By the year 2050, some 52 percent of the world's projected 9.7 billion people will be living in water-stressed regions, according to MIT researchers.
For some countries, water is already a problem, and the city-state Singapore with its 5.7 million population is one of them.
This is because Singapore doesn't have enough natural water resources, to begin with. For the longest time, the city-state had to rely on Malaysia to deal with its water problems; however, this is no longer the case.
The government has developed a sophisticated sewage treatment system involving a network of tunnels and high-tech plants and can transform sewage into safe drinkable water, according to a press release on Phys.org.
According to Singapore's water agency's estimates, around 40 percent of the city-state's water demand can now be met with recycled wastewater, and that figure is expected to rise to 55 percent by the year 2060.
The majority of recycled water is used for industrial purposes, while some is added to water supplies in reservoirs. Only a small portion of the treated water is discharged into the sea, which helps reduce pollution.
What's the interesting engineering behind Singapore's plant?
The city-state is collecting every drop of water and reusing "endlessly," as explained by Low Pei Chin, chief engineer of the Public Utilities Board's water reclamation department.
The Changi Water Reclamation Plant, located on the city's eastern coast, is at the heart of the recycling efforts. It is partially underground, with some sections even reaching depths of up to 25 stories. Wastewater that flows through a huge, 30-mile (48-km) tunnel connected to sewers feeds the facility.
The complex, which consists of a maze of steel pipes, tubes, tanks, filtration systems, and other machinery, has the capacity to treat up to 237 million US gallons (900 million liters) of wastewater per day, which is an astonishing amount — This number is reportedly enough to fill an Olympic-sized swimming pool every 24 hours for a year.
When wastewater reaches the plant, it is filtered before powerful pumps send it to facilities above ground for further treatment. The processed water goes through further cleaning there thanks to advance filtration processes. Impurities such as bacteria and viruses are removed and disinfected with ultraviolet rays.
This is how the final product, called "NEWater", is achieved. This water is mostly used in microchip manufacturing plants, which require high-quality water and are commonplace in Singapore. During dry seasons, it goes through further treatment and flows through people's faucets.
It seems like this is only the beginning though. Singapore is expanding its recycling system and intends to spend $7.4 billion (Sg$10 billion) in water treatment infrastructure upgrades. The city-state plans to add an extra underground tunnel and construct a large water reclamation plant by 2025.