Applications of flat sheet ceramic membrane for surface water and seawater treatments – introduction of performance in large-scale drinking water plant and seawater pretreatment pilot system in Singapore

摘要

PUB, Singapore's National Water Agency, has been using polymeric UF membrane in drinking water plants to produce high quality water whilst requiring a smaller footprint. Submerged polymeric hollow-fiber membrane has been used since 2003 in Chestnut Avenue Water Works (CAWW). PUB decided to use submerged-type ceramic membranes for enhancement of production capacity at CAWW. The flat-sheet ceramic membrane system was retrofitted into two spare, empty tanks with a combined design capacity of 36,400 m~3/d. The system has been successfully put into operation, running at a net flux of 160 L/m~2-h (LMH) since June 2017. Membrane integrity testing is automatically carried out once a week to ensure the membranes' integrity. Stable filtrate quality has been achieved with a low turbidity of 0.018 NTU on average. Pretreatment for seawater desalination is another application in which a ceramic membrane system can be operated at higher flux compared to that for polymeric membranes. A pilot scale system was installed at PUB R&D facility in Tuas to investigate sustainable operating flux and permeate quality. FeCl_3 was used as a coagulant before ceramic filtration, with a dosage of 4-6 mg/L. It was shown that sustainable flux can be 181-249 LMH in seawater treatment system with flat sheet ceramic membranes. The silt density index and turbidity of permeate were 1.6-2.2 and 0.04-0.10 NTU, respectively, which indicates that the system can produce high quality water for feed of reverse osmosis systems.