SAFETY CHECKS ON RECYCLED DRINKING WATER

Column: 825

**

SAFETY CHECKS ON RECYCLED DRINKING WATER

25.

Dr Lim Wee Kiak asked the Minister for the Environment and Water Resources in view of the wide acceptance of using recycled water for drinking in Singapore (a) what are the safety checks in place to monitor and ensure that the membranes used to filter the water are in good working condition; (b) what are the additional safety measures to supplement the filtration process should there be any compromise in the membrane technology used by the Public Utilities Board; and (c) how is the system audited to ensure that there are no human lapses in overseeing the process.

Assoc. Prof. Dr Yaacob Ibrahim: NEWater is high-grade reclaimed water that is produced using advanced membrane technologies. Assurance that NEWater is safe for drinking and for use by the industries is a priority of PUB at all times.

Given NEWater's high purity, it is largely supplied to industrial and commercial users with high end processes like wafer fabrication that require water of higher quality than for drinking. Currently, only a small amount of NEWater is blended with raw water in the reservoirs which undergoes further treatment for supply as drinking water.

Column: 827

PUB ensures safety standards by employing the following measures in the production of NEWater:

• A multi-barrier approach is adopted in the design of the NEWater plants. For example, UV disinfection is installed as an additional safety barrier, after the microfiltration (MF) and reverse osmosis (RO) treatment stages.

• A comprehensive preventive maintenance programme is in place to ensure all equipment and RO membrane treatment units are in tip-top working condition. The membranes are replaced at the end of their lifespan, typically every five to six years.

• NEWater plants are equipped with sensitive on-line instruments to constantly monitor water quality. Critical operation control points are set in the NEWater plants to raise alarms and alert the operators; plant operation will automatically shut down in the unlikely event of membrane failure. This has thus far not happened, but in such an eventuality, PUB can draw from service reservoirs to ensure uninterrupted supply of water to users.

PUB has in place a water quality monitoring programme to ensure that NEWater and tap water supplied by PUB are well within international drinking water standards including those of WHO and USEPA. About 290 parameters are monitored, which are more than the 130 parameters specified in international drinking water standards. More than 80,000 tests on water quality are conducted monthly, spanning the entire water supply network, ie, from reservoirs to taps, to ensure that the water is safe to drink.

The test results and plant design and operations are audited every three months by an independent Internal Audit Panel chaired by a water expert from NUS. This is further backed by an external audit every six months. The External Audit Panel comprises five overseas water experts from US and Europe and two local experts from NUS. This auditing framework has been in place since the introduction of NEWater in 2003. Both Audit Panels have consistently found high standards upheld in plant design and operation, and, most importantly, the quality of NEWater.