Tuas Seaport and Tuas

Incineration Plant are located.

1 The Ramsar Convention is the Convention on Wetlands of International Importance for the conservation and sustainable utilization of wetland. It is named after the town of Ramsar in Iran where the treaty was developed and adopted on February 2, 1971. The Ramsar List of Wetlands of International Importance is known as Ramsar sites.




Figure 1.2-1: General Location Map of Proposed Plants

(Source: EIA Report, 2011)




1.2.2 Layout of Process Units and Storage Areas

The site, approximately 400mx400m in square, will be separated by internal roadways into several

distinct sectors: three sectors for the desalination plant, one for the power plant and one for PUB‟s

R&D facility. The sectors for the desalination plant include the pre-treatment, post-treatment, and

UF-RO zone. The pre-treatment zone will be located at the northern end of the site, adjacent to the

sea. At the southern end of the site, likewise adjacent to the sea, the UF and RO facilities occupy a

large section of the site. The post-treatment facilities are located east of the UF-RO zone and are

adjacent to Tuas South Avenue 3. The power plant will be located east of the pre-treatment zone.

The R&D facility occupies space at the south-eastern corner of the site, facing Tuas South Avenue 3.

Major project components and their locations are listed below. For more details, refer to Figure

1.2-2.

1.2.2.1 Pre-treatment Zone

The pre-treatment zone is located at northern end of the site and adjacent to the sea. The zone

consists of the following equipment and structures:

Seawater intake screening and pumping station, which is located at the most northern tip

adjacent to the sea and is linked to the seawater intake pipe;

UF Feed Auto-strainers;

Electro-chlorination facilities that contains NaOCl Tank;

Intake water collection tank;

Electrical Switchroom area;

As part of the pre-treatment zone, the UF facilities consist of the following equipment and

structures:

RO Feed pumps

UF Backwash tank

UF Filtered water and Backwash tank

UF Buildings

Intermediate sump

UF CIP tanks

Transformer room

Electrical switchroom

Chemical storage area




1.2.2.2 Reverse Osmosis (RO) Zone

The RO facilities consist of the following equipment and structures:

RO/LPRO CIP tank and pumps

LPRO feed

RO Buildings

LPRO system

LPRO feed/flushing tank

RO flush pump

LPRO feed pump


Air compressor

Power transformer room

Neutralization pit

Attenuation tank

The administration building is located between the UF building and RO building at the seaward side.

1.2.2.3 Post-treatment Zone

The post-treatment zone consists of the following equipment and structures:

Treated water tank – volume size 27,000 m3

Treated water pumping station

Chlorine contact tank

Carbon dioxide storage area

Lime storage area


Power substation

Canteen, parking lots and guardhouse will be located within this zone




1.2.2.4 Power Plant Zone

The Power plant zone consists of the following equipment and structures:

Hydrogen storage area

NG Booster and conditioning station

Turbine house

Demin water tank

Switchgear facility

Fuel oil storage facility

Oil waste water facility




Figure 1.2-2: Overall Site Layout of Proposed Facility

(Source: Hyflux design)




1.3 Description of the processes and the main pollution problems

expected including process flow diagrams

The desalination process can be separated into 3 main stages, namely pre-treatment, Reverse

Osmosis (RO) process and post-treatment. The proposed treatment process is similar to other

existing RO plants in California and Florida.12Similar plants in other countries include the Dheklia

Plant at Larnaca in Cyprus3 and the Boujdour desalination plant in Morocco4.

Raw seawater is first abstracted from the sea through the shoreline intake pipe located 50m

perpendicular to the shoreline at -2mCD depth, situated at the most northern point of the proposed

plant. The raw seawater is then pre-treated to prepare the water for the RO process. The main

objective of the pre-treatment process is to minimize membrane fouling on the RO plant, which is

achieved through the process of screening, chlorination and ultra-filtration (UF).

Once the seawater enters the pre-treatment stage, a biocide, chlorine, is added to kill micro-

organisms such as algae. The chlorinated water is then fed into self-cleaning strainer for removal of

solids larger than 200 micron to avoid damage of UF membranes due to unnecessary wear. The

screened water then flows to the ultra-filtration process to remove colloidal particles remaining in

water. The use of an ultra-filtration system eliminates the requirement for coagulants, which are

commonly used in a conventional pre-treatment process. The UF membrane is also able to filter oil

contaminated seawater to a certain extent. During the filtration process, solids are retained by the

membrane. These solids must be periodically removed via backwashing to maintain system

performance. The waste water of this process is discharged through the offshore outfall.

Downstream of the UF system, sodium bisulphite and caustic soda are added to remove chlorine and

aid in boron reduction downstream, respectively. The last pre-treatment process stage is the

injection of a scale inhibitor to reduce scale formation within the RO units. The filtered water

produced by the UF trains is stored in the closed filtered water/backwash tank.

1 California Coastal Commission, Seawater desalination in California, (1993) 2 P.J. Malaxos & O.J. Morin, Surface Water Discharge of Reverse Osmosis Concentrates, (1990) Desalination Vol. 78, pp 27 – 40 3 O. V. Sallangos, E. Kantilaftis, Operating experience of the Dhekelia seawater desalination plant, Desalination Vol 139 (2001) pp 115 – 123. 4 M. Hafsi, Analysis of Boujdour desalination plant performance, Desalination Vol 134 (2001) pp 93-104.




The RO process consists of two units: the high-pressure Seawater Reverse Osmosis (SWRO) unit

and the Lower Pressure Reverse Osmosis (LPRO) unit. The filtered seawater is pumped from the

filtered water tank by high pressure pumps to SWRO unit. Water is forced through micro pores of

the membranes, leaving behind a highly saline and pressurised brine reject stream. Up to 45% of the

input seawater can be recovered as freshwater in this unit. The high-energy brine reject is then

allowed to flow through isobaric pressure exchangers to recover hydraulic energy. The recovered

energies are then transferred to supplement pump pressure in the LPRO units. The isobaric device is

used due to its high recovery efficiency of up to 98%, less maintenance and easy operation. SWRO

permeate will flow from SWRO system into LPRO feed tank, which acts as buffer storage; some

portion will bypass the LPRO feed tank and flow directly into the chlorine contact tank. The water at

LPRO feed tank is then pumped into LPRO unit; 90% of which will be converted to permeate with

10% being the waste stream (brine). The brine reject from the SWRO is returned to the sea through

an outfall pipeline. The brine reject from the LPRO is recycled back to be used as backwash water to

clean the UF units in the pre-treatment stage and is stored in UF CIP tank.

Clean water from the reverse osmosis (RO) process is then pumped to the post-treatment stage for

further treatment to produce potable water. Limewater and carbon dioxide are added into the

potable water stream to re-mineralise the water to prevent corrosion of pipes downstream.

Following this, chlorine and ammonia is dosed as a disinfectant to prevent downstream

contamination. Fluoride is also dosed by adding silicofluoride as an additive for hardening tooth

enamel. The end product is then pumped to a water storage tank.

Schematic flow of the above-mentioned processes is shown on Figure 1.3-1.




Figure 1.3-1: Process flow of the proposed facilities

(Source: Hyflux design)




1.3.1 Pre-Treatment – Desalination Plant

Raw seawater, in most instances, requires pre-treatment to remove particulates in order to prolong

the membrane‟s lifespans. Water is pre-treated so that salt precipitation or microbial growth does

not occur on the membranes.

The pre-treatment process consists of the followings.

Seawater abstraction and Pre-screening

Pre-chlorination

Screening

De-chlorination

Ultra-Filtration

Anti-scalant injection

1.3.1.1 Seawater abstraction and pre-Screening

Withdrawal of seawater will be done by submerged intake system. The water will be drawn into the

intake chamber located at approximately 50 meter offshore via 2 pipelines. Downstream of the flow,

the pipes will be connected to three channels, each of which will be fitted with Coarse Bar Screens

(20 mm of aperture openings), Fine Screens (2 mm of aperture openings) and a dedicated pump. All

screens will be able to run in automatic mode based on differential levels on the upstream and

downstream. The finer screen will also be able to remove debris accumulated overtime by activating

its self-cleaning mechanism. Two slots for stop logs will be put at each channel, one at upstream of

coarse screen and one at downstream of fine screens.

The channels are designed to take full intake load of the plant intake needs. The channels will run at

33% capacity during normal operation. During periodical maintenance, flow to a channel under

maintenance will be halted by the stop log, leaving the remaining two being operated at 50% capacity.

Several potential problems arise from this process: entrainment of larger fish or other marine life due

to high velocity of intake water at intake well screen of intake chamber; entrapment of juvenile fish

and smaller organism upstream of coarse bar screen or fine screens, depending on the size of

organism. EIA study (PUB, 2011) advises the maximum velocity of 30 cm/s if intake chamber is used;

otherwise the velocity shall be less than 10 cm/s. An example of an advised configuration is shown on

Figure 1.3-2.




Figure 1.3-2: Example of intake chamber configuration where intake head is located inside the chamber. Advised maximum intake velocity using this configuration is 30 cm/s; otherwise is10 cm/s.

Source: EIA study (PUB, 2001 page 55)

1.3.1.2 Pre-chlorination

Periodic or continuous dosing of liquid Sodium Hypochlorite to the influent seawater is carried out

at the seawater intake screen to reduce the growth of algae and other microorganisms. This process

is required to protect the UF and RO membranes from biological fouling. It is important to note that

there will be no chlorine gas stored on site.

1.3.1.3 Screening of solids

Screening for solids bigger than 200 micron is performed by self-cleaning strainers located upstream

of UF system. These strainers protect the UF membrane from unnecessary wear. A pressure switch

senses the pressure differential across the strainer and triggers the self-cleaning process when the

pre-set differential value is reached. This process will take place downstream of intake tank. As such,

the filtered solids and flushing water may contain chlorine that could cause potential pollution

problem if directly discharged through offshore outfall. The rejected water from this process needs

to undergo de-chlorination before being released through the offshore outfall.

1.3.1.4 De-chlorination

Sodium bisulphite is added to remove any residual chlorine as the UF, SWRO and LPRO membranes

cannot tolerate chlorine. This also prevents the release of chlorinated water from the RO reject

brine streams into the environment.




Sodium bisulphite is a very reactive chemical that reacts with chlorine and oxygen, with a preference

to chlorine. In the event that there is excess sodium bisulphite without the presence of chlorine,

dissolved oxygen level in the water may be reduced. However, according to process design, no

significant de-oxygenation is expected as a result of the addition of sodium bisulphite. Therefore, no

negative net effect in dissolved oxygen levels at the discharge is expected.

1.3.1.5 Ultrafiltration

Ultrafiltration (UF) is provided to filter the screened seawater to remove colloidal particles

remaining in solution and produce filtrate with low SDI and turbidity by using membrane

technologies similar to those membranes of RO. As such, the use of this system eliminates the dosing

of coagulant, which is commonly used in conventional pre-treatment process. The system is also able

to filter seawater contaminated with oil/hydrocarbon to a certain degree. This feature is particularly

important during a minor oil spill event at sea.

During the filtration process, solids will be retained by the membrane. When accumulation of solids

upstream of the membrane exceeds certain pre-set threshold, backwashing will be activated to

remove the solids. The automated backwash sequences will be synchronized with the introduction of

air scouring to improve the effectiveness of backwashing. This backwashing process will be carried

out periodically every 30-45 minutes, the backwash stream will be discharged directly to the outfall.

Complementing the automatic backwash process, continuous UF performance will require regular

maintenance cleaning (MC) of the membrane trains. The MC will occur at 5 to 7 days intervals based

on the fouling characteristics of the water, using either an alkaline chlorine solution or an acid

solution with preferences towards the alkaline chlorine solution.

After several weeks in service, the trans-membrane pressure (TMP) may not be able to be controlled

by the backwashing and maintenance cleaning alone. At this stage, a Recovery Cleaning-In-Place (CIP)

will be effective using an acid CIP, which subsequently followed by a sodium hypochlorite CIP. At the

end of the CIP, the train will return to service. Used CIP solutions will be directed to the

neutralization tank for pre-discharge treatment.

The UF process generates wastewater attributed to backwashing, maintenance MC and CIP. While

there is potential hazard presented by the use of chemicals in the process, the risk of it will be

minimized at the neutralization tank where used solutions will be treated prior to final discharge

through offshore outfall.




1.3.1.6 Anti-scalant injection

As water passes through the membrane, the increase concentration of the remaining ions causes the

precipitation of inorganic salts including those of calcium carbonate, calcium sulphate, calcium

fluoride and barium sulphate. If precipitation is not controlled, membrane performance will quickly

decline. Introduction of an anti-scalant will inhibit the precipitation and therefore will extend the

membrane lifespan. A tank is provided to store the anti-scalant solution and is continuously dosed

into the filtered seawater upstream of the SWRO unit.

The organic polyphosphonate anti-scalant is not toxic. Though the chemical composition of the anti-

scalant is not available in detail, its two main components are water and organic phosphonate. Its

estimated discharge concentration is 1.5 mg/L at SWRO feed and 3 mg/L at LPRO.

1.3.2 Reverse Osmosis - Desalination Plant

The proposed RO facilities will perform 2 stages of RO process, first process at SWRO which uses

high pressure water and the second at LPRO using lower pressure water.

1.3.2.1 SWRO process

The pressurized water will be split into 2 streams, a low pressure permeate (product) stream and a

high pressure waste or brine stream by forcing the process water through membranes. The major

energy requirement is for operating pumps. Process water is pressurized to overcome the natural

osmotic pressure of ambient seawater (reverse osmosis). As the pressurized process water flows

through the membrane, the salt is removed and permeate is produced as potable water. Of the feed

water to the SWRO trains, 45% will be converted to permeate; 55% being waste water (brine).

Primary desalination of the seawater will occur in this SWRO system.

1.3.2.2 LPRO process

Product water quality is improved by adding a second pass of membranes, whereby 72% permeate of

SWRO being fed to the LPRO unit consisting of a 2-stage reverse osmosis system. Of the feed water

to the LPRO trains, 90% will be converted to permeate; 10% being waste water (brine). To achieve

the required standard of potable water, the final product water will consist of 30% SWRO permeate

and 70% LPRO permeate. The LPRO brine will be recycled into filtered sea water tank for mixing

with the filtered seawater which in turn being fed into SWRO trains.




The SWRO reject brine is the main wastewater stream from the proposed plant, totalling up to

455.5 MLD under full plant capacity. The RO brine may cause an increase in seawater salinity in close

vicinity of the discharge point. To mitigate the expected pollution problems, a discharge outfall will

transport the brine 120m offshore to a water depth of approximately 8m. A diffuser port with 12

horizontally directed nozzles will be used to induce initial mixing of the discharged brine with the

ambient seawater. Modelling studies conducted have shown favourable mixing of brine discharge with

ambient seawater given a sufficient operating flowrate. Results from computer simulation suggest that

the discharge brine plume is confined to a relatively small area of about 70 m from the outfall

location.

