Desalination: a viable option?

iceberg for water supply
Some people have suggested towing icebergs to places that need freshwater. Photo: SERPENT Project

Drought. Scarcity. Pollution. Climate change. Demand. Overpopulation. These are all issues with our nation’s water supply with which we have become all too familiar. Engineers and water systems are scrambling for solutions, and countless possibilities — some as basic as conservation and water bans and some as complicated as water reclamation and transporting icebergs — have been considered. Communities struggle to meet demand with dwindling supply and a limited budget, and many have begun to give desalination serious consideration.

Desalination, or the process of removing salt from water, used to be summarily dismissed as a supply option due to its expense and energy consumption. However, in light of the increase in water scarcity, desalination has become a feasible option for many water-stressed communities. Already commonplace throughout the Middle East, desalination plants are now popping up all over southern California and Texas. Let’s look at some facts about global desalination:

  • carlsbad desalination plant
    When complete, the Carlsbad, CA desalination plant will be the largest in the western hemisphere

    Dubai sources over 98% of its potable water supply from desalination

  • Global leaders in desalination are Saudi Arabia with 17% of global output, United Arab Emirates with 13.4%, and the United States with 13%
  • Nearly 70% of Israel’s domestic water consumption comes from desalination
  • Most desalination plants are in the Middle East, where energy is less expensive and environmental regulations are less stringent
  • Currently under construction, the $1 billion, 50 mgd Carlsbad desalination plant in Carlsbad, CA will be the largest in the western hemisphere when completed
  • Costing $2 billion, the Sydney, Australia desalination plant has not produced any water since 2012 due to high dam levels

desalination diagramThe most commonly utilized desalination technology is reverse osmosis (RO), which was invented in California in the 1950s. RO uses high pressure to force water through fine membranes that leave the salt behind. For every two gallons of salty water, only one gallon is made available as freshwater. The whole process utilizes an exorbitant amount of energy, with energy accounting for up to half the total cost of desalination. In fact, desalinated water costs about $2,000 per acre-foot, which is approximately the amount of water used by a family of four in six months. Because less salty water requires less energy for processing, the most cost-effective desalination plants treat brackish, or slightly salty, water rather than seawater.

desalination fish
Impinged fish

There are some environmental concerns surrounding desalination as well. The highly concentrated salt brine left behind requires disposal. However, because it is twice as dense as seawater, it sinks to the ocean floor and spreads, suffocating bottom-dwelling marine life. Therefore, the brine byproduct must be mixed with freshwater, typically in the form of treated wastewater or cooling water from a power plant, prior to being released into the ocean. In addition, fish and other marine life are often sucked toward the intake pipes where they are killed on the intake screens (impingement), and smaller marine life, such as plankton, larvae, and fish eggs, pass through the screens and are killed during the desalination process itself (entrainment). Fortunately, there have been some recent innovations to address these concerns. For example, subsurface intakes pull seawater from beneath the seafloor, virtually eliminating impingement and entrainment. An added bonus to subsurface intakes is the fact that the sand acts as a natural filter that pre-filters the water, reducing the plant’s chemical and energy usage.

central_valley_california
California’s Central Valley is largely agricultural and relies heavily on irrigation

This summer, HydroRevolution, a subsidiary of San Francisco-based agricultural and commercial water producer WaterFX, announced its plans to build California’s first commercial solar desalination plant in the state’s heavily agricultural Central Valley. The plant will run solely off solar thermal energy and will utilize Aqua4, a new desalination technology that produces only solid salt and freshwater, with zero excess discharge. In addition, it will utilize unusable irrigation water from a 7,000-acre ditch rather than seawater. The plant will provide the necessary freshwater for the area’s irrigation needs without the energy consumption or concentrated briny discharge of traditional desalination plants. Admittedly, having the 7,000-acre ditch from which to draw the water helps immeasurably, and isn’t an option for most other areas.

