SINGAPORE will soon be calling for tenders for water and waste infrastructure projects that are estimated to cost S$9.5 billion in total.
Starting from the third quarter of this year, Singapore's national water agency PUB will be calling for consultancy and construction tenders for various project components for the second phase of the Deep Tunnel Sewerage System (DTSS).
The DTSS, termed "a used water superhighway", are deep sewer tunnels that carry wastewater using gravity to centralised water reclamation plants in Changi and Tuas. The used water is treated and reclaimed into NEWater, with excess treated effluent discharged into the sea.
The project is part of Singapore's efforts in closing the water loop, said Prime Minister Lee Hsien Loong on Monday.
Speaking at a dialogue at the Lee Kuan Yew Prize Award Ceremony, he said that Singapore will face challenges through the increased rainfall and droughts brought about by climate change.
"We have to prepare for our own water supply which for us has always been a strategic and high priority issue," he said. While recycled water now makes up about 30 per cent of Singapore's water supply, "it can be more and we will do more".
The DTSS will help with recycling more wastewater, he added.
The first phase of DTSS, comprising the North and Spur tunnels and the Changi plant, cost S$3.4 billion and was completed in 2008.
The second phase - which includes deep tunnels extending from the downtown area to the western part of Singapore, the Tuas Water Reclamation Plant (TWRP) and an integrated NEWater factory - will cost some S$6.5 billion. It will be completed by 2025.
After that, existing water reclamation plants at Ulu Pandan and Jurong, plus the intermediate pumping stations, will be phased out and the land freed for other uses.
The entire DTSS, one of Singapore's most ambitious water projects that is expected to serve the country's used-water needs till the next century, will free up about 150 hectares of land that is now occupied by six water reclamation plants and over 130 pumping stations.
As it uses gravity through pipes up to 50m deep and does not rely on mechanical pumping, it is more reliable, said PUB. The project will also notch up several firsts for the country.
The TWRP uses membrane bioreactor (MBR) technology, which combines the two separate used water and NEWater treatment processes, reducing land required for the plant. When completed, it will be the largest MBR facility in the world with an initial capacity of 176 million gallons a day (mgd).
The plant is also co-located with an Integrated Waste Management Facility (IWMF), allowing both to process used water and waste in a more efficient manner.
It will be the first of its kind in the world planned from the greenfield stage, said PUB, adding that Amsterdam has a similar co-located project but its facilities were not designed and built to maximise synergies from the outset. The IWMF, estimated to cost S$3 billion, will be able to treat four waste streams: incinerable waste, household recyclables, food waste and dewatered sludge from the TWRP. Singapore's current four waste-to-energy plants can only process incinerable waste.
Designed to meet Singapore's long-term demand for solid waste management in view of a growing population, IWMF will have four different facilities: waste-to-energy (5,800 tonnes a day), materials recovery (250 tonnes a day), food waste treatment (400 tonnes a day) and sludge incineration (800 tonnes a day).
The National Environment Agency (NEA) will, between this year and next, shortlist potential consultants that can bid to provide professional engineering services for the IWMF project. Between 2017 and 2018, it will pre-qualify companies for engineering, procurement and construction (EPC) tenders, and from 2019 onwards it will move into the detailed design, construction and commissioning stage.
Having both TWRP and IWMF sited together will bring about several synergies, such as the transfer of dewatered sludge, grit, biogas and water from TWRP to IWMF, and the movement of food waste, power supply, and steam the other way.
Mr Lee said: "You have the sludge, you process it, you incinerate it, you generate electricity from it, and the energy goes back to the wastewater plant."
"So, in Singapore, nothing is wasted," he said. "But it requires foresight planning, determination, and you need the resources."