PUB, Singapore’s National Water Agency, and the National Environment Agency (NEA) will be calling tenders with a total estimated value of more than S$5 billion over the next five years for civil, mechanical and electrical engineering works for the Tuas Nexus.
Tuas Nexus – the integration of PUB’s Tuas Water Reclamation Plant (Tuas WRP) with NEA’s Integrated Waste Management Facility (IWMF) – is the first of its kind in the world planned from the ground up. It marks Singapore’s first initiative to harness potential synergies of the water-energy-waste nexus by integrating used water and solid waste treatment processes. Construction of the two facilities is expected to commence in 2019 and will be completed in phases from 2023 onwards.
Tuas WRP Features
Tuas WRP is a key component of Singapore’s Deep Tunnel Sewerage System (DTSS) Phase 2 and is expected to be ready by 2025. At an initial treatment capacity of 800,000 m³/day, it will be the largest membrane bioreactor (MBR) facility in the world, with an overall 30 per cent more compact footprint compared to conventional plants. A used water superhighway, the DTSS is the backbone of Singapore’s used water management system and also ensures long-term water sustainability by contributing to the goal of increasing NEWater supply from 40 per cent to up to 55 per cent of total water demand in the long term.
Unlike conventional WRPs, the Tuas WRP will receive domestic and high-strength industrial used water flows from two separate deep tunnels. It will also feature a unique combination of advanced physical, biological and chemical treatment processes. This includes space-efficient lamella primary sedimentation tanks, two energy-efficient MBR systems to treat the two used water streams separately to higher quality standards for NEWater and Industrial Water production, and a thermal hydrolysis process to increase biogas production and energy recovery, as well as reduce sludge for disposal.
The plant will also be equipped with solar panels on its rooftop in the long term, which is expected to generate up to 8MWpeak of additional power.
In another first, PUB will also reclaim high-strength industrial used water to produce Industrial Water at Tuas WRP. Currently, Industrial Water is produced using treated domestic used water at Jurong and Ulu Pandan WRPs. Tuas WRP’s MBR system will effectively treat high-strength industrial used water for reuse by industries mainly in Jurong Island and Tuas.
Tenders for Tuas WRP
A total of about 11 construction tender packages is expected to be called over the next five years for Tuas WRP, estimated to be valued at over S$2 billion. The first tender was called in May 2018 for development works at the Tuas WRP site such as support infrastructure, utilities and a near-shore outfall for discharge of excess treated used water into the sea.
The second tender is scheduled to be called by Q4 2018 for the construction of the plant’s Influent Pumping Stations. This pumping station will be PUB’s deepest pumping station yet, consisting of five deep shafts up to 80 metres (or 30-storeys) underground, which receives used water from the deep tunnels and pumps it up to the treatment modules.
PUB plans to call the third tender by early next year for the construction of the Industrial Liquids Module for the treatment of industrial used water to produce Industrial Water. Tenders for eight more contract packages for the construction of other components of Tuas WRP will be called progressively from 2019 onwards.
The IWMF is an integral part of NEA’s long term plan to meet Singapore’s solid waste management needs. Unlike a typical Waste-to-Energy plant which treats only incinerable waste, the IWMF will be built with treatment processes for multiple waste streams namely incinerable waste, household recyclables, source-segregated food waste and dewatered sludge from PUB’s Tuas WRP. Integrating these processes in one facility will better enable the IWMF to maximise both resource and energy recovery from waste while minimising its environmental footprint.
The IWMF will be built in two phases, with an initial incineration capacity of 2,900 tonnes per day for incinerable waste when the Waste-to-Energy incineration facility is completed in 2023. The remaining facilities in the first phase of the IWMF comprising the Materials Recovery Facility, Food Waste Treatment Facility and Sludge Incineration Facility, will be completed by 2024, which would mark the completion of Phase 1 of the IWMF.
The current plan is to eventually increase the incineration capacity at the IWMF to 5,800 tonnes per day in 2027. The heat from the incineration process will be recovered to generate electricity. Part of the electricity generated will be used to operate the IWMF and Tuas WRP whereas most of the electricity generated will be fed to the grid and will be sufficient to power 300,000 four-room HDB apartments.
Tenders for IWMF
A total of three Engineering, Procurement and Construction (EPC) tender packages and one build tender, estimated to be valued at over S$3 billion will be called over the next five years. The pre-qualification of EPC tenderers will be called in July 2018 to shortlist potential EPC tenderers for the development of key facilities within IWMF Phase 1. The second stage tender for EPC tenders will be called by January 2019.
Separately, the build tender for the development of a 230kV Electrical Substation for the Tuas Nexus will be called by December 2018.
Harnessing Synergies in Tuas Nexus
The Tuas Nexus will maximise efficiencies in energy and resource efficiency, by employing the latest technologies to harness the synergies of the water-energy-waste nexus from used water and solid waste.
A highlight of Tuas Nexus is its ability to achieve full energy self-sufficiency. The codigestion of sludge and food waste, and the Thermal Hydrolysis pre-treatment (THP) process at Tuas WRP using steam from IWMF, will enable Tuas WRP to improve the yield of biogas. The biogas will be utilised at IWMF to increase IWMF’s overall plant efficiency and boost electricity production.
“The Tuas Nexus is a bold innovation in the action for climate change and sustainability. This pioneering facility was designed to maximise the full potential of the integration of Tuas WRP and IWMF, and marks a new way in which used water and solid waste will be treated in Singapore. We look forward to working with industry partners and technology providers to build Tuas WRP, which aims to be the most energy-efficient MBR plant in the world and the cornerstone of Singapore’s used water management strategy,” said Mr Yong Wei Hin, Director, DTSS Phase 2, PUB.
Instead of being transported out for disposal, dewatered sludge which is the final byproduct from the Tuas WRP’s used water treatment process, will be sent to the IWMF for incineration and for energy recovery. Excess treated effluent from used water treatment will also be used by the IWMF for its processes to reduce potable water demand. Integrating both facilities in a compact space also optimises land use.
This integration will result in national carbon savings of more than 200,000 tonnes of CO2 per year, equivalent to taking 42,500 cars off the roads for Singapore.
“The IWMF is an integral part of Singapore’s solution towards long term environmental sustainability. Leveraging state-of-the-art advanced technologies for the treatment of solid waste, the IWMF will maximise energy and resource recovery while keeping its environmental footprint to the minimum. IWMF’s integration with Tuas WRP will further enhance the performances of both facilities and make Tuas Nexus truly an iconic water-energy-waste nexus” said Mr Joseph Boey, Project Director IWMF, NEA.
PUB and NEA also unveiled a joint Tuas Nexus showcase at the Singapore International Water Week (SIWW) and CleanEnviro Summit Singapore (CESS) 2018.