As global freshwater reserves dry up, desalination plants are receiving greater attention as an option for providing both drinking water supplies and agricultural irrigation. But a new study released on Thursday raises several concerns about the environmental impact and cost effectiveness of the widely touted technology to convert seawater to fresh water. Desalination plants pose a risk to marine species when the water is collected from ocean areas, as well as when the salty discharge is deposited into coastal estuaries, according to the report, which was released by the U.S. National Research Council (NRC).
As global freshwater reserves dry up, desalination plants are receiving greater attention as an option for providing both drinking water supplies and agricultural irrigation. But a new study released on Thursday raises several concerns about the environmental impact and cost effectiveness of the widely touted technology to convert seawater to fresh water.
Desalination plants pose a risk to marine species when the water is collected from ocean areas, as well as when the salty discharge is deposited into coastal estuaries, according to the report, which was released by the U.S. National Research Council (NRC). Also, current desalination technology often does not adequately remove the chemical element boron, which occurs naturally in seawater and is considered toxic to humans, the report said.
Despite the "considerable amount of uncertainty" regarding desalination impacts, however, the study concluded that the projects can safely continue, though further research is necessary to help reduce potential risks. "It was the committee's feeling that the uncertainties are not at the level that we should stop moving forward," said Amy Zander, chair of the council's Committee on Advancing Desalination Technology. "There are environmental effects of any water source, so let's mitigate them."
A quarter of the world's low-income population lacks access to at least 20 liters of dependable water on any given day, according to the World Bank. As climate change intensifies, water scarcity will likely persuade more nations to develop desalination technology, especially in the arid regions like the Middle East. Although seawater desalination provides only 1 percent of the world's drinking water currently, its global capacity more than doubled between 1994 and 2004, according to the International Desalination Association.
The discharge from desalination plants is almost entirely water, and .01 percent is salt. While estuary species in brackish water can survive at a known limit of this discharge, it is not well understood how the increased salt content will affect estuary or saltwater wildlife throughout their development. Because of this uncertainty, desalination operations that remove salt from brackish water (the most cost-effective option for landlocked arid regions) should avoid releasing the discharge into freshwater ecosystems, said Zander, an environmental engineering professor at Clarkson University. "Discharging into sea water is probably okay. We need to better understand it, but it's probably okay. Discharge into freshwater is not a long-term solution," she said.
The amount of boron that remains in drinking water after most "reverse-osmosis" desalination practices exceeds World Health Organization (WHO) guidelines, the report notes. High boron intake has been linked to testicular lesions in rats, mice, and dogs. In the United States, concerns about boron levels have stalled desalination plant permits, Zander said. "In other countries [desalinated water] may be served as drinking water with higher boron levels than recommended because no regulations say it needs to be lower than the WHO guidelines."
These issues have led environmental organizations to criticize
desalination technology. "Desalination proponents envision a chain of
expensive plants framing our coastlines and providing steady profits
for investors. In this possible future, the costs are paid by water
customers and the environment," said Wenonah Hauter, executive director
of Food & Water Watch, in a prepared statement. "Desalination facilities have the potential to create more problems than they solve."
But Tom Pankrataz, director of the International Desalination Association, said Hauter's comments reflected a selective analysis of the report. Across the world, desalination plants are using advanced modeling to limit wildlife casualties and better diffuse the salt discharge. "Generally in the International Desalination Association, we're not proposing to use desal other than where it can be responsibly applied and effectively used," he said.
Energy costs, rather than environmental concerns, have been the main deterrent to desalination plant expansion. Zander said the NRC panel convened with expectations that technological improvements could lower the cost of desalination, but they found that the technology is nearly as efficient as possible at present. The most a plant can reduce its energy consumption is 15 percent, the report predicts.
"What we found is we're near the energy minimum already, which is great," Zander said. "It shows the technology is mature and ready to be used, but the cost will remain a factor."
This story was updated April 28 at 12:40 p.m.