One of Singapore’s four national “water taps” is to reclaim water from wastewater. After years of research, the Public Utilities Board (PUB), Singapore’s national water agency, started to supply high quality reclaimed water, referred to as NEWater. The majority of NEWater is supplied to industries for non-potable purposes. The rest is discharged into reservoirs for indirect potable use. Currently NEWater meets 30% of Singapore’s current water demand, and there are plans to increase this to 50% by 2060. At this moment there are four NEWater treatment plant in service (Bedok, Kranji, Ulu Pandan and Changi). NEWater is produced from treated sewage, termed “used water”, that is further purified in three different steps:
- Microfiltration (MF) is the first step in the NEWater production. 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 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.
- The third stage of the NEWater production process 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 (PUB).