Straits Times 18 Jun 09;
'WASTE not' might just as well be the motto for Singapore's latest water reclamation plant in Changi.
To save space, the Republic's fifth Newater factory, due to be completed next year, is being built on top of the Changi Water Reclamation Plant's (CWRP) underground facilities.
Mr Young Joo Chye, deputy director of best sourcing department at national water agency PUB, said the stack concept is a unique feature: 'If we had not adapted we would have required three times the land.'
The Ulu Pandan water reclamation plant is spread over 46ha and can treat 79 million gallons per day (MGD). The CWRP covers 32ha but can treat 176MGD - or 320 Olympic-size pools - of waste.
Singapore produces 300 million gallons of sewage a day. The CWRP's deep tunnel sewerage system, buried beneath expressways running from north to east, has been built to last for 100 years.
The Changi Newater factory will have a capacity of 50MGD and with similar plants at Ulu Pandan, Kranji and Bedok will reclaim one-third of Singapore's waste water by 2011. The Seletar Newater plant and its water reclamation facility will be axed in 2011.
CWRP and its sewerage system is phase one of PUB's plans for waste water. Two water reclamation facilities at Bedok and Kim Chuan, have been phased out. In the next 10 to 20 years, another deep tunnel sewerage system and water reclamation plant will be built at Tuas and two or all of the remaining such plants at Kranji, Ulu Padan and Jurong will be shut down.
VICTORIA VAUGHAN
Changi Water Reclamation Plant to open next week
Hasnita A Majid, Channel NewsAsia 17 Jun 09;
SINGAPORE : Singapore's largest and most advanced water reclamation plant - the Changi Water Reclamation Plant - will open next week.
The pumping station at the new Changi Water Reclamation Plant is as high as a 25-storey building.
The station collects all used water from the deep sewerage tunnels via gravity.
The water then undergoes a treatment process at the plant before being discharged into the sea.
Part of that treated water will be processed into NEWater when the NEWater plant, which is being built on the rooftop of treatment facilities, is ready.
The NEWater factory which will be operational by May next year can produce 50 million gallons of treated water daily.
This is equivalent to the volume of water in 90 Olympic-sized swimming pools.
PUB said the Changi Water Reclamation plant stands out in its land use.
"The designers have incorporated a space saving design concept - things like stack treatment tanks and also stack treatment facilities like our sludge treatment facilities. All the treatment facilities are stacked on top of the other so as to save space," said Yong Wei Hin, assistant director of Changi Water Reclamation Plant.
Such a concept is the first in the world. With the stack concept, the Changi Water Reclamation Plant takes up only 32 hectares of land, which is about the size of 45 football fields.
PUB said that without this concept, it would have needed 3 times more land for the construction of the plant.
Another unique feature of the reclamation plant is a Sludge Dryer, which reduces the volume of sludge to be disposed. The sludge will then be incinerated and used as landfill.
PUB said the completion of the Changi Water Reclamation Plant concludes the first phase of its Deep Tunnel Sewerage System - a used water superhighway.
The second phase of the project will see a similar reclamation plant built in Tuas. It is expected to be ready in 10 to 20 years' time.
The Changi Water Reclamation Plant, which costs some S$3.7 billion to build, can treat 176 million gallons of water per day. This is equivalent to the volume of water in about 320 Olympic-sized swimming pools.
And with its completion, PUB said a few of the existing water reclamation plants will be shut down.
Two such reclamation plants - in Bedok and Kim Chuan - have already ceased operations. - CNA /ls
Singapore sewerage: No space to waste
Jessica Rowson, New Civil Engineer 17 Jun 09;
Increasing demands on Singapore’s constrained sewerage system has seen its water authority radically rethink its strategy. Jessica Rowson reports.
The treatment of wastewater in Singapore steps into the future next week with the opening of phase one of a deep tunnel sewerage system and the Changi water reclamation plant.
The project will be opened on Tuesday by Singapore’s prime minister Lee Hsien Loong as the centrepiece for Singapore International Water Week.
The concept for Singapore’s deep tunnel sewerage system was first conceived in the late 1990s. At that time, Singapore had in place a comprehensive wastewater system, comprising over 3,000km of sewers and pumping mains, 100 pumping stations and six water reclamation plants serving the tiny 704km² island.
A bold and radical approach
The demands on the system increased in line with population and industrial growth, but the option to continue expanding the treatment capacity of the plants and adding more pumping stations was unsustainable in land-scarce Singapore.
Confronted with these challenges, Singapore’s Public Utilities Board (PUB), embarked on a bold and radical approach with the plan to build an entirely new wastewater infrastructure that would take up less space and progressively phase out the existing system.
A £1.6bn deep tunnel sewerage system is PUB’s solution to meet Singapore’s wastewater needs for the next 100 years.
“One of the drivers was to reduce land take,” says PUB assistant director Yong Wei Hin. “Singapore has only around 700km² of land.”
Wastewater is collected in sewers and conveyed to the 48km long deep tunnel sewer which runs 20m to 55m below ground. The deep tunnel sewer takes the water to the centralised Changi Water Reclamation Plant for treatment. The new system depends on gravity − it is graded towards one end so there is no need for intermediate pumping.
“The new system doesn’t take up much space on top,” says Wei Hin. “It goes deep underground. Also the new plant takes up less space.”
Minimising the impact
Eight earth pressure balance tunnel boring machines (TBMs) were used concurrently to drive the 48km long tunnel, which varied between 3.3m and 6m in diameter.
The depth of the tunnel varies between 20m and 55m. In addition, TBMs and pipe jacking were used to create 60km of link sewers between 300mm to 3m in diameter between 10m to 55m below ground.
As the TBMs advanced, the team erected reinforced concrete pre-cast segments, before sealing and bolting them together in rings to provide primary ground support.
The route of the tunnels was specifically selected to minimise the impact on existing structures.
“We aligned the tunnel along the major expressway and not beneath buildings,” says PUB assistant director Yong Wei Hin.
For corrosion protection, concrete cast insitu with 225mm thick lining and 2.5mm thick high density polyethelene (HDPE) membrane were placed inside the bored tunnel.
This project has involved 49 main contractors and consultants, with over 300 subcontractors and suppliers. A joint venture of consultants CH2M Hill and Parsons Brinckerhoff carried out a feasibility study of the deep tunnel sewerage system and designed the 48km long tunnels.
An efficient new source
The Changi Water Reclamation Plant is efficient in its land use. The plant has doublestacked treatment tanks and a six-storey building with three storeys of basement that houses the sludge handling facilities.
At 32ha, it has taken up only a third of the conventionally designed water reclamation plant’s land area, according to PUB.
The treated wastewater is channelled to a processing facility called Changi Newater Factory on the rooftop of the reclamation plant.
Here it is further purified through advanced membrane technologies. The processed water can be consumed by humans and is used in industry where high purity water is required. “It’s another source of water for us,” says Wei Hin.
Besides being used as feedstock for the new Changi Newater Factory, treated wastewater the new reclamation plant is used for purposes such as tank flushing and for cooling systems in machinery and buildings.
