Population growth and urbanization continue to increase the stress on available fresh water resources. Water scarcity is a challenge faced by many regions of the world.
As urban life has taken the dominant role, water reuse today typically concerns the reuse of municipal wastewater. Today there are many applications for reclaimed water. The most significant in terms of volume is agricultural irrigation. Other typical applications include landscape irrigation, groundwater recharge, industrial use, as well as potable and nonpotable urban use.
Reliable water supply will be short by as early as 2025
Though water reuse has expanded, the pace of human development continues to outstrip available water. “In Mexico 80% of the population lives in an area with only 20% of the nation’s hydraulic resources,” tells Dr. Blanca Jiménez, water treatment and reuse specialist at the Universidad Nacional Autónoma de México.
“Everyone must understand the fact that we have a limited available fresh water supply,” emphasizes Dr. Takashi Asano, professor emeritus in environmental engineering at the University of California, Davis. “With projections showing 50% of the world’s population living in urban areas soon, reliable water supply will be short by as early as 2025.”
Positive examples of water reuse
In the late 1970s, Dr. Asano was recruited to the State of California to help develop water recycling research and groundwater recharge. After the aqueduct was completed, California policy turned to reuse, implementing several projects to use reclaimed water for irrigation, groundwater recharging, and urban use.
Mexico City is facing the fact its population has outgrown current water supply. The city is also feeling the effects of over-reliance on ground water. Restrictions on ground water use are in place, and water reuse has been implemented to recharge canals, lakes and aquifers, as well as for urban uses like car washing.
The main focus in Australia has been industrial water reuse. The earliest example, reusing municipal water for boiler feed water at a power station, goes back nearly 20 years. In Western Australia, due to major climatic changes natural water supply has dropped significantly. Perth uses two sea water desalination plants for additional fresh water.
Mexico City is facing the fact its population has outgrown current water supply.
The biggest challence is lack of information
Cost-benefit economics of water reuse can be quite complex, but the main obstacles are with public perceptions. “We see public agreement on water reuse for industry and with agriculture, but it is more complex social issue when it comes to potable reuse,” says Dr. Anthony Fane, Director of the Singapore Membrane Technology Centre at Nanyang Technical University. “The real challenge is education; how to use these solutions, how to easily test water quality, and how to maintain water quality,” he reminds.
The quality of reclaimed water today is much better than many natural sources of fresh water. “The main thing people need to understand is that wastewater is still mostly water,” says Jiménez. “Namibia has been using direct potable reuse for more than 35 years already with no health problems.”
“Before you embark on water reuse, you have to educate the general public, to reassure them that with the right management, operations and technology, water reuse is safe,” says Dr. Harry Seah, Director of Technology & Water Quality at pub, Singapore’s national water agency.
Desalination is expanding 10-15% a year
Even in regions with extensive water reuse, sometimes water demand is greater than the supply. In such cases, desalination of sea water or brackish water can be used to augment fresh water supply. “Desalination is a vigorously growing area, expanding 10-15% a year world-wide,” says Fane. Adoption of desalination had been slowed by the high energy demands of the process. Environmental regulations can also present hurdles to desalination. Studies are needed to ensure intake of water or brine discharge does not damage local habitats.