NEWater in Singapore: From waste to water

During Singapore’s National Day Parade in 2002, the entire nation drank a toast of NEWater, led by then-Prime Minister Goh Chok Tong, to the republic’s 37th birthday.

This is where NEWater made its public debut. A term coined by Singapore’s Public Utility Board (PUB), NEWater is a form of high-grade reclaimed water derived mainly from sewage wastewater, and subsequently purified for mainly industrial purposes.

Over the years, NEWater not only withstood over 130,000 scientific tests and surpassed the World Health Organisation’s (WHO) standards, but earned global recognition in terms of the various water awards won. Little wonder that NEWater is included as the third of Singapore’s “Four National Taps”, the PUB’s long-term strategy to provide Singapore with a sustainable and clean water supply after its water treaty with Malaysia expires in 2061.

Initially, the used water is treated via conventional water treatment to remove larger debris like stones and gravel. From here on, the treated water undergoes 3 stages of purification to be transformed into the NEWater that we know.

Source: PUB

Stage 1: Microfiltration

Via membranes with minute pores, microfiltration comprises of filtering suspended sediments and various bacteria, viruses and pathogens out, leaving behind dissolved salts and organic molecules in the filtrate which is subjected to reverse osmosis in the next stage.

Stage 2: Reverse Osmosis

Simply put, reverse osmosis is the movement of water molecules against its concentration gradient via a semi-permeable membrane, so extremely high water pressures are required to overcome the energy barrier. The pressurised water is forced through layers of semi-permeable membranes to trap any organic impurities (industrial chemicals, pesticides etc) or bacteria/ virus particles which got through microfiltration there. The final permeate should only consist of incredibly tiny molecules like H2O molecules at the end of this stage.

ch4-introduction

Reverse osmosis membrane systems are used in the production of NEWater, an ultra-clean and high grade of reclaimed water. It will form an important component of Singapore’s future water supply.

Stage 3: UV post-treatment

This stage is serves as a precautionary final step before NEWater is released to the public, since the water’s quality is already considered to be ultra-pure. Negligible levels of residual micro-organisms could still remain in the permeate, so the water is passed through pipes lined with UV lamps to disinfect/ inactivate them. After chemicals are added to restore the water’s pH balance, NEWater is then ready to be pumped out for storage and distribution.

Being extremely pure, industries often use NEWater for cleansing and cooling purposes, while during dry periods, NEWater could be mixed in with reservoirs to be supplied to households as tap water. Already supplying up to 30% of Singapore’s current water needs, the current NEWater capacity is estimated to triple to cater up to 55% of the nation’s future water demand by 2060.

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