NEWater
|
|
NEWater is the brand name given to reclaimed water produced by Singapore's public utilities. More specifically, it is treated wastewater (sewage) that has been purified using dual-membrane (via microfiltration and reverse osmosis) and ultraviolet technologies, in addition to conventional water treatment processes.
Singapore commissioned the construction of two NEWater factories, located at the Bedok and Kranji Water Reclamation Plants, which were completed at the end of 2002. Another factory was completed at Seletar Water Reclamation Plant in February 2004. At present, the total capacity of the three factories is about 20 million gallons per day (Mgd). About 3 Mgd of this is used for indirect potable use, which contributes 1 percent of Singapore's potable water requirements of 300 Mgd. The rest of the water is used at wafer fabrication plants and other non-potable applications in industries.
The main reasons NEWater is not used for direct consumption, according to authorities, are that filtering processes may remove minerals that are present in standard drinking water (making it "too clean" for human consumption), and also because humans may face psychological barriers against drinking reclaimed water.
According to authorities, the quality of NEWater consistently exceeds the requirements set by USEPA and WHO guidelines and is, in fact, cleaner than the other sources of Singapore's water.
Plans are under way to increase the amount of NEWater in indirect potable use up to 2.5 percent by 2011.
Introduction
The Singapore Water Reclamation Study (NEWater Study) was initiated in 1998 as a joint initiative between the Public Utilities Board (PUB) and the Ministry of the Environment and Water Resources (MEWR). The primary objective of the joint initiative was to determine the suitability of using NEWater as a source of raw water to supplement Singapore's water supply. NEWater is treated used water that has undergone stringent purification and treatment process using advanced dual-membrane (microfiltration and reverse osmosis) and ultraviolet technologies. NEWater could be mixed and blended with reservoir water and then undergo conventional water treatment to produce drinking water.
Water reclamation is a growing ‘trend’ in the U.S. and around the world. In the U.S., there are several other water reclamation projects that are now being planned or under construction. In 2001, PUB embarked on a new initiative to increase water supply from unconventional sources for non-potable use. The use of NEWater for wafer fabrication processes, non-potable applications in manufacturing processes as well as air-con cooling towers in commercial buildings would free large amount of potable water for other potable purposes.
The NEWater Factories at Bedok and Kranji Water Reclamation Plants was commissioned at the end of 2002. Following that since Feb 2003, NEWater has been supplied to wafer fabrication plants at Woodlands and Tampines/Pasir Ris and other industries for non-potable use. In Jan 2004, another milestone in the NEWater initiative was accomplished with the commissioning of the third NEWater Factory at Seletar Water Reclamation Plant which began supplying NEWater to the wafer fabrication plants at Ang Mo Kio. The total capacity of the 3 NEWater factories is 92,000 m3/day or 20 mgd.
How NEWater is purified
NEWater is the product from a multiple barrier water reclamation process. The first barrier is the conventional wastewater treatment process whereby the used water is treated to globally recognised standards in the Water Reclamation Plants.
The second barrier is the first stage of the NEWater production process known as Microfiltration (MF). In this process, the treated used water is passed through membranes to filter out and retained on the membrane surface 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. The third barrier or the second stage of the NEWater production process is known as Reverse Osmosis (RO). In RO, a semi-permeable membrane is used. The semi-permeable membrane has very small pores which only allow very small molecules like water molecules to pass through. Consequently, undesirable contaminants such as bacteria, viruses, heavy metals, nitrate, chloride, sulphate, disinfection by-products, aromatic hydrocarbons, pesticides etc, cannot pass through the membrane. Hence, NEWater is RO water and is free from viruses and bacteria and contains very low levels of salts and organic matters.
At this stage, the water is already of a high grade water quality. The fourth barrier or third stage of the NEWater production process really acts as a further safety back-up to the RO. In this stage, ultraviolet or UV disinfection is used to ensure that all organisms are inactivated and the purity of the product water guaranteed. With the addition of some alkaline chemicals to restore the acid-alkali or pH balance, the NEWater is now ready to be piped off to its wide range of applications.
In fact, RO is a widely recognized and established technology which has been used extensively in many other areas. This includes the production of bottled drinking water and production of ultra-clean water for the wafer fabrication and electronics industry. RO is also becoming increasingly popular as one of the technologies used in desalination of seawater for human consumption. It is also used to recycle used water to drinking water on space shuttles and on International Space Stations.