For more details, refer to Chapter 3 on water pollution. A waiver will be requested by NEA for the

discharge concentration of Boron, Iron and TSS.

1.3.3 Post-Treatment processes – Desalination Plant

Post treatment is required to make the water potable and non-corrosive. The processes involved in

post treatment include limewater dosing, chloramination and fluoride dosing. Limewater dosing

consists of the addition of limewater (calcium carbonate), followed by carbon dioxide for re-

mineralization, pH correction and to generate calcium bicarbonate. Calcium bicarbonate acts as an

inhibitor to prevent corrosion on the piping and storage systems for the potable water. During

chloramination process, chlorine is injected, followed immediately by ammonium sulphate. Adequate

mixing and contact time is provided. As a result, chloramines, a mild disinfectant and effective

bactericide are formed. Fluoride dosing is carried out in order to harden tooth enamel by the

addition of sodium silicofluoride. No wastewater stream is expected from this stage.

1.3.4 Other processes – Desalination Plant

1.3.4.1 Membrane cleaning

The membranes of the RO units have to be cleaned approximately 5 times per year, to remove

scales and other bio-fouling that may adhere to the membranes. The cleaning chemicals used are

dilute alkaline and acid aqueous solutions and phosphate based solutions. Wastewater generated

from the cleaning process is then pumped into a neutralization tank for pH adjustment prior to

discharge into the sea, together with other wastewater streams.




This waste stream cause a temporarily increase in salinity of the final effluent discharge. Short-term

elevated levels of polyphosphate may occur in the discharge during the cleaning process. However,

these are temporary events linked to the frequencies of membrane cleaning. The hydrolysis product

of polyphosphate is orthophosphate, which is a macronutrient used in biological processing. Overall,

it is important to realize that, in the absence of corrosion products and with good chemical control

and use of non-toxic additives, desalination processes mainly redistribute (concentrate) which is

present in the raw water.

1.3.5 Power generating processes

During the course of this study, the design process of the proposed power plant was still on-going.

However, it was understood that the plant will run either solely on natural gas or a combination of

natural gas and diesel fuel. Although natural gas remains the cleanest amongst all fossil fuels, gaseous

emissions containing several pollutants into the atmosphere are expected.

1.3.5.1 Potential pollution problems expected

Emissions of air pollutants: An air dispersion study was conducted to estimate the

concentrations of the following pollutants: Nitrogen Oxide (NO), Carbon Monoxide (CO),

Sulfur Dioxide (SO2), Carbon Dioxide (CO2) and Respirable Particulate Matters (PM10).

Discharge of elevated temperature cooling water at the shoreline outlet and at the offshore

outfall: The main concern with regards to the power plant impacts on water is the potential

elevated ambient temperature of the receiving water body caused by the cooling water

discharges, both at offshore outfall and the shoreline outlet. PUB‟s EIA study estimated the

maximum excess temperature to be 5.8°C at the diffuser port. Detailed hydrodynamic

modelling developed during the EIA study suggests that turbulence mixing, dilution and

dispersion within the mixing zone will rapidly reduce the temperature back to ambient level,

so that at the boundary of the mixing zone the mean temperature should be no more than

1°C above ambient to comply with the recommended Ambient Water Quality Guidelines1

(PUB, 2011 page 83).

1 The Ambient Water Quality Guidelines (AWQG) sets out the limit of water discharge parameter. It is developed during the EIA study of the proposed

plants to preserve high water quality in the ambient marine environment and is specific to regional waters within Singapore. For more details, see section 8.1.2 of EIA final report (PUB, 2011)


Chapter 2 – Air Pollution Control


Chapter 2 - AIR POLLUTION CONTROL

2.1 Sources of air pollution and sources of odour

The proposed industrial development contains of several potential pollution sources, which emit air

pollutants during different operational modes at variable quantities. The main pollutant source will be

the power plant. The identified potential pollution sources are presented in Table 2.1-1.

Table 2.1-1: Identified sources of air pollution

Identified source Description

Power Plant The process to generate the electricity power is expected to emit air

pollutants which are to be released through a 60m high stack. The

dispersion of pollutants is investigated in this study; findings are presented

on Section2.3.3, detail of the dispersion model is given in Appendix E.

Back up generator The activated backup generator is expected to emit air pollutants. Given its

role as the back up generator, the operational frequency is difficult to assess

and assumed to be low. Therefore, it was not considered for air dispersion

modelling.

No continuous air emissions are expected from the proposed desalination plant during normal

operations. However, there may be fugitive air emissions in event of accidental leakages from

chemical storage tanks; some of which will introduce a pungent smell. Identified possible sources of

odour are given at Table 2.1-2.

Table 2.1-2: Possible sources of odours and fugitive air emission from proposed plants

Identified

source Gas Description

Storage tank CO2 The leakage of Carbon Dioxide storage tank could introduce fugitive

emission of such greenhouse gas.

Storage tank Cl2 The leakage of Chlorine gas will introduce pungent smell of bleach.

Chlorine also a toxic gas which could cause damage to respiratory

system.

Combustion

process

SO2 Sulphur dioxide is a colourless gas, about 2.5 times as heavy as air, with

a suffocating smell, faint sweetish odour. It is a by product of

combustion process at power plant and generator burning fuel. Power

plant running of natural gas is estimated to have a low SO2 pollutant. Its

odour threshold is 2.7 ppm

Combustion

process

H2S Hydrogen Sulphide is a highly toxic, flammable and colourless gas

associated with pungent smell which resemble those of rotten eggs. Its

odour threshold is approximately at 0.2 ppt.




It is important to note that the proposed power plant is designed to run on natural gas which is the

cleanest of all fossil fuel, as shown in the data comparison chart of the U.S. Environmental Protection

Agency as of year 2010 at Table 2.1-3.

Table 2.1-3: Fossil Fuel Emission Levels at Pounds per Billion Btu of Energy Input

Pollutant Natural Gas Oil Coal

Carbon Dioxide 117,000 164,000 208,000

Carbon Monoxide 40 33 208

Nitrogen Oxides 92 448 457

Sulfur Dioxide 0.6 1,122 2,591

Particulates 7 84 2,744

Mercury 0.000 0.007 0.016

Source: EIA - Natural Gas Issues and Trends 1998

2.2 Quality, rates and quantities of air emissions

No continuous emission of air pollutant is expected to be generated by the desalination plant, except

for accidental spills from chemical storage tanks as mentioned before. The power plant is estimated

to continuously generating various air pollutants during its operations at the rate shown at Table

2.2-1.

Table 2.2-1: The emission rate of air pollutants of natural gas power plant

No. Pollutant Estimated rate of emission (g/s)

1. NOx 38.6

2. CO 77.5

3. SO2 2.2

4. CO2 52,685

5. PM10 3.9

Source: Hyflux, 2011




2.3 Assessment of the impacts of the air emissions, including

odorous emissions using dispersion modelling or other

acceptable methods

During the course of this study, the design of power plant is still on-going, however, it is understood

that the power plant will be running on natural gas or a combination of natural gas and fuel oil. For

the purpose of this study, it is assumed that the power plant will run primarily on natural gas; the

plant will switch to fuel oil as a backup for a short period when shortages of natural gas may occur.

Air pollution from industrial developments such as the proposed power plant could potentially cause

environmental and human health impacts. Table 2.3-1 below shows some of the potential negative

effects on the human body system, when exposed to high concentrations of air pollutants, usually

associated with power plants and fuel burning industrial facilities.

Table 2.3-1: Summary of potential health impact of air pollutants

Air Pollutant Summary of Potential Health Impact

NOx (as NO2) Asphyxiation, reproductive effects, deep breathing, dizziness,

nausea and unconsciousness.

Carbon Monoxide Reduce oxygen delivery to the body's organs and tissue. Death

could occur at when 40-50% of haemoglobin occupied by CO.

SO2 Pulmonary edema, permanent lung injury or death.

Carbon Dioxide Asphyxiation

Particulate

matter (PM10) Cardiovascular and respiratory diseases

The National Environmental Agency (NEA) stipulates two compliance standards for any activity

potentially polluting the air. The air emission, measured at the discharge point of the source (i.e. tip

of stack) shall comply with the NEA emission standard. The ambient air concentrations of pollutants,

measured at or near the locations of sensitive receptors, which are located mostly at ground level,

shall comply with the National Ambient Air Quality Standard (NAAQS) of the U.S. Environmental

Protection Agency (US-EPA). The following Table 2.3-2 presents the upper-threshold limit of the

mentioned standards for each considered pollutant.




Table 2.3-2: The Limit of Emission Standard (NEA) and Ambient Standard (US-EPA)

Emission

NEA Emission

Standards (gas

power plant)

(mg/Nm3)

US National Ambient Air Quality Standard (NAAQS)

Concentration Averaging Time

NOx (as NO2) 700 53 ppb ~ 100,000 μg/m3

Annual

(Arithmetic Average)

100 ppb ~ 188,000 μg/m3 1-hour

Carbon Monoxide 625 9 ppm ~ 10,000 μg/m3 8-hour

35 ppm ~ 40,000 μg/m3 1-hour

SO2 5

0.03 ppm ~ 80 μg/m3 Annual

(Arithmetic Average)

0.14 ppm ~ 370 μg/m3 24-hour

75 ppb ~ 196 μg/m3 1-hour

Particulate

matter (PM10) 5 150 µg/m3 24-hour

Carbon Dioxide N.A. N.A.

Note:

The NEA Emission Standard is applicable for power plant built after 2008, as advised by NEA.

The NAAQS at unit of μg/m3 is provided for a clearer comparison with the result of dispersion model. The NAAQS

is available at http://www.epa.gov/air/criteria.html

2.3.1 Existing Ambient Air Conditions at Project Location

The air quality of Singapore, according to the 2009 Annual Report of Environmental Protection

Division (EPD) of National Environmental Agency (NEA), is classified as „Good‟ as shown by the

summary of the Pollutant Standards Index (PSI) presented at Table 2.3-3. The 2009 data of most

pollutants concerned by this study are well below the NAASQ of USEPA which is adopted by the

NEA. Exception was found on concentration of fine particulate matter (PM2.5), which is 27% higher

than the NAAQS standard.

Based on the fact that the proposed site is located in an industrial zone, for the purpose of this study,

the industrial concentration level of concerned pollutant at 2009, shown at Table 2.3-4, were

retrieved and were used as background ambient air information for the assessment of impacts.

http://www.epa.gov/air/criteria.html




Table 2.3-3: Summary of Pollutant Standard Index of Singapore

Year Days

No. of days in which the PSI was

classified as Percentage

Good

(0-50)

Moderate

(51-100)

Unhealthy

(0-50)

Good

(0-50)

Moderate

(51-100)

Unhealthy

(0-50)

2008 366 353 13 0 96% 4% 0%

2009 365 333 32 0 91% 9% 0%

Source: 2009 Annual Report of EPD of NEA, page 30

Table 2.3-4: Average ambient conditions of concerned pollutants in Singapore industrial area in 2009

Pollutant Concentration

μg/m3

USEPA

Standard

μg/m3

Averaging Time

Method

NO2 (a) 22 100 Annual mean

CO (b) 1700 10,000 2nd max 8 hour mean

SO2 (c) 18 80 Annual mean

PM10 (d) 80 150 2nd max 24 hour mean

NOTE: Values are retrieved from 2009 Annual Report of EPD of NEA for selected air quality parameters.

2.3.2 Methodology for Air Dispersion Study

To estimate the impacts of the air pollutants released by the proposed power plant, an air dispersion

study was conducted as part of this PCS. The dispersion study aims to estimate the concentrations of

five considered air pollutants (NOx, SO2, CO, CO2 and PM10) expected to be released by the power

plant. The dispersion model was carried using the Breeze AERMOD software, a specially designed

software application, which provides a convenient graphical user interface to the latest USEPA

regulatory air dispersion model known as the version 11103 of AERMOD.

Input data for the dispersion model are stated as follows:

The emission rate for each pollutant, the exit velocity and the stack properties were provided

by short-listed vendors for the proposed power plant.

The relevant meteorological datasets were retrieved from Changi Meteorological station.

The receptors locations are defined purposively to cover the area where the peak

concentration can be expected.

To investigate the trend of dispersion toward the nearest international border with Malaysia, the

profile of concentration for each pollutant were developed. The profile graph is composed from

predicted concentration level at 50 m intervals from stack to up to 1,500 m away along the profile

line. The profile line crosses the international border at approximately 1150 meter away from the

stack, as shown at Figure 2.3-1.




Figure 2.3-1: Cross-border profile line and points of predicted concentrations.

The results from the model are the predicted concentrations for each parameter, which were then

being compared to the allowable limit of USEPA ambient air quality standards. The results of the

model represent the additional concentrations of air pollutants which are contributed by the

proposed power plant. They do not represent the actual ambient air quality in the vicinity of the

power plant, which is affected by other industrial facilities and their air pollutant emissions. However,

the probability of exceedance at ground level considering background ambient air pollution (based on

NEA air pollution monitoring) was assessed here.

2.3.3 Findings of Air Dispersion Study

2.3.3.1 Dispersion of Pollutant

The results of the dispersion model suggest that the additional air pollutants introduced by the

proposed power plant are relatively small. When the maximum predicted GLC is normalized by the

NAAQS value, it is estimated that a maximum of 1.8 % of the allowable concentration limit is added

by the power plant air emissions (see Table 2.3-5). Thus, additional air pollutant emissions remain

well below the NAAQS allowable limits according to the air dispersion model results.




During the southwest monsoon, the concentrations of air pollutant emissions are higher at the north

due to the prevailing wind conditions; peak concentrations are predicted to occur within the distance

of 500 m to 1,000 m from the stack. During the northeast monsoon, maximum concentrations are

expected to occur south of the stack. During the transitional season, as represented by the month of

May, winds will blow air pollutants towards the Johor Strait.

There are no exceedances expected at the international marine border with Malaysia. Elevated

annual maximum concentrations are expected to occur typically to the south of stack. Typical

dispersion of concentrations at ground level is shown in the PM10 concentration map presented at

Figure 2.3-2. PM10 was selected as the indicator pollutant with concentrations closes to the allowable

standard limits. Dispersion maps for each of the other pollutants are presented at Appendix E.

Table 2.3-5: Maximum additional ground level concentrations

Air

Pollutant

Averaging

Time

Maximum predicted ground level

concentrations NAAQS

Allowable Limit

(ug/m3) μg/m3 Normalized by NAAQS

limit (%)

NO2 1-hour 48.655 0.026 188,000

CO 1-hour 97.689 0.244 40,000

8 -hour 79.518 0.795 10,000

SO2 1-hour 2.773 1.415 196

24-hour 1.51 0.408 370

PM10 24-hour 2.679 1.786 150

CO2 24-hour 36,187 - N/A

* Note: Normalization is not applicable to CO2 as its allowable limit is yet to be regulated.




Figure 2.3-2: Estimated ground level concentrations of PM10 showing typical dispersion pattern of

pollutants at ground during different seasons.




2.3.3.2 Dispersion of pollutant toward the International Border of Singapore-Malaysia

At the nearest border point, the maximum additional concentrations of any investigated air pollutant

is estimated to be less than 1% of the allowable limit of NAAQS as shown in Table 2.3-6. The highest

concentrations are estimated to occur during the transitional season from Northeast monsoon to

Southeast monsoon, within which a fraction of wind will blow toward the border located at

approximately 1,150 m west of the stack, as shown at Figure 2.3-2.

Table 2.3-6: Maximum predicted increase of ground concentrations at border

Pollutant Averaging

Time

Maximum predicted increase of

ground concentrations at border NAAQS US-EPA

Allowable Limit

(μg/m3) Concentration,

μg/m3

Normalized

concentration by Allowable limit

NOx 1-hour 30.66 0.02 % 188,000

CO 1-hour 61.57 0.15 % 40,000

8-hour 30.37 0.30 % 10,000

SO2 1-hour 1.75 0.89 % 196

24-hour 0.34 0.09 % 370

PM10 24-hour 0.61 0.41 % 150

CO2 24-hour 8,260.37 - N/A

Regardless of pollutant type, the concentration profiles suggest that the highest concentrations occur

at some distance, approximately between 500 m to 800 m away from the stack. Approaching the

border and beyond, the concentrations are decreasing. Graph showing the trend for PM10 is

presented at Figure 2.3-3. Graphs for other pollutants can be found at Appendix E.

Figure 2.3-3: Spatial profile of additional PM10 concentration at ground level towards the border




2.3.3.3 Estimation of Probability of Air Pollution Exceedances at Ground Level

Assessment of the probability of exceedances was done using the values normalized by the upper

limit of NAAQS, which results in a set of comparable values for each pollutant. The normalized

values of background conditions were derived from NEA‟s monitoring data of 2009 and are

considered as baseline of background pollution near the study area. As shown at Table 2.3-7, the

highest normalized total concentration is expected to be approximately 55%, slightly higher than a

half of permissible limit. Based on this estimation, the likelhood of exceedances of pollutants at

ground level is deemed low.

Table 2.3-7: Estimation of Normalized Total Ground Level Concentration

Pollutant

Ambient Concentration(a) Normalized

Additional

Ground Concentration(c)

Normalized

Total

Ground Concentration(d)

Value

μg/m3

NAAQS

μg/m3

Normalized

value (b)

NO2 22 100 22.00% 0.03% 22.03%

CO 1700 10000 17.00% 0.80% 17.80%

SO2 18 80 22.50% 0.41% 22.91%

PM10 80 150 53.33% 1.79% 55.12%

Note:

(a) the ambient concentration value are based on 2009 Annual Report of EPD-NEA. See Table 2.3-4

(b) normalization was done by division of concentration value by NAAQS limit. Normalized value above100% indicates

an exceedance of the respected threshold.

(c) see Table 2.3-5

(d) sum of normalized ground concentration (c) and normalized ambient concentration (b)

2.3.3.4 Limitation of the Air Dispersion Study

It is important to note that the dispersion study did not consider the scenario of future development

of at the vicinity of the power plant stack. Future buildings near to the site with height of 25 m or

higher, - approximately half of stack height -, will potentially introduce diversion of near ground

winds and hence affect the distribution of ground level concentration of air pollutants. Further details

of the model which include model setup, location of receptors and detailed results are provided at

Appendix E.




2.4 Measures to control air pollution and ensure compliance with

emission standards and requirements in the Code of Practice on

Pollution Control

The following measures should be used to prevent and control accidental release of gases from

chemical storage tanks and pipes:

Leakage indicator devices to be installed with alarms with air operated valves for emergency

shut off in event of leakage.

Mechanical ventilation shall be provided for all chlorine and carbon dioxide indoor dosing

facilities.

Limiting the storage quantity of gaseous chemicals to a minimum required for normal

operations.

The following measures should be used to control the continual release of gases from power plant:

Control of NOx emissions can be accomplished by installation of low-NOx burners and with

the application of post-combustion pollution control equipment such as Selective Catalytic

Reduction. Low-NOx burners were installed by Senoko Power Plant and were successful in

lowering the NOx emission level in line with the new statutory requirement.

Control of CO emissions from incomplete combustion in furnace can be accomplished with

the application of post-combustion pollution control equipment.

Control of polluted air emissions from air intake system can be accomplished by installation of

proper air filter systems and additional precautions may be necessary and require optional

filtration or moisture removal equipment (Wilkes, 2007).

Control of PM10 emissions by installation of post-combustion pollution control equipment

such as gravity settling chamber, mechanical collectors, particulate wet scrubbers, electrostatic

precipitators, fabric filters.

More specific control measures for power plant emissions will be available upon proposal of a more

detailed power plant design by the appointed vendor.

2.5 Measures to control and prevent odour nuisance

Both desalination and power plants are designed to ensure minimal fugitive emissions of such gases.

Chlorine gas and sulphur dioxide are odorous. Measures to be implemented for chlorine gas are as

mentioned in the previous section.

Installation of odour monitoring devices.

Post combustion treatment technologies such as Wet scrubbing/Absorption, mist filtration,

thermal oxidation/ Incineration.


Chapter 3 - Water Pollution


Chapter 3 - WATER POLLUTION

3.1 Sources of trade effluent and pollutant

The potential source of trade effluent and pollutants attributed to the proposed facilities during

construction phase and operational phase are listed on Table 3.1-1.

Table 3.1-1: Identified sources of water pollution

Identified source

Description

Accidental spill

from vessel

construction

Construction activities at sea like the installation of intake pipes, outfall

structures will be carried out using vessel construction. This will pose the risk

of accidental spill of vessel fuel and oil.

Increased

surface run-off

Site clearing activities will convert the land-cover into bare land which will

introduce the increase of surface run-off. This process is expected to cause

erosion which in turn will increase the turbidity in the receiving water-body.

Re-suspension

of sediment

Movement of vessel at shallow water and the installation of offshore pipes and

facilities will likely to cause the re-suspension of material which leads to a

temporary increased turbidity of seawater in the vicinity of the project.

Inadvertent

flow or

chlorinated

water

The chlorinated seawater at pre-treatment facilities could flow back to the

seawater during times when the seawater intake pumps are not in operational

state.

Release of

reject brine

from

desalination

plant

The increased salinity of wastewater from desalination plant will be discharged

at outfall diffuser. The waste stream will contain increased concentration of

existing marine substances by factor of 1.8 as well as additional pollutants

introduced along the process of desalination. At times when power plant

operates, the cooling water will be used to feed desalination plant; the resulted

waste from the integrated operation is anticipated to have elevated temperature

at the order of 7 degree Celcius above background.

Release of

reject cooling

water from

power plant

The proposed design allows for both plants to operate independently for

greater reliability. At times when desalination plant is off, the power plant shall

be able to operate independently delivering power to the national grid. The

reject cooling water will not be released through offshore outfall but through

the shoreline outlet. It is expected that the waste water will have a temperature

of approximately 37.4° C at discharge outlet.




3.2 Quality, rates and quantities of all wastewater streams and final

trade effluent discharges

Table 3.2-1 gives a summary of the flow rates and characteristics of all the individual wastewater

streams from the desalination plant and power plant, assuming that both plants operate at full

capacity.

Table 3.2-1: Flow Rates and Characteristics of All Wastewater Stream

No. Stream Description

Instantaneous

flow rate

m3/hr

Maximum

Flow rate

(MLD)

pH

Total

Suspended

Solids

(mg/l)

Total

Dissolved Solids

(mg/l)

Constituent

of final discharge

(mg/l)

1

Discharged cooling

water from

powerplant

through shoreline

outlet

- 162 8 - - Yes

2

Discharged brine

through offshore

outfall

17,630 509 8 - 58,845 Yes

3

Reject waste

stream from UF-

Feed auto strainer

396 9.5 8 1,200 33,000 Yes

4

Reject waste water

from UF-

Backwashing

process

990 73.7 8 1,000 33,000 Yes

5

Reject waste water

from UF-Cleaning

process

850 0.82 8 1,200 750 Yes

6.

Wastewater from

the CIP activities at

SWRO

2,000

0.15 8 500 350

Yes

7.

Wastewater from

the CIP activities at

LPRO

1,000 Yes

Source :Hyflux design, 2011.




3.2.1 Ambient seawater quality

During the EIA study of the proposed activities, investigations of ambient seawater quality conditions

were conducted extensively. The following description discusses the quality of existing seawater

based on baseline data of the EIA report (PUB, 2011), unless stated otherwise. Locations of ambient

seawater in-situ measurements and water sampling locations for seawater laboratory analysis are

shown on map at Figure 3.2-1.

Figure 3.2-1: Location of EIA's water quality survey station

(Source: EIA report)




3.2.1.1 Temperature

The measured temperatures revealed a mean seawater temperature of 30.6°C. Changes between

depths were small, as typical in shallow tropical waters. The highest average temperature was

recorded during the spring ebb at 31.1 °C. Average temperature for each station during each tidal

season is presented in Table 3.2-2.

Table 3.2-2: Average temperature of seawater in the vicinity of the site

Station

Average Temperature (°C)

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 30.46 30.81 31.22 29.98

WQ02 30.28 30.60 31.26 30.49

WQ03 30.35 30.50 31.18 30.29

WQ04 30.45 30.27 31.20 30.50

WQ05 30.34 30.52 31.16 30.49

WQ06 30.32 30.57 31.15 30.31

WQ07 30.34 30.28 31.16 30.59

WQ08 30.33 30.47 31.14 30.36

WQ09 30.30 30.34 31.13 30.49

WQ10 30.40 30.83 31.10 30.33

WQ11 30.38 30.47 31.19 30.69

MEAN 30.36 30.51 31.17 30.41

Source: EIA baseline data (PUB, 2011)

In December 2010, EnviroPro conducted measurements of seawater surface temperature adjacent to

the proposed site. The measured seawater surface temperature has shown variations across sample

locations between 29.9°C – 33°C, with the mean value of 31.2°C and standard deviation of 0.76°C.

Measurement record at each sampling point is presented at Table 3.2-3. Measurement report is

provided at Appendix G.




Table 3.2-3: Seawater surface temperature of adjacent to the proposed site

Sampling

Point Time Latitude Longitude Temp 01 Temp 02

T01 1.20pm 1°18‟14.28”N 103°37‟14.40”E 32.00 31.00

T02 1.21pm 1°18‟10.92”N 103°37‟12.09”E 31.10 30.80

T03 1.22pm 1°18‟07.61”N 103°37‟07.83”E 31.90 30.20

T04 1.23pm 1°18‟02.77”N 103°37‟07.00”E 32.30 30.70

T05 1.24pm 1°17‟59.21”N 103°37‟02.14”E 33.00 31.10

T06 1.25pm 1°18‟02.32”N 103°36‟58.35”E 30.90 31.30

T07 1.26pm 1°18‟07.81”N 103°36‟57.99”E 31.50 30.50

T08 1.27pm 1°18‟14.18”N 103°37‟03.97”E 31.40 30.80

T09 1.28pm 1°18‟18.60”N 103°37‟10.98”E 31.80 30.90

T10 1.29pm 1°18‟22.29”N 103°37‟02.25”E 30.30 29.90

MEAN 31.62 30.72

Source: Enviro Pro, Seawater Surface Temperature Measurement Report, 2010.

3.2.1.2 Salinity

On average, salinity levels recorded as parts of the EIA baseline studies were lower than typical

marine water i.e. 30 PSU. This could be due to proximity of survey stations to the shoreline, where

rainfall run-off might have diluted the marine water. Similar to the temperature profile, there was a

relatively uniform salinity vertically throughout the water column. The highest average salinity level

was recorded during the spring flood at 31.5 PPT. Average salinity per station at various tidal seasons

is presented in Table 3.2-4.

Table 3.2-4: Average salinity of seawater in the vicinity of the site

Station

Average Salinity (PPT)

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 28.44 29.20 30.85 27.44

WQ02 29.27 28.62 31.57 28.69

WQ03 29.03 28.21 31.59 29.07

WQ04 28.34 27.97 31.57 28.89

WQ05 29.21 28.92 31.56 29.11

WQ06 28.96 29.09 31.57 29.10

WQ07 29.23 27.94 31.59 28.72

WQ08 29.49 29.16 31.64 29.38

WQ09 29.33 28.98 31.51 29.42

WQ10 30.30 30.24 31.46 29.49

WQ11 29.18 28.56 31.60 28.51

MEAN 29.16 28.81 31.50 28.89





3.2.1.3 Dissolved oxygen and PH

The mean dissolved oxygen (DO) concentration in seawater in the vicinity of the site is 6.55 mg/l.

The highest average DO was recorded during the Neap Ebb season at 7.39 mg/l. Average DO

concentration per station at various tidal seasons is presented in Table 3.2-5.

Table 3.2-5: Average DO in the vicinity of the site

Station

Average DO (mg/L)

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 6.14 6.10 6.38 5.90

WQ02 5.93 7.35 6.48 6.69

WQ03 6.11 7.84 6.36 6.27

WQ04 6.87 8.27 6.14 6.65

WQ05 6.07 7.59 6.23 6.51

WQ06 6.14 7.38 6.24 6.32

WQ07 6.10 8.14 6.04 6.75

WQ08 6.15 7.32 5.88 6.35

WQ09 6.14 7.55 6.18 6.47

WQ10 5.99 6.22 5.77 6.38

WQ11 6.35 7.48 6.20 6.81

MEAN 6.18 7.39 6.17 6.46


Levels of pH were also relatively consistent through water column. pH levels ranged between 7.92 to

8.25. The highest average pH was recorded during the Neap Ebb and Spring Flood season at 8.18.

Table 3.2-6: Average pH in the vicinity of the site

Station

Average pH

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 7.92 8.06 8.21 7.96

WQ02 7.93 8.16 8.20 8.04

WQ03 7.94 8.20 8.19 8.01

WQ04 7.96 8.25 8.18 8.03

WQ05 7.94 8.19 8.18 8.03

WQ06 7.93 8.17 8.18 8.01

WQ07 7.95 8.25 8.17 8.04

WQ08 7.97 8.18 8.16 8.02

WQ09 7.96 8.21 8.18 8.03

WQ10 8.02 8.09 8.17 8.02

WQ11 7.96 8.18 8.18 8.04

MEAN 7.95 8.18 8.18 8.02





3.2.1.4 Turbidity &Secchi Depth

Generally, turbidity levels were higher during ebb tide, likely as a result of sediment discharge from

Malaysian rivers. The lowest recorded value was 0.08 NTU at WQ09 during Neap Flood while the

highest value was 10.21 NTU at WQ1. Average turbidity value is 2.9 NTU. Average turbidity level

per station at various tidal seasons is presented in Table 3.2-7

Table 3.2-7: Average turbidity in the vicinity of the site

Station

Average Turbidity (NTU)

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 4.96 8.92 10.21 5.33

WQ02 1.03 4.24 0.76 3.17

WQ03 0.47 3.56 0.76 4.00

WQ04 2.57 3.44 2.39 4.01

WQ05 0.77 3.22 1.66 3.55

WQ06 0.37 3.09 0.93 3.93

WQ07 2.61 3.32 2.18 3.34

WQ08 0.82 2.96 1.57 3.51

WQ09 0.08 2.97 1.43 3.45

WQ10 3.65 2.58 0.54 4.00

WQ11 1.91 4.13 2.01 3.37

MEAN 1.75 3.86 2.22 3.79


All measured Secchi disc depth were above 1.2m depth, the shallowest distance was 1.5 m during

spring ebb at WQ01 site while the deepest distance was 4.3 m at WQ11 site. The least clear

seawater was recorded during neap ebb season at average vision distance is 2.05 meter. Measured

secchi depth per station at various tidal seasons is presented in Table 3.2-8.




Table 3.2-8: Measured secchi depth around the site

Station

Secchi Depth (m)

Neap Flood

(22 June 2010)

Neap Ebb

(8 June 2010)

Spring Flood

(26 May 2010)

Spring Ebb

(28 June 2010)

WQ01 2.4 1.7 2.2 1.5

WQ02 2.6 1.9 2.9 2.4

WQ03 2.9 1.9 2.6 2.5

WQ04 2.9 2.0 1.7 2.0

WQ05 2.9 2.0 2.3 2.5

WQ06 3.1 2.1 2.9 2.5

WQ07 2.5 2.0 1.9 2.2

WQ08 2.9 2.1 2.5 2.3

WQ09 2.9 2.5 2.3 2.0

WQ10 4.3 2.4 1.9 2.2

WQ11 2.5 2.0 2.4 2.5

MEAN 2.90 2.05 2.33 2.24


3.2.1.5 Heavy Metals

Laboratory tests for heavy metal ions included cadmium, chromium, copper, lead, nickel, zinc and

mercury were performed on seawater taken from seven stations. With the exception of Boron, all

heavy metals were recorded at relatively low levels, mostly below detection limits, and well below

the recommended AWQG levels. It is noted that waiver will be requested for the two metals Boron

and Iron.

3.2.1.6 Total Suspended Solids (TSS)

The average laboratory-determined TSS was 5.05 mg/l. Sediment concentrations ranged from 5mg/l

to 45mg/l. At certain times, the prevailing suspended solids concentrations within the raw seawater

taken in by proposed plan will potentially exceed the NEA Trade Effluent Discharge Standards. It is

noted that a waiver will be requested for TSS.




3.2.1.7 Seawater Condition at Proposed Outfall and Intake location.

As shown at Figure 3.2-1, the nearest survey station to the proposed intake and outfall location is

WQ07 and WQ04, respectively. Data from both stations are summarized and compared to NEA

limits at Table 3.2-9.

Table 3.2-9: Measured water quality at Intake and outfall of proposed plants

PARAMETERS Unit Intake

(WQ07)

Outfall

WQ04

NEA Effluent

Discharge Limits Recommended AWQG

Secchi Disc m 1.9 1.70 - ≥ 1.2 m (10th

percentile)

≥ 2.0 m (median)

Temperature °C 30.22 30.26 45 °C ≤ 1°C from background

Salinity PPT 31.62 31.63 - ≤ 5 % from background

pH - 7.92-8.26 7.95-8.26 6 – 9 7.5 ≤ pH ≤ 8.5

Turbidity NTU 4.94 6.15 - ≤ 2.5 NTU (median)

≤ 5.5 NTU (90th

percentile)

DO mg/L 5.36 5.95 - ≥ 3.0 mg/l (any time)

≥ 4.0 mg/l (median)

BOD mg/L 2.32 2.16 50 -

TSS * mg/L 25 11.8 50 ≤ 10 % from

background

Oil and Grease mg/L < 0.1 † < 0.1 † 10 mg/l (total)

10 mg/l

(hydrocarbons)

≤ 3.5 mg/l (median)

≤ 5.0 mg/l (any time)

Iron as Fe * μg/L 647 276 10 mg/l or

10,000 μg/L

-

Boron as B- * mg/L 3.96 4 5 -

Cadmium as Cd μg/L <5 † <5 † 0.1 mg/l ≤ 5.5 µg/l

Chromium as Cr μg/L <5 † <5 † 1 mg/l ≤ 4.4 µg/l

Copper as Cu μg/L <5 † <5 † 0.1 mg/l ≤ 1.3 µg/l

Lead as Pb μg/L <5 † <5 † 0.1 mg/l ≤ 4.4 µg/l

Mercury as Hg μg/L <0.1 † <0.10 † 0.05 mg/l ≤ 0.4 µg/l

Nickel as Ni μg/L <5 † <5 † 1 mg/l -

Phospate as

PO43-

mg/L 0.04 0.04 5 mg/l ≤ 0.07 mg/l (median)

≤ 0.20 mg/l (anytime)

Nitrate as NO3- mg/L 0.41 0.06 - ≤ 0.06 mg/l (median)

≤ 0.09 mg/l (anytime)

Note: † the actual concentration is below detection limit of APHA method

* waivers will be obtained for the concerned parameters




3.2.2 Property of discharged water

The list of substances contained in the final effluent discharge is dependent on the presence and

concentrations of matters in raw seawater and the inclusion of other chemical during the desalination

process. Table 3.2-10 shows the seawater condition upon which the desalination plant is designed.

Table 3.2-10: Seawater content for design condition of desalination plant

Description Unit Data

Plant output (at design

conditions, 100% production)

ml/d

MIGD

136,380

30

Seawater water design

temperature

°C

26-32

Seawater salinity design value g/kg 28-35

pH - 7.8-8.4

Silt density index

(According to ASTM

D4189)

≤7

Total dissolved solids mg/l ≤35,000

Total suspended solids mg/l ≤60

Free carbon dioxide as

CO2 mg/l ≤2.6

Total hardness as

CaCO3 mg/l ≤6,260

Ammonium as NH3 mg/l ≤0.5

Bicarbonate as HCO3 mg/l ≤119.0

Carbonate as CO3 mg/l ≤30

Chloride as Cl mg/l ≤20,000

Sulfate as SO4 mg/l ≤2,900

Nitrate as NO3 mg/l ≤1

Fluoride as F mg/l ≤2

Oil & Grease mg/l ≤10

Biochemical oxygen

demand as O2 mg/l ≤2

Total organic carbon µg/l ≤2,500

Calcium mg/l ≤1100

Magnesium mg/l ≤1500

Sodium mg/l ≤10,000

Potassium mg/l ≤800

Barium mg/l ≤0.1

Strontium mg/l ≤8

Boron mg/l ≤5

Iron mg/l ≤2

Manganese mg/l ≤0.03

Copper mg/l ≤0.03

Zinc mg/l ≤1

Silica mg/l ≤5

Source: Hyflux Design Data, Seawater Content for Design Conditions, 2011

http://en.wikipedia.org/wiki/Calcium

http://en.wikipedia.org/wiki/Calcium

http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/Carbon




http://en.wikipedia.org/wiki/Oxygen




The concentration of each water quality parameter in the effluent discharge will be affected by

operational mode of both plants; 2 of 6 proposed potential operational scenarios were identified as

potential worst case scenarios for the purpose of this study. The determining factor for the selection

of scenarios is the discharge aspect: under scenario 1, the power plant cooling water will discharge

directly to shoreline outfall; under scenario 2, the reject brine of elevated temperature (from power

plant cooling water) will be discharged through offshore outfall diffuser.

Table 3.2-11: Considered scenario for the purpose of this study

Scenario ID Plant operation Remarks

1 Power Plant in

service at 100%

load

Desalination Plant

not in service

Outfall temperature higher than incoming seawater

temperature

Cooling water from power plant will be discharged through

shoreline outfall

2 Power Plant in

service at 100%

load

Desalination Plant

in service at 100%

output

Cooling water from power plant will be desalinated by

desalination plant.

Rejected brine of elevated temperature will be discharged

through offshore outfall.

Excess flow of cooling water from power plant will be

discharged through shoreline outfall

Note : see Table 1.2-2 for complete list of potential operational mode of proposed plants

The projected discharge characteristic will be as follows.

Under scenario 1, the properties of incoming seawater will remain the same as properties of

discharge cooling water, with the exception of the temperature aspect. Estimated temperature

of the discharged of cooling water is 36.4°C, which is approximately 7°C above ambient

condition. The warmer water will be discharged through shoreline outfall at flow rate of

990 MLD.

Under scenario 2, the concentration of water quality parameters of intake seawater will

increase in the reject brine through the RO process. In addition, temperatures of the brine

discharge are predicted to be elevated by approximately 7°C at the offshore outfall, as cooling

water from the power plant will be fed to the RO plant. The elevated temperature brine will

be discharged through the offshore outfall diffuser at a flow rate of 509 MLD. Excess flow of

cooling water from the power plant will be discharged through the shoreline outfall at a

maximum rate of 162 MLD

Detail of estimated properties of discharged water is presented on Table 3.2-12.




Table 3.2-12: Properties of discharged water for Scenario 1 and 2

Description Units Scenario 1 Scenario 2

Calcium mg/l as Ca 382 621

Magnesium mg/l as Mg 1,268 2,062

Sodium mg/l as Na 10,060 16,365

Potassium mg/l as K 361 587

Ammonia mg/l as NH3 ND ND

Barium mg/l as Ba 0.01 0.02

Strontium mg/l as Sr 7.2 11.71

Bicarbonate mg/l as HCO3 130 221

Sulphate mg/l as Ca 2,537 4,125.63

Chloride mg/l as SO4 18,255 29,686.02

Fluoride mg/l as F 1.9 3.09

Nitrate mg/l as NO3 0.9 1.46

Boron mg/l as B 4.5* 7.32*

Silica mg/l as SiO2 5.2 8.46

TDS mg/l 33,000 53,679

pH 8 8.6

Temperature 36.4 36.4

Suspended solids 17 27.6

Scale inhibitor 0 2.6

Source: Hyflux design, 2011

3.2.3 Potential impact during construction stage

3.2.3.1 Impact of the increased surface water run-off

Any increase of surface water or stormwater over the construction site, may lead to reduced light

penetration and smothering of sessile benthic organisms, which in turn may result in reduced

photosynthesis activities. This is expected to be an impact of temporary nature on the marine life and

will cease after construction is completed. Given the small footprint of site (approximately 14 ha),

the additional run off volume could be regarded as minimal and highly localized, thus the impact is

deemed negligible. Off surface water run-off, only 50% will be discharge directly to the sea, the

remaining half will be discharge to the PUB surface water drainage system in Tuas South Avenue 3.

Implementation of erosion control measure specified in section 3.3.1 will mitigate the risk of

unnecessary erosion.




3.2.3.2 Impact of accidental spill from vessel construction

Vessel spill during marine construction could occur and may affect marine biota and

ecosystems, water column, nearby SingSpring desalination plant, reservoirs in the region (3.5km)

and the intertidal community of neighbouring country (3.1km). The level of impact is dependent on

the types of chemical used and their toxicity. However, the effects are likely to be temporary and

localised on any communities or ecosystems because quantities of chemicals stored and used would

generally be small. Medium or significant spills are considered unlikely to occur. The risk of an

accidental spill affecting the neighbouring reservoirs and intertidal community of neighbouring

country were rated as low because the quantity of any spill is likely to be small and the reservoirs

and nearest shore are located at a sufficient distance from the Project area to minimise the

impact. The risk of an accidental spill affecting the SingSpring desalination plant were rated high

because of the close distance between SingSpring desalination plant and Project area.

Implementation of vessel spill measure, explained in section3.3.1, will mitigate the risk of

unnecessary vessel spill.

3.2.3.3 Impact of Dredging for Intake and Outfall Structures

The proposed project requires dredging to place the intake and outfall pipeline at the desired levels

into the seabed. Dredging work is estimated to excavate the seafloor material at the volume of 2,400

m3 and 2,160 m3 from intake area and the outfall area respectively. Dredging will be carried by

clamshell bucket or long arm excavator mounted on barge. It has been estimated that the dredging

work would require, in a longest stretch, continuous dredging-covering work of 2 weeks duration.

This would likely disturb some biological habitats and affect the associated biological communities,

although disturbance would likely be localized to around the SEPs. Benthic communities are most

likely to be affected by seabed clearing. There may be localized damage to the seabed and the plants

and animals that inhabit the affected areas. Generally, marine mammals are expected to avoid

disturbed areas due to noise and vibration from construction activities, so it is unlikely that clearing

activities would affect these species. The consequence of these activities are not considered to be

significant as long arm excavator mounted on barge would be removed from the marine environment

upon completion of construction of the marine outfall and it is expected that these communities

would recover to their original state after construction activities are complete, provided no further

disturbance takes place. Secondary impacts due to dredging (such as dispersal of sand from the

seabed) would also only occur for a short period of time. An increase in turbidity of the seawater

reduces light penetration and leads to reduce sunlight reaching benthic communities.




It is understood that the seabed material is one of course silty materials which is coarse, non-

cohesive when loosen, and settle readily in a water column. It is also known from past land

reclamation and dredging activities in the vicinity of the project area that such dredging work could

generate local higher concentration of suspended solids. The TSS concentration has been known to

be in the range of 200 – 400 ppt which is assumed at the sustained rate, generated in the dredging

zone for the duration of the works..i.e. 2 weeks. After that the TSS concentration will decrease and

return to the ambient condition. The spreading of the TSS to the intakes in its vicinity, if any, will be

most severe during that period of 2 weeks. As such, the following initial and boundary conditions are

assumed as shown at Table 3.2-13.

Table 3.2-13: Assumed Initial Boundary Condition

Parameter Assumed Initial Condition

Ambient TSS 10 ppt

TSS at source Scenario A - 200 ppt

Scenario B – 400 ppt

Source: Report on Assessment of Dredging Effect. See Appendix F

The tidal hydrodynamic package used is DELFT-3D and the period of simulation is set for 2 weeks

(Feb 01 – Feb 15, 2011), and the appropriate tidal harmonics are used as the boundary conditions to

simulate the tidal flow in Singapore waters.




Scenario A: Source TSS – 200 ppt

Figure 3.2-2 shows the TSS distribution corresponding to Scenario A over a typical tidal cycle (at 2

hours interval). The ambient TSS is 10 ppt. It can be seen that the TSS plume adheres to the shore

and the TSS envelope of (10.0 + 0.05 ppt) lies well within the Singapore waters. The high

concentration TSS plume is not present. The TSS concentration in Singspring intake location does

not rise beyond +0.05 ppt.

Figure 3.2-2: Distribution of TSS plume in West Johore Strait over 1 tidal cycle (12 hours),

at 2-hour interval – Scenario A (source TSS – 200 ppt).

(Source: Dr. Tan Soon Keat, 2011)




Scenario B: Source TSS – 400 ppt

Figure 3.2-3 shows the TSS distribution corresponding to Scenario A over a typical tidal cycle (at 2

hours interval). The ambient TSS is 10 ppt. It can be seen that the TSS plume adheres to the shore

and the TSS envelope of (10.0 + 0.05 ppt) lies well within the Singapore waters. The high

concentration TSS plume is not present. The TSS concentration in Singspring intake location does

not rise beyond +0.05 ppt.

Figure 3.2-3: Distribution of TSS plume in West Johore Strait over 1 tidal cycle (12 hours),

at 2-hour interval – Scenario B (source TSS – 400 ppt).


The far field simulation studies of the dispersion of TSS (continuous sustain TSS concentration of 200

ppt and 400 ppt) show that the area covered by marginally higher TSS concentration is small despite

the rather high TSS concentration at source. The plume has a marginally higher TSS concentration,

i.e. 0,05 ppt above the ambient of 10 ppt.




It can be concluded that the TSS generated due to dredging operation has relatively little or negligible

impact on the coastal waters around the project area. Any impact on seawater quality will be

temporary and will cease when construction is completed. On the other side, there may be some

beneficial effects of dredging. Locally, it can increase dissolved oxygen content of the water column,

achieved through induced mixing by the dredging activities, thus reintroducing air into the seawater.

The removal of the dredged sediments also helps to remove possible polluted sediments, which may

induce adverse chemical reactions on the seabed if left alone.

3.2.4 Potential impact during operational stage

At operational stage various impacts to the receiving watercourse were identified and summarized in

the followings.

3.2.4.1 Impact of Increased Salinity

RO concentrates are often denser then seawater of natural salinities, hence, plumes tend to extend

further along the seafloor than at the surface. Therefore, macro-benthic organisms tend to be at

greater risk of exposure to RO concentrate discharges as compared to pelagic and planktonic

organism. Sedentary organism living on or in the seafloor in proximity to outfall diffuser, which are

unable to move from the impact zone and are intolerant to high salinity, will be likely to be more

affected.

In addition, potential seawater quality impacts within a mixing zone from the outfall discharge point

need to be considered. Depending on the design of the outfall, bathymetry at the outfall discharge

point and marine ambient conditions (i.e currents and tides), the RO concentrate could lead to

visible seawater quality impacts, which may extend to or beyond the marine border with Malaysia.

A quantitative assessment of the potential seawater quality impacts by the brine discharge / RO

concentrate from the proposed TuasSpring desalination plant was conducted. The proposed

desalination plant makes use of the RO process for water treatment. Seawater is drawn in from the

coastal intake and discharge at a higher reject concentration. As a result, the salinity-values of the

source and discharge seawater are as follows:

TDS (Salinity Water temperature

Source (ambient) seawater 29.5 ppt 29.0 deg C

Discharge seawater 54.6 ppt 36.4 deg C *

* Caused by elevated temperature power plant cooling water as source water to desalination plant




A power plant will be built on site to provide power as well as warmer seawater to the desalination

plant, either as source water or as dilution water in the reject stream. For evaluation purposes, focus

was on the outfall discharge of the RO plant, including the scenarios when the desalination is

operated at 10% and 100% capacity, and with and without using the cooling water from the power

plant. There are 4 scenarios as summarised in Table 3.2-14.

Table 3.2-14: Test scenarios of outfall discharge (TDS and Temperature)

Scenario Discharge rate

(MLD)

Total Dissolved

Solids (ppt)

Temperature

(deg C)

1 54.0 54.6 36.4

2 509.8 54.6 36.4

3 54.0 54.6 29.0 (ambient)

4 509.8 54.6 29.0 (ambient)

The design for the offshore outfall discharge is shown in the schematic sketch in Figure 3.2-4 and

Figure 3.2-5. The outfall pipe conveys the discharge from the plant to the outfall diffuser, and

terminated approximately 120 m away from the shore as shown in Figure 3.2-4. The diffuser nozzles

are located elevated at the top cap and are set at 90.259 MRL, corresponding to -8.105 below Chart

Datum. There are 12 nozzles directed radially and horizontally outwards, issuing at 10 m/s at the

nozzle (250 mm diameter). The nozzles are about 1 m above the seabed.

Figure 3.2-4: A schematic sketch of the outfall pipe.

(Source: Hyflux, 2011)




Figure 3.2-5: A schematic sketch of the outfall diffuser with discharge nozzle.

(Source: Hyflux, 2011)

Seabed Contour

The seabed bathymetry nearer the shore (within ~150 m) is generally straight and parallel to the

shoreline. However, the vertical gradient is generally steep reaching –8 m within 100 m from the

shore.

As the brine discharge is a negatively buoyant, i.e. the discharge stream is denser than the receiving

water, the plume issued from the discharge outlet would sink to the bed and be carried by the

momentum of the discharge into the deeper water, following the sloping terrain, and away from the

shoreline. The plume mixes with the receiving water and is diluted in the process. In the case where

the discharge water temperature is elevated at 36.4 deg C, the discharge plume is approximately

neutrally buoyant. In any case, the design of the diffuser is to create turbulent mixing (by the jet

impinging in the ambient water), whereby the discharged plume is diluted to close to ambient

seawater salinity within a certain distance from the diffuser.

While the interpretation is generally correct, the discharging flow actually sets up entrained flow

along its trajectory. Figure 3.2-6 shows a diagrammatic representation of the core flow and the

entrained flow. Therefore, while the core of the plume exhibits the highest TDS (saline)

concentration, part of the saline content is also being spread radially from the core.




Depending on its distance from the core flow, the salinity could be elevated. It follows that there is

an optimum distance from the outlet location beyond which the plume‟s influence is insignificant.

Figure 3.2-6: A diagrammatic representation of the core flow and the secondary flow

as a result of flow entrainment in the receiving water body.


In the case of the neutrally buoyant plume, the trajectory will be one of horizontal distribution. It is

to be noted that the above general assessment is based on still receiving water body such as an inland

lake or an enclosed basin. The effect of tide and current/wave would modify the picture.

The design for outfall discharge shown in the original drawings is a vertical-diffuser or vertical riser at

the end of the transport pipe and 12 horizontal discharge ports/nozzles at the top cap, issuing the

discharge radially and horizontally at 10 m/s at the nozzles, see Figure 3.2-5. The nozzles are

approximately 1 m above seabed and set at -8.105 below the Chart Datum.

In general, the longer the plume trajectory is designed, the better the initial mixing with the ambient

seawater. Better initial mixing will reduce the salinity build-up near the discharge area and the return

point, where the plume sinks back to the seafloor. Longer plume trajectories from the discharge

ports can be designed through an inclined angle of the discharge nozzles. Research has shown that

60 degrees inclined dense jets for brine discharge from desalination plants achieve a maximum mixing

efficiency. However, the terminal rise may be relatively high and thus not suitable for disposal in

shallow coastal waters without the risk if the discharge plume rising to the surface. For this reason

and the purpose of this assessment, a horizontal discharge direction has been assumed.

Core

flow

Plan view Elevation




Figure 3.2-7: The trajectory at an inclined 60 degree angle with a terminal rise height (Zt) and return

point (Xr). Zo indicates the height of the height of the discharge point above seafloor level. The shades in the plume are indicative of the brine dilution.

(Source: Shao and Law, 2010.)

Simulation study – near field mixing of TDS and thermal plume

Of the 4 scenarios, Scenarios 1 and 2 are less critical (10% capacity) as the mass of salinity (TDS) are

much lower when the plant is operating at full capacity, Scenarios 2 and 4. The near field evaluation is

carried out for Scenarios 2 and 4 first. If under these scenarios and the entrainment mixing near field

could produce satisfactory dilution, then scenarios 1 and 3, being of lower TDS mass discharge,

satisfactory dilution will also be achieved within the distance stipulated. The near field

entrainment/mixing (in quiescent water) assessment is performed using CORMIX. The results of

analysis for Scenarios 2 and 4, as well as the distribution of the thermal plume at near field (mixing) in

quiescent water are presented below.

Scenario 2: TDS of 54.6 ppt at 36.4 deg C, Q = 509.8 MLD

Figure 3.2-8 shows the dilution profile of the salinity (TDS) for Scenario 2. The ordinate (vertical

axis) shows the TDS expressed in part per thousand (ppt). The minimum TDS, based on minimum

dilution, refers to the minimum dilution or largest ppt at the cross-section (distance from the

nozzle).

It can be seen from Figure 3.2-8 that the dilution is rapid immediately after the flow leaves the nozzle,

reducing to a minimum dilution to about 34 ppt (about 6 times dilution or 84% reduction in TDS

concentration) within 10m from the nozzle. Mixing dilution reaches lower than 30.5 ppt at about 45

m from the nozzle. In terms of average dilution, the TDS plume could be viewed as completely mixed

and diluted to ambient condition within 20 m from the nozzle. It is also noted that the plume would

have touched the seabed about 8 m from the nozzle.




Figure 3.2-8: The dilution profile (minimum and averageTDS concentration) – Scenario 2.





Scenario 4: TDS of 54.6 ppt at 29 deg C, Q=509.8 MLD

It is noted that the elevated temperature in Scenario 2 is not large, and the effect of buoyancy within

the mixing zone with an exit speed of 10 m/s is relatively minor. This is shown by the result in for

Figure 3.2-9. For all intent and purposes, Figure 3.2-8 and Figure 3.2-9 could be considered identical.

Figure 3.2-9: The dilution profile (minimum and average TDS concentration) – Scenario 4.

(Source: Dr. Tan Soon Keat)

29




Thermal Plume – discharge of 509.8 MLD and temperature of 36.4 deg C

Figure 3.2-10 shows the temperature distribution over longitudinal distance from the nozzle. It can

be seen that the temperature of the plume decreases rapidly, dropping to within 1 deg C above

ambient within 15m (minimum temperature). The temperature drops to less than 0.2 deg C above

ambient within 70 m from the nozzle.

29.00

30.00

31.00

32.00

33.00

34.00

35.00

36.00

37.00

0 10 20 30 40 50 60 70 80 90

Tem

pe

ratu

re (d

eg

C)

Distance from nozzle (m)

Nearfield Dispersion of Thermal Plume

Minimum Temperature Average temperature

Figure 3.2-10: The dilution profile (minimum and average temperature) – Q = 509.8 MLD at 36.4 deg C.


The near field mixing assessment shows that the salinity/TDS concentration and temperature plume

will be diluted to close to ambient condition within 70 m from the nozzle based on the current

outfall configuration design.




Dispersion of TDS and thermal plume

Although it has been shown that the TDS and thermal plume could be diluted to close to ambient

condition within 70 m from the nozzle, in quiescent water, it is of interest to evaluate the worst

cases of non-mixing scenario at source, and the plume is advected and dispersed by the tidal

currents. The simulation is performed using DELFT-3D.

Scenario 2: TDS of 54.6 ppt at 36.4 deg C, Q = 509.8 MLD

Figure 3.2-11 shows the TDS distribution corresponding to Scenario 2 over a typical tidal cycle (at 2

hours interval). The ambient TDS is 29.5 ppt. It can be seen that the plume adheres to the shore and

the TDS envelope of (29.5 + 0.1 ppt) lies well within the Singapore waters.

Figure 3.2-11: Distribution of TDS plume in West Johore Strait over 1 tidal cycle (12 hours), at 2-hour

interval – Scenario 2.





Scenario 4: TDS of 54.6 ppt at 29 deg C, Q = 509.8 MLD

Figure 3.2-12 shows the TDS distribution corresponding to Scenario 4 over a typical tidal cycle (at 2

hours interval). The ambient TDS is 29.5 ppt. It can be seen that the plume adheres to the shore and

the TDS envelope of (29.5 + 0.1 ppt) lies well within the Singapore waters.

It can be seen that the results are consistent with that of scenario 2 and that the effect of

temperature is insignificant in this case.

Figure 3.2-12: Distribution of TDS plume in West Johor Strait over 1 tidal cycle (12 hours),

at 2-hour interval – Scenario 4.





Thermal Plume – discharge of 509.8 MLD and temperature of 36.4 deg C

Figure 3.2-13 shows the temperature distribution at the shore of the project area. The ambient

temperature is taken as 29 deg C. It can be seen that the thermal plume adheres to the shore,

dropping to within 0.1 deg C within a short distance from the shore and well within the international

boundary.

Figure 3.2-13: Distribution of thermal plume in West Johore Strait over 1 tidal cycle (12 hours), at 2-hour

interval. The discharge rate is 509.8 MLD.

Source: Dr. Tan Soon Keat, 2011




Overall, the findings of the far-field simulation are consistent with the findings of the near-field

mixing. The plumes‟ TDS diffuse and disperse to marginally higher levels than the ambient seawater

within a short distance (~70m) from the discharge and has minor to negligible impact on the marine

environment and the international boundary. The following summary statements are made:

The intensity of mixing with the discharge port/nozzle (250 mm diameter) issuing the jets at 10

m/s produced rapid mixing and dilution of the TDS and temperature.

Within 70 m of the nozzle, the concentration and temperature of the plume has been diluted /

reduced to close to ambient conditions.

The TDS and thermal plume, at full discharge (509 MLD, 54.6 ppt of TDS, and warmer

temperature of 36.4 deg C) do not appear to cause significant changes to the TDS

concentration and temperature at the international boundary.

Neighbouring intake, if any, will not be affected as long as the structure is located more than

70 m away from the outfall diffuser.

3.3 Measures to ensure compliance with requirements in the Code

of Practice

3.3.1 Measure during construction stage

3.3.1.1 Measure to mitigate the risk of accidental spills

Periodic inspection of vessel condition

Limit on-vessel storage and/or use of hazardous substances and dangerous goods

Arrange mechanical containment such as booms, barrier and, skimmer as well as natural

sorbent materials to capture and store the spilled oil until it can be disposed of properly

around the vessel

Desalination plant owner could prepare mechanical containment near intake port as a

secondary protection

3.3.1.2 Measure to minimize Erosion, Site Run-off and Water Quality Impacts

Before Site Preparation can be done, Earth Control Measures (ECM) are proposed to be put in place

throughout the duration of the construction activities to prevent silt from being washed into

neighbouring water bodies during storm events.




The ECM includes an Erosion Control Plan, which is to minimize the formation of bare surfaces that

can be exposed to rainfall to prevent erosion. The Sediment Control Plan is to capture sediments

washed down from the construction site to minimize pollution to nearby waterways. The

implementation of the ECM is to facilitate earthworks, which will generate large volumes of loose

earth and will greatly increase the sediment particles in the runoffs when exposed to rain. Since the

construction site is at a higher ground and is close to water bodies, any increase in sediment particles

in the runoffs will eventually pollute the environment.

An Environmental Control Officer (ECO) should be engaged throughout the construction activities

to provide advice in the following:

Control of disease-bearing vectors and rodents

Proper management and disposal of solid and liquid waste

Control of noise and dust pollution

Drainage Control

General Housekeeping

Mitigation measures will be required during the construction to prevent unacceptable water quality

impacts from storm-water runoff and other sources that could enter the marine environment during

construction. Water pollution control will need to comply with requirements in Environmental

Protection and Management Act and associated water regulations and standards, and be conducted in

a manner to minimize on water quality within and outside the site. PUB‟s relevant regulations, codes

and trade effluent standards need to be complied with. For instance, NEA‟s/PUB‟s Trade Effluent

Standards for Discharge into Watercourses and Controlled Watercourses prescribe a Total

Suspended Solids (TSS) concentration of not more than 50mg/L (Watercourse) and 30mg/L

(Controlled Watercourse).

A number of mitigation measures are recommended to avoid unacceptable water quality impacts

during the shaft construction phase. These include:

No construction site runoff should be allowed to enter any public sewer, natural watercourse

or canals adjacent to the site;

Temporary perimeter surface water drainage channels and inert solid removal facilities should

be constructed in advance of site formation and earth works to divert drainage to treatment

areas and avoid unacceptable impacts on natural water courses and adjacent marshlands.

Surface run-off sites should be directed into adequately designed sand and silt removal facilities

such as sand traps, silt traps and sediment basins before discharge into any natural drainage

channel.




Earthwork surfaces should be compacted and the subsequent surface protected (i.e. gravel) to

prevent erosion caused by rainstorms. A temporary access road should have proper

temporary side drainage systems installed.

Temporary, open storage of excavated materials shall be covered with tarpaulin or similar

fabric during storm events. Any washout of construction or excavated materials from

excavation and site formation should be diverted to appropriate sediment traps, to achieve a

controlled flow of storm flow and construction runoff.

Any groundwater pumped out of boreholes, bored piles or any other subsurface structure

should be discharged into sediment traps to enhance deposition rates and remove silt before

discharge into adjacent watercourses.

A wheel washing facility should be provided at every site exit. Wheel washing activities, which

ensure that no earth, mud and debris is deposited on roads, shall be settled out and removed

before discharging into storm drains.

Wastewater discharged from the wash-down of trucks and drums should, wherever

practicable, be recycled. To prevent pollution from wastewater overflow, the pump sump of

any water recycling system should be provided with an on-line standby pump of adequate

capacity.

Oil interceptors should be provided in the construction site runoff drainage system, in addition

to the silt removal facility, and be regularly (weekly) emptied to prevent the release of oils and

grease into the storm-water drainage system after any accidental spillage. The interceptor

should be provided with a bypass to prevent flushing during periods of rainfall.

All generators, fuel and oil storage facilities on site should be adequately bunded for minimum

containment of 1.5 times storage volume. Any drainage from these areas shall be connected to

storm drains via an oil interceptor device.

If any office, site canteen or toilet facilities is erected at the construction site, then foul water

effluent shall be directed to a foul water sewer or to a sewage treatment and disposal facility

either directly or indirectly by means of pumping or approved method.

Vehicle and plant servicing areas, vehicle wash bays should be located under roofed structures.

The drainage in these covered areas should be connected to foul sewers via an oil interceptor

or be tinkered away for proper disposal. Oil spillage or leakage should be contained and

cleaned up immediately. Waste oil should be collected and stored for recycling in accordance

with the EPMA (Hazardous Substances) Regulations.

Debris and rubbish shall be properly handled and disposed of to avoid entering watercourses

and causing water quality impacts.




3.3.1.3 Measure to minimize the re-suspension of sediments from dredging

Dredging of sand will be done from designated approved area of the river following MPA guidelines

The dredging is carried out within the areas specified in the application and the dredging depth

does not exceed 1.0m of the specified dredging depth.

Dredging will be limited to a maximum of two weeks continuously.

Minor dredging of the trench shall be carried by clamshell bucket or long arm excavator

mounted on barge. Small bucket of size 3m3 shall be deployed to minimise seabed disturbance.

The seabed material to be removed from this dredging has been tested and found to be non-

toxic.

Random checks are required to ensure that the dredging activities are carried out in

accordance with the application.

The inverted trapezoidal trench of 4m x 14m x 2m height shall extend 120m seawards for

outfall pipeline.

The inverted trapezoidal trench of 7m x 25m x 3m height shall extend 50m seawards for

Intake pipeline.

The GRP pipes for Intake and Outfall are 2 x 2.5m diameter and 1.6m diameter respectively.

A number of management techniques and mitigation measures have been developed, such as tidal

dredging, physical barriers e.g. silt screens, which may be used to mitigate effects of dredging on

sensitive organisms.

3.3.2 Measure to minimize impacts during operations

To avoid the flow of chlorine into the sea from intake tank, the chlorine pump operates should

only be operated when intake pumps are in operation.

Continual monitoring of chlorine concentration at inlet of intake pipe, the monitoring system

should be able to alert operator at control room or de-activates the chlorine pump.

To avoid entrainment and entrapment of fish within intake, the flow velocity at the openings

shall not exceed 10 cm/s for open intake and 30cm/s for opening connected to intake bay.

Wastewater shall be directed to neutralization tank prior to disposal through outfall.

Limiting the discharge velocity to maximum 10 m/s to ensure that the temperature will be

diluted close to ambient condition within 50 m from the nozzle.




3.3.3 Measure to minimize water quality impacts during operations

Iron oxide, boron and TSS concentrations exceed the NEA Trade Effluent Discharge Standards

at the desalination outfall, due to the relatively high background levels and the concentration

effect of the desalination process. A waiver has been requested in from NEA to allow for these

exceedances within the mixing zone.

Recommended Ambient Water Quality Guidelines for salinity and temperature are exceeded

within the 70m outfall diffuser mixing zone. The concentrations for these parameters are

brought back to compliant levels at the boundary of the mixing zone.

As no exceedances of the recommended Ambient Water Quality Guidelines for is predicted

outside the mixing zone for ammonia, nitrate, nitrite, phosphate, or chlorophyll-a, there is no

additional measures needed.

There are no significant adverse visual effects predicted from the outfall discharge stream.

3.4 Monitoring programme – Parameters monitored, type of

monitoring equipment, frequency of monitoring

Continual monitoring of Chlorine concentration at the intake port and outfall diffuser. The

system should be able to alert operator immediately or synchronized with intake pumps and

chlorine pumps.

Continual monitoring of seawater properties at the boundary of mixing zone near diffuser

outfall

Continual monitoring of seawater properties at points near power plant‟s shoreline outfall


Chapter 4 – Noise Pollution


Chapter 4 - NOISE POLLUTION

4.1 Sources of noise pollution

There is potential noise and vibration during construction work from pile driver, loader, truck, and

dredging and vessel movement.

The sources of noise from the desalination plant have been identified. Noise may originate from

high-energy pumps used to pressurize seawater during Reverse Osmosis process, the pumps are

used to force seawater through the RO membranes. The other 2 potential sources of noise come

from blowers and back-up generator.

The potential sources of noise from the combine-cycle power plant are from main buildings and

cooling towers.

4.2 Existing ambient noise

During the course of the study, the Consultant conducted the ambient noise measurement at five

points at the boundary of the proposed site; three of which were located along pedestrian way along

the eastern perimeter; the remaining two were positioned at the corner at seaward direction from

the site. Details of location can be found at Figure 4.2-2.

The measurement of existing ambient noise at the proposed site shows that the higher noises were

received at the locations along pedestrian way than those at points near the sea. Along pedestrian

lane, the measured range of noise level is 52 – 91 dBA at the mean value of 65.8 dBA; The prominent

source of which are trucks and other form of heavy vehicles. The summary graph and table are

presented in Figure 4.2-1and Table 4.2-1.




Figure 4.2-1: Ambient Noise at Proposed Site. Point N1 & N5 are located at seaward corner, N2, N3, N4

are located at pedestrian lane at eastern border of the site. The bar indicates the range of recorded value; the dot indicates mean value.

Table 4.2-1: Summary of Ambient Noise at Proposed Site

Point Time of measurement Noise Level, dBA

Min Max Mean Stdev

N1 12:15:21 - 12:32:54 45.2 63.0 49.491 2.270

N2 11:24:54 - 11:44:04 58.2 83.7 68.557 5.356

N3 10:54:32 - 11:11:35 52.7 91.6 66.370 6.139

N4 10:15:01 - 10:32:52 52.2 87.0 65.808 6.010

N5 12:45:02 - 13:04:48 40.4 73.9 44.933 4.993




Figure 4.2-2: Location of noise measurements at Tuas area

4.2.1 Estimates of noise levels emitted during construction

The noise emitted during construction work on land will be mainly from the pile driver, loader and

trucks. The estimated noise level 15 meter from source is estimated to be in the range of 85dBA to

101dBA (refer to Appendix H) The implementation of noise control measures, explained in section

4.4, will mitigate the risk of noise pollution.

The vibration emitted during construction work on land will be mainly from the same sources as

mentioned above. The proposed site is an industrial area whith no presence of fragile buildings or

hospitals or clinics. The construction period is expected to be 24 months. It is expected that there is

no prolonged distrubance or damage from construction vibration.




No impacts are predicted at any aquaculture facility or any seagrass, coral or mangrove habitat due

to the small scale of the marine component by noise and vibration during dredging and vessel

movement.

Reference to the noise level at desalination plant was obtained through measurement of noise at

boundary of a similar operational plant, the SingSpring desalination plant, which is located at north to

the proposed site as shown at Figure 4.2-3. Based on field observation, two points (N6 and N8) were

considered representative as the main source of noise is the process from within the plant. N6 was

located at southern perimeter of the plant; N8 was located at northern perimeter. Of the two

representative measurement points, noise at N8 point is the highest, yet it is still below the allowable

limit of noise level stipulated by NEA.

Figure 4.2-3: Noise level at the perimeter of SingSpring Desalination Plant.

The measurement was conducted at day time for about 15 minutes at frequency of 1 reading per

second.




Being closer to the main road, point N7 deemed inappropriate for the purpose of reference, as

higher value of recorded noises at this point was primarily attributed to moving heavy vehicles.

Summary at Figure 4.2-2 suggest that existing plant emits less noise to pedestrian as compare to

those traffic during the day.

Table 4.2-2: Summary of ambient noise at Singspring perimeter


Min Max Mean Stdev

N6* 13:11:23 - 13:29:57 44.8 63.7 47.67 2.04

N7 13:58:00 - 14:17:57 57.3 92.7 68.107 4.503

N8 14:22:34 - 14:40:14 51.5 66.9 54.535 1.705

Source: Enviro Pro, Analysis of noise data.

Note : * with noises attributed to the passing by fighter plane removed

Noise emitted from the desalination plant‟s back-up generator is estimated to be 1.5 dBA. However,

as this is a back-up generator, no noise will be emitted from the generator during routine operation.

Additional reference with regards to the noise levels at the proposed power plant was obtained

through the measurement of ambient noise at the boundary of similar power plant‟s configuration,

which is the Senoko power plant (See Figure 4.2-4). Four data points were obtained; Points S1 and

S2 were collected at the south and southwest portion of the site while points S3 and S4 were

located at the southeast and eastern perimeter of the plant. Based from the four representative

measurement points, noise collected at S4 yields the highest reading and still remains below the

allowable limit stipulated by NEA (see Figure 4.2-5).




Figure 4.2-4: Location of noise measurements at Senoko Power Plant Area




Figure 4.2-5: Representative noise level data collected at the perimeter of Senoko Power Plant

The measurement was conducted at day time and operation‟s peak load for about 15 minutes at a

frequency of 1 reading per second. Be noted that noises attributed to the passing by vehicle

removed.

The noise data from S4 were collected from 11:03:13 to 11:18:12, whereby, the power plant was

operating at peak load. It is noted that the noise level readings ranged from 57.4dBA to 67.1dBA,

which was collected from a distance of approximately 70 meters east of the power station‟s main

building. Generally, the readings showed allowable limit per noise regulations for industrial standards

in Singapore. Other noise generating sources were also noted, which were primarily from the nearby

metal welding factory and passing vehicles.

If the configuration of Senoko power plant is to be adapted by the proposed natural gas power plant

in Tuas, it is potential the the generated noise emissions will also be below the allowable limit. The

summary shown in Table 4.2-3 suggests that the existing power plant emits noise in compliance with

the limit per noise regulations for industrial standards.




Table 4.2-3: Summary of Ambient Noise at Senoko Perimeter


Min Max Mean Stdev

S1* 12:51:11 - 12:06:10 44.4 58.7 47.479 1.806

S2 12:27:49 - 12:42:48 46.4 56.5 48.330 0.904

S3 11:39:44 - 11:58:43 52.2 62.7 54.444 1.479

S4* 11:03:13 - 11:18:12 57.4 67.1 59.479 1.397

Source: Enviro Pro, Analysis of noise data.

Note : * removed noises attributed to the passing by vehicle.

4.3 Impacts of the noise emissions i.e. the noise levels at the

receptors surrounding the plant especially residential housing

The nearest sensitive receptors with regard to noise are the Singspring Desalination Plant and the

Tuas South Incinerator Plant, which are sited, in close proximity to the proposed plant. The

proposed plant is not expected to impact upon these nearby facilities in terms of noise pollution.

4.4 Measures to control noise pollution and ensure compliance with

noise emission standards and requirements in the Code of

Practice on Pollution Control

As the proposed area is an industrial area, there is no residential sensitive receiver nearby. However

measures to control noise emission should be taken and ensure compliance with the standard.

Avoid use of an impact pile driver where possible in noise-sensitive areas. Drilled piles or the use of a

sonic or vibratory pile driver are quieter alternatives where the geological conditions permit their

use. As it is an industrial area, re-route of truck traffic is unnecessary.

Enclosures of noise-generating equipment e.g. pumps, blowers and back-up generator are

implemented as a measure to control noise generated from the proposed plant to meet the

requirements as set in the Code of Practice on Pollution Control. It is anticipated that when properly

placed noise barrier will provide noise control in the 10 to 15 dBA range.

The boundary noise requirements set in the Code of Practice on Pollution Control are given in Table

4.4-1 below.




Table 4.4-1: Boundary Noise Requirements

Type of Premises

Maximum permitted noise level in decibels (dBA)

Day

7 am – 7 pm

Evening

7 pm – 11 pm

Night

11 pm – 7 pm

Factory Premises 75 70 65

Source: NEA 2004

Equipment inspection and noise measurements are to be carried out by the manufacturer‟s

workshop and after installation on site to ensure that the noise emission limits stipulated in

regulation are met.

4.5 Monitoring programme – Type of monitoring equipment/test

carried out, frequency of monitoring

Due to the insensitive nature of surrounding industries and far distance to residential areas, routine

monitoring is proposed only during the construction phase. However after facility commissioning an

assessment of boundary noise levels could be undertaken to ensure the plant operations is within

permissible limits.


Chapter 5 – Management of Hazardous Chemicals


Chapter 5 - MANAGEMENT OF

HAZARDOUS CHEMICALS

5.1 Inventory and storage of hazardous chemicals

Table 5.1-1 provides a full inventory of all substances stored in bulk storage and following sections

details the management measures undertaken for each to ensure proper storage.

Table 5.1-1: Chemicals used in proposed facilities

Item Designation Storage type & size

DESALINATION PLANT

1 Ammonium sulphate 52 x 50kg bags

2 Carbon dioxide 2 x 28 tonnes vertical steel tanks

3 Citric acid 4 x 50kg

4 Hydrated Lime 2 x 36 tonnes silos

5 Permatreat® PC-1020 24980 x 1.169 kg drums

6 Sodium bisulphite 12 x 50kg bags

7 Sodium hydroxide 2 x 60 tonnes FRP tanks

8 Sodium hypochlorite 10.5% concentration: 2 @ 25 m3 tanks.

0.2% concentration: 2 @ 100 m3 tanks.

9 Sodium lauryl sulphate 15 x 20kg

10 Sodium silicofluoride 50 x 50kg bags

11 Sodium tripolyphosphonate 404 x 50kg bags

12 Tetrasodium EDTA 180 x 50kg bags

POWERPLANT

13 Ammonia No Information Provided

14 Argon No Information Provided

15 Hydrazine No Information Provided

16 Hydrogen (H2) No Information Provided

17 Nitrogen Gas (N2) No Information Provided

18 Phosphate No Information Provided

Source: Hyflux preliminary design data, 2011

Note that according to the Code of Practice on Pollution Control (CPPC), the following substances

are classified as hazardous substances in Singapore

Ammonia;

Hydrazine;

Sodium hydroxide; and,

Sodium silicofluoride




5.2 Evaluation of the acute and chronic hazardous impacts of each

hazardous chemical and/or by-products to the environment and

public health

Table 5.2-1: Human Health & Environmental Risks of Stored Chemicals

Chemical Carcinogenic Other health hazards Environmental Impact

Ammonium

Sulphate

No Inhalation: Causes irritation to the

respiratory tract.

Ingestion: Causes irritation to the

gastrointestinal tract.

Skin contact: Causes irritation to

skin.

Eye contact: Causes irritation,

redness and pain.

#

Sodium bisulphite No Irritating to skin, eyes and

respiratory tract

Harmful to aquatic life

in very low

concentrations

Sodium hydroxide No Inhalation:

Mild irritation to destructive burns

to respiratory system / lung

inflammation

Skin contact: Irritation, can cause

severe burn with scarring

Eye contact:

Severe damage to the eye, risk of

blindness if not removed quickly

Ingestion:

Severe burn to tissue in mouth,

throat and gastro-intestinal tract.

May be fatal

Toxic to aquatic

organisms, may cause

long-term adverse

effects in the aquatic

environment

Toxic effect on fish and

plankton, harmful effect

due to pH shift

Sodium

hypochlorite

No Inhalation: Strong irritating to

mucous membranes in the nose,

throat and respiratory tract

Skin contact: irritation,

redness, pain and drying and cracking

of the skin

Eye contact: Strongly irritating to

eyes. Exposure to vapor can cause

tearing, conjunctivitis and burning of

the eyes. Eye contact may cause a

corneal injury

Ingestion: Corrosive. Can cause

severe corrosion of and damage to

the gastrointestinal tract

Acutely toxic to aquatic

lifes. The chlorine in

bleach can also bind

with organic material in

the marine environment

to form

organochlorines, toxic

compounds that can

persist in the

environment

# In powder form, hence not expected to result in spillage/leakage




Table 5.2-1 (Cont’d): Human Health & Environmental Risks of Stored Chemicals


Argon No May cause suffocation,

dizziness, drowsiness,

nausea, vomiting, excess

salivation, diminished mental

alertness, loss of

consciousness and death.

No adverse ecological

effects are expected. It

does not contain any

Class I or Class II Ozone

depleting chemicals (40

CFR Part 82). Argon is

also not listed as a marine

pollutant by DOT (49

CFR Part 171)

Citric acid No Irritating to eyes and skin

when exposed.

Products of

biodegradation: Possible

hazardous short-term

biodegradation products

are not likely, however

long term biodegradation

products may arise.

Nitrogen Gas (N2) No Simple asphyxiant, loss of

balance or dizziness,

Tightness in the frontal area

of the forehead and/or

death.

No adverse ecological

effects are expected.

Nitrogen does not contain

any Class I or Class II

ozone depleting chemicals.

Nitrogen is not listed as a

marine pollutant by DOT

(49 CFR 171)

Permatreat® PC-1020 No Eye contact: May cause

irritation with prolonged

contact.

Breakdown of this

compound in the marine

environment could elevate

phosphorous levels in

marine water increasing

the risk of eutrophication.

Sodium lauryl sulphate No Irritating to eyes and skin.

Harmful if swallowed.

Toxic for aquatic

organisms.

Sodium

tripolyphosphate

No Pain and redness when

contact with skin or eye,

cough or sore throat upon

inhalation

High pH may affect

effluent and sewage

processes.

Tetrasodium EDTA No Eye contact: Causes eye

irritation. May cause

chemical conjunctivitis.

Skin contact: May cause skin

irritation.

Inhalation: Dust may cause

irritation of the respiratory

tract. Can produce delayed

pulmonary edema.

Harmful to aquatic

organisms, may cause

long-term adverse effects

in aquatic environment.




Table 5.2-1 (Cont’d): Human Health & Environmental Risks of Stored Chemicals


Ammonia No Ingestion will result to

freeze burns of the mouth,

throat and stomach. Eye

contact can cause corneal

burns and/or freeze burns to

the eye. Skin contact may

cause burns. Inhalation may

cause suffocation, chest pain,

bronchospasm, pink frothy

sputum and pulmonary

oedema. May be developed

to acute bronchitis and

pneumonia. Long term

exposure may cause

chemical pneumonitis and

kidney damage.

Very toxic to aquatic

organisms. It is strongly

absorbed to soil and

sediment particles and

colloids in water. It

also affects smog and

decreased visibility

when combined with

NOx and SOx by

forming fine

particulates.

Calcium hydroxide,

(Hydrated lime)

No Moderately caustic irritant

to all exposed surfaces of

the body including the eyes

and the respiratory tract.

Not expected to bio

accumulate.

Carbon dioxide No High concentration may

cause asphyxiation.

Symptoms may include loss

of mobility/consciousness

When discharged in

large quantities may

contribute to the

greenhouse effect

Hydrazine Yes

(Probable)

Corrosive, Burning

sensation, cough, headache,

nausea, convulsion, skin

burns, redness, eyes deep

burns, abdominal cramps,

confusion, unconsciousness,

vomiting and weakness.

Very toxic to aquatic

organisms and may

cause long-term

damage in the

environment.

Hydrogen No Dizziness, deeper breathing,

possible nausea and eventual

unconsciousness

Potentially be

considered as an

indirect greenhouse gas

with the potential to

increase global

warming.

Phosphate No Mild skin irritation, digestive

tract and mucous membrane

irritation, nausea, vomiting,

abdominal discomfort,

diarrhea, dermatitis, mental

confusion, muscle weakness,

accelerated breathing, heart

block, cardiac arrythmias,

peripheral vascular collapse

and flaccid paralysis,

Excessive phosphates

in water bodies may

result to algae growth.

Sodium silicofluoride No Toxic by ingestion and skin

contact

Harmful to aquatic life




5.2.1 Human Health Risk

Most of the chemicals used here are non-carcinogenic aside from Hydrazine, which is identified as a

probable carcinogenic substance. Usual health effects of all the substances used at the facilities are

mainly burns, irritations, suffocation, pains and even death, if over exposed. Thus, extra safety

measures must be taken into consideration during the operation.

5.2.2 Environment

In terms of environmental impact, a major issue is water quality. Most of the gases and liquids used

and stored are classified as harmful to aquatic organisms. Impacts upon the seawater quality and

marine organisms could be derived from the accidental release of these chemicals from storage into

the environment directly.

It is concluded that many of the chemicals held on site, if not handled and stored properly, according

to the MSDS and guidelines, could have impacts upon health and the environment. However this

must be put into perspective in terms of the risks of spills and/or leaks, the resultant probability that

any will enter surface waters and/or create toxic gases and most importantly, the control and safety

measures undertaken to prevent leakage and spillage of the chemicals, discussed in the next section.

5.3 Measures for safe storage and handling of hazardous substances

to ensure compliance with requirements in the code of practice

on Pollution Control and EPMA and to safeguard the

environment and public health

Carbon dioxide will be stored in pressurised double skinned storage steel tanks that will be

located outdoors. Dosing equipment will be located indoors and leak detectors will be

provided.

All chlorine and CO2 facilities which are located indoor (if any) will be provided with

mechanical ventilation.

Nitrogen must only be used only in well-ventilated areas. Valve protection caps must remain in

place unless cylinder is secured with valve outlet piped at use point.

For Argon, Hydrogen and Phosphate, the cylinders must be protected from physical damages,

do not drag, roll, slide, or drop. Prevent entrapment of liquid in closed systems or piping




without pressure relief devices. Store in a well-ventilated area with valve protection cap in

place, and firmly secured.

Personal protective covering (e.g. safety glasses, face shields, spacesuits etc.) should be worn

by workers handling hazardous chemicals.

All liquid chemical bulk storage tanks will be located in bunds, to enable leakages and spillages

to be contained for control discharge by dilution or neutralisation and dilution, depending on

the quantities, into drainage pits. Major leakages: Due to tank rupture or tank outlet pipe

break contained in the bunds and removed by a specialist contract for off-site disposal. Bunds

will be provided with level switches for alarm initiation.

Chemicals include: Caustic soda

All tanks where chemical delivered in bags or liquids delivered in carboys will also be located in

bunds and handling of leakages and spillages will be as described above.

Chemicals include: Sodium silicofluoride, ammonium sulphate, sodium bisulphite, anti-

scalants and RO cleaning chemicals.

All chemical solution/slurry-dosing pumps will also be located in bunds and leakages will be

contained as described for storage tanks.

Spillages and leakages in bunded areas will be washed down and collected in drain pits. These

pits will also collect washings from solution / slurry tanks, when they are cleaned. Non-

compatible chemicals will not be collected in the same pit. Of the chemicals only lime tanks

will be drained frequently. Cleaning of other solution preparation tanks will be infrequent;

washing down of spillages will also be infrequent and concentrations will be low as leakages will

be very small.

The connection point for a filling pipe of chlorine and carbon dioxide bulk storage tanks shall

be provided with measures to contain spillage.

The control measures to prevent leakage of chemicals that are harmful to marine life

are as follows:

Sodium Silicofluoride: Should be stored where it cannot come in contact with acidic substances

for fear of development of hydrogen fluoride in the event of damage of containers or leakage.

Ammonia: Should be stored in a cool, well ventilated area, away from sources of heat or

ignition and foodstuffs. Storage away from oxidising agents, boron halides, acids, acid

anehydrides, acid chlorides, halogens (i.e chlorine), interhalogens, heavy metals and their salts,

ethylene oxide, hypochlorous acid and acetaldehyde, Check cylinders regularly for leaks. The

transport of liquefied ammonia in a tank or bulk container made of quenched and tempered




steel is prohibited unless liquefied ammonia contains not less than 0.2% water mass. Ensure

pressure gauges and fittings are not made of copper, zinc or alloys (i.e. brass).

Hydrazine should be stored in tightly closed, well-labelled containers in an inert atmosphere, in

a clean, well-ventilated area with controlled drainage. Store away from oxidizing agents, acids,

metals, metal oxides, porous materials, direct sunlight, or other sources of heat or ignition.

The containers should be connected to earth to prevent static sparks.

5.4 Policy and procedure to ensure all necessary measures to

prevent accidents involving hazardous substances would be

adopted

The company shall:

Prepare an emergency action plan to cover all eventualities of accidents and emergencies.

Keep records of all accidents and conduct review of existing emergency action plan in line with

changes in the plant process.

Conduct safety audits to systematically identify and rectify weakness in their management

systems and practices for handling hazardous substances on a regular basis. The companies can

either conduct their own safety audits in-house or engage accredited consultants to do so on

their behalf.

Maintain and ensure an updated and relevant hazardous substance license and records of the

quantity of hazardous substances stored.

5.5 Monitoring programme – Type of monitoring equipment to

detect any leakage of hazardous substances, frequency of checks

Leak Detectors will be provided for Chlorine and CO2 facilities

Visual inspection of storage tanks on routine basis to check for leaks.


Chapter 6 – Toxic Wastes Management


Chapter 6 - TOXIC WASTES

MANAGEMENT

6.1 Inventory and storage of toxic industrial wastes, including waste

oil, solvent and other solid wastes

The processes within the proposed plant do no generate any continuous toxic wastes streams that

require storage, treatment and disposal. But as a result of toxic chemicals usage and consumables,

there is some solid industrial waste generated. These wastes are proposed to be treated off-site by

licensed contractor or collected back by suppliers for disposal. They are:

Empty bags with residue of chemicals

Empty chemical drums with residue of chemicals

Used membranes

6.2 Measures for safe storage and handling of toxic industrial wastes

to ensure compliance with requirements in the code of Practice

on pollution control

Empty bags of powdered chemicals will be collected and stored in disposal containers within a

hazardous waste store. They will be collected and disposed by licensed contractor for off-site

disposal

Empty tanks and containers will be stored in designated areas within their respective chemical

storage areas. They will be collected back by the respective supplier for recycling.

Used membranes will be collected and send for off-site disposal by licensed contractor.

6.2.1 System of checks on the safe storage and handling of toxic

industrial wastes

The plant shall:

Clearly labelled all empty chemical containers of their original contents

Maintain proper inventory records of wastes collected and disposed

Ensure all wastes are stored in a hazardous waste store, following guidelines in CPPC 2000.

Ensure all industrial wastes collection and disposal is carried out by a licensed waste collector

as approved by NEA.


Chapter 7 – Recycling and Resources Conservation


Chapter 7 - RECYCLING AND

RESOURCES CONSERVATION

The plant has been designed to minimise the used of water and electricity through reuse of water

and energy recovery. All water used within the proposed plant is derived from the process itself.

7.1 Study the feasibility and recommend measures to reduce, reuse

and recycle wastes generated from the plants

7.1.1 Water

It is projected that no sludge will be generated at the proposed facilities. When the system operates

at warranted capacity, the second pass RO unit is estimated to generate of approximately 1.2 million

meter cubic of brine on monthly basis. This reject stream is proposed to be re-used as backwash

water to clean the UF unit in the pre-treatment stage. Additional backwash water required will be

drawn from the filtered seawater.

A rainwater recycling system for the use in toilet flushing within the Administration Building will be

built. For this purpose, a rainwater harvesting and storage tank will be located on top of the roof of

the Administration Building. A dual piping system will allow for the provision of rainwater for toilet

flushing. Stormwater from more than 10% of the site‟s surface area will be collected, retained and

treated in a Bio-Retention Basin.

7.2 Study the feasibility and recommend measures to conserve

energy and water use in the plant

7.2.1 Energy

The majority of consumption is derived from pumping of the water and waste streams through the

process and the power to air blowers. A pressure exchanger or DWEER (isobaric devices) is

proposed to recover hydraulic energy from the SWRO system and transfer it to LPRO feed water.

ERS booster pumps will then boost up the pressurized feed water from energy recovery unit to the

required pressure for the operation of the SWRO membranes.


Chapter 8 – Prevention of Land Contamination


Chapter 8 - PREVENTION OF LAND

CONTAMINATION

8.1 Sources of potential land contamination

Potential sources of land contamination originating from the site and associated operations include

leakage from the bulk storage tanks and pipelines. These potential sources are described under the

hazardous substances management section detailed in chapter Chapter 5 -

8.2 Estimates of impacts from such sources on land contamination

Possible scenarios that may arise from impacts of land contamination from these potential sources

include:

Where contamination remains on-site;

Where the contamination is transported off-site; and

Where the contamination is present on-site as well as is transported off-site

Depending on the affected media, i.e. soil, these scenarios can be identified. Issues that may arise

from land contamination comprise of adverse effects on human health and on surrounding sensitive

receptors. Effects on human health may either be acute or chronic depending on the type of impact

and may be limited to only site-users or people not associated with site use depend on whether the

contamination remains on-site or is transported off-site. For contamination to pose threats to

surroundings sensitive receptors, including those of an ecological nature, the contamination would

have to have travelled off-site.

In addition to the above, it should be noted that the site and its surrounding areas are used for heavy

industrial purposes and the following should also be considered:

Where practicable, each storage area is design with aboveground tanks where any leaks would

be visible and could thus be acted upon before any significant impact occurs.

Each chemical storage area has containment facilities and leak detectors thus if systems act in

accordance with design then no land contamination should occur.

The majority of hazardous substances stored on-site are solids and gases. Leakages will be

contained in bunds and leakage detectors with alarms will shut off transfer valves upon

detection.

Groundwater in Singapore, including that of Jurong Island, is not considered a resource and

thus is not abstracted for potable or any other use presently and is not planned for in the

future.




The potential impacts from contaminants stored on-site are discussed briefly below should a spill or

leak occur.

Sodium hydroxide is completely soluble in water and may infiltrate soils to contaminate

groundwater. The alkaline nature of sodium hydroxide will cause a shift in pH of water bodies

it contaminates, causing possible toxic effect on marine life.

Sodium bisulphite is miscible in all proportions in water and is highly reactive. It will lower pH

of groundwater and is harmful to aquatic life.

Permatreat 1020 is an organic phosphonate that is completely soluble in water. It distributes

itself to water and soil in the following respective percentages: 30-50%; 50– 70%. Its stronger

affinity to soil indicates that it may persist in the environment. It is not expected to bio-

accumulate.

Ammonia is strongly absorbed to soil and sediment particles and colloids in water.

Contaminating waterways should be avoided.

Hydrazine degradation in water may be slow, depending on the conditions. Hydrazine may

present hazard for aquatic organisms and plant life.

Of the chemicals discussed, all of them are highly soluble in water, thus they are not expected to

persist in the environment, except for Permatreat 1020, which have a stronger affinity to soil, the

Ammonia, which colloids in water, and Hydrazine, which may have slow degradation state.

8.3 Measures to prevent land contamination

As stated under the hazardous substance management section above various measures are

incorporated into the design of the facility to minimize the risk of contamination of soil and ground

water, specifically:

Storage of chemicals shall be in bunded areas with spill containment facilities and ventilation.

Where practicable, all tanks are above ground for easy inspection and gas tanks are equipped

with gas detectors that would switch off all concerned transfer valves upon detection of

leakage.

All industrial activities, including storage, shall be carried out within a sheltered area, to

prevent pollution. Industrial activities are not allowed in open areas.

Wastewater generated from industrial activities shall be collected and discharged into the

public sewer via an appropriate wastewater treatment plant. A sampling sump shall also

be provided at the discharge point for monitoring of treated effluent discharge. The quality of

the treated effluent shall comply with the Sewerage & Drainage (Trade Effluent) Regulations.




8.4 Monitoring programme, if appropriate

Continuous leak monitoring of storage areas and tanks.

Routine visual inspection of storage areas and tanks.


Chapter 9 - Conclusion


Chapter 9 - CONCLUSION

9.1 Whether the proposed measures in part 2 to 8 are adequate to

insure compliance with statutory requirements and the Code of

Practice on Pollution Control

This study has quantified and evaluated the potential emissions and environmental impacts for

TuaSpring‟s proposed desalination plant to be housed on Tuas South Ave 3. The basic findings of the

study are summarised in Table 9.1-1below.

Table 9.1-1: Summary of pollutive emissions from proposed plants

Report Section Emission Type Proposed Abatement Technology

Predicted

Emission/ Waste

Air Air pollutants emitted by

power plant: NO, CO,

SO2, CO, CO2.

Leakage of fugitive gas

from storage tank

Installation of low-NOx burners, air

filter, particulate wet scrubbers.

Installation of leak detector system.

630 m3/s ~

54,532 MLD

Water Trade effluent (saline

wastewater) discharge to

sea

Treated wastewater at neutralizing

tank prior to discharge at point of

8m seawater depth, 120 m offshore

509.8 MLD

Noise Noise from operating

pumps, air blowers and

back-up generator

Enclosures for all noise generating

equipment

< 65 dBA

at site

boundary

Management of

Hazardous

Chemicals

Accidents and leaks Containment bunds for all chemical

bulk storage tanks, chemicals

delivered in bags or carboys,

chemical dosing pumps.

Various procedures and emergency

action plans

None

Toxic Waste

Management

Empty packaging of

chemicals such as drums,

bags and tanks

Off site disposal by licensed

contractor or returned to supplier

for disposal or recycling

Not available

Prevention of

Land

Contamination

Chemical storage tanks

and drums

Storage of chemicals shall be in

bunded areas with spill containment

facilities and ventilation.

All chemical storage tanks above

ground for easy inspection. Gas

tanks are equipped with gas

detectors that would switch off all

concerned transfer valves upon

detection of leakage.

None




9.1.1 Air

The proposed desalination plant is designed to international best practice and no odour, air pollution

or heat emission is expected from storage, handling and utilization of chemicals. Appropriate

measures will be implemented to arrest any accidental fugitive emissions.

The proposed power plant is designed so as the emission of air pollutant to the atmosphere will

comply with the NEA Emission Standard. The air dispersion study has shown that the ground level

concentration of released pollutant will be well below the National Ambient Air Quality Standard of

the US-EPA. Appropriate measure will be implemented during the design phase to ensure that the

released air pollutant concentration will be minimal.

9.1.2 Water

Trade effluent discharge to the sea will comply with international practice. Offshore discharge of

saline plume using a submerged outfall is employed as a mitigation measure to dilute the saline plume

with seawater through jet and natural mixing. The outfall pipe carries the brine effluent to a distance

of 120m off the shoreline. The outfall pipe has a single diffuser port at horizontal orientation and

discharges perpendicularly away from the shore. The bed bathymetry around the outfall, shown in

the bathymetric survey, shows a gentle downward slope away from shore that will further direct the

negatively buoyant plume away from the intake near the proposed discharge point. To achieve the

optimum seawater depth of 8 m or more, this gentle downward slope will be extended to meet the

discharge point through dredging. Proper mitigation and monitoring measures will be implemented

to ensure minimum temporary pollution impacts during dredging. Overall, the findings of the far-field

simulation are consistent with the findings of the near-field mixing. The plumes‟ TDS diffuse and

disperse to marginally higher levels than the ambient seawater within a short distance (~70m) from

the discharge and has minor to negligible impact on the marine environment and the international

boundary. A waiver on a highly saline discharge will be requested from NEA.

Another parameter of concern is total suspended solids (TSS). The far field simulation studies of the

dispersion of TSS (continuous sustain TSS concentration of 200 ppt and 400 ppt) show that the area

covered by marginally higher TSS concentration is small despite the rather high TSS concentration at

source. The plume has a marginally higher TSS concentration, i.e. 0,05 ppt above the ambient of 10

ppt.

It can be concluded that the TSS generated due to dredging operation has relatively little or negligible

impact on the coastal waters around the project area. Any impact on seawater quality will be

temporary and will cease when construction is completed.




Discharge TSS concentrations during operations are estimated to be between 17-27 mg/L, based on

NEA‟s ambient seawater quality data. The potential problem of high TSS discharge is closely

correlated to fluctuating levels of TSS concentrations in ambient seawater. These can exceed

Singapore Trade Effluent Regulations in the Tuas area at intake, for which a waiver will be requested.

Though levels of other parameters such as COD and nutrients are estimated not to be excessive,

potential localised pollution of marine water, following discharge of brine water from the proposed

outfall location of the plant, may occur under certain conditions (e.g. membrane cleaning, accidental

leakages). Under normal plant operating conditions, overall levels of process chemicals (e.g. anti-

scalants) in the final trade effluent are estimated to be within allowable limits. It must be noted that

ambient seawater quality in the area is impacted by other sources. For example, the drainage channel

at the northern end of the site influences quality characteristics of surrounding seawater.

9.1.3 Noise

Noise from workshop/factory operations is expected to meet EPMA standards.

9.1.4 Management of Hazardous Substances

Storage, containment and operational procedural plans for hazardous substances expected to be

stored on site conforms to international best practices and complies with EPMA and CPPC.

9.1.5 Toxic Waste Management

No continuous toxic waste streams will be generated by the desalination process. As a result of toxic

chemicals usage and consumable, there are some solid industrial wastes generated. These empty

packaging of chemicals and consumable will be collected and sent for off-site disposal by licensed

contractor or returned to supplier for recycling. The measures implemented for the storage of such

wastes are expected to meet EPMA standards.

9.1.6 Recycling and Resources Conservation

The proposed plant has been designed to minimize the use of water and electricity through reuse of

water and energy recovery using isobaric pressure exchanger as Energy Recovery System.

9.1.7 Prevention of Land Contamination

The proposed development has been designed to minimize risks of future impacts to soil and

groundwater.




The findings of this study are based upon plans and information as submitted by TuasSpring and

Hyflux. The measures proposed to mitigate potential environmental impacts described herein are

adequate to ensure compliance with the Environmental Protection and Management Act and the

Code of Practice on Pollution Control.

9.2 Whether the proposed plants and their operations would pose

any significant pollution impact on the environment and on

developments in their vicinity, including odour, noise and dust

nuisances

The site is zoned for heavy industry use. Immediate neighbours are the SingSpring Desalination Plant

at North and the Tuas Incinerator Plant at South. The site‟s sensitive receptor is seawater with

elevated levels for certain seawater quality parameters, with the nearest residential area of

substantial distance away. As such potential impacts upon the general public are minimised.

No pollutive air emission is expected from the proposed desalination plant. Continues emission of air

pollutant is expected from the proposed power plant. The study on the dispersion of pollutant has

shown that the ambient ground level concentration will be well within the US-EPA standard for any

pollutant concerned. Emission level of pollutant will be compliant to the NEA Emission standard for

power plants built after 2008. Noise generating equipments within both plants will be housed in

enclosures to attain the boundary noise levels as stipulated by Singapore EPMA. The proposed

desalination plant will produce up to 318.5 MLD of potable water to PUB and stores and uses

various hazardous substances. The desalination process has been designed to minimised waste. An

isobaric energy recovery system will recover the excess energy from the high pressure reject SWRO

brine. Hazardous substance storage and containment facilities will meet Singapore EPMA and

International best practice, except for substances for which waivers had been obtained. Hazardous

wastes generated by the proposed plant will be collected safely and sent for off-site disposal by

licensed contractor or sent back to supplier for recycling.

For all the activities discussed, it has been demonstrated that the facility generally meets regulations

and guidelines detailed within the EPMA and CPPC. The proposed discharge to the sea was designed

with reference to international practice and waivers will be obtained from relevant authorities for

Boron, Iron, TDS and TSS at a minimum.

Based upon these findings, it is concluded that the development and its proposed control, treatment

and disposal methods, including proposed discharge to the sea will not pose a significant pollution

impact on the environment, as long as the recommendations for abatement technologies and

operations are implemented.




9.3 Limitations

This report was written for the client TuasSpring, for the purposes of required submission to the

Ministry of Environment Singapore.

The findings of the report were based upon information and discussions as follows:

Information submitted to the consultant from Hydrochem, namely:

Site layout and plans

Power plant emission data

Process flow charts, description and data

Chemicals usage storage inventory and MSDSs

Information from Environmental Impact Assessment Report for the proposed facilities.

Near field and far field discharge modelling reports from Dr Tan Soon Keat of NTU.


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