California's Mega-Drought: Nuclear Power To The Rescue

The nuclear plant desalinates ocean water using reverse osmosis and ultrafiltration. The nuclear plant depends on a desalination plant as its sole source of fresh water, used for the plant's two nuclear reactors as well as all other water needs such as drinking water for its employees and irrigation of its grounds.

Although a relatively small plant, Diablo Canyon's seawater desalination plant is presently the largest operating desal facility on the West Coast, producing about 675,000 gallons of freshwater a day.

But the desal facility is not running at maximum capacity. It can actually produce a million and a half gallons of fresh water a day, and can ramp up right now, with very little upgrade and additional costs.

After four consecutive years of drought, San Luis Obispo County sees the additional 825,000 gallons per day of freshwater production as key to helping it cope with the drought.

Diablo Canyon's desal facility will fall to second place in California when a commercial desalination plant in Carlsbad begins producing about 50 million gallons per day in November. In addition, Santa Barbara is evaluating whether to restart its mothballed desalination plant. And the city of Marina Coast in Monterey Bay is planning to develop large desal capabilities. These would increase the state's capacity to almost 100 million gallons per day.

Desalination is not a new idea. Most of Abu Dhabi's gas-fired power plants provide electricity to their huge desalination plants that deliver over a billion gallons of drinking water a day. Desalination is the country's only source of drinking water.

Pacific Gas and Electric Company, which owns the Diablo Canyon plant, is happy to maximize production at the desal plant. The main requirement is additional reverse osmosis filters and storage tanks, fairly easy considering that the system is highly modular and there is plenty of space. In addition, a water pipeline is needed to connect the plant to the water users in town.

The seawater intake pipes can drag in and kill small ocean organisms, but proper filters can fix that. Even better, the intake pipes can be placed under the ocean floor to use the sediment as a natural filter. And the volume of water is comparatively small compared to the local area around the intake.

About half of the seawater that is treated in a desalination plant becomes fresh water. The salt removed stays in the other half, doubling the saltiness of the wastewater and making it a brine. The brine is generally returned to the ocean, as Diablo Canyon does, where it is quickly diluted back to normal.

The claims that the cost of desalination is huge and energy-intensive are also a bit overblown. The cost is certainly higher relative to river and groundwater that just need to be pumped to users. But relative to the effects of the drought, a fraction of a cent per gallon just isn't that much. Buying RO water from the supermarket costs about 40¢/gallon, so the public should not be too upset at a fraction of a cent per gallon to address something as grave as a megadrought.

The amount of electricity needed to desalinate seawater is also pretty low, only about 1 kWh per 100 gallons of drinking water produced (WRA). A kWh costs an average of 12¢ in America, so this is a tenth of a cent per gallon. But the Canyon Diablo nuclear plant produces this electricity at only 4¢/kWh, cheaper than most other energy sources in California, and so the cost is even less.

If desalination were to increase significantly in the state, monthly water bills might rise $10 or so. This is not much of a price to pay to ward off the worst effects of a megadrought. And new desal plants can be kept in reserve for when they are needed most, as was the case with Santa Barbara's mothballed plant.

Of course, we should exhaust all other options at the same time, particularly reusing wastewater, and capturing and treating stormwater runoff. California only reuses 9 percent of its wastewater. While this is far ahead of other states, it's only scratching the potential surface. Significant increase of wastewater treatment across California could provide over a hundred million gallons a day to the drought-stricken state.

But right now, this nuclear power plant can contribute to helping with this drought.

This article was originally posted on the Forbes website, and has been reprinted with Mr. Conca's full permission.

James Conca is a Ph.D. scientist in the fields of earth and environmental sciences for over 30 years, and is a contributor to Forbes.com. He writes extensively on energy issues. You can follow him on Twitter.