How NEWater is obtained

NEWater is a high-grade reclaimed water which is obtained from used water which has been treated using the latest membrane and fi ltration technologies.

NEWater has also surpassed the requirements set by the World Health Organisation, and thus, it is absolutely safe for consumption.

NEWater is part of the “Four National Taps” of Singapore which aims to provide Singapore citizens with a safe and sustainable supply of drinking water.

WHAT IS NEWATER?

Obtaining NEWater requires 4 main steps, namely:1)Waste Water Treatment2)Microfiltration3)Reverse Osmosis4)Ultra- Violet Disinfection.

THE PROCESSES INVOLVED

What is Waste Water Treatment?Waste Water Treatment is the process

whereby used water is treated to globally recognised standards.

This is to prevent the further pollution of water sources after it is released into another body of water.

How is Wastewater Treated?Wastewater is treated by levels, namely, the

Preliminary, Primary, Secondary, and Tertiary level.

THE FIRST BARRIER: WASTE WATER TREATMENT

Preliminary- The water which fi rst enters the treatment plant is screened to remove any large solid objects which are present in the water. Then they are moved to a grit tank to separate smaller objects

Primary- This stage allows for the physical separation of solids and greases. The water is then held in a tank to separate the water from the solids and the greases.

The Treatment Process

Secondary- In this stage, the water is mixed with micro- organisms which use oxygen to consume the remaining organic matter left in the wastewater. The oxygen and micro- organisms are supplied by the aeration tank where the water is stored

Tertiary- The wastewater is finally disinfected using chlorine and ultraviolet . The water can then be discharged to other water bodies as it has already been cleansed and is deemed safe to be released.

THE TREATMENT PROCESS

A Diagram of Wastewater Treatment

After going through the waste treatment process in the waste treatment plants, the treated water is used as a source to produce NEWater.

This process basically forces the water is forced through membranes with hollow fibres to fi lter out solids which are suspended in the water, bacteria, and other harmful substances. The water after microfi ltration would contain only dissolved salts and organic molecules.

THE SECOND BARRIER: MICROFILTRATION

So, basically, Microfi ltration in NEWater is actually just normal fi ltration, but on a higher and more specifi c level. This is because we are not just trying to separate the suspended solids from the water, but also the harmful bacteria which are present in it.

Thus, the holes in the membranes have to be smaller than the size of the bacteria to be able to trap them and prevent them from entering the next stage of purifi cation.

So, like normal fi ltration, where fi lter paper is used, Microfi ltration makes use of the membranes to separate water from bacteria and other solids particles which are present. And the reason why fi lter paper is not able to be used in microfi ltration is because its holes are too big and allows the bacteria to pass through.

THE SECOND BARRIER: MICROFILTRATION

After going through micro- fi ltration, the water would then move on to the next stage of the purification process. This process is known as Reverse Osmosis

What is Reverse Osmosis?Reverse Osmosis is basically the process

whereby the water is passed through a semi- permeable membrane. For this to happen, pressure must be applied to push the water through the membrane. This uses the concept of reversing the flow of water in normal osmosis and using the semi- permeable membrane as a fi lter.

THE THIRD BARRIER: REVERSE OSMOSIS

DIAGRAM OF NORMAL OSMOSIS

DIAGRAM OF REVERSE OSMOSIS

The Outcome of Reverse OsmosisIn Reverse Osmosis, when the water passes through the semi- permeable membrane, only water molecules are allowed to pass through, thus impurities like chemicals drugs, viruses and dissolved salts are left behind. So, by the time the water has completed the process of Reverse Osmosis, the water is already of a high- grade quality.

THE THIRD BARRIER: REVERSE OSMOSIS

This is the final stage of purification. After going through the process of Reverse Osmosis, the water would already be of a high- grade quality.

However, as an added safety precaution, the water is then exposed to UV (Ultraviolet) radiation. This is to make sure that any micro- organisms left in the water are inactivated.

After this stage, chemicals that restore the water's pH balance are added before the NEWater is ready for use.

THE FOURTH BARRIER: ULTRAVIOLET DISINFECTION

Some of the separation techniques involved in the process of purification are:

1) Filtration2) Reverse Osmosis

Filtration was used in the removal of bacteria and suspended solids from the water. This kind of fi ltration is known as Microfi ltration as the holes are very small and are able to separate water from bacteria

Reverse Osmosis was used in the separation of chemicals, drugs, viruses and dissolved salts so as to purify the water even further. After this stage of purification, the water would be of a very high- grade.

SEPARATION TECHNIQUES INVOLVED

DIAGRAM OF MICROFILTRATION

Retort Stand

Beaker

Filter Funnel

Filter Paper

The previous diagram actually shows a simple fi ltration set- up, however, it encompasses the basic structure and concept of Microfi ltration.

The beaker in the set-up, represents the tank where water would be sent to the next stage of purification after Microfi ltration.

The fi lter paper in the set- up represents the membrane which is used to fi lter out the bacteria and suspended solids which are present in the water.

The fi lter funnel represents the holding tank where the suspended solids and bacteria are kept after being trapped by the membrane.

DIAGRAM OF MICROFILTRATION

DIAGRAM OF MICROFILTRATION

The picture on the right shows a hollow fibre which is used to make up the membrane used in microfiltration. This hollow fibre has many extremely fine and tiny holes and these holes are used to trap suspended solids and bacteria and prevent them from entering the next stage of purification. Thus, when the water is passed through this membrane made up of hollow fibres, bacteria and other solids would be left behind.

DIAGRAM OF REVERSE OSMOSIS

Flow of water

Water is of high- grade

quality.

Semi- permeable Membrane

In reverse osmosis, a semi- permeable is used to purify the water. This semi- permeable membrane is similar to the one which is used in normal osmosis.

In reverse osmosis, pressure has to be added to the water to force it to go through the semi- permeable membrane. After this stage, substances like chemicals, drugs, viruses and dissolved salts would be removed. Thus, after this stage of purification, the water would already be of a high- grade quality.

DIAGRAM OF REVERSE OSMOSIS

About Wastewater Treatmenthttp://

www.regulatorystaff.sc.gov/orscontent.asp?pageid=654http://en.wikipedia.org/wiki/Sewage_treatmenthttp://

esa21.kennesaw.edu/activities/ww-treatment/ww-treat.pdf

NEWaterhttp://en.wikipedia.org/wiki/NEWaterhttp://www.pub.gov.sg/about/historyfuture/Pages/NEWa

ter.aspxhttp://

infopedia.nl.sg/articles/SIP_1555_2009-08-11.htmlhttp://www.adb.org/Water/Actions/sin/NEWater-Sewage-

Safe.asp

BIBLIOGRAPHY

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