PUB awards $433 million Tuas WRP biosolids treatment contract to Sembcorp Design and Construction

National water agency PUB has awarded the contract to build the biosolids treatment facility for the Tuas Water Reclamation Plant (WRP) – a major component of the Deep Tunnel Sewerage System (DTSS) Phase 2 project – as the construction of the plant gathers steam this year. 

Sembcorp Design and Construction Pte Ltd, a wholly-owned subsidiary of local construction and property group Chip Eng Seng Corporation Ltd, will construct Tuas WRP’s biosolids building, digesters and greasy waste receiving facility. Works will start in April 2020 and are due to complete in 2025. 

The contract is valued at S$433 million and was awarded following an open tender exercise in August 2019, during which a total of 11 bids were received. 

These facilities will form the key interface between Tuas WRP and the National Environment Agency’s (NEA) Integrated Waste Management Facility (IWMF). Collectively, Tuas WRP and IWMF are known as Tuas Nexus, Singapore’s first initiative that integrates water and solid waste treatment processes to harness synergies of the water-energy-waste nexus. 

At Tuas WRP’s biosolids treatment facility, used water sludge will be co-digested with IWMF’s food waste to increase the yield of biogas, which will then be combusted at the IWMF to boost power generation and improve its overall plant energy efficiency. The IWMF will thereby be able to generate more electricity. The total electricity generated at the IWMF will be sufficient to power 300,000 four-room HDB apartments. A portion of this will be used to operate Tuas WRP and IWMF, which will make the whole Tuas Nexus complex fully energy self-sufficient. The rest will be sold to the grid. 

“This is a key contract that will build components critical to realising the synergies between Tuas WRP and IWMF, with PUB and NEA working together closely to make Tuas Nexus a reality. Once completed, Tuas Nexus will set the bar for addressing long-term resource sustainability and climate change,” said Mr Yong Wei Hin, Director, DTSS 2, PUB. 

PUB’s DTSS Phase 2 project consists of a 100km network of deep tunnels and link sewers. Slated for completion in 2025, it will channel used water via gravity from the western half of Singapore to Tuas WRP for treatment. Existing conventional WRPs in Ulu Pandan and Jurong will be progressively phased out. 

With an initial treatment of capacity of 800,000 m3 per day – enough to fill over 300 Olympic-size swimming pools – Tuas WRP will house the largest membrane bioreactor facility in the world, with an overall 30 per cent more compact footprint compared to conventional plants. 

In July 2019, PUB appointed a joint venture to construct Tuas WRP’s Influent Pumping Stations, which are responsible for pumping used water from the underground sewerage tunnels to the plant for treatment. Another 14 construction tenders for Tuas WRP will be called over the next two years, including for the construction of the plant’s domestic and industrial liquids modules.