All rights reserved. More brine than expected The literature had long assumed a one-to-one ratio. Correction: This story was updated on January 16, to clarify that the desalination plant in California mentioned provides 10 percent of the water for the county of San Diego, not seven percent for the city. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city.
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Poseidon is a private, investor-owned company that develops water and wastewater infrastructure. The Water Purchase Agreement assigns appropriate risks to the private sector while keeping costs for water rate payers as low as possible. The agreement transfers to Poseidon and its investors the risks associated with design, construction and operation of the desalination plant.
The boom in desal brings with it a tidal wave of brine. Because this stuff is denser than typical seawater, it sinks to the seafloor and disrupts vibrant communities of life, which find themselves wanting far less salt and far more oxygen. Facilities can mitigate the environmental impact by, for example, mixing the brine with seawater before pumping it out, to dilute it. They might also take care to expel the byproduct where currents are strongest, thus dissipating the brine quicker.
Inland, a plant might evaporate the water in pools and cart away the remaining salt. But brine is more than just hypersaline water—it can be loaded with heavy metals and chemicals that keep the feedwater from gunking up the complicated and expensive facility. Dilution may help with the hypersalinity problem, but it doesn't get rid of the chemical toxins. But herein lies opportunity: The discharge can also contain precious elements like uranium.
This might be enough incentive to turn desal brine from a noxious byproduct into a source of revenue. Or you might use evaporative pools inland to produce commercial road salt for deicing roads. Share Tweet. The Sydney Desalination Plant in Kurnell.
Step one: get your seawater First, you need a source of seawater, or brackish water a mixture of sea and freshwater. Step two: pretreatment Prior to being desalinated, the water needs to be pre-treated — this treatment process is very similar to that done for fresh water.
These pre-treatment filters can be sand-based, or materials called ultrafiltration membranes. Step four: the parting of the ways The end result of reverse osmosis is not dry salt and pure water. Step five: de-purifying the pure stuff Completely pure water, like the permeate made with reverse osmosis, is actually quite dangerous to drink.
The desalination process. Ellen Phiddian Ellen Phiddian is a science journalist at Cosmos. More from:.
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