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Corrosive, erosive, eroding, corroding, oxidizing, rusting eating away, biting, disinfecting properties of water or wastewater.

Activated carbon

Adsorptive particles or granules of carbon usually obtained by heating carbon (such as wood). These particles or granules have a high capacity to selectively remove certain trace and soluble materials from water.

Active, Beautiful, Clean (ABC) Waters Programme

The Active, Beautiful, Clean Waters (ABC Waters) programme was launched in 2006 as a long-term initiative by national water agency PUB to transform Singapore’s drains, canals and reservoirs beyond their traditional functions of drainage, flood control and water storage into beautiful streams, rivers and lakes that are well-integrated with the surrounding parks and spaces. 

The ABC Waters programme is part of PUB’s strategic objective to bring Singaporeans closer to water so that they can better appreciate and cherish this precious resource, and at the same time, create new focal points and recreational spaces for the community to enjoy. These ABC Waters projects will also enhance our quality of living, in line with the vision of transforming Singapore into a ‘City of Gardens and Water’.

More than 20 projects have been completed island-wide by PUB. More than 100 potential sites have been identified for implementation by 2030.


The acid-neutralizing capacity of water or wastewater. Alkalinity in wastewater results from the presence of carbonate, bicarbonate and hydroxide. The quantitative determination of alkalinity involves neutralizing the bases found in water with standardized strong acid.


Ammonia is a colorless gas with a very distinct odor. This odor is familiar to many people because ammonia is used in smelling salts, many household and industrial cleaners, and window-cleaning products.

Ammonia occurs naturally and is produced by human activity, e.g. bacteria found in the intestines can produce ammonia. It is an important source of nitrogen which is needed by plants and animals. Ammonia is applied directly into soil on farm fields, and is used to make fertilizers for farm crops, lawns, and plants.

Ammonia gas can be dissolved in water. This kind of ammonia is called liquid ammonia or aqueous ammonia. Once exposed to open air, liquid ammonia quickly turns into a gas.

Ammonical Nitrogen (NH3-N)

A measure for the amount of Ammonia.


Biochemical oxygen demand (BOD)

A chemical procedure for determining how fast biological organisms use up oxygen in a body of water. It is usually performed over a 5-day period at 20° Celsius. BOD is not an accurate quantitative test, although it could be considered as an indication of the quality of a water source. BOD is used as a gauge of the effectiveness of wastewater treatment plants.


Chemical Oxygen Demand (COD)

A test commonly used to indirectly measure the amount of organic compounds in water.


Compounds formed by the reaction of hypochlorous acid (or aqueous chlorine) with ammonia.

Chloride (Cl-)

Chloride, in the form of Cl-, is one of the major inorganic ions in water and wastewater. The salty taste produced by chloride concentrations is variable and depends on the chemical composition of the water. Some waters containing 250 mg Cl-/L may have a detectable salty taste if the cation present is sodium. But when the predominant cations are calcium and magnesium, the salty taste may be absent in water containing as much as 1,000 mg/L.

City of Gardens and Water

By integrating the streams, rivers and lakes with the parks and gardens in a holistic way, new community spaces can be created. These will be bustling with life and activities, and transform Singapore into a City of Gardens and Water, a vision outlined by Singapore’s Prime Minister Lee Hsien Loong in 2007.


Chemicals that cause very fine particles to clump (floc) together into larger particles. This makes it easier to separate the solids from the water by settling, skimming, draining or filtering.


The clumping together of very fine particles into larger particles (floc) caused by the use of chemicals (coagulants). The chemicals neutralize the electrical charges of the fine particles, allowing them to come closer and form larger clumps. This clumping together makes it easier to separate the solids from the water, by settling, skimming, draining or filtering.

Coliform Bacteria

A group of bacteria commonly found in the intestines of animals and humans beings. Coliform count is used as a hygiene indicator. The test is performed via membrane filtration, and filters placed onto selective agar. After incubation, plates are counted and suspect colonies confirmed with confirmation tests (lactose fermentation)


Very small, finely divided solids (particles that do not dissolve) that remain dispersed in a liquid for a long time due to their small size and electrical charge. When most of the particles in the water have negative electrical charge, they tend to repel each other. This repulsion prevents the particles from clumping together, becoming heavier, and settling out.


