With mandatory water restrictions now in effect across the state, seawater desalination may seem more attractive than ever. Why restrict car washes and landscape watering when there's an ocean of water just offshore, and all you have to do is remove the salt? Tempting as it sounds, however, seawater desalination has proven a poor choice for California ci
ties in the past, as Michael Hiltzik's column in last week's LA Times explains. Santa Barbara started building a $34 million desalination plant to deal with a severe drought in the 1980s; by the time the plant was complete, the drought was over and the plant was mothballed.
The problem is one of efficiency and economics. Even though desalation taps into a virtually limitless supply of water, it's significantly more expensive and consumes a lot more energy than water recycling. That's why Santa Barbara never used their desal plant; the water from the plant cost much more than water from other sources to the point where it wasn't competitive. So while desal sounds appealing in theory, in practice it eats up too much power and cash to compete with alternatives. And it's also undesirable from an environmental perspective; it consumes more power and hence is associated with more greenhouse gas emissions than either recycling or conservation. Desalination probably will have a role to play for California in the long run, but for now the hefty price tag means it should be an option of last resort.
The same considerations of price and efficiency often make water recycling a better bet. Take Orange County for example; their groundwater replenishment system purifies reclaimed wastewater to exceed drinking water standards, then returns it to their groundwater aquifer. The process they use is very similar to the one used by modern desalination plants but is significantly cheaper and less energy-intensive because reclaimed water has a much lower salt content than seawater, which means it takes a lot less pressure to filter it through a reverse osmosis membrane. The lower operating cost associated with water recycling explains why Orange County's system produces up to 70 million gallons of purified water a day, while Santa Barbara's desal plant currently lies idle.
Politicians sometimes forget these factors and sign on to expensive new desal projects like the one now under construction in Carlsbad. These projects are attractive because they promise a drought-proof supply of water, but tempting as that sounds at a time like the present, we have to ask: how much is it going to cost? are there cheaper and more efficient alternatives? and if so, why don't we implement those first? If we're already getting about as much as we can from water recycling and conservation, then responsible desalination may be considered. But across most of California at the moment, these other options are far from fully tapped. Desalination should be where we finish, not where we start.
By a Surfrider volunteer