In Singapore, 3 water reclamation plants were installed between 2002 and 2004 and they produce today a capacity of 92,000 m3/day for industrial use and groundwater recharge.

Problem

The primary objective of the initiative for the project NEWater was to determine the suitability of using treated wastewater as a source of raw water to supplement Singapore's water supply because of the increasing water demand and decreasing water resources in Singapore.

Solution and process overview

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 matter.

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.

Table 6: Water quality of NEWater in Singapore (http://www.pub.gov.sg/NEWater_files/newater_quality/index.html)

Please look for more information in http://www.pub.gov.sg/NEWater_files/overview/index.html