A measure of the ability of an aqueous solution to carry an electric current. This phenomenon is not only shown in metals such as iron but also in water. The conductivity value of water depends on the presence of ions, total concentration, mobility of ions and valence, and also the water temperature during measurement. Ion concentration and temperature have a proportional effect on water conductivity. Solutions of most inorganic compounds are relatively good conductors, whereas molecules of organic compounds that do not dissociate in aqueous solution show poor conductivity.

Conserving water

Securing an adequate supply is only half of the water equation – managing the demand side is just as crucial. PUB has a wide-ranging water conservation plan that encourages customers to use water wisely. Singapore’s per capita domestic water consumption has been brought down from 165 litres per day in 2003 to the current 155 litres. The target is to lower it to 140 litres by 2030.



Design, Build, Operate and Own – A contract awarded under the Public Private Partnership (PPP) initiative by PUB.

Deep Tunnel Sewerage System (DTSS)

Deep Tunnel Sewerage System - The $3.65 billion DTSS is Singapore's superhighway to meet its used water needs for the next 100 years. Conceptualised and managed by Singapore's national water agency, PUB.

Desalinated Water

Like its predecessor NEWater, desalinated water is the result of PUB's continued investments in water technologies and research. Recent advancements in technology and cheaper membrane prices have made desalinated water another viable source of water supply for Singapore.


The removal of dissolved salts (such as sodium chloride, NaCl) from water by specific water treatment processes.


The process designed to kill or inactivate most microorganisms in water, including essentially all pathogenic (disease-causing) bacteria. There are several ways to disinfect, with chlorination being the most frequently used in water treatment.



Liquid waste, especially chemicals produced by factories or sewage.

Enjoying Water

To encourage Singaporeans to enjoy our waterbodies, PUB has worked with sports organisations to introduce watersports such as canoeing, kayaking and sailing at selected reservoirs. This is to encourage more Singaporeans to develop a relationship with water and bond with it. PUB believes that people who play with water will treasure it even more and want to be guardian of it. This is key to ensuring Singapore’s water sustainability for the future generations.



The gathering together of fine particles after coagulation to form larger particles by a process of gentle mixing.


Fluoride may occur naturally in water or it may be added in controlled amount. A fluoride concentration of approximately 0.5 mg/L in drinking water effectively reduces dental caries, especially in children, without harmful effects on human health. Toothpastes are normally fortified with fluoride to prevent tooth decay. However, too much fluoride causes adverse effects on teeth.

Four National Taps

Singapore has four different sources of water known as the Four National Taps (water from local catchment areas, imported water, reclaimed water known as NEWater and desalinated water)

Free chlorine

That portion of the total available residual chlorine composed of dissolved chlorine gas (Cl2), hypochlorous acid (HOCl), and/or hypochlorite ion (OCl-) remaining in water after chlorination. This does not include chlorine that has combined with ammonia, nitrogen, or other compounds.

Friends of Water

Friends of Water is a programme that recognises individuals and organisations who contribute towards raising awareness about water and what it takes to sustain Singapore’s water supply.


Galvanised iron

A coating of zinc on iron or steel to protect the iron from corrosion.


Heterotrophic Plate Count

This measures the general bacteria population per milliliter of water. The test is performed via pour plate method where 1 ml of water sample and/or its dilution is plated and molten agar added. The plates are incubated at 35 deg C for 48 hours before colonies are counted.

Hydrated lime

Limestone that has been “burned” and treated with water under controlled conditions until the calcium oxide portion has been converted to calcium hydroxide, Ca(OH)2. Hydrated lime is quicklime combined with water. CaO + H2O = Ca(OH)2.


Imported Water

Imported water is one of Singapore’s Four National Taps. The two water agreements that supply Singapore this water are due to expire by 2011 and 2061 respectively.