But desalination isn’t only being used in the southwestern part of the country. In Massachusetts, the Town of Swansea recently opened the first publicly held desalination facility in the Northeast. A coastal town, Swansea experienced a population boom that led to groundwater supplies running low, which in turn allowed seawater to seep into the aquifers. The result was a water crisis that forced the enactment of water bans, steep fines – and even left 30% of the town without water for a brief period one summer.

According to Robert Marquis, who has acted as Swansea’s water manager for over 40 years, “We just couldn’t support a burgeoning population or commercial growth,” he said. “Anything that came into Swansea, we were objecting to it if it was going to be water intensive.”

Designed with the help of Tata & Howard’s own John Cordaro, P.E., the Swansea desalination facility has been online for over a year, and took home a third place global finish at the 2014 Global Water Awards, losing only to Dubai, Singapore, and Sorek, Israel.

reverse osmosis membrane
A semipermeable reverse osmosis membrane coil used in desalination

There is one matter with RO that, while a non-issue in sunny southern Californian, is a primary concern to the Northeast: RO filters are delicate and highly intolerant of ice, and cease being functional below 36°F. To address this issue, Swansea installed two miles of pipes in order to sufficiently heat the incoming river water prior to its entering the plant.

For water-stressed Swansea, desalination has been a successful solution. But nearby Brockton, Massachusetts has not realized the same benefit from their desalination facility. Costing roughly $120 million, the plant was constructed to utilize brackish river water as opposed to seawater, which Brockton officials believed would make the whole process affordable. However, seven years later, the water produced by the Brockton desalination plant is still too expensive, so the city has turned to a local lake as its source, leaving the costly desalination plant largely in disuse.

While desalination is heavily utilized throughout the Middle East, it has only recently come under serious consideration in the United States. As water scarcity increases due to population growth, climate change, and growing demand, alternative water source options are receiving close attention. Once not even considered due to energy costs and environmental concerns, desalination has become a frequent and sincere topic of conversation for meeting future needs. And with further advances in technology that address both energy usage and environmental impact, there remains a strong possibility that desalination could become a widely acceptable solution nationwide. Now if folks could just get on board with water reclamation
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Does west coast drought affect east coast life? You bet.

USGS drought monitor week of 8.4.15
USGS drought monitor week of 8.4.15

Drought. Every day, there are multiple news stories about the historic drought affecting America’s west and south. In April, Governor Jerry Brown mandated that Californians cut their water usage by 25%. Almond growers are being lambasted for growing a thirsty crop, golf courses are allowing their greens to turn into browns, and aquifers are being depleted at a rate far greater than they are being replenished. The outlook is bleak. Seven states are literally running out of water, and scientists are scrambling to try to address the unprecedented drought.

Yet in the midst of all of this, New Englanders are rather lackadaisical. After all, Lowell, Massachusetts just experienced the snowiest winter on record with an unprecedented 120.6 inches, earning the city the title of “snowiest city in the United States” for the 2014-2015 winter, and the summer has been fairly mild. On August 6, the USGS drought monitor showed a couple of areas of mild drought, but New Englanders have come to expect regular, soaking rains, and nobody seems too concerned. After all, New England isn’t affected by the exceptional drought of the west coast. Or is it?

Extreme Weather on Both Coasts

Newton's Third Law: for every action, there is an equal and opposite reaction
Newton’s Third Law: for every action, there is an equal and opposite reaction

Sir Isaac Newton’s Third Law states that for every action, there is an equal and opposite reaction; and while the law refers to motion, it can also be applied to weather. The severe drought and high heat of the west is directly related to the cold and snow in the northeast, and both extremes have been attrributed to global climate change. In the period of January to March of 2015, New England experienced its coldest winter on record. Providence, RI, Worcester, MA, and Hartford, CT broke all cold records during that time, while Boston, MA experienced its third coldest winter on record, with its top two coldest periods dating all the way back to the 1800s. On the opposite coast, Sacramento, CA experienced its hottest March on record, with temperatures rising to those that are more typical to May than March. Weather balances the atmosphere, so when an extreme takes place in one geographic location, the opposite extreme will occur somewhere else in the world.

