More than $5 billion in tenders will be called for a new plant in Tuas that will utilise waste to expand Singapore's water supply and extend the lifespan of its only landfill on offshore Semakau Island.

The tenders, to be called over the next five years, involve civil, mechanical and electrical engineering works. They are for a first-of-its kind facility in Tuas, which will incorporate used water and waste management plants in one facility, national water agency PUB and the National Environment Agency (NEA) said yesterday.

Tuas Nexus will enable PUB to reclaim industrial used water for use by industries on Jurong Island and Tuas. Traditionally, industrial used water is treated before being discharged into the sea. It will also be the first to treat both used water and food waste in the same plant to produce biogas.

Used for electricity generation, biogas is produced when organic material in food waste or sludge from used water react with bacteria. By combining sludge with food waste, Tuas Nexus can increase the amount of biogas produced by 10 per cent.

Coupled with other renewable energy sources at Tuas Nexus - including solar panels and the conversion of heat produced by the incinerators to electricity - the plant will be completely energy self-sufficient. In fact, excess electricity, enough to power up to 300,000 homes, will be exported back to the national grid.

Construction is expected to start next year, and will be completed in phases from 2023. The facility is expected to be fully ready by 2027.

Mr Yong Wei Hin, director of PUB's deep tunnel sewerage system phase 2, said Tuas Nexus "marks a new way in which used water and solid waste will be treated in Singapore". He was speaking to the media at the Singapore International Water Week and CleanEnviro Summit Singapore conferences. The integration of used water and waste management plants will reduce carbon dioxide emissions by more than 200,000 tonnes every year - equivalent to taking 42,500 cars off the road.

The plant, which will also allow incineration bottom ash (IBA) to be extracted from waste, will expand the lifespan of the Semakau landfill, said Mr Joseph Boey, project director of NEA's integrated waste management facility.

Audrey Tan and Luke Anthony Tan