World’s first facility designed to integrate used water and solid waste treatment, the energy self-sufficient Tuas Nexus will export excess electricity to the grid that can power up to 300,000 homes.  

JOINT NEWS RELEASE BETWEEN PUB AND NEA

Singapore, 9 July, 2018 – 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.

2          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

3          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% to up to 55% of total water demand in the long term.

4          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.

5          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

6          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.

7          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.

IWMF Features

8          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.  

9          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.

10        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

11        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.

12        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

13        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.

14        A highlight of Tuas Nexus is its ability to achieve full energy self-sufficiency. The co-digestion 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.

15        “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.

16        Instead of being transported out for disposal, dewatered sludge which is the final by-product 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.

17        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. 

18        “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.

19        PUB and NEA also unveiled a joint Tuas Nexus showcase at the Singapore International Water Week (SIWW) and CleanEnviro Summit Singapore (CESS) 2018. The showcase at Water Expo is located Basement 2, Marina Bay Sands Convention Centre. The Tuas Nexus Business Forum will take place on 11 July 2018 (Wednesday) from 10:30am to 1:00pm, at Level 4 of the Convention Centre.

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MEDIA FACTSHEET

TUAS NEXUS

The Deep Tunnel Sewerage System (DTSS) Phase 2 and the Integrated Waste Management Facility (IWMF) are iconic flagship projects undertaken by PUB and NEA respectively in the area of used water and solid waste treatment. One of the highlights of the two projects is the co-location of DTSS Phase 2’s Tuas Water Reclamation Plant (Tuas WRP) with the IWMF. This will allow PUB and NEA to effectively harness process synergies from used water and solid waste treatment.

Tuas Nexus Synergies

Synergies derived through the co-location of the Tuas WRP and IWMF include:

About the Deep Tunnel Sewerage System (DTSS)

A superhighway for used water management, the DTSS is a core water infrastructure which provides a cost-effective and sustainable solution to support Singapore’s continued growth and meet its long-term needs for used water collection, treatment, reclamation and disposal.

The DTSS uses deep tunnel sewers to convey used water entirely by gravity to centralised WRPs located at the coastal areas. The used water is then treated and further purified into ultra-clean, high-grade reclaimed water called NEWater, with excess treated effluent discharged to the sea.

DTSS Phase 1, comprising the North and Spur Tunnels, the associated link sewers, the Changi WRP and outfall, was completed in 2008. Two NEWater factories, located on the rooftop of the Changi WRP, were officially opened in 2010 and 2017 to facilitate large-scale water recycling.

The DTSS Phase 2 conveyance system comprises the South Tunnel which conveys domestic used water, the Industrial Tunnel for non-domestic used water and associated link sewers. Expected to complete by 2025, DTSS Phase 2 will extend the deep tunnel system to cover the western part of Singapore, including the downtown area and major upcoming developments such as Tengah Town and Jurong Lake District.

Under DTSS Phase 2, a NEWater factory to be integrated with the Tuas WRP will be built to facilitate water recycling, contributing to the goal of increasing NEWater supply from 40% to up to 55% of total water demand in the long term. Tuas WRP will also be integrated with NEA’s Integrated Waste Management Facility (IWMF), to harness potential synergies of the water-energy-waste nexus.

Unlike conventional WRPs, the advanced Tuas WRP will be receiving used water flows from the western part of Singapore via two separate deep tunnels – a tunnel to convey domestic used water and another to convey high-strength industrial used water. It will also use membrane bioreactor (MBR) technology to treat both used water sources and to higher standards. Domestic used water will be treated at a 650,000m3/day (or 143 million imperial gallons per day) module and then further purified to NEWater, while industrial used water will be treated at a separate 150,000m3/day (or 33 million imperial gallons per day) module to become Industrial Water and sent back to industries for reuse.

With an initial total treatment capacity of 800,000m3/day (176 million imperial gallons per day or 320 Olympic-size pools), Tuas WRP will be the largest MBR facility in the world, but with an overall 30% more compact footprint compared to conventional plants. Tuas WRP’s integrated NEWater factory will have an initial capacity of 25 million imperial gallons per day.

The compact Tuas WRP will also incorporate a novel combination of advanced technologies and treatment processes to improve its energy efficiency – doubling the energy recovery compared to conventional plants, reduce plant footprint, produce less sludge for disposal and will be highly automated to minimise manpower needs.

In preparation for this, PUB is testing and validating various used water treatment technologies at the Ulu Pandan wastewater treatment demonstration plant before implementing them in Tuas WRP. This 12,500m3/day (2.75 million imperial gallons per day) demonstration plant won the Water/Wastewater Project of the Year Award at the 2018 Global Water Awards.

The completed DTSS will also streamline the used water network with three centralised collection and treatment points: Changi WRP in the east, Kranji WRP in the north and Tuas WRP in the west.

Once Phase 2 is in place, the existing conventional WRPs at Ulu Pandan and Jurong, as well as intermediate pumping stations, will be progressively phased out and the land freed up for higher value development. The implementation of the entire DTSS will result in a 50% reduction in land taken up by used water infrastructure once it is fully completed, from 300 hectares in the 1990s to 150 hectares in the long term. The land freed up by DTSS is equivalent to about 214 football fields.

Innovative and advanced technologies at Tuas WRP

Lamella Primary Sedimentation Tanks

Used in the initial stages of wastewater treatment, primary sedimentation tanks separate the solids from liquid wastewater by allowing solids to settle to the bottom of these tanks. The settled solids, also known as sludge, will be removed for biogas generation while the liquid wastewater is then sent for secondary treatment. Lamella primary settling tanks uses inclined plates which increases the maximum efficient surface area for solids to settle on with the same tank space.  The use of Lamella technology saves up to 40% land footprint compared to conventional Primary Sedimentation.

