This land, to be developed for other purposes, is roughly three times the size of the Central Business District.

But the benefit goes beyond land use, said Mr Lee.

The Changi building will have a Newater plant built on its rooftop to turn the treated used water into water safe enough to drink.

When ready next year, the Newater plant, with the existing four, can double Newater capacity to meet one-third of Singapore's water needs.

These benefits were highlighted by Mr Lee at the opening ceremony of the Changi Water Reclamation Plant.

It was a main attraction of the Singapore International Water Week, attended by some 10,000 policy-makers and industry leaders from around the world.

Through the five-day annual conference, now in its second year, Singapore also hopes to promote an international exchange of ideas on innovative water solutions, Mr Lee said.

With rapid urbanisation and population growth draining the world's natural resources, 'cities will require a combination of far-sighted planning, sustained investment in infrastructure and breakthroughs in technology', he added.

In Singapore, the approach involves a network of underground tunnels that will pipe waste water from all over the island to two centralised treatment plants.

The Changi plant is the first in this deep tunnel sewerage system. A second plant in Tuas will be built over the next 10 to 20 years.

The Changi plant can treat 800,000 cu m of used water, piped daily from the northern and eastern parts of Singapore. This will form a vital feedstock for the Newater factory.

The Changi complex was 15 years in the making, and 'we pressed on despite economic downturns and the Sars crisis', Mr Lee noted.

The ultimate goal is to have an adequate supply of water for Singaporeans for years to come, he said.

Singapore imports 40 per cent of its water from Malaysia under two international agreements, one expiring in 2011 and the other in 2061. The rest of its supply comes from Newater, rainwater capture and desalination.

The plant is also significant in another way, noted Mr Lee.

It is part of Singapore's overall strategy for sustainable development, showing that environmental sustainability is not incompatible with economic development.

Although the population has soared from 1.6 million in 1959 to 4.8 million today, the environment has not suffered but improved.

Said Mr Lee: 'Singaporeans enjoy fresh air, clean water and good public health and almost half the island is covered with greenery, parks and nature areas.'

But a challenge awaits Singapore: sustaining the environment as the city grows and gets denser.

An inter-ministerial committee made its first recommendations in April on how Singapore can develop sustainably.

The water industry is a key plank of this green policy, Minister for the Environment and Water Resources Yaacob Ibrahim said yesterday.

He pointed to the Changi plant as a good showcase of cutting-edge water technology, involving about 350 local and overseas contractors, consultants and suppliers.

Visitors touring the facility yesterday were keen to find out more about it.

India's S.R. Roop Kumar, a chief engineer of the Bangalore Water Supply and Sewerage Board, said he is planning for an underground waste water reclamation plant in the southern Indian city.

-end of ST article