Reduce, reuse, recirculate

Reduce, reuse, recirculate

Decreasing water resources and growing populations are forcing cities around the world to look for ways to improve their water supply and educate consumers in water use and reuse.

In a growing number of urban areas around the world water scarcity is or will soon become a major problem. A 2007 report from the United Nations Environment Programme (UNEP) predicts that by 2025 freshwater withdrawals will have increased by 50 percent in developing countries and by 18 percent in developed countries. Already 60 percent of European cities with more than 100,000 people use groundwater at a faster rate than it can be replenished, according to figures from the World Business Council for Sustainable Development.

 “One fairly new solution is reclamation of already used water, but it is still at the early stages,” says Per-Arne Malmqvist, professor at Stockholm International Water Institute (SIWI).

Public acceptance cannot be taken for granted

Basically, this means reclaiming the water content of wastewater, treating it until it is clean again. However, public acceptance for reusing water cannot be taken for granted.

“There are negative connotations to words like ‘sewage’ or ‘wastewater,’” says Malmqvist. “Those who have worked with wastewater treatment have used different terminology.”

That is the case in Singapore, for example, where the source is called “used water” and the treated water “NEWater.” However, in water-strapped southern California, Orange County took another approach when talking to its 2.4 million residents about the Groundwater Replenishment System (GWRS). The GWRS is a freshwater supply project based on purification of wastewater, launched in the 1990s as a joint effort between the local water and sanitation districts, OCWD (Orange County Water District) and OCSD (Orange County Sanitation District).

“We were very proactive in saying the word ‘sewer’ many times over so that people really understood what the source of the water was,” says Eleanor Torres, director of public affairs at OCWD.

Torres says it was a lesson learned from earlier projects in other parts of California, which had been shelved due to public reaction such as “You didn’t tell us it was sewer water.” This was not going to happen to the GWRS.

“We went out in full force to talk to every single group in the community that would listen to us, to earn their trust and support,” Torres says.

The GWRS purifies wastewater through microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. About half of the 70 million gallons (260,000 cubic meters) of purified water per day is injected into an underground seawater barrier that has been designed to protect the groundwater from saltwater intrusion. The other half is pumped into spreading basins where it takes the same path as rainwater to the groundwater basin. The system went online in 2008, and according to Torres it has been fully embraced by the public.

Across the Pacific Ocean in Phnom Penh, the capital of Cambodia, the Water Supply Authority (PPWSA) faced a different hurdle. It had to educate users about the reality of paying for public water. When Ek Sonn Chan became appointed general manager of PPWSA in 1993, some of the more affluent people in the city, including certain public authorities, didn’t see why they should have to pay for their water. After years of neglect, the city’s water supply system was in mess, with numerous unauthorized connections. But Ek Sonn Chan recognized that a sustainable water supply required sound economics, and PPWSA installed functioning water meters after refurbishing the system.

“When you install a water meter it affects how customers think,” he said in a TV documentary produced in association with the Asian Development Bank (ADB). “The water consumption is measured so for sure they have to pay.”

It took some time and eff ort to convince customers of this reality, but today PPWSA provides the entire inner city with water, and the network is being expanded to surrounding districts. According to ADB, the number of connections rose from less than 30,000 to almost 150,000, including 15,000 families in poor communities. At the same time, water losses due to leakages have been reduced from 72 percent to just six percent.

In wealthier countries, water losses can be 20 percent or more. In its 2007 report European Water-Saving Potential, the Ecologic Institute, a U.S.-based think tank, argues that leakage reduction of the water supply system combined with water-saving devices and more efficient household appliances would allow savings of up to 50 percent within the European Union.

Restricting water loss is one way to increase water supply. For areas bordering oceans, desalination of seawater is another option.

“Many large desalination plants are being built around the world right now,” says Malmqvist of SIWI. “Of course, if you use fossil fuels to run them, there will be a backlash in the form of increased emissions of carbon dioxide.”

The use of solar power and the implementation of efficient energy-recovery technology can help solve that problem. According to Australian water authority WaterSecure in Southeast Queensland, its Tungun desalination plant recovers 97 percent of the process energy remaining in the seawater concentrate before it is returned to the ocean.

by Åke R. Malm