Membrane Bioreactor (MBR)

MBR technology is used in the secondary stage of wastewater treatment. A bioreactor houses naturally-occurring bacteria which break down waste products in wastewater, after which microfiltration/ ultrafiltration membranes – with fine pores invisible to the eye – filter the remaining impurities. MBR is a more efficient method as it optimises the wastewater treatment process, enabling wastewater to be treated using less steps and less space compared to conventional systems. It also produces a higher quality treated effluent. The treated water is then used as feedwater for NEWater production or supplied to industries. 

At Tuas WRP, an integrated NEWater Factory streamlines the production process of NEWater from treated used water. The advanced MBR system eliminates the need for both the secondary settlement tanks found in conventional used water treatment process and the microfiltration/ultrafiltration step in conventional NEWater treatment process. This results in the liquids treatment module in Tuas WRP having a 30% more compact footprint compared to conventional liquids treatment.

Thermal Hydrolysis Process (THP)

THP is part of the solids treatment module at Tuas WRP. The aim of the solids treatment is to recover energy from sludge and reduce the sludge volume for disposal. THP pre-treats sludge for digestion using high temperature (165 degrees Celsius) and pressure to improve the rate of sludge breakdown in digesters, so that more organic content can be converted to biogas. This also reduces the residual amount of solid waste to be disposed.

Upcoming Tenders for Tuas WRP

About the Integrated Waste Management Facility

In 2017, a total of 7.70 million tonnes of solid waste was generated. While about 61 per cent of waste generated was recycled, our four Waste-to-Energy (WTE) plants incinerated about 2.85 million tonnes in 2017. The amount of waste generated is expected to grow with an increasing population and growing economy. To meet Singapore’s long term solid waste treatment needs, NEA is building an Integrated Waste Management Facility (IWMF).

Unlike the existing WTE plants which only incinerate waste, the IWMF will adopt an integrated approach to process various waste streams for higher resource and energy recovery while minimising environmental and land use footprint. The waste streams that IWMF will be handling include incinerable waste, household recyclables collected under the National Recycling Programme, source-segregated food waste and dewatered sludge from the Tuas Water Reclamation Plant (Tuas WRP). A summary of the treatment facilities and capacities is in the table below:

Table 1 – Summary of the tentative capacities for the treatment of the four waste streams at IWMF

IWMF will be developed in phases. The first phase of IWMF will be completed in 2024 while the whole facility is tentatively planned to be completed in 2027.

Timeline of IWMF Development

NEA will be conducting a Pre-qualification exercise to shortlist potential Engineering, Procurement and Construction (EPC) contractors for the development of the IWMF. The appointed EPC contractors will carry out detailed engineering, construction and commissioning of the IWMF. 

Waste Streams to be Treated at IWMF

Incinerable Waste

• Of the 8,443 tonnes / day of waste disposed of daily in 2017, about 60 per cent comes from domestic sources while the remaining 40 per cent is from non-domestic sources such as industrial and commercial premises.
• The electricity generated by the existing Waste-To-Energy (WTE) plants is enough to meet about two to three per cent of Singapore’s total electricity needs.

• NEA is adopting WTE incineration as it is able to reduce the volume of waste by 90 per cent and thereby help Singapore conserve landfill space.

• The incinerable waste treatment capacity of the IWMF is expected to be 5,800 tonnes/day.

Household Recyclables collected under National Recycling Programme (NRP)

• Public Waste Collectors (PWCs) are required to collect commingled recyclables (paper/cardboard, plastic, metal and glass) from all residential properties.
• Currently, the recyclables are sorted at Materials Recovery Facilities (MRF) operated by PWCs before they are sent to the recycling plants.
• To optimise both process and land use efficiency, the sorting of recyclables will be consolidated and carried out at IWMF’s MRF. With better economies of scale and through the use of advanced automatic sorting equipment, the MRF will achieve a high yield of sorted recyclables.

Food Waste

• In 2017, 676,800 tonnes of food waste were generated, of which 16 per cent was recycled. The rest of the food waste was disposed of at the WTE plants via incineration.
• Currently, food waste that is recycled is mainly homogenous food waste from food manufacturers such as spent yeast/grains from beer brewing, soya bean and bread waste. The food waste is segregated at source and sold to recyclers for conversion into animal feed. In addition, more than 50 premises, including hotels and schools, currently segregate their food waste treated them on-site into compost for landscaping purposes or water for non-potable use.
• As part of NEA’s overall waste management plan, several initiatives have been planned to help increase food waste recycling in Singapore. One of the initiatives is to collect food waste separately for treatment at the IWMF and subsequently co-digestion with used water sludge at Tuas WRP.
• IWMF’s Food Waste Treatment Facility will be able to segregate the inorganic from the organic fractions before turning the latter into bio-pulp suitable for co-digestion with used water sludge at the Tuas WRP. The co-digestion of food waste and used water sludge will increase biogas production at the Tuas WRP. The biogas produced will be utilised at the IWMF to enhance its overall plant thermal efficiency and power production.

Dewatered Sludge

• The IWMF will also be receiving dewatered sludge from the Tuas WRP for incineration at the Sludge Incineration Facility.
• Fluidised bed incineration technology will be adopted at IWMF’s Sludge Incineration Facility.

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