NEWater—multi safety barrier approach for indirect potable use

Abstract

Singapore, a small island city-state depends on four sources, namely local catchment, imported water from Malaysia, desalinated water, and NEWater, to provide for its daily water consumption of about 1.36 million m3 per day. NEWater, a high grade reclaimed water, is key in achieving water sustainability through the multiplying effect of water reuse. In addition to being used for direct non-potable use (DNU) in wafer fabrication processes and other industrial processes, NEWater is being injected into surface reservoirs for indirect potable use (IPU). To ensure the safety of NEWater for IPU, PUB has adopted a multi barrier safety approach. The multi safety barrier approach starts from source and extends to taps in households in stages, namely source control; greater than 85% of wastewater from domestic source; comprehensive secondary wastewater treatment; microfiltration (MF) process, reverse osmosis (RO) process and ultra-violet (UV) disinfection in NEWater production; natural attenuation in surface reservoirs; as well as conventional water treatment process of coagulation, flocculation, sand filtration and disinfection. The approach is further enhanced by a comprehensive water quality monitoring programme that includes emerging contaminants of concern and a strict operating philosophy. The water quality test results are in turn reviewed by experts from local universities as well as overseas experts of international standing. Over the years of operations, NEWater has been found to be well within WHO Drinking Water Guidelines and USEPA Drinking Water Standards and each safety barrier has a significant role to play in ensuring the safety of NEWater for IPU.