Tapping Into the Ocean With San Diego’s Billion Dollar Desalination Plant
Tuesday, October 7, 2014
Aired 10/7/14 on KPBS News.
San Diego is about a year away from turning seawater into fresh drinking water. The billion-dollar Carlsbad desalination plant is scheduled to open sometime next fall.
San Diego's water supplies could be seriously tested if a punishing four-year drought extends through another winter. But there is relief on the horizon.
It's not coming from rain clouds; relief is coming from the West Coast's first seawater desalination plant in Carlsbad.
The construction work is 65 percent complete and the facility is on schedule to begin making drinking water in about a year.
Surveying the construction site, Project Manager Chris Stiedemann said seawater will come from the Encina power station next door. That gas-fired power plant draws salt water from the Agua Hedionda lagoon.
"They're taking that seawater from their discharge channel," Stiedemann said. "You can see the pipe staged on the trench right there. It comes all the way up the hill. Heads over that way. And over to our first stage of filtration."
Once the water goes through a rigorous pre-treatment process it is sent to a huge pump. Leaning over, Steidemann pointed to the huge, metal-encased coil that uses electricity to drive the pump.
"When you run a current through there, it'll cause a stater to start spinning around. That spinning around happens through this shaft right here. The propeller right here, or the pump. That starts scooping the water," Stiedemann said.
That scooping action pressurizes the water to 900 pounds per square inch. That pressure forces the seawater through stacks and stacks of reverse osmosis filters.
"And, this is where the magic happens. The salinity of the water changes," Steidemann said. "So you'll get double salty water on one side and very clean, almost a clean slate of pure water on the other side."
The fresh water is treated then pumped into the regional water grid and the salty water goes back into the ocean.
Vice President Peter MacLaggan of Poseidon, which is building the desalination plant, said the $1 billion investment will generate 50 million gallons of drinking water a day. It will be the largest desalination plant in the Western Hemisphere.
"The reason why we're doing this is because the Pacific Ocean is not dependent on rain or snowfall. It's always going to be there. It's the largest reservoir in the world for that matter. So here we have a truly drought-proof supply," MacLaggan said.
If the Carlsbad facility works, MacLaggan said that success will prime the pumps for more desalination projects along the California coast. In fact, his company is already trying to develop a plant in Huntington Beach. Environmental advocate Marco Gonzalez knows what's at stake.
"There have been more than 20 proposals of various size and types of desalination plants around California," said Gonzalez, an attorney with the Coast Law Group. "We know with increasing drought conditions there's going to be a lot more pressure for that."
Gonzalez is worried about the environmental impact on sea-life. Tiny creatures will be sucked into the plant and others might be hurt by the briny discharge. Because it takes a lot of electricity to remove the salt, he's also worried about the cost.
"It'll be more than two times the cost of what we currently pay for imported water out of the gate," Gonzalez said. "Now over time those numbers will come into parity for imported and produced water at a desalination plant. But the big problem we have at Carlsbad: We still don't know how we're going to pay for it."
San Diego County water managers said every water user in the county will share in the cost, beginning next year (details are yet to come). There's a chance spreading the cost of the plant could turn into a flat fee to consumers throughout the region by 2016. Yet some water departments — like the city of San Diego — won't actually buy any desalinated water.
Even so, The San Diego County Water Authority's Ken Weinberg said developing new supplies of water remains a key strategy.
"What we're seeing now, in this drought, is really the benefits of pursuing that strategy," Weinberg said. "We've got local supplies. We've conserved water. Use is down 20 percent from just 2007. And we've got recycled water. We've got brackish ground water."
And soon desalinated water.
In fact, there have been talks about a Camp Pendleton desalination plant that would be three times the size of the Carlsbad facility. Weinberg said that is mostly long-term planning, but he said reducing reliance on imported water is very much a present-day concern.
"In the future we're going to be about half local supplies and conservation and about half imported water. And that local supply is a mix of seawater desalination, recycled water and ground water, and continued and expanded conservation," Weinberg said.
How the Carlsbad plant performs will likely influence how other California projects are viewed. The people building the facility remain confident the technology will prove itself.
"We think once the plant does go on line, everyone's going to realize this source of water from the Pacific Ocean can be and should be a part of our future water portfolio," MacLaggan said.
Operators should be ready to begin testing the plant next spring. Full-blown water production could begin a year from now.
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