Kolam Ayer ABC Water Front

The first Active, Beautiful, Clean Waters pilot project, Kolam Ayer ABC Water Front was officially opened to the public in April 2008. This demonstration project for the ABC Waters Programme features a makeover of a 200m stretch of the Kallang River. The project brings waterfront living to the doorstop of HDB heartlanders.

Five beauty spots:

  • Viewing decks
  • Floating deck
  • Water wheel
  • Archimedes Screw
  • Biotope

Lee Kuan Yew Water Prize

The Lee Kuan Yew Water Prize is the highlight of the Singapore International Water Week. This award honours outstanding contributions towards solving global water problems by either applying technologies or implementing innovative policies and programmes which benefit humanity.

This prestigious award is named after Singapore’s first Prime Minister and present Minister Mentor Lee Kuan Yew, who through his foresight and leadership, has enabled Singapore to attain sustainable water supply. The winner receives S$300,000, an award certificate and a gold medallion. As sole sponsor for the Lee Kuan Yew Water Prize, the Singapore Millennium Foundation, a philanthropic body supported by Temasek Holdings, has pledged S$1.5million over five years from 2008.

Local Catchment Water

Singapore uses two separate systems to collect rainwater and used water. Rainwater is collected through a comprehensive network of drains, canals, rivers and stormwater collection ponds before it is channelled to Singapore's 17 reservoirs for storage. This makes Singapore one of the few countries in the world to harvest urban stormwater on a large scale for its water supply.


Marina Barrage

Built across the mouth of the Marina Channel, the Marina Barrage creates Singapore’s 15th reservoir, and the first in the heart of the city. With a catchment area of 10,000 hectares, or one-sixth the size of Singapore, the Marina catchment is the island’s largest and most urbanised catchment. Together with Punggol and Serangoon Reservoir, the Marina Reservoir has increased Singapore’s water catchment from half to two-thirds of the country’s land area.

Marina Bridge

Built across the mouth of the Marina Channel, the Marina Barrage creates Singapore’s 15th reservoir, and the first in the heart of the city. With a catchment area of one-sixth the size of Singapore, the Marina catchment is the island’s largest and most urbanised catchment. Together with two other new reservoirs, the Marina Reservoir has increased Singapore’s water catchment from half to two-thirds of the country’s land area.


Thin barriers or films of material with a large number of small pores of a predetermined size. Membranes allow solvent and other smaller molecules, ions or particles to pass through the pores while preventing the passage of other materials.


Microfiltration is a process commonly used in water reclamation. It is applied to filter out suspended solids, colloidal particles, disease-causing bacteria, some viruses and protozoan cysts. The filtered water that goes through the membrane contains only dissolved salts and organic molecules.



NEWater is high-grade reclaimed water produced from treated used water that is purified further using advanced membrane technologies, making the water ultra-clean and safe to drink.

NEWater Plants

The first NEWater plants were opened in Bedok and Kranji in 2003, followed by Seletar in 2004, and Ulu Pandan plant in March 2007. Together the NEWater produced by the four plants has met 15% of Singapore’s water needs.

The 5th and the largest NEWater plant at Changi with a capacity of 50mgd was launched in 2010. With this addition, coupled with the expansion of the existing plants, NEWater now meets 30% of Singapore’s current water needs.

NEWater Visitor Centre

At the NEWater Visitor Centre, visitors can expect more full-filled activities and interactive exhibits to take them on an exciting journey through the Singapore water story. Admission to the centre is free.

NEWater Visitor Centre’s popularity has won it the Best Sightseeing/Leisure/Educational Programme, 20th Tourism Awards 2005, IWA Marketing & Communication Award 2006.


Nitrate is part of the nitrogen cycle and is used mainly in inorganic fertilizers. Sodium nitrite is used as a food preservative, especially in cured meats. The nitrate concentration in groundwater and surface water is normally low but can reach high levels as a result of agricultural runoff, refuse dump runoff, or contamination by human or animal wastes.


