Renewed water

  • Environment
  • Monday, 16 Jun 2014

SINGAPORE has been recycling wastewater since 2003. Treated sewage effluent, instead of being discharged, is further purified with tertiary treatment processes, making it ultra-clean and safe to drink.

Called NEWater, the reclaimed water meets up to 30% of the island republic’s water needs and by 2060, 55%. The reclaimed water is primarily for non-potable industrial and commercial uses and is delivered via a separate distribution network.

It is supplied to wafer fabrication, electronics and power generation industries for process use, and also piped to commercial and institutional buildings for air-conditioning cooling purposes. This frees up potable water for domestic consumption. A small amount of the reclaimed water is blended with raw water in the reservoir for domestic water supply.

The effluent first passes through membranes to filter out suspended solids, colloidal particles, bacteria, some viruses and protozoan cysts. It then goes through a semi-permeable membrane in the reverse osmosis process, to remove contaminants such as bacteria, viruses, heavy metals, nitrate, chloride, sulphate, disinfection by-products, aromatic hydrocarbons and pesticides. Ultraviolet or UV disinfection is then used to destroy any remaining organisms. With the addition of some alkaline chemicals to restore the pH balance, the reclaimed water is then piped off for use.

Australia’s largest residential recycled water scheme is at Rouse Hill in Sydney’s north-west which commenced in 2001. Over 16,000 homes use 1.7 billion litres of recycled water annually for flushing toilets, watering lawns, washing cars and outdoor uses. The scheme has reduced demand for potable water by 35%.

The Sydney Olympic Park has separate pipelines for drinking and recycled water. Taps carrying recycled water are lilac in colour. The recycled water is used primarily for toilet flushing. Some 850 million litres of drinking water is saved each year.

At the Carlton Industrial Area in the Sydney suburb of Kogarah, stormwater is intercepted and channelled to an underground storage tank. It is then filtered for use in irrigation.

Water that is treated to higher quality is used for non-potable purposes in homes. Recycling will provide up to 12% of Sydney’s water needs by 2015.

In south-east Queensland, the Western Corridor Recycled Water Project, completed in 2008, supplies 230 million litres of recycled water each day to power stations, industries and farms. In the city of Hervey Bay in Queensland, treated sewage effluent is used at golf courses, turf farms, cane farms and tree plantations.

In the Yarra Valley region of Victoria, over 2,000 homes in several nominated areas are supplied with recycled water through an additional pipe system constructed by developers. The recycled water is produced from water discharged from the shower, toilet, sink and washing machine, and is suitable for washing clothes and cars, flushing toilets and the garden.

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