The practice of the Public Utilities Board (PUB) of Singapore is to provide the Singapore public with high quality drinking water. In 2001, in keeping with this practice and due to an increased emphasis on diversification of its water supply, the PUB undertook a major project to expand the capacity of the Chestnut Avenue Waterworks (CAWW) by 273,000 m3/d (60 Migd) using membrane technology. In 2003, Zenon Environmental, as part of a team with the owner's engineer, Black & Veatch, main contractor Thames Water Projects/SembCorp Engineers & Constructors and local Zenon licensee, Hyflux Engineering, installed and commissioned a 273,000 m3/d enhanced coagulation /ultrafiltration membrane plant — the largest of its type in the world at the time.

This paper describes the innovative aspects of the CAWW membrane plant design and summarizes the results of its first year of operation. Certain aspects of the full-scale system design are particularly noteworthy. Whereas typical immersed membrane systems employ expensive process pumps to create the vacuum necessary to produce filtrate, the CAWW system relies on a simple siphon to produce filtrate. No permeate pumps are required and this dramatically reduces capital and operating cost through simplified design, reduced controls and minimized floor space. The land area needed for membrane filtration and related process equipment is equivalent to obtaining 180 m3/d of capacity per m2 of land area.