For desalination plants treating seawater, the problem of brine disposal is potentially even greater. One 1985 study of the contaminated ag waste water in the Central Valley’s heavily polluted San Luis Drain showed the water contained 9.2 grams of total dissolved solids per liter of water. Clean seawater from the Pacific Ocean has around 38 grams of dissolved solids per liter.
That might not seem like a huge problem: after all, people will shell out between five and ten bucks a pound for sea salt, which is just seawater with the water removed. But it adds up. If the Carlsbad plant puts out 50 million gallons of freshwater a day as advertised, that means (at 38 grams per liter, converted from the metric) it’s removing 417,270 pounds of salt and other solids a day from that water.
And unless the people of San Diego start eating a pound of sea salt for every three gallons of freshwater they drink, bathe in, or water their gardens with, that means a surplus of removed solids piling up at the desal plant.
Chris Clarke explains more of the waste realities for desalination here.
Photo credit: NBC News