Tuaspring Desalination and Integrated Power Plant, Singapore

Artist's impression of Tuaspring Plant

Tuaspring Desalination Plant (Tuas II), the biggest seawater reverse osmosis desalination plant in Asia, integrates a combined-cycle power plant (CCPP), which was connected to the national grid in August 2015.

The desalination plant is designed for a capacity of 318,500m³ (70 million gallons) a day, whereas the CCPP has an installed capacity of 411MW. The CCPP supplies electricity to the desalination plant, while any excess power is fed to the national grid.

Construction of the desalination plant started in July 2011 and commissioning was completed in September 2013. The construction of the integrated CCPP was completed in late 2014, while commissioning is expected in early 2016.

The integrated project was implemented on a design, build, own and operate (DBOO) basis by Hyflux's subsidiary, Tuaspring. The construction works were performed by Hydrochem, another subsidiary of Hyflux Group. The operations and maintenance (O&M) services for the CCPP are being provided by NAES Corporation, a subsidiary of Itochu International.

"The construction of the integrated CCPP was completed in late 2014, while commissioning is expected in early 2016."

Hyflux supplies potable water from the plant to PUB, Singapore's national water agency, under a 25-year water purchase agreement (WPA) signed in 2011.

Tuaspring desalination plant details

The project site covers an area of approximately 14ha, adjacent to the 136,000m³ SingSpring Desalination Plant (Tuas I Desalination Plant), which came online in September 2005. The two desalination plants together account for approximately 25% of Singapore's current water demands.

The Tuaspring desalination plant uses Hyflux's proprietary Kristal ultra-filtration membrane technology for the pre-treatment process, which removes suspended solids and microorganisms. The technology consumes less chemicals and energy, and is touted to be the first ultra-filtration membrane to achieve NSF International's certification for removal of cryptosporidium.

The desalination plant further integrates a two-stage seawater reverse osmosis (SWRO) process, where seawater is passed through semi-permeable membranes. The process is completed by a post-treatment for re-mineralisation of the water before being supplied to PUB.

The desalination plant is equipped with 17 trains of R80S 8 series SWRO pressure vessels, comprising 216 units a train, and nine trains of R80S 8 series low-pressure reverse osmosis (LPRO) pressure vessels, comprising 132 units a train.

Tuaspring CCPP make-up

The combined-cycle power plant is equipped with Siemens' LNG-fired and single-shaft SGT5-4000F turbine, a heat-recovery steam generator (HRSG), a SST5-3000 steam turbine, a common Sgen5-2000H series hydrogen-cooled generator, and the SPPA-T3000 plant control system.

Contractors involved with the desalination and integrated power project

The RO membranes for the desalination plant were supplied by Toray Industries, whereas the high-pressure pumps were supplied by Torishima Pump.

The CCPP's gas turbine was transported to the project site by Bok Seng Logistics in February 2015, deploying SCHEUERLE self-propelled modular transporters (SPMTs).

Flowserve supplied 68 of its CALDER Dual Work Exchange Energy Recovery (DWEERTM) units, which are used to recover energy from the high-pressure brine stream of the SWRO process.

The 66kV/22kV/6.6kV/LV electrical and drive systems for the project were supplied and installed by Alstom.

Financing Singapore's biggest desalination plant

The total cost for the construction of the integrated desalination and power plant is S$890m ($635m approximately).

The project received a $14.4m buyer's credit loan from the Japan Bank for International Cooperation (JBIC) in June 2014, to finance the desalination components acquired from Japanese suppliers.

In May 2013, Hydrochem signed a $139m export credit financing agreement with KfW-IPEX Bank to fund the power plant. The financing facility is guaranteed by Euler Hermes Deutschland.

An S$720m ($512m) 18-year term loan for the integrated project was provided by Maybank Singapore and Maybank Kim Eng Securities. The project also received a S$150m ($106m approximately) fund from DBS Bank, Mizuho Corporate Bank, and Sumitomo Mitsui Banking Corporation.