“Ridiculously Resilient Ridge”

Photo Brett Albright/NWS San Diego
Photo Brett Albright/NWS San Diego

Stanford University Ph.D. candidate Daniel Swain, who writes The California Weather Blog, coined the alliterative nickname for the high-pressure area that sits over the eastern Pacific Ocean for months at a time. And, like the Ridiculously Resilient Ridge itself, the name has stuck. The ridge is basically a mountain of air that stalled off the coast of California and British Columbia, causing any storms that would typically hit California to trend farther north instead to the Alaskan panhandle and northward. The trough, just as alliteratively coined the “Terribly Tenacious Trough” by Jennifer Francis, Research Professor at Rutgers University, in turn sat over the east coast, bringing with it unusually cold, wet weather. This weather pattern, which would be typical if it lasted just a short period of time, has been extreme in that it has been incredibly persistent, developing for months at a time since 2012. In addition, climatologists are scratching their heads over it, as there is no clear reason why it has been so persistant.

Economic Impact

This car was almost completely covered after a blizzard in January 2015
This car in Massachusetts was almost completely covered after a blizzard in January 2015

New Englanders took a significant economic hit during the extreme winter of 2014-2015 due to exhausted snow removal budgets, damaged property, and high utility and heating bills. Ice dams and roof issues from the excessive amount of snow caused damage to many homes, and insurance companies are still reeling from the claims processed over the winter, which also included higher than average vehicle and accident claims. Many accidents were attributed to the severe winter and snowfall, and to the gargantuan snow piles that made driving and maneuvering in parking lots even more treacherous. And even more problems ensued when the snow began to melt in the spring.

Flooding

Flooding is not just caused by extreme rainfall but is in fact influenced by many factors, such as soil conditions and sea level. In the northeast, excessive precipitation, like the record snowfall experienced this past winter, increases soil moisture content, which in turn increases the potential for flooding. In addition, northeast sea levels have risen over a foot since last century, which already puts New Englanders at increased risk for flooding.

Food Supplies

It takes about 400 gallons of water to produce one pound of almonds
It takes about 400 gallons of water to produce one pound of almonds

California grows more food for consumption in the United States than any other state. In fact, nearly half of all the fruits, vegetables, and nuts grown in the entire country are grown in California, and the state is the fifth largest supplier of food in the world. Growing over 450 different crops, California is the exclusive U.S. producer of many crops including almonds, artichokes, clover, dates, olives, pistachios, and raisins. In addition, California also produces almost all of the grapes, lemons, lettuce, and tomatoes grown in the nation.

Prices of these crops have already risen, and are expected to rise even more. 80% of the water used in California is used by farmers and ranchers, and with the exceptional drought, many farmers have had to leave their fields fallow or pay to pump water from the ground. The economic hits to farmers are passed onto consumers, resulting in higher priced produce and nuts for the rest of the nation. If the drought continues, California farmers may be forced out of business, resulting in national food shortages. And over on the opposite coast, Florida experienced freezing temperatures that affected the 2014-2015 orange crop, resulting in the smallest yield of oranges since the 1964-1965 season.

Looking Ahead

"The blob" is a very large area of warm water that scientists are hoping may end the California drought
“The blob” is a very large area of warm water that scientists are hoping may end the California drought

At this time, forecasters are hoping that the extreme drought in California may be coming to an end. The combination of El Nino and “the blob” create a high possibility for a temperate, wet winter in the Pacific Northwest, and California residents and businesses are keeping their fingers crossed — as should New Englanders. Once again referring to Newton’s Third Law, we can safely assume that a mild, wet winter for California would likely produce a mild, dry winter for the east coast. And that is something the whole nation should celebrate.Subscribe-to-our-newsletter1