Organic Matter

Organic matter in a reverse osmosis feed is customary expressed as the total organic carbon (TOC).


Ozone (O3) is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic species O2. Ozone is a strong disinfectant.



A term used to describe the hydrogen ion activity of a system. The pH scale ranges from 0-14. A solution with a pH below 7 is acidic, while a pH above 7 is basic (alkaline). A pH of 7 is neutral.



Often called a polymer, a polyelectrolyte is a high-molecular-weight (relatively heavy) substance having points of positive or negative electrical charges that is formed by either natural or manmade processes. Natural polyelectrolytes may be of biological origin or derived from starch products and cellulose derivatives. Manmade polyelectrolytes consist of simple substances that have been made into complex, high-molecular-weight substances. Used with other chemical coagulants to aid in binding small suspended particles to larger chemical flocs for their removal from water.


A quarterly lifestyle magazine produced by PUB.


Raw water

Water in its natural state, prior to any treatment, usually the water entering the first treatment process of a water treatment plant.


Singapore has 17 reservoirs including Punggol and Serangoon Reservoir.

Residual Chlorine

During water treatment, chlorine is added to destroy or deactivate disease-producing microorganisms. However, chlorination may produce an adverse taste and odor in the water. Chlorine applied to water in its molecular or hypochlorite form initially undergoes hydrolysis to form free chlorine consisting of aqueous molecular chlorine, hypochlorous acid and hypochlorite ion.

Reverse Osmosis

Second process of NEWater -This is the next process where the MF filtrate (feed) undergoes Reverse Osmosis (RO). RO involves applying pressure for water to flow from the concentrated side to the less concentrated side through a semi- permeable membrane to remove inorganics like heavy metals, nitrate, chloride, sulphate etc, and organics such as disinfection by-products, aromatic hydrocarbons, pesticides etc present in the microfiltration filtrate. The RO membrane has a pore size of 0.0001 microns and through this process, 95 percent of Total Dissolved Solids (TDS) can be removed. The RO membrane also removes viruses.



A chemical compound of a metal and an acid.


A water treatment process in which solid particles settle out of the water being treated in a larger clarifier or sedimentation basin.


The common aqueous forms of silica are H4SiO4 and H3SiO4-. In the presence of magnesium, silica can form scale deposits in boilers and stream turbines. It is considered a nonessential trace element for most plants, but essential for most animals.


Sulphate is widely distributed in nature and may be present in natural waters in concentrations ranging from a few to several thousands mg/L. Mine drainage wastes may contribute large amounts of SO42- through pyrite oxidation.

Suspended matter

Matter that either floats on the surface or suspended in water, wastewater, or other liquids and which is largely removable by filtering.

Sustainable Singapore Gallery (SSG)

Located at the Marina Barrage, the SSG is an information and sensory extravaganza showcasing Singapore’s efforts towards environmental sustainability.


Total Dissolved Solids (TDS)

An expression for the combined content of all inorganic and organic substances contained in a liquid or water which are present in a molecular, ionized or micro-granular suspended form that cannot be removed by filtration.

Total Hardness

Water hardness is mainly contributed by calcium and magnesium ions. Originally, water hardness was understood to be a measure of the capacity to precipitate soap. Soap is precipitated chiefly by the calcium and magnesium ions. In conformity with current practice, Total Hardness is defined as the sum of the calcium and magnesium concentrations, both expressed as calcium carbonate, in mg/L. In households, high water hardness can cause scaling of heating elements, such as the heating coil in an electric kettle. The formation of scale is greatly increased with the rise of temperature; it reduces heat transfer during boiling and therefore causes more electricity to be consumed.

Total Organic Carbon (TOC)

A measure of the amount of organic materials suspended or dissolved in water. TOC is a quicker sampling method than measuring COD or BOD for determining the quality of the effluent.

Total Solids (TS)

A measure of the amount of material that is dissolved or suspended in a water sample, by weight. Total solids is determined by allowing a known volume to evaporate and then weighing the remaining residue. TS = TDS + TSS

Total Suspended Solids (TSS)

A measure of the solids found in water that can be removed by filtration.

Total Trihalomethanes (THMs)

THM compounds can be found in chlorinated water samples. The formation of these compounds is a function of precursor concentration, contact time, chlorine dose and pH. Some of the common THMs are Chloroform, Bromoform, Bromodichloromethane and Dibromochloromethane.


A measure of the clarity of a solution often measured in Nephelometric Turbidity Units [NTU] caused by sediment or foreign particles stirred up or suspended in water. Highly turbid waters are muddy or cloudy.


Ultra-violet disinfection

Third process of NEWater -Ultra-violet disinfection is a safety back-up to remove any bacteria or viruses should the RO membrane be compromised and the viruses and bacteria go through the RO process.


Valuing Water

PUB urges all Singaporeans to take greater ownership of our reservoirs and waterways and value our water resources by keeping the waters in the reservoirs and catchment areas clean. The Our Waters programme, Watermark Award, and MacRitchie Volunteer programme are just some of the key initiatives to inspire people to get involved.


Water Efficiency Fund

To balance the ever-increasing water needs of industry, individuals and the environment, PUB has set up the Water Efficiency Fund (WEF) to encourage companies to look into efficient ways to manage their water demand or promote water conservation in the community.

Water Efficient Building programme (WEB)

The Water Efficient Buildings programme is a water conservation initiative. It offers cost-effective solutions and guidelines for non-domestic customers to lower their water consumption and thus their operating costs.
The programme covers:

  • Commercial buildings
  • Industrial buildings
  • Factories
  • Educational institutions
  • Shopping complexes/centres
  • Hotels
  • Food courts
  • Coffee shops
  • Shop houses

Non-domestic customers can transform their premises into Water Efficient Buildings simply by applying the “S.A.V.E” strategy of water conservation in their management and use of water.

Water Efficient Home programme (WEH)

Water Efficient Homes (WEH) is a programme to help residents save water at home and cut down on their water bills. The programme encourages residents to install water saving devices and practice good water conservation habits. As part of the programme, PUB officers visit households in Singapore to install free-of-charge water saving devices such as thimbles and cistern water saving bags.

Water Tariff

Tariff since 1 Jul 2000

Tariff CategoryConsumption Block
(m3 per month)

[before GST]

Water Conservation Tax
(% of tariff)
[before GST]

Domestic 0 to 40 1.1700 30
Above 40 1.4000 45
Non-Domestic All units 1.1700 30
Shipping All units 1.9200 30

Tariff Category

Consumption Block
(m3 per month)

Waterborne Fee
[before GST]

Waterborne Fee
[after GST]

Sanitary Appliance Fee
[before GST]

Sanitary Appliance Fee *
[after GST]

Domestic All units 0.2803 0.30 $2.8037/- per chargeable fitting per month $3.00/- per chargeable fitting per month
Non-Domestic All units 0.5607 0.60
Shipping All units 0.56070.60


NEWater Tariff

Tariff since 1 Apr 2012

Tariff Category Consumption Block
(m3 per month)
[before GST]
[after GST]
(% of tariff)
[before GST]
[after GST]
NEWater All units 1.22001.3054- 0.56070.6000


Industrial Water Tariff

Tariff since 1 Oct 2013

Tariff Category Consumption Block
(m3 per month)
[before GST]
[after GST]
(% of tariff)
[before GST]
[after GST]
Industrial Water All units 0.65000.6955- 0.56070.6000


Water Wally

To encourage the public to take ownership of the precious water resource, PUB’s mascot Water Wally was created in 2005 to bring life to PUB’s messages in a fun and interactive way.

Watermark Award

The Watermark Award was introduced in 2007 to recognise individuals and organisations for their outstanding contributions and commitment to protect and raise awareness of Singapore’s precious water resources. The aim is to inspire and encourage Singaporeans to take ownership of our water resources and contribute towards Singapore’s water sustainability.


World Health Organisation (WHO) is an organisation that regulates global